Assessing the firing temperature of Uruk pottery in the Middle Euphrates Valley (Syria): Bevelled rim bowls Microchem. J. (IF 3.034) Pub Date : 2018-06-07 Jorge Sanjurjo-Sánchez, Juan Luis Montero Fenollós, Victor Barrientos, George S. Polymeris
In geochemical studies on ancient pottery, different methods have been attempted to assess the firing temperature. One of the most successful methods has involved studying mineral phase transformation sequences produced during firing despite the imprecise results usually obtained. The most commonly used methods assess the mineral composition of samples and thermal analysis. In this work, we used optical microscopy, X-Ray Diffraction, Fourier Transform Infrared Spectroscopy and thermal analyses to assess the firing temperature of a particular type of pottery from Mesopotamia. The Middle Uruk phase in Mesopotamia (3600–3500 BCE) has been characterised by the massive production of the so-called bevelled rim bowls (BRB). They are very similar in shape in Mesopotamia and surrounding areas but their production method is unknown, including the little knowledge about their firing temperature although short recent studies have shown that they were probably fired at mild temperatures. We have studied samples from archaeological sites of this period in the Middle Euphrates Valley in Syria. Results indicate very similar mineral composition, probably due to the use of the same raw materials and very similar mineral sequences that can be attributed to the same firing temperature probably below 500–650 °C and below 900 °C for some isolated samples.
Sensing of formetanate pesticide in fruits with a boron-doped diamond electrode Microchem. J. (IF 3.034) Pub Date : 2018-06-15 Francisco Wirley Paulino Ribeiro, Camila Pinheiro Sousa, Simone Morais, Pedro de Lima-Neto, Adriana Nunes Correia
This study describes the development of a simple and accurate methodology for carbamate pesticide formetanate (FMT) analysis in fruits based on the use of a boron-diamond doped electrode (BDDE) cathodically pretreated and on the forward component of the current of square-wave voltammetry (SWV). FMT exhibits a well-defined irreversible oxidation process, which reaction mechanism is diffusion-controlled, involves the participation of one electron and is influenced by the electrolyte pH. However, protonation does not participate in the rate-determining step in the redox process. The optimum experimental and voltammetric conditions were pH 7.0 (0.04 mol L−1 Britton-Robinson buffer), pulse potential frequency of 20 s−1, amplitude of the pulse of 25 mV, and height of the potential step of 3 mV. Under the optimum conditions, calibration curve was linear from 4.98 × 10−7 to 1.70 × 10−5 mol L−1 FMT with a limit of detection of 3.7 × 10−7 mol L−1. FMT sensing was performed in different fruits (mango and grape). Recoveries ranged from 95.2 ± 2.8 to 104.0 ± 3.5% for mango and 96.5 ± 2.5 to 105.2 ± 3.5% for grape proving the accuracy and precision of the electroanalytical methodology. The attained data validated the applicability of the developed approach for FMT quantification in fruits.
Classification of organic olives based on chemometric analysis of elemental data Microchem. J. (IF 3.034) Pub Date : 2018-06-05 Melisa J. Hidalgo, María T. Pozzi, Octavio J. Furlong, Eduardo J. Marchevsky, Roberto G. Pellerano
The aim of this study was to discriminate organic from conventional olive samples based on the levels of macro and trace elements, combined with chemometric techniques. Ten elements (Na, K, Ca, Fe, Mg, Cu, Zn, Se, S and P) were determined in organic (n = 30) and conventional (n = 30) olive samples by inductively coupled plasma optical emission spectrometry analysis (ICP-OES). The classification of samples was performed by using a well-known chemometric techniques, linear discriminant analysis (LDA), partial least square-discriminant analysis (PLS-DA), support vector machine-discriminant analysis (SVM-DA), k-nearest neighbors (k-NN) and random forest (RF). The k-NN technique showed the best performance in discriminating organic from conventional samples (Accuracy: 94%) using all chemical variables. After variable reduction, an accuracy of 83% was found by using only the elements K and P. The use of a fingerprint based on multielemental levels associated with classification chemometric techniques may be used as a simple method to authenticate organic olive samples.
Reference measurements of cadmium and lead contents in candidates for new environmental certified materials by isotope dilution inductively coupled plasma mass spectrometry Microchem. J. (IF 3.034) Pub Date : 2018-06-15 Agnieszka Anna Krata, Marcin Wojciechowski, Mateusz Kalabun, Ewa Bulska
The analytical procedures for the reference measurements of cadmium and lead concentrations in four candidates for new environmental certified reference materials were developed. Cadmium and lead content was determined in bottom sediment (M-2 BotSed), Baltic herring tissue (M-3 HerTis), cormorant tissue (M-4 CormTis) and codfish tissue (M-5 CodTis). The measurements were carried out with the use of a direct isotope dilution inductively coupled plasma mass spectrometry (ID ICP-MS). The isotope dilution approach and the combined uncertainty of results are based on the mathematical equations as from definition of a primary method of measurement. All factors influencing the final results included: the procedural blank, the moisture content in the materials, the factors affecting the blend ratio measurements (instrumental background, spectral interferences, dead time, mass discrimination effects and the repeatability of measured isotopic ratios) as well as the isotopic equilibrium were systematically investigated and included in the uncertainty budget. The content of cadmium in candidates for new environmental reference materials, after correction for moisture contents, matrix separation on ion-exchange resin AG1-X8 of the blended samples and after using for the ICP-MS measurements ratio of pair of isotopes n(110Cd)/n(111Cd) was found to be: (2.18 ± 0.06) μg g−1 in M-2 BotSed, (337 ± 2) ng g−1 in HerTis, (16.4 ± 0.6) ng g−1 in CormTis) and (2.7 ± 0.4) ng g−1 in CodTis, respectively. The content of lead in candidates for new environmental reference materials, after correction for moisture contents, matrix separation on ion-exchange resin AG1-X8 of the blended samples and after using for the ICP-MS measurements ratio of pair of isotopes n(208Pb)/n(207Pb) was found to be: (108 ± 5) ng g−1 in M-3 HerTis, (2.34 ± 0.12) μg g−1 in M-4 CormTis and (43 ± 2) ng g−1 in M-5 CodTis, respectively. The Cd and Pb contents determined in this work were used as a contribution of the Faculty of Chemistry, Biological and Chemical Research Centre University of Warsaw in the characterisation of the abovementioned candidates for new certified reference materials in the frame of the Inter-Laboratory Comparison, organized by the Institute Nuclear Chemistry and Technology (Warsaw, Poland). The obtained excellent agreement within uncertainties with the reference values further validated the methods developed in this study.
Larrea divaricata volatilome and antimicrobial activity against Monilinia fructicola Microchem. J. (IF 3.034) Pub Date : 2018-06-14 Joana Boiteux, Carolina Monardez, María de los Ángeles Fernández, Magdalena Espino, Pablo Pizzuolo, María Fernanda Silva
Monilinia fructicola is the most destructive pre- and postharvest pathogen in stone fruit worldwide. A great attention has been paid to plant extracts, a rich source of bioactive chemicals, for the sustainable pest control. Volatile organic compounds from plant matrices have proved important antimicrobial activity. In the present work, an analytical procedure for the characterization of the volatile profile in L. divaricata extract by headspace solid-phase microextraction (HS-SPME) coupled to gas chromatography/mass spectrometry (GC–MS) was proposed. Moreover, the biological activity of L. divaricata extract was evaluated for their contact-phase and vapor-phase effects on M. fructicola mycelial growth. In order to improve the absorption of volatile compounds, the following experimental parameters were optimized: fiber coatings, time and temperature extraction. As a result of the optimization, CAR/PDMS fibers, 30 °C and 30 min were selected for the extraction volatile compounds from L. divaricata extract. A total of 79 VOCs were identified in the extract. Among them, aromadendrene was found at highest concentration. Other bioactive volatile compounds were detected such as eugenol, carvacrol, limonene and thymoquinone. The antimicrobial activity of L. divaricata extract on M. fructicola mycelial growth was evaluated under contact- and vapor-phase conditions. L. divaricata extract showed significant antimicrobial activity on M. fructicola mycelial growth in both conditions. The results reveal that L. divaricata is a promising antifungal agent which could be used as bio-fungicide in the protection of fruits and vegetables against postharvest infections.
NiMnO3 nanoparticles anchored on graphene quantum dot: Application in sensitive electroanalysis of dobutamine Microchem. J. (IF 3.034) Pub Date : 2018-06-09 Foroozan Hasanpour, Mohsen Nekoeinia, Abolfazl Semnani, Sahar Shojaei
Chlorate ion standard solution established by multipath titration techniques Microchem. J. (IF 3.034) Pub Date : 2018-06-14 Toshiaki Asakai
Analyses of chlorate ion are essential in evaluating water quality; however, there is no standard solution of chlorate ion characterized by a metrologically valid procedure. This paper describes the measurement procedures and assays of chlorate ions with the linkage to the International System of Units (SI) by multipath gravimetric titration techniques. Three different titration techniques were employed to assay chlorate ions: oxidimetric-reductometric back titration with an iron(II) solution standardized with standard potassium dichromate, precipitation titration with a silver nitrate solution standardized with standard sodium chloride, and oxidimetric-reductometric titration with a thiosulfate solution standardized with standard potassium iodate. The results obtained through three different reactions were in good agreement with each other within their uncertainties. A certified reference material of chlorate ions with the linkage to the SI was first established by evaluating the storage stability of the solution and estimating measurement uncertainties. The assay (mass fraction) of sodium chlorate was characterized by using a weighted mean of the results of three methods; 99.829% ± 0.029% (the value following ± gives a level of confidence of approximately 95%, coverage factor k = 2). Providing with the standard solution through Japan Calibration Service System (JCSS) under Japanese Measurement Act widely allows all analysts to obtain their reliable analytical results.
Cysteine functionalized bio-nanomaterial for the affinity sensing of Pb(II) as an indicator of environmental damage Microchem. J. (IF 3.034) Pub Date : 2018-05-31 María L. Ramírez, Cecilia S. Tettamanti, Fabiana A. Gutierrez, Jose M. Gonzalez-Domínguez, Alejandro Ansón-Casaos, Javier Hernández-Ferrer, María T. Martínez, Gustavo A. Rivas, Marcela C. Rodríguez
Development of an electrochemical method for the detection of quinolones: Application to cladoceran ecotoxicity studies Microchem. J. (IF 3.034) Pub Date : 2018-05-23 Silvina V. Kergaravat, Ana María Gagneten, Silvia R. Hernandez
This work presents the development of a sensitive and friendly environment electrochemical methodology with high analytical performance for quinolone detection. The method is based on square-wave anodic stripping voltammetry which is simple and reliable for determination of quinolone family on the bismuth film electrode (BiFE). The deposition potential, deposition time, buffer solution pH, voltammetry detection technique and bismuth concentration at fixed quinolone concentration (1 μg L−1) were evaluated by fractionated factorial and central composite designs. The high cross-reactivity obtained in the evaluation of different quinolones showed that this methodology could be applied to quinolone family with limits of detection (LOD) close to 0.5 ng L−1. Since is widely known that quinolones can reach aquatic ecosystems, the developed electroanalytical method was applied in the monitoring of moxifloxacin (MOXI) concentrations in ecotoxicity studies by means of acute toxicity test using two cladoceran species as biological models: Daphnia magna and Ceriodaphnia dubia. As a result of ecotoxicity, both species showed comparable sensitivities at MOXI. Toxicity studies of quinolones on aquatic organisms are very limited so the effects of MOXI to cladoceran species are highlighted. The interaction of both disciplines –Chemistry and Ecology- would allow knowing of global behavior of quinolones in natural environments, from an integrative perspective.
Ethinylestradiol quantification in drinking water sources using a fluorescent paper based immunosensor Microchem. J. (IF 3.034) Pub Date : 2018-05-22 María L. Scala-Benuzzi, Eduardo A. Takara, Mara Alderete, Galo J.A.A. Soler-Illia, Rudolf J. Schneider, Julio Raba, Germán A. Messina
In this work we report a novel paper-based analytical device read-out via LED-induced fluorescence detection (FPAD) for the quantification of the emerging pollutant ethinylestradiol (EE2) in river water samples. The PAD was used as a reaction platform for a competitive enzyme immunoassay. For the PAD development, microzones of filter paper, printed by a wax printing method, were modified with amino-functionalized SBA-15 and subsequently, anti-EE2 specific antibodies were covalently immobilized. The determination of EE2 in water was carried out by adding a fixed concentration of EE2 conjugated with the enzyme horseradish peroxidase (HRP) to samples and standards. Then, the FPAD were added and incubated for 10 min. Finally, the detection was performed by the reaction of 10-acetyl-3,7-dihydroxyphenoxazine (ADHP) whose oxidation is catalyzed by HRP in the presence of H2O2, obtaining the highly fluorescent resorufin (R). Resorufin was detected by LED excitation at 550 nm, observing emission at 585 nm. The EE2 concentration in the samples was inversely proportional to the relative fluorescence obtained from the enzymatic reaction products. The FPAD assay showed a detection limit (LOD) of 0.05 ng L−1 and coefficients of variation (CV) below 4.5% within-assay and below 6.5% between-assay, respectively. The results obtained show the potential suitability of our FPAD for the selective and sensitive quantification of EE2 in river water samples. In addition, it has the PADs advantages of being disposable, easy to apply and inexpensive.
Infrared spectroscopic study of the formation of fossil resin analogs with temperature using trans-communic acid as precursor Microchem. J. (IF 3.034) Pub Date : 2018-05-21 Óscar R. Montoro, Álvaro Lobato, Valentín G. Baonza, Mercedes Taravillo
For million years resin exudates have undergone chemical alterations by heat, pressure, radiation, water, oxygen, microorganisms, and have suffered processes of sedimentation and diagenesis. These agents have affected the organic functional groups present in the terpenes of the resins, giving rise to what we nowadays know as fossil resins. In this work, we try to get further insight in the chemical formation of fossil resins. As the simulation of the natural process is quite complex, we have focused on the temperature induced reactivity of the trans-communic acid, the main component of the Class I resins. Using this terpene derivate as a very basic model of a resin exudate, we have monitored their thermal changes by infrared spectroscopy, Differential Scanning Calorimetry and Thermogravimetric Analysis within the range of 25 to 340 °C. The temperature-induced transformation, both in presence and absence of inert atmosphere, is discussed on the basis of the reactivity of the conjugated double-bond, the exocyclic bond and the carboxylic acid group present in the trans-communic acid. The results obtained in these series of experiments agree with the maturation scheme accepted in the literature for natural resins, i.e. an initial cross-linked polymerization and a subsequent maturation reaction. From combined DSC/TGA and infrared spectroscopy results, we conclude that chemical changes produced in the trans-communic acid in the range 130–175 °C may mimic the initial polymerization-like process in the natural resins, whereas those produced between 180 and 340 °C seem to correspond to the maturation pathways described in the literature for fossil resins Class Ib. Spectral assignment of the most relevant infrared-active modes of the trans-communic acid at 25 °C is also provided with the aid of Density Functional Theory calculations.
Nickel determination in oily sludge leachates using isotope dilution inductively coupled plasma mass spectrometry following photochemical vapor generation: A feasibility study Microchem. J. (IF 3.034) Pub Date : 2018-05-17 Graziela Salvador, Bárbara Souza Soares, Daniel L.G. Borges
The feasibility of photochemical vapor generation for the production of volatile Ni species was evaluated and applied to the analysis of acetic acid leachates obtained from oily sludge samples. Sludge samples originating from a petrochemical plant were submitted to extraction using standardized procedures with solutions adjusted to pH 2.88 or 4.93, with acetic acid. The leachate solutions were subsequently treated with a mixture of acetic and formic acid and exposed to UV radiation from a Hg discharge lamp; the irradiated solution was pumped to a gas-liquid separator and the volatile species were transported by a stream of argon for detection using inductively coupled plasma mass spectrometry. Experimental variables, including the nature and concentration of low molecular weight acids, irradiation interval, carrier gas flow rate and the effect of concomitant species on the efficiency of photochemical production of volatile Ni species were systematically evaluated. Oxygenated anions, particularly nitrate, were found to suppress the analytical signal, whereas the effect of cationic species depended on the nature of the cation. Lead was found to induce substantial signal suppression even at ppb levels. Considering the significant influence of concomitant species on the overall efficacy of the photochemical process, isotope dilution calibration was adopted as a strategy to overcome non-spectral interferences. Under optimized conditions, relative standard deviations better than 8.5% were achieved, along with detection limits better than 40 μg L−1. The accuracy was statistically attested upon comparison of the results to those obtained from the analysis of leachates using sample introduction via pneumatic nebulization. The proposed photochemical vapor generation setup was proven efficient to carry out the determination of Ni in the leachates, although the technique is highly sensitive to the presence of concomitants.
Nanomaterials in fluorescent laser-based immunosensors: Review and applications Microchem. J. (IF 3.034) Pub Date : 2018-05-16 Pedro R. Aranda, Germán A. Messina, Franco A. Bertolino, Sirley V. Pereira, Martín A. Fernández Baldo, Julio Raba
A liquid chromatography-mass spectrometry study on the spirocyclization of ninhydrin with the aminothiols Microchem. J. (IF 3.034) Pub Date : 2018-05-26 Salvatore Sotgia, Angelo Zinellu, Mauro Forteschi, Panagiotis Paliogiannis, Giovanni A. Deiana, Gerard A. Pinna, Arduino A. Mangoni, Ciriaco Carru
Ninhydrin reacts with some aminothiols to form spiranes adducts whose optical and chromatographic properties have proved to be useful for chiral recognition. Liquid chromatography-mass spectrometry data along with spectroscopic analysis reveal that under certain conditions, in addition to the known single-spirane configuration, the spirothiazolidinic complexes can exist also as double- and mixed double-spiranes. The reaction was exploited to check the enantiomeric purity of two commercially available dosage form of D-penicillamine and to measure the aminothiol concentration in the urine sample from a subject under treatment with the drug. Separation of diastereoisomers was achieved on a C18 column in isocratic mode by using a mixture of an aqueous solution of formic acid (30 mmol/L)/acetonitrile (90:10, v/v) as a mobile phase. Diastereoisomers were detected by a fluorescence detector and mass spectrometer in short times and with a good resolution. Intra- and inter-assay reproducibility were under 4% with an average recovery of 98%. At a LOD of 0.01%, no evidence of the toxic distomer (l-enantiomer) was found in the biological sample and drugs.
Microwave-assisted facile synthesis of mono-dispersed Ba/Ho co-doped nanohydroxyapatite for potential application as binary CT imaging contrast agent Microchem. J. (IF 3.034) Pub Date : 2018-05-25 Xiaoke Zheng, Shanling Wang, Lan Wu, Xiandeng Hou
It is appealing to develop a facile way to prepare a binary CT contrast agent with good biocompatibility and CT contrast efficiency for potential clinical applications. In this work, a novel binary CT contrast agent based on the biocompatible nano-hydroxyapatite (nHAp, the main inorganic component of human bone and teeth) was prepared facilely and rapidly through doping two kinds of CT contrast ions (Ba2+ and Ho3+) into the nHAp host via microwave-assisted synthesis. The Ba/Ho co-doped nHAp with pure nHAp phase composition and good mono-dispersion was obtained simply with microwave heating for 30 min. The as prepared CT contrast agent is very promising as a novel binary CT contrast agent for CT imaging.
Organic matter from bevelled rim bowls of the Middle Euphrates: Results from molecular characterization using pyrolysis-GC–MS Microchem. J. (IF 3.034) Pub Date : 2018-05-02 Jorge Sanjurjo-Sánchez, Joeri Kaal, Juan Luis Montero Fenollós
The Middle and Late Uruk period (3600–3100 BCE) is characterised by the diffusion of the Uruk culture in Mesopotamia and surroundings. Uruk sites are recognised by a special kind of pottery called bevelled rim bowls (BRBs), which comprise up to 80% of all recovered Uruk pottery. BRBs are very basic, handmade bowls produced in large quantities but their function is still under debate. Several uses have been proposed, including cooking, measurement of cereal rations, bread preparation, salt making or as votive bowls. Searching for evidence that supports the proposed hypotheses we studied BRB samples from several archaeological sites in the Middle Euphrates (Syria). We analysed fragments of pottery by pyrolysis coupled to gas chromatography and mass spectrometry (Py-GC–MS) to identify organic molecules that could be related to past BRB contents. Additionally, we cooked bread in experimentally produced BRBs to compare results. Up to 93 organic compounds could be identified, including polysaccharides, lignin products and fatty acids. The unequivocal presence of lignocellulose residues (especially 4-vinylguaiacol and other guaiacols, which were also found in experimentally charred bread heated below 450 °C), is compatible with the proposed hypothesis of leavened bread cooking, but a source of incomplete burn off of organic temper cannot be discarded.
A novel methodological approach for the assessment of surface cleaning of acrylic emulsion paints Microchem. J. (IF 3.034) Pub Date : 2018-05-04 Theodora Fardi, Valentina Pintus, Elli Kampasakali, Eleni Pavlidou, Konstantinos G. Papaspyropoulos, Manfred Schreiner, Giorgos Kyriacou
In the present study a novel methodology was developed for the assessment of surface cleaning treatment of acrylic emulsion paints, with the use of Pyrolysis–Gas Chromatography/Mass Spectrometry (Py–GC/MS). In order to assess the degree of invasiveness of surface treatments applied on acrylic emulsion paints, Py–GC/MS was employed for the direct analysis of the cleaning extracts, aiming to simultaneously detect the main organic components of the acrylic emulsion paints extracted from the paint during cleaning. Commercial acrylic emulsion paints were chosen for the study, containing four different synthetic organic pigments: Hansa yellow (PY3), diketopyrrolopyrrole red (PR264), phthalocyanine blue (PB15) and phthalocyanine green (PG7). Mock ups of paint films were prepared and subjected to artificial soiling and thermal ageing. Py–GC/MS and Fourier Transform Infrared Spectroscopy in Attenuated Total Reflection mode (FTIR–ATR) were used for the identification of the main organic components found in the prepared acrylic paints. Cleaning tests were conducted simulating actual surface cleaning treatment conditions, using a set of different types of wet cleaning systems, including water, aqueous solutions with chelating agents, water in oil (w/o) microemulsion and a siloxane based w/o emulsion. For an integrated physicochemical and aesthetic approach towards the evaluation of the cleaning tests, in parallel with the Py–GC/MS analysis carried out on the cleaning extracts, the degree of soil removal was comparatively evaluated through visual observation and documented in macro and micro scale. Moreover, statistical analysis was performed in the aim of correlating the aesthetic and the physicochemical cleaning assessment results. The study showed that Py–GC/MS is very useful tool for assessing the cleaning of acrylic emulsions and the action of different cleaning systems, making possible to detect minor quantities of the paint's components, through the direct analysis of the cleaning extracts. Some new information on the impact of cleaning treatments on emulsion paints as regards the synthetic organic pigments and the acrylic binder is presented.
Improving reproducibility between batches of silver nanoparticles using an experimental design approach Microchem. J. (IF 3.034) Pub Date : 2018-05-12 Rodrigo Nicolás Núñez, Alicia Viviana Veglia, Natalia Lorena Pacioni
An optimized method for the synthesis of silver nanoparticles (AgNP) using gallic acid as reductant was achieved using design of experiment strategies based on response surface methodologies. Fractional Factorial Design was used in the screening stage, the Box-Behnken method was employed to model the target responses and finally, the optimization step was done using Desirability function. The obtained AgNP presented improved repetitivity and reproducibility of photophysical properties between batches compared to the synthesis method reported in literature. Intra-assays, intermediate precision and reproducibility tests were performed and proved the different AgNP batches presented equal optical responses, average size and size distribution at a 95% confidence level. In addition, a test on shelf life estimated the optimized AgNP preserve their properties at least for 38 days and especially, zeta potential measurements indicated their low tendency to flocculation as long as 120 days. Furthermore, a remarkable improvement in obtaining reproducible Stern-Volmer constants in fluorescence quenching experiments using Carbazole as fluorophore was observed compared to nanoparticles synthesized by a non-optimal method.
Nutritional characterization of healthy and Aphelenchoides besseyi infected soybean leaves by laser-induced breakdown spectroscopy (LIBS) Microchem. J. (IF 3.034) Pub Date : 2018-05-08 Anielle C. Ranulfi, Giorgio S. Senesi, Jonas B. Caetano, Maurício C. Meyer, Aida B. Magalhães, Paulino R. Villas-Boas, Débora M.B.P. Milori
Acid-base responsive probes for mercury(II) ions in aqueous solution Microchem. J. (IF 3.034) Pub Date : 2018-05-12 Tiziana Del Giacco, Raimondo Germani, Giada Lucci, Matteo Tiecco
A simple ratiometric optical method for mercuric ion sensing has been developed using an ensemble of an indicator, such as 7-hydroxy-4-methylcoumarin (7H4MC) and bromothymol blue (BTB), and a receptor, such as N,N-bis(p-methoxybenzyl)-3,6-dioxaoctane-1,8-diamines (bis-pMDODA) and cryptand [2.2.2] (C222), in aqueous solution. The equilibrium between indicator and receptor is perturbed by adding Hg2+ ions (0.8–80 μM), due to the formation of a receptor-metal complex, resulting in a change of the UV/Vis spectra. Both sensitivity and selectivity are explained in terms of association constants between receptor and metal ions and equilibrium constants of the reaction between indicator and receptor. Indicator bromothymol blue has also presented a color variation from light blue to yellow upon coordination of Hg2+ to the receptor, which allows a metal naked-eye detection. The detection limit of the system was found to be about 3 μM and the relative standard deviation for five measurements of 20 μM concentration was 5.6%. BTB/7H4MC arrangement showed a particular selectivity over different interfering cations, suffering only interference from Cu2+ ions for Hg2+ sensing.
LC–MS/MS assay for assessing medical adherence in patients under warfarin maintenance therapy Microchem. J. (IF 3.034) Pub Date : 2018-05-03 Faten Farouk, Samir Nabhan, Wilfried M.A. Niessen, Hassan M.E. Azzazy
Warfarin (WRN) use is plagued by response fluctuation which is managed by dose adjustment. The plasma WRN level had always been an abandoned prerequisite for dose adjustment. However, recent reports had correlated WRN level to the consumed dose. More importantly, the intra-individual alteration in WRN level was found proportional to response fluctuation. This renewed the interest to use WRN level prior to dose adjustment to account for dispensing errors or inadequate adherence. Detection of possibly interacting drugs may further assess compliance and enable a wiser dose adjustment. In this study, an LC–MS/MS assay was developed and validated for the determination of the WRN and the simultaneous detection of interacting drugs in citrated plasma samples normally collected for monitoring international normalized ration (INR). Samples were prepared by liquid-liquid extraction. Separation of WRN and interacting drugs (n = 19) was achieved on an Inertsil®C18 column using a gradient elution program. The assay was applied in 96 plasma samples from patients. The developed method was linear, accurate and precise for WRN determination with average recovery of 99.5 ± 8.4% and no relative matrix effect. WRN plasma level was measured in all samples and possible interacting drugs were detected. An improved WRN-response correlation was observed inter-individually when patient variability was reduced. Our results support the significance of WRN monitoring and suggest the additional monitoring of other interacting drugs for integrated evaluation of patient adherence. The developed method enables ruling-out inadequate adherence prior to unnecessary dose adjustment and highlights the need to strengthen patient education procedures.
A traffic light-type sensitive visual detection of mercury by golden nanoclusters mixed with fluorescein Microchem. J. (IF 3.034) Pub Date : 2018-05-17 Wenqing Deng, Rui Dai, Pingyue Hu, Qianqian Li, Xiaoli Xiong, Ke Huang, Feng Huo
A novel colorimetric sensor based on red-emitting bovine serum albumin‑golden nanoclusters (BSA-AuNCs) and green-colored fluorescein that exhibited traffic light-type color change was developed for ratiometric and visual detection of mercury (Hg). In the presence of Hg2+, the red fluorescence from BSA-AuNCs was quenched while the green fluorescein was inert thus as a reference. And it presented traffic light-type (red, yellow and green) color in the low, middle and high concentration of Hg2+. A potential mechanism was investigated by Energy Dispersive Spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS). The selective quenching mechanism may be due to the formation of gold amalgam bonds between BSA-AuNCs and Hg2+. A linear correlation was constructed for Hg2+ in the concentration range of 10–500 μg L−1. A limit of detection (LOD) of 7.4 μg L−1 and a relative standard deviation (RSD, n = 7) of 0.4% were obtained, which can be used to monitor the concentration of Hg2+. In visual detection, as low as 0.1 μg mL−1 of Hg2+ can be easily discriminated from the blank with the naked eye. The proposed method was validated by analysis of certified environment and food samples with satisfactory results.
Development of a ruthenium(II) complex-based luminescence probe for detection of hydrogen sulfite in food samples Microchem. J. (IF 3.034) Pub Date : 2018-05-18 Wenzhu Zhang, Hua Liu, Feiyue Zhang, Yong-Lei Wang, Bo Song, Run Zhang, Jingli Yuan
Removal of Cu2+ and Ni2+ from aqueous solution using SnO2 nanomaterial effect of: pH, time, temperature, interfering cations Microchem. J. (IF 3.034) Pub Date : 2018-05-14 Abigail M. Zepeda, Daisy Gonzalez, Luis Gonzalez Heredia, Karina Marquez, Cesar Perez, Erika Pena, K. Flores, C. Valdes, T.M. Eubanks, J.G. Parsons, J. Cantu
Tin oxide, SnO2, nanomaterial was synthesized and tested for the removal of Cu2+ and Ni2+ ions from aqueous solutions. Various parameters for the binding were investigated in batch studied, which included pH, time, temperature, and interferences. In addition, isotherm studied was performed to determine the maximum binding capacity for both Cu2+ and Ni2+ ions. The optimal binding pH determined from the effects of pH were to be at pH 5 for both the Cu2+ and Ni2+ ions. The isotherm studies were performed at temperatures of 4 °C, 25 °C, and 45 °C for both the Cu2+ and Ni2+ ions and were found to follow the Langmuir isotherm model. The binding capacities for the Cu2+ ions were 2.63 mg/g, 2.95 mg/g and 3.27 mg/g at the aforementioned temperatures, respectively. Whereas the binding capacities for Ni2+ were 0.79 mg/g, 1.07 mg/g, and 1.46 mg/g at the respective temperatures. The determined thermodynamic parameters for the binding showed that the binding processes for the reactions were endothermic, as the ΔG was observed to decrease with decreasing temperatures. As well the ∆H was 28.73 kJ/mol for Cu2+ (III) and 13.37 kJ/mol for Ni2+. The ∆S was observed to be 92.65 J/mol for Cu2+ and 54.53 J/mol for Ni2+. The free energy of adsorption for the Cu2+ was determined to be 13.99 kJ/mol and the activation energy for the binding of Ni2+ was determined to be 8.09 kJ/mol. The activation energy data indicate that the reaction was occurring through chemisorption.
Optimization of simultaneous determination of metals in commercial pumpkin seed oils using inductively coupled atomic emission spectrometry Microchem. J. (IF 3.034) Pub Date : 2018-05-19 Milan Mitić, Aleksandra Pavlović, Snežana Tošić, Pavle Mašković, Danijela Kostić, Snežana Mitić, Gordana Kocić, Jelena Mašković
In this work, the inductively coupled plasma atomic emission spectrometry (ICP-AES) was developed and validated for determination of 27 metals in nine pumpkin oils from two production processes (cold pressed and roasted). A microwave assisted digestion was applied for the dissolution of the samples. To evaluate plasma robustness and analytical performance, the Mg II 280.270 nm/Mg I 285.213 nm (Mg II/Mg I) line intensity ratio was used. The robust plasma conditions in axial/radial view mode were reached at an RW power of 1150 W and an argon nebulizer flow rate of 0.5 L/min. The method is evaluated by application of the standard addition method and by recovery test. In general, the recoveries for all elements in pumpkin seed oils were between 90% and 110% except, only for Cd, Pb and As they were <90% and >110%. The most abundant element is K followed by, Mg, P, Ca and Na. Pumpkin seed oils were also found to be a good source of Fe, Zn, Cu and Mn. The highest levels of analyzed elements were found in pumpkin seed oils producing from the roasted pumpkin seed paste. In all samples, the content of heavy metals was below the recommended tolerable levels proposed by Joint FAO/WHO Expert Committee on Food Additives and does not a pose a health risk for the consumer. The levels of the metals in pumpkin seed oils were also compared with those reported by the literature. Cluster analysis (CA) of the analytical data confirmed the observed differences between oils from two production processes.
In vivo investigation of the volatile metabolome of antiphytopathogenic yeast strains active against Penicillium digitatum using comprehensive two-dimensional gas chromatography and multivariate data analysis Microchem. J. (IF 3.034) Pub Date : 2018-05-21 João Raul Belinato de Souza, Katia Cristina Kupper, Fabio Augusto
Penicillium digitatum is the responsible for green mold decay on citrus fruits, which contributes to economic losses in agriculture industry during storage, transportation and in the market. Biocontrol agents may be a viable and low-cost alternative in the control of different plant pathogens: metabolites from some yeast strains can prevent infection, decreasing host tissue colonization and reducing pathogen survival and sporulation with varying degrees of efficiency. Eight S. cerevisae strains and one Candida stellimalicola strain all were evaluated in vitro as biological control agents against P. digitatum. After in vitro tests the headspace of yeast strains were extracted in vivo using an optimized HS-SPME + GC × GC–MS method. The correlation between antiphytopathogenic activity with the volatile metabolite profiles was assessed using principal component analysis. Nine compounds were associated with the volatile metabolome of strains with higher antifungal action: ethyl propionate, 3-methyl-1-butanol, 2-methyl-1-butanol, ethyl butyrate, 3-methylbutyl acetate, 3-methylbutyl propionate, n-pentyl butyrate, phenylethyl alcohol and 2-phenethyl acetate. This study allowed for the first time a comprehensive overview of the effect of individual volatile metabolites from yeast strains on P. digitatum infection.
Two-stage probe atomization GFAAS for direct determination of trace Cd and Pb in whole bovine blood Microchem. J. (IF 3.034) Pub Date : 2018-05-19 Artyom V. Volzhenin, Natalya I. Petrova, Tatyana V. Skiba, Anatoly I. Saprykin
Graphite furnace atomic absorption spectrometry (GFAAS) is rarely used for direct trace analysis of whole blood because of strong interferences caused by the organic matrix. Especially it concerns bovine blood samples, containing more proteinaceous and lipid components in comparison with human blood. In our work, the novel two-stage probe atomization (TPA) technique for Cd and Pb determination by GFAAS in whole bovine blood with minimum sample pre-treatment has been developed. Making use of TPA and chemical modifier has eliminated matrix suppression and decreased the non-selective absorption level by several times. It allowed us to dispense with brief sample pre-treatment by a mixture of nitric acid and hydrogen peroxide (1:1) without autoclave digestion. The pyrolysis temperatures were 650 °C for Cd and 900 °C for Pb in the presence of Pd modifier. The analytical signal dependence on the number of concentrating cycles has been studied. The maximal number of capturing cycles was found (15 and 10 for Cd and Pb). Applying of multiple probe concentrating has additionally decreased the limits of detection (LODs) comparing with single TPA. The achievable LODs in optimized conditions were found to be 0.01 and 0.2 μg/L for Cd and Pb, respectively (3 s test). The accuracy of the proposed technique was confirmed by anodic stripping voltammetry (ASV). The relative standard deviation for 5.1 μg/L Cd and 26 μg/L Pb concentrations was 6.4% and 7.5%, respectively.
Investigation of organic media and surfactant sensitization in non-aqueous phase hydride generation-atomic fluorescence spectrometric determination of antimony Microchem. J. (IF 3.034) Pub Date : 2018-05-18 Luqiong Chen, Zirong Lei, Kan Hu, Shengchun Yang, Xiaodong Wen
This work was the expansion and in-depth study based on the previously established non-aqueous phase HG system. Aiming at the determination of antimony by the developed non-aqueous phase HG, the effect of different organic media and the sensitization effect of surfactant on the non-aqueous phase HG reaction were investigated. As an important condition, organic media has an important influence on this method. This study found that the surfactant Triton X-114 had very good sensitization effect for non-aqueous HG reaction. The sensitization effect of surfactant in different organic media was different. Among the investigated media, the comprehensive performance of octanol was the best under the sensitization effect of surfactant. Compared with the analytical performance of not adding surfactant, the sensitization factor of the surfactant was 1.55. The sensitization effect of surfactant Triton X-114 on the HG reaction in the octanol media was very significant, which greatly improved the analytical performance of the non-aqueous HG method. Under the optimal conditions, the limit of detection (LOD) was 0.04 μg/L. Compared to conventional HG-AFS, the efficiency of non-aqueous phase HG and the analytical performance of the developed method was considerably improved.
Quantitative determination of the veterinary drug monensin in horse feed samples by square wave voltammetry (SWV) and direct infusion electrospray ionization tandem mass spectrometry (DI–ESI–MS/MS) Microchem. J. (IF 3.034) Pub Date : 2018-05-18 Konrad Rudnicki, Pavlína Landová, Monika Wrońska, Sławomir Domagała, Josef Čáslavský, Milada Vávrová, Sławomira Skrzypek
Advancements in the chemical structures of Ergot acyl glycerides by high performances liquid chromatography coupled with high resolution mass spectrometry Microchem. J. (IF 3.034) Pub Date : 2018-05-17 Jacopo La Nasa, Jeannette J. Lucejko, Hans-Ulrich Humpf, Erika Ribechini
A comprehensive picture of the chemical composition and structure of the acyl-glycerides from ergot (fungi of the genus Claviceps) sclerotia was carried out using liquid chromatography coupled with high resolution mass spectrometry (HPLC-ESI-Q-ToF) following microwave solvent extraction. The method allowed us to study the chemical structures of >70 compounds being most of these reported and characterized here for the first time in ergot sclerotia. Diglycerides, triglycerides and estolides were proper preliminary separated using reverse phase chromatography and the unambiguous chemical structure of each species was characterized using high resolution tandem mass spectrometry. Our data and results could be useful for anyone interested in detecting ergot contaminations in cereals and deriving products, as alternative to the identification of alkaloids, in better understanding the behavior of ergot fungi in biological contest and in evaluating the potential uses of ergot estolides in industrial applications.
Analytical applications of Cu@PtPd/C nanoparticles for the quantification of hydrogen peroxide Microchem. J. (IF 3.034) Pub Date : 2018-05-17 F.A. Gutierrez, I.S. Giordana, V.C. Fuertes, A.E. Montemerlo, J.M. Sieben, A.E. Alvarez, M.D. Rubianes, G.A. Rivas
This work reports a non-enzymatic amperometric sensor for hydrogen peroxide based on the use of a glassy carbon composite electrode modified with core-shell Cu@PtPd/C nanoparticles. Cu@PtPd/C presents an important electrocatalytic activity towards hydrogen peroxide reduction. The comparison of the sensitivities and the charge transfer resistances for hydrogen peroxide at the glassy carbon composite electrode modified with 5.0% w/w Pt/C, Pd/C, Pd/C + Pt/C and Cu@PtPd/C demonstrate a clear synergism on the catalytic reduction of hydrogen peroxide at −0.100 V when having Pt, Pd and Cu incorporated in the core-shell nanostructure. The best compromise between sensitivity, reproducibility and response time was reached with 20.0% w/w Cu@PtPd/C. For the selected sensor (glassy carbon composite electrode containing 20.0% w/w GCPE/Cu@PtPd/C) the analytical parameters are highly competitive compared to similar devices reported in the last years, with a linear relationship between current and hydrogen peroxide concentration between 5.0 × 10−6 and 2.5 × 10−4 M, sensitivity of (5.30 ± 0.09) × 105 μAM−1 cm−2 (r2 = 0.998) and detection limit of (3.7 ± 0.5) × 10−7 M. The resulting sensing platform was successfully used for the quantification of hydrogen peroxide in a mouth-wash sample.
Mixture design and Doehlert matrix for optimization of the ultrasonic assisted extraction of caffeic acid, rutin, catechin and trans-cinnamic acid in Physalis angulata L. and determination by HPLC DAD Microchem. J. (IF 3.034) Pub Date : 2018-05-17 Gisele Chagas Moreira, Fabio de Souza Dias
The present article describes the development of an ultrasonic assisted extraction of phenolic compounds in Physalis angulata and determination of caffeic acid, rutin, catechin and trans-cinnamic acid by HPLC DAD. The mixtures were composed of extractor solvent and its ratio optimized using a mixture design. Doehlert matrix was used to optimize the extractor solvent volume and sonication time while using total phenolics as analytical response. The optimized conditions for the extractor solvent were the ratio of: 57% water, 35% ethanol and 8% methanol. The best experimental conditions for ultrasound were a sonication time of 10 min and extractor volume of 15 mL. The limit of detection varied from 5.0 to 30 μg L−1. The methods precision was expressed as relative standard deviation (RSD) and presented values lower than 3.0% for all analytes. The accuracy was evaluated using spike test with recoveries between 91% and 107%. The method was applied for the determination of caffeic acid, rutin, catechin and trans-cinnamic in four samples of Physalis angulata aerial parts and the concentration varied from 15.5 to 22.5 μg g−1 for catechin, from 25.0 to 32.5 μg g−1 for caffeic acid, 75.6 to 88.2 μg g−1 for rutin and varied from 23.5 to 110.7 μg g−1 for trans-cinnamic acid.
High throughput screening of phenolic constituents in a complex sample matrix using post-column derivatisations employing reaction flow HPLC columns Microchem. J. (IF 3.034) Pub Date : 2018-03-16 Andrew Jones, Agustín Acquaviva, Gary R. Dennis, R. Andrew Shalliker, Arianne Soliven
This communication is the first to demonstrate the high throughput power of a 30 mm in length reaction flow (RF) column to conduct a targeted analysis of phenolics in a complex sample matrix (tea) utilising post-column derivatisation (PCD). Sensitivity, speed and efficiency could be tuned via the selection of the RF column separation flow rate. RF-PCD compared to conventional PCD approach with a 100 μL loop resulted in a gain of up to 150% in sensitivity. The reaction loop volumes employed in conventional PCD approaches will always be the limitation for compatibility with low dispersion chromatography systems and/or columns.
A silver nanoparticle-based colorimetric assay of trace selenium with hydride generation for sample introduction Microchem. J. (IF 3.034) Pub Date : 2018-05-22 Shixu Huang, Yongna Jin, Guoming Cao, Yunfei Tian, Kailai Xu, Xiandeng Hou
A highly selective, sensitive yet simple colorimetric assay was developed for Se(IV) detection based on the silver nanoparticles (AgNPs), with hydride generation for separation and sample introduction. The proposed method could be easily performed by introducing the hydride vapor of the analyte (H2Se) into a thioglycolic acid (TGA) capped AgNPs solution. A combination of experimental and theoretical studies was used to illustrate the mechanism of this AgNPs colorimetric assay. The strong interaction of AgNPs with Se0 (oxidation product of H2Se) and/or H2Se weakens the stabilizing effect of TGA on AgNPs, leading to the aggregation of AgNPs and thus the color change of the AgNPs solution from bright yellow to light yellow or even colorless with the increase of Se(IV) concentration. The limit of detection was found to be 5 μg L−1 with UV–vis spectrophotometric detection, and 50 μg L−1 with the naked eye visual observation. The proposed method showed excellent selectivity and was successfully applied for Se(IV) determination in fish protein and sea water samples.
NMR and multivariate data analysis to assess traceability of argentine citrus Microchem. J. (IF 3.034) Pub Date : 2018-05-22 Mario O. Salazar, Pablo L. Pisano, Manuel González Sierra, Ricardo L.E. Furlan
Argentine citrus industry stands out among the top ten largest producers of citrus of the world. Traceability is a key point of the quality control in the international trade context. Discrimination between orange juices produced from different geographical regions in Argentina (San Pedro and Entre Ríos), has been achieved by applying principal components analysis (PCA) and partial least-squares – discriminant analysis (PLS–DA) to 1H NMR spectra of the juices. Different regions of the spectra were analyzed in view of the large range of signal intensities and the chemometric treatment of the NMR data has successfully distinguished the juice of different origins/varieties, as well as the metabolites responsible for their separation. Examination of the PCA loadings showed that citric acid and ethanol levels were the main chemical variables for sample discrimination.
A new copper mediated on-off assay for alkaline phosphatase detection based on MoOx quantum dots Microchem. J. (IF 3.034) Pub Date : 2018-05-17 Li Zhang, Ming Fang Hong, Zhao Jun Chu, Han Xu, Shan Ping Wang, Xiao Jing Zhao, Sai Jin Xiao
Trace arsenic speciation analysis of bones by high performance liquid chromatography-inductively coupled plasma mass spectrometry Microchem. J. (IF 3.034) Pub Date : 2018-05-21 Huimin Yu, Huan Du, Li Wu, Ruolin Li, Qun Sun, Xiandeng Hou
The speciation analysis of arsenic (As) has always received great attention, in which the analysis of complex matrix samples remains challenging, mainly manifested in selection of suitable sample pretreatment methods and sensitive analytical spectrometers. In this work, microwave-assisted extraction of total As and various As species in bones, with their respective determination by ICP-MS and HPLC-ICP-MS, was studied, and was successfully utilized to determine As species in panda and pig bones. The results reveal the content of As ranging from 28 to 75 μg g−1 in the panda bone samples and 0.27 μg g−1 in pig bone, in which >90% is inorganic AsV except for little AsIII and organic As. The method could be applicable to the analysis of diverse bone samples.
Speciation analysis of thallium in tobaccos using liquid chromatography inductively coupled plasma mass spectrometry Microchem. J. (IF 3.034) Pub Date : 2018-05-12 Wei-Tsun Chen, Shiuh-Jen Jiang, A.C. Sahayam
An inductively coupled plasma mass spectrometer (ICP-MS) was used as a liquid chromatographic detector for the speciation analysis of thallium in tobacco and cigarette ash samples. In this study, ionic Tl species, namely Tl(I) and Tl(III) were well separated in less than 2 min by reversed-phase high performance liquid chromatography (RP-HPLC). The stationary and mobile phases were C8 column and 7 mmol L−1 tetrabutylammonium phosphate (TBAP), 6 mmol L−1 diethylenetriamine pentaacetic acid (DTPA) in 2% (v/v) methanol solution (pH 5) respectively. Effluent from the HPLC column was delivered to the nebulizer of the ICP-MS for the determination of Tl. Detection limit was 0.003 ng mL−1 for both Tl(I) and Tl(III) compounds based on peak height. The relative standard deviation of peak areas for five injections of a mixture containing 1 ng Tl mL−1 each species was better than 1%. The Tl species were quantitatively leached from the tobacco and the ash into a solution of 5 mmol L−1 DTPA in 100 mmol L−1 ammonium acetate with/or without HF in an ultrasonic bath during a period of 20 min. The addition of HF improved the extraction of Tl from the ash sample. The extraction efficiency of Tl from tobacco was in the range 98–110%. Speciation analysis by HPLC-ICP-MS on tobacco samples showed a satisfactory agreement with the total Tl concentration obtained by ICP-MS analysis of completely dissolved samples. Tl(I) was the only detectable Tl species in tobacco samples analyzed, however both Tl(I) and Tl(III) were present in the cigarette ash.
Performance of Streptomyces rimosus biomass in biosorption of heavy metals from aqueous solutions Microchem. J. (IF 3.034) Pub Date : 2018-05-09 Mohamed Nasser Sahmoune
The removal of heavy metals by Streptomyces rimosus has been the subject of many investigations. This review paper focuses on the removal of heavy metals from aqueous solution through Streptomyces rimosus, produced from pharmaceutical industry as solid waste, as adsorbent, and discusses the effect of various process parameters like pH, temperature, metal concentration etc., on the metal removal efficiency of this bacterium. The paper also evaluates the different kinetic, equilibrium, and thermodynamic models used in Streptomyces rimosus sorption of heavy metals. Biomass characterization and sorption mechanisms as well as elution of metal ions are also discussed. The literature revealed that Streptomyces rimosus had a good affinity for binding lead and iron compared with other heavy metals. The adsorption of heavy metals is well described by Langmuir isotherm, which expresses the existence of monolayer adsorption. The kinetic data followed both pseudo first order and pseudo second order models. Thermodynamic studies showed spontaneous and exothermic nature of the sorption processes in most case. Dilute acids (HCl and H2SO4) are quite effective in desorption of heavy metals. Ion exchange played the chief role in the adsorption mechanism of metal, and carboxyl groups are mainly involved in this mechanism.
Designing an electrochemical aptasensor based on immobilization of the aptamer onto nanocomposite for detection of the streptomycin antibiotic Microchem. J. (IF 3.034) Pub Date : 2018-05-12 Mahmoud Roushani, Kazhal Ghanbari, S. Jafar Hoseini
Streptomycin (STR), an aminoglycoside antibiotic, was used in human and veterinary to treat gram-negative infections. STR residue causes serious side effects on human health. Accordingly, to achieve a novel and sensitive method for detection of STR, we attempted to develop electrochemical sensing system based on graphene quantum dots (GQDs) functionalized with amine ( NH) and thiol ( SH) groups (GQDs-N-S) as the promising newest carbon-based nanomaterial. In this sensing system, gold nanoparticle (AuNPs) was deposited on the GCE surface. Then GQDs-N-S was coated on the AuNPs/GCE surface. After, the silver nanoparticle (AgNPs) coated on the GQDs-N-S/AuNPs/GCE. Finally, the STR thiol-aptamer (SH-Apt) was covalently attached on the AgNPs/GQDs-N-S/AuNPs/GCE via bonding formation of Ag S. This system showed linear range from 0.01 pg·mL−1 to 812.21 pg·mL−1 with limit of detection of 0.0033 pg·mL−1; it was as good as or better than other similar assays, and also the proposed system, in the presence of different interferences, displayed good selectivity in detecting STR. The proposed aptasensor showed excellent results in quantitatively the detection of STR in serum samples.
Label-free optical detection of thrombin using a liquid crystal-based aptasensor Microchem. J. (IF 3.034) Pub Date : 2018-05-09 Heesang Kim, Zongfu An, Chang-Hyun Jang
We describe a real-time, label-free aptasensor that utilizes the orientational properties of nematic liquid crystals (LCs) for detection of thrombin. The imaging principle is based on the homeotropic orientation of LC films, which can be influenced by thrombin-specific aptamers and N,N-dimethyl-N-(3-(trimethoxysilyl)propyl)-1-octadecanaminiuchloride (DMOAP) immobilized on glass slides. The interactions between thrombin and its specific aptamer, including ionic and hydrogen bonds, can interfere with the homeotropic alignment of LCs, leading to changes from ‘dark’ to ‘bright’ responses that can be visualized simply using crossed polarizers. We describe the condition for maintaining the homeotropic state of LCs, which are suitable for thrombin-specific aptamer experiments, and reactions between aptamer and several enzymes, including thrombin. This novel simple LC-based aptasensor has not only high specificity, but also high sensitivity (low detection limit of 1 pg/mL (26.7 fM)). We also note the blood coagulation reaction between fibrinogen and thrombin, which confirms that the aptamer-bound thrombin is auto-enzymatic. Our result shows that the sensitivity of the proposed sensor increases (1 pg/mL to 0.1 pg/mL) using fibrinogen.
Quantitative analyses of α-dicarbonyl compounds in food samples by HPLC using 4-(2,3-dimethyl-6-quinoxalinyl)-1,2-benzenediamine as a derivatizing reagent Microchem. J. (IF 3.034) Pub Date : 2018-05-08 Xin-Jie Wang, Feng Gao, Lu-Chao Li, Xian Hui, Heng Li, Wen-Yun Gao
α-Dicarbonyl compounds, such as 3-deoxyglucosone (3-DG), glyoxal (Gly), methylglyoxal (MGly), diacetyl (DA), and pentane-2,3-dione (PD) have been widely studied because they are the main precursors of advanced glycation end products. In this work, an analytical procedure was developed for the determination of these compounds by HPLC-UV using 4-(2,3-dimethyl-6-quinoxalinyl)-1,2-benzenediamine (DQB) as a novel derivatizing reagent. After derivatization at pH 9.0 and ambient temperature for 30 min, these five compounds were analyzed by HPLC. The results showed that the linear correlation coefficients (R2) of the method for the five analytes are between 0.994 and 0.999 in broad concentration ranges, the limits of detection are 0.050 μM (3-DG), 0.050 μM (Gly), 0.050 μM (MGly), 0.020 μM (DA), and 0.025 μM (PD), respectively. The method was further evaluated in the analyses of many kinds of food samples employing the standard addition method with the RSDs ranging from 0.43 to 4.07% and the recoveries from 85% to 103%.
High-throughput chemometrically assisted flow-injection method for the simultaneous determination of multi-antiretrovirals in water Microchem. J. (IF 3.034) Pub Date : 2018-05-09 Lesly Paradina Fernández, Romina Brasca, Mirta R. Alcaráz, María J. Culzoni
This work is focused on the simultaneous determination of different nucleosides (lamivudine, abacavir, zidovudine) and non-nucleoside (nevirapine, efavirenz) reverse transcriptase inhibitors (antiretrovirals) in river, tap and well water by pH-gradient flow-injection analysis with diode-array detection (FIA-DAD) and further multivariate curve resolution-alternating least square (MCR-ALS) processing. Previous to the development of the analytical method with quantitative purpose, the acid-base characterization was conducted for all the analytes by determination of the experimental pKa. The pKa values, obtained by UV spectrometric titration coupled to MCR-ALS data modeling, were in agreement with those found in the literature, and, interestingly, a non-reported pKa of 12.27 was identified for nevirapine. Eventually, the analytical method was developed and its performance on the quantitation of the antiretrovirals was evaluated through its application to validation and environmental samples. The recovery studies showed values between 85 and 115% with relative errors of prediction below 10%. The figures of merit were satisfactory for all the studied drugs, with limits of detection between 25 and 40 μg L−1. Therefore, the proposed method, which is based on the generation of high-throughput data, is a simple and suitable alternative to determine the concentration of antiretroviral drugs in complex matrices, without pre-concentration or extraction steps. Additionally, MCR-ALS demonstrated to be a useful tool for solving mixtures of analytes with high spectral overlapping, in the presence of unknown interferences.
Protecting and stimulating effect on the degradation of eosin lakes. Part 1: Lead white and cobalt blue Microchem. J. (IF 3.034) Pub Date : 2018-05-07 Alba Alvarez-Martin, Koen Janssens
An important problem encountered during the preservation of paintings and other artworks is the fading of the original colors due to exposure of the colorants to light. This fact is clearly evidenced in some of Vincent Van Gogh's paintings in which an organic red, eosin or geranium lake, is present. The identification of eosin and the characterization of its degradation products in paintings represents a challenge because of (i) the generally low concentration of the pigment remaining after an aging period of ca 100 years, (ii) the scarcity of the paint micro samples available for analysis and the difficulty of obtaining additional ones and (iii) the complexity of the degradation behavior of eosin when it is mixed with organic or inorganic pigments, binding media or varnish. This study presents an accelerated aging experiment of eosin paint models in order to understand better the discoloration process; more specifically the influence of different metals with which eosin forms complexes and of the presence of admixture pigments such as lead white and cobalt blue on the lightfastness of eosin is evaluated. Paint model samples were prepared using eosin, lead white, and cobalt blue in different mixing ratios and were characterized with several techniques before and after aging. The possible formation of intermediate molecular forms during the aging experiment and the influence of pigment ratios on the discoloration process were monitored at periodic intervals using a combination of UV–Visible and attenuated total Reflectance-Fourier transform infrared (ATR-FTIR) spectroscopies. Raman spectroscopy, scanning electron microscopy coupled to energy-dispersive X-ray analysis (SEM-EDX) and optical microscopy (OM) analyses were performed to gain information about the discoloration processes taking place within the paint models. Eosin precipitated on lead, aluminum and potassium/aluminum salts was used. These three lakes showed similar discoloration rates under light exposure. In contrast, the presence and relative abundance of the admixture pigments lead white and cobalt blue had a significant influence on the (speed of the) eosin discoloration process. The presence of lead white and cobalt blue appears to stimulate the eosin degradation. However, the cobalt blue shows less influence in the discoloration process, showing a protective effect during the first stages of the aging. This may be qualitatively explained in terms of the ability of lead white to scatter light towards eosin molecules and the absorption characteristics of cobalt blue in the green range of the electromagnetic spectrum, shielding eosin from incoming light. The color changes observed in the paint reconstructions are similar to discoloration phenomena visible in some Van Gogh paintings and can offer an explanation of the gradual discoloration process that took place over the years. These insights will be helpful to estimate the original hues color used/intended by the artist.
1H NMR depth profiles combined with portable and micro-analytical techniques for evaluating cleaning methods and identifying original, non-original, and degraded materials of a 16th century Italian wall painting Microchem. J. (IF 3.034) Pub Date : 2018-05-01 Valeria Di Tullio, Giorgia Sciutto, Noemi Proietti, Silvia Prati, Rocco Mazzeo, Chiara Colombo, Emma Cantisani, Valentina Romè, Davide Rigaglia, Donatella Capitani
In this study, portable NMR was applied to monitor and evaluate cleaning treatments on the surface of a 16th century Italian wall painting. Due to the complexity of the state of degradation of the wall painting, a campaign of measurements was carried in situ to evaluate the performance of traditional and innovative eco-friendly cleaning systems such as sulphate-reducing bacteria D. vulgaris confined in hydrogels, and to compare two different cleaning systems used to remove a degraded hydrophobic organic layer. Specifically, NMR stratigraphy allowed to determine the thickness of the organic layer covering the surface of the wall painting, its distribution in the wall painting, the presence of residues after applying the cleaning treatment, and to evaluate and compare the effectiveness of applied treatments. A new analytical parameter here named the solubilization degree of the cleaning system permitted the selection of the most performing treatment. 1H NMR depth profiles allowed to evaluate changes in the permeability of the wall painting caused by the presence of organic substances during the application of water-based cleaning systems, and to evaluate the water content and its depth of penetration in the wall painting. Changes in permeability were estimated calculating another new analytical parameter, i.e. the percentage of water saturation before and after the application of the cleaning treatment. Depth profiles also permitted the evaluation of the degree of wettability of the wall painting surface as a function of the time of application, and the obtainment of a detailed information about the interaction between water molecules, the gel network and the surface of the wall painting. Finally, to obtain the chemical characterization of the artefact surface a multi analytical approach was applied using both portable and micro-invasive analytical methodologies.
Detecting molecular changes in UV laser-ablated oil/diterpenoid resin coatings using micro-Raman spectroscopy and Laser Induced Fluorescence Microchem. J. (IF 3.034) Pub Date : 2018-05-05 Daniele Ciofini, Mohamed Oujja, Maria Vega Cañamares, Salvatore Siano, Marta Castillejo
Naturally occurring diterpenoid resins were extensively applied, mainly as oily mixtures, through the ages as protective and decorative coatings on paintings, metals and wood artifacts. When these coatings age, tend to generate tougher films than triterpenoid resins, completely insoluble, increasingly subject to darkening, and then very hard to remove using conventional methods. In this regards, laser sub-micrometric ablative techniques are being increasingly used in the cultural heritage field also for the treatment of synthetic and natural polymer coatings. Here, in the wake of the positive outcomes achieved on triterpenoid resin films, the present approach has been applied and extended to diterpenoid resin coatings, which have never been thoroughly studied yet. In detail, colophony, sandarac and Manila copal resin films, prepared as solvent and linseed oil formulations, were subject to light-ageing and then systematically irradiated at various exposure conditions using the 4th (266 nm) and 5th (213 nm) harmonics of a Q-Switched Nd:YAG laser. UV–Vis absorption spectroscopy was used as preliminary characterization of the films optical properties. The assessment of physico-chemical modifications induced by artificial light-ageing and ns UV laser irradiation were assessed non-invasively by μ-Raman spectroscopy, Laser Induced Fluorescence (LIF) and microscopic examination. The results underlined that, due to the presence of a polymer network, sandarac and copal resin coatings showed higher Fth than those composed of colophony. Morphologically, all the coatings were subject to bubbling upon 266 nm irradiation, while damage-free at 213 nm. At molecular level, irradiation at 266 nm produced minor changes to ν(CH3)/ν(CH2), ν(C O) and ν(C C) modes, thus confirming an ablation mechanism mainly driven by photo-thermal bond-breaking through the ejection of gaseous by-products. Raman background fluctuations along with shifting and broadening of LIF maxima were supportive in the assessment of laser-induced surface modifications. Finally, the work performed indicates that the 213 nm wavelength is the most indicated for the treatment of aged solvent and oil diterpenoid-based coatings, as no side effects occurred. This outcome, corroborated by the previous results obtained in triterpenoid resin films, may have important implications in the field of cultural heritage conservation, as it extends the application range of solid-state Nd:YAG lasers to all types of protective and decorative terpenoid coatings.
Determination of indium using vortex assisted solid phase microextraction based on oleic acid coated magnetic nanoparticles combined with slotted quartz tube-flame atomic absorption spectrometry Microchem. J. (IF 3.034) Pub Date : 2018-05-03 Birgül Çelik, Erhan Akkaya, Sezgin Bakirdere, Fırat Aydin
Chemical composition and mineralogical residence of sesame oil from plants grown in different Yemeni environments Microchem. J. (IF 3.034) Pub Date : 2018-05-03 Faez Mohammed, Nada Abdulwali, Dominique Guillaume, Noël Tenyang, Roger Ponka, Kamal Al-Gadabi, Rahma Bchitou, Abdul Hafeedh Abdullah, Khalid Mohammed Naji
Sesame seeds collected in eight provinces of Yemen were used to prepare cold-pressed sesame oil over three consecutive years. After ascertaining the nutritional quality and compliance with official norm of each batch of oil, mineral composition was determined by ICP-OES. No major and significant variations were detected over three years indicating the high reproducibility of Yemeni sesame oil composition as a function of its geographic origin. Three physico-chemically distinct sub-groups were identified. A subgroup includes sesame oil from Al Bayda, Marib, Ibb, and Taiz; a second is constituted by sesame oil from Abyan, Shabwa, and Hadhramount while sesame oil from Hodeida presents its own specificity. Calcium content was between 3.02 and 9.66 mg/kg, this cation making up 50% of the total mineral content. The two other most abundant minerals were potassium (0.824–4.251 mg/kg) and magnesium (0.811–4.742 mg/kg). Potentially toxic metal (Cd, Pb, Cu, Sn and Zn) content was very low in all samples. Principal component analysis showed that Abyan oil presents a unique metal-content profile. The precise geographic origin of Yemeni sesame oil can be determined by element content analysis.
Quantification of nicotine and major solvents in retail electronic cigarette fluids and vaped aerosols Microchem. J. (IF 3.034) Pub Date : 2018-05-01 Jun Dai, Ki-Hyun Kim, Jan E. Szulejko, Sang-Hee Jo, Kyenghee Kwon, Dal Woong Choi
The main ingredients used in e-liquid formulations (propylene glycol (PG), vegetable glycerol (VG), and nicotine (Nic)) in a total of 16 retail e-liquids (half containing nicotine)) were analyzed by an analytical method developed recently by our research group. The measured nicotine concentrations in e-liquids varied in a range of 5.7 to 14.7 mg g−1 and differed up to 9.0% from the declared label concentrations (two tailed P = 0.5424 at a 0.05 confidence level). The concentrations of Nic and PG in vaped aerosol samples were lower (by an average of 12.7% and 17.4%, respectively) than those in e-liquid samples, while the opposite was true for VG (1.95% higher on average). The composition (w/w) of 16 retail e-liquids varied: 82.6 to 94.9% PG + VG (n = 16), 0.68 to 1.63% nicotine (n = 8), and 5.1 to 16.2% unidentified compounds (water, flavors, etc., n = 16). For the corresponding vaped aerosols, the results were: 75.4 to 92.1% PG + VG (n = 16), 0.57 to 1.47% nicotine (n = 8), and 7.86 to 24.0% unidentified compounds (water, flavors, etc., n = 16). The relative proportion of unidentified compounds in vaped aerosols was two times higher than those in e-liquids. The mean nicotine vaping emission factor (39.6 μg puff−1) was about two times lower than that of a Kentucky 2R4F reference cigarette (75 μg puff−1). The measured e-cigarette vaping emission factors varied in a range of 22.5–61.5 μg Nic puff−1 (n = 8), 1.04–2.45 mg PG puff−1 (n = 16), and 1.35–2.09 mg VG puff−1 (n = 16).
Fast and non-destructive determination of active pharmaceutical ingredient concentration in an electrospun nanofiber patch using infrared spectroscopy Microchem. J. (IF 3.034) Pub Date : 2018-04-19 Donghyun Ryoo, Yusik Oh, Theerasak Rojanarata, Lawan Sriphong, Hoeil Chung
Infrared (IR) spectroscopy has been successfully utilized to non-destructively determine the concentration of α–arbutin (ABT) loaded on cellulose acetate (CA) electrospun-nanofiber patches. Initially, the homogeneity of the ABT distribution over the CA nanofiber mat, which would directly influence the sample representation of the acquired transmission IR spectra, was evaluated. IR microscopic mapping performed on the 3.0 wt% ABT sample covering an area of 800 × 800 μm2 revealed that ABT concentrations were moderately homogeneous (relative standard deviation: 3.3%). Another issue to consider for accurate analysis is the potential thickness variation from sample to sample, which makes the ABT peak intensity considerably less concentration-representative. The absolute amount of loaded ABT varies depending on the thickness of the nanofibers, thereby causing the intensity of the ABT peak to fluctuate. To resolve this problem, a method involving the peak area ratio between the ABT and CA band was used. When the IR sampling area was 800 × 800 μm2, the correlation between the ABT concentration (1.5–4.8 wt%) and the peak area ratio was linear, but the accuracy was not sufficient. Increasing the sampling area to 4 × 4 mm2 yielded better accuracy with a standard error of prediction (SEP) of 0.10 wt%. The acquisition of more concentration-representative sample spectra with wide area coverage was attributed to accurate concentration determination. In addition, the potential of utilizing near-infrared (NIR) and Raman spectroscopy for the same analysis was evaluated and discussed.
HR-CS FAAS based method for direct determination of total concentrations of Ca, Fe, Mg and Mn in functional apple beverages and evaluation of contributions of the bioaccessible fraction of these elements by in vitro gastrointestinal digestion and chemical fractionation Microchem. J. (IF 3.034) Pub Date : 2018-05-01 Pawel Pohl, Anna Dzimitrowicz, Piotr Jamroz, Krzysztof Greda
Functional apple beverages, including organic apple juices and apple juices with added species, were studied on the content of total concentrations of Ca, Fe, Mg and Mn as well as bioaccessibility of these elements and their chemical fractionation patterns. A new simplified sample preparation procedure was developed and validated for determination of Ca, Fe, Mg and Mn by high resolution-continuum source flame atomic absorption spectrometry (HR-CS FAAS). Bioaccessibility of Ca, Fe, Mg and Mn from analyzed apple beverages was assessed using in vitro simulated gastrointestinal digestion while chemical partitioning of elements species was carried out with the aid of tandem-column solid phase extraction (SPE). It was established that Ca, Mg and Mn are highly bioaccessible from functional apple beverages (>94% of total concentrations), significantly contributing to recommended daily intakes (RDIs) of these elements, i.e. up to 11%, 19% and 21% per 1 L, respectively, for Ca, Mg and Mn.
Determination of tetracycline and cefotaxime residues in honey by micro-solid phase extraction based on electrospun nanofibers coupled with HPLC Microchem. J. (IF 3.034) Pub Date : 2018-04-30 Batoul Arabsorkhi, Hassan Sereshti
In the present study, electrospun polyethylene terephthalate nanofibers doped with graphene oxide nanoparticles (GO-PET) was fabricated and used as an effective adsorbent in micro-solid phase extraction (μ-SPE) of tetracycline (TC) and cefotaxime (CF) from honey samples prior to HPLC. The UV–vis spectrophotometer was utilized in the optimization step. The adsorbent was fully characterized using SEM, FT-IR, BET, and BJH methods. The specific surface area and average pore size of the adsorbent were 79.5 m2 g−1 and 4.83 nm, respectively. The honey samples were dissolved in water (5% w/v) at 50 °C for 10 min, centrifuged at 4000 rpm for 15 min and finally filtered using a filter paper before performing the extraction. The important factors of the method were studied to obtain the optimal conditions. Under the optimum conditions (sample solution, 100 mL; adsorbent, 40 mg; pH 5; extraction time, 10 min; desorption solvent; MeOH, 200 μL), the limits of detection for TC and CF were 15.3 and 3.0 μg kg−1. The linear dynamic range (LDR) was obtained as 10–5000 μg kg−1 with the determination coefficients (R2) of 0.9939 and 0.9959, respectively. The real sample extraction recoveries were 89–94% and 95–98% for TC and CF, respectively. The intra-day and inter-day precisions were 5.6 and 4.9% (n = 3) for TC, and 3.6 and 4.5% (n = 9) for CF.
Experimental and molecular docking study on graphene/Fe3O4 composites as a sorbent for magnetic solid-phase extraction of seven imidazole antifungals in environmental water samples prior to LC-MS/MS for enantiomeric analysis Microchem. J. (IF 3.034) Pub Date : 2018-04-26 Zhaokun Wang, Pengfei Zhao, Jia Yu, Zhen Jiang, Xingjie Guo
In this work, a graphene modified by Fe3O4 nanoparticles (G-Fe3O4) was prepared and characterized. Seven chiral imidazole antifungals, including ketoconazole, econazole, miconazole, butoconazole, sertaconazole, fenticonazole and isoconazole were extracted from three environmental water samples by magnetic solid-phase extraction based on the G-Fe3O4, followed by enantiomeric analysis on a Chiralcel OJ-RH column coupled with a triple quadrupole mass spectrometry to evaluate their possible stereoselectivity during the degradation process occurring in the environment. Method detection and quantification limits for all the enantiomers were 0.11–0.32 ng/L and 0.28–0.67 ng/L, respectively. Satisfactory recovery (70–92%), good intra-day precision (RSD 3.1–12.0%) and inter-day precision (RSD 3.0–10.1%) were also obtained. Furthermore, the possible interactions between the analyte and graphene, such as electrostatic attraction, cation-π interaction, hydrophobic interaction and π-π stacking were discussed by combining the experiment results and molecular docking study, which provided a new insight into the adsorption mechanism of analytes on graphene.
Rapid detection of hydrogen sulfide produced by pathogenic bacteria in focused growth media using SHS-MCC-GC-IMS Microchem. J. (IF 3.034) Pub Date : 2018-04-27 Ryan Thompson, John D. Perry, Stephen P. Stanforth, John R. Dean
A new rapid method for the detection of hydrogen sulfide from pathogenic bacteria is reported. The developed method, static headspace – multi-capillary column - gas chromatography - ion mobility spectrometry (SHS-MCC-GC-IMS), has been applied to detect hydrogen sulfide evolution from 61 bacteria. The developed method has been compared against a standard triple sugar iron (TSI) agar approach, and a modified single sugar iron (SSI) agar approach. Hydrogen sulfide detection by SHS-MCC-GC-IMS using an initial inoculum of 1–1.5 × 105 CFU/mL can be achieved within 6 h, after incubation at 37 °C, with a limit of detection of 1.6 ng/mL. Data for the standard agar method against the new instrumental approach, and the modified agar method against the new instrumental approach, are compared. The specificity for the new method compared against the standard method and the modified agar approach across all 61 strains was 85.2% and 88.5% respectively, and 86.7% and 91.3% across the 23 Salmonella strains tested.
Quantification and speciation of mercury in streams and rivers sediment samples from Paracatu, MG, Brazil, using a direct mercury analyzer® Microchem. J. (IF 3.034) Pub Date : 2018-04-27 Patrícia Sueli Rezende, Nayara Carolinne Silva, William Douglas Moura, Cláudia Carvalhinho Windmöller
This paper describes the application of a method for the direct speciation of Hg in sediment samples by thermal desorption using a Direct Mercury Analyzer®. The different thermal behavior of the Hg species allowed direct chemical speciation by DMA. The set of temperature steps was as follows: 50 °C, 100 °C, 150 °C, 200 °C, 250 °C, 300 °C, 400 °C, 500 °C, 600 °C and 700 °C. Sediment samples presented total Hg concentrations varying over a range of 36 to 1996 μg·kg−1, with 78% of the samples being over of the TEL (threshold effect level). According to the speciation analysis, a prevalence of oxidized Hg was observed. This method was efficient, simple and adequate for determining the Hg speciation in sediment samples. The great advantage is that the method does not require pretreatment of the samples, and it is applicable to homogeneous solid samples.
A novel luminescence method for the estimation of uranyl ions using trimesic acid‑cadmium complex Microchem. J. (IF 3.034) Pub Date : S. Maji, Satendra Kumar, K. Sundararajan, K. Sankaran
Cadmium ion (Cd2+) with trimesic acid forms water insoluble complex. When uranyl ion (UO22+) is present with Cd2+, the complex shows intense luminescence of UO22+ and it is used for the trace level determination of UO22+ ions. A linear response of luminescence intensity of UO22+ ions was obtained over a concentration range of 1–75 ng mL−1. Analytical data showed that the detection limit of 0.2 ng mL−1 (7.4 × 10−10 M) of UO22+ ion is achieved with a relative standard deviation (RSD) 8.5% (n = 5). The proposed method was successfully applied for quantification of UO22+ ions in natural water and waste water from nuclear fuel processing plant. Furthermore, the estimation of UO22+ ions in cadmium matrix also has been carried out. This study provides a very simple, promising and a novel alternative method for the detection of UO22+ ions in environment.
Mercury and risk assessment from consumption of crustaceans, cephalopods and fish from West Peninsular Malaysia Microchem. J. (IF 3.034) Pub Date : 2018-04-24 Zurahanim Fasha Anual, William Maher, Frank Krikowa, Lokman Hakim, Nurul Izzah Ahmad, Simon Foster
Mercury (Hg) is a toxic element and has no known biological functions in humans. This study measured total Hg and methyl mercury (MeHg) concentrations in commonly consumed fish and seafood as well as to estimate the risk of Hg contamination through seafood consumption by Malaysians. The concentrations of total Hg and MeHg in 8 species of crustaceans (n = 15), 5 species of cephalopods (n = 12), and 29 species of fish (n = 78) from West Peninsular Malaysia are reported. Total mercury concentrations in crustaceans, cephalopods and fish were 0.033 ± 0.033 μg/g, 0.040 ± 0.025 μg/g and 0.106 ± 0.128 μg/g wet weight respectively. The proportion of methyl mercury in fish was 81–99% with a mean of 93 ± 5% (n = 15). Significantly higher mercury concentrations were observed in demersal fish, fish on higher trophic level and fish with body length of >20 cm. All fish and seafood were below the Malaysian Food Regulations of 0.5 μg/g wet weight mercury for fish and fishery products and 1.0 μg/g wet weight mercury for predatory fish. The consumption of fish from certain seafood species, however, should be taken into consideration to ensure that the Provisional Tolerable Weekly Intake (PTWI) of MeHg does not exceed 1.6 μg/kg body weight/week.
Effect of variable ultraviolet wavelength and intensity on photochemical vapor generation of trace selenium detected by atomic fluorescence spectrometry Microchem. J. (IF 3.034) Pub Date : 2018-04-12 Zhirong Zou, Yunfei Tian, Wen Zeng, Xiandeng Hou, Xiaoming Jiang
Selenium was taken as an example to investigate the effect of variable ultraviolet (UV) wavelength and intensity on its photochemical vapor generation (photo-CVG) process. A broadband laser-driven light source (LDLS) and a UV lamp were utilized as irradiation sources for the photo-CVG of trace selenium which was sensitively detected by atomic fluorescence spectrometry (AFS). Five filters with bandpass at different wavelength (254 nm, 285 nm, 315 nm, 365 nm and 395 nm) were used to filtrate the light from the LDLS and the UV lamp. The signal change of Se(VI) by photo-CVG-AFS was monitored when a TiO2-coated quartz coil was irradiated by variable wavelength and intensity. The experimental results indicated: (1) the efficiency of Se(VI) photo-CVG varied with irradiation wavelength; (2) a synergistic effect existed for the photo-CVG, and the efficiency of the full spectrum was thus better or close to the sum of all wavelengths; and (3) the efficiency of Se(VI) photo-CVG was also affected by the UV intensity.
Quantum chemical computation-based strategy for alternating least squares initialization in multivariate curve resolution analysis of spectral-pH data Microchem. J. (IF 3.034) Pub Date : 2018-04-18 Romina Brasca, Anne-Marie Kelterer, Marcel Maeder, Mirta R. Alcaráz, María J. Culzoni
The main motivation of this work is to provide initial estimates for the initialization of the iterative optimization within the multivariate curve resolution - alternating least squares (MCR-ALS) algorithm for the decomposition of second-order data. It is demonstrated that the combination of quantum chemical calculations with chemometrics constitutes a novel strategy for the ALS initialization in the MCR resolution of pH-modulated chemical data. In this work, the second-order data arise from acid-base experiments of p-nitrophenol (pNP) done under a pH-gradient generated by an automated flow injection (FI) system monitored by UV–vis spectroscopy. The absorption spectra of the species involved in the chemical equilibrium were simulated by means of time-dependent density functional theory (TD-DFT) methods and were utilized to start the ALS optimization. The new approach based on the Tamm-Dancoff-approximation (TDA) CAM-B3LYP method is recommended to obtain the simulated spectra to initialize MCR-ALS, as an alternative to the routinely methods used to generate initial estimates.
Multivariate optimization techniques in analytical chemistry - an overview Microchem. J. (IF 3.034) Pub Date : 2018-04-10 Sergio L.C. Ferreira, Valfredo A. Lemos, Vanessa S. de Carvalho, Erik G.P. da Silva, Antonio F.S. Queiroz, Caio S.A. Felix, Daniel L.F. da Silva, Gilson B. Dourado, Rafael V. Oliveira
This review presents fundamentals and a critical evaluation of the multivariate optimization techniques employed by the analytical chemistry. Characteristics of the surface response methodologies (SRM) are shown and compared. Additionally, a bibliographic survey was performed in the web of science database using as keywords names of the chemometric tools utilized for experimental designs. Papers classified in the analytical chemistry area demonstrated that the two-level full factorial design had often been used for preliminary assessment of factors. For determination of critical conditions using quadratic models, the central composite design (CCD) is the technique most utilized by the analytical chemists. Remarks about standardized effects and the Pareto chart, description of the several multiple response functions employed in experimental designs, efficiencies of the SRM's and robustness tests are also discussed.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
- Acc. Chem. Res.
- ACS Appl. Mater. Interfaces
- ACS Biomater. Sci. Eng.
- ACS Catal.
- ACS Cent. Sci.
- ACS Chem. Biol.
- ACS Chem. Neurosci.
- ACS Comb. Sci.
- ACS Earth Space Chem.
- ACS Energy Lett.
- ACS Infect. Dis.
- ACS Macro Lett.
- ACS Med. Chem. Lett.
- ACS Nano
- ACS Omega
- ACS Photonics
- ACS Sens.
- ACS Sustainable Chem. Eng.
- ACS Synth. Biol.
- Acta Biomater.
- Acta Crystallogr. A Found. Adv.
- Acta Mater.
- Adv. Colloid Interface Sci.
- Adv. Electron. Mater.
- Adv. Energy Mater.
- Adv. Funct. Mater.
- Adv. Healthcare Mater.
- Adv. Mater.
- Adv. Mater. Interfaces
- Adv. Opt. Mater.
- Adv. Sci.
- Adv. Synth. Catal.
- AlChE J.
- Anal. Bioanal. Chem.
- Anal. Chem.
- Anal. Chim. Acta
- Anal. Methods
- Angew. Chem. Int. Ed.
- Annu. Rev. Anal. Chem.
- Annu. Rev. Biochem.
- Annu. Rev. Environ. Resour.
- Annu. Rev. Food Sci. Technol.
- Annu. Rev. Mater. Res.
- Annu. Rev. Phys. Chem.
- Appl. Catal. A Gen.
- Appl. Catal. B Environ.
- Appl. Clay. Sci.
- Appl. Energy
- Aquat. Toxicol.
- Arab. J. Chem.
- Asian J. Org. Chem.
- Atmos. Environ.
- Carbohydr. Polym.
- Catal. Commun.
- Catal. Rev. Sci. Eng.
- Catal. Sci. Technol.
- Catal. Today
- Cell Chem. Bio.
- Cem. Concr. Res.
- Ceram. Int.
- Chem. Asian J.
- Chem. Bio. Drug Des.
- Chem. Biol. Interact.
- Chem. Commun.
- Chem. Educ. Res. Pract.
- Chem. Eng. J.
- Chem. Eng. Sci.
- Chem. Eur. J.
- Chem. Mater.
- Chem. Phys.
- Chem. Phys. Lett.
- Chem. Phys. Lipids
- Chem. Rev.
- Chem. Sci.
- Chem. Soc. Rev.
- Chin. J. Chem.
- Combust. Flame
- Compos. Part A Appl. Sci. Manuf.
- Compos. Sci. Technol.
- Compr. Rev. Food Sci. Food Saf.
- Comput. Chem. Eng.
- Constr. Build. Mater.
- Coordin. Chem. Rev.
- Corros. Sci.
- Crit. Rev. Food Sci. Nutr.
- Crit. Rev. Solid State Mater. Sci.
- Cryst. Growth Des.
- Curr. Opin. Chem. Eng.
- Curr. Opin. Colloid Interface Sci.
- Curr. Opin. Environ. Sustain
- Curr. Opin. Solid State Mater. Sci.
- Ecotox. Environ. Safe.
- Electrochem. Commun.
- Electrochim. Acta
- Energy Environ. Sci.
- Energy Fuels
- Energy Storage Mater.
- Environ. Impact Assess. Rev.
- Environ. Int.
- Environ. Model. Softw.
- Environ. Pollut.
- Environ. Res.
- Environ. Sci. Policy
- Environ. Sci. Technol.
- Environ. Sci. Technol. Lett.
- Environ. Sci.: Nano
- Environ. Sci.: Processes Impacts
- Environ. Sci.: Water Res. Technol.
- Eur. J. Inorg. Chem.
- Eur. J. Med. Chem.
- Eur. J. Org. Chem.
- Eur. Polym. J.
- J. Acad. Nutr. Diet.
- J. Agric. Food Chem.
- J. Alloys Compd.
- J. Am. Ceram. Soc.
- J. Am. Chem. Soc.
- J. Am. Soc. Mass Spectrom.
- J. Anal. Appl. Pyrol.
- J. Anal. At. Spectrom.
- J. Antibiot.
- J. Catal.
- J. Chem. Educ.
- J. Chem. Eng. Data
- J. Chem. Inf. Model.
- J. Chem. Phys.
- J. Chem. Theory Comput.
- J. Chromatogr. A
- J. Chromatogr. B
- J. Clean. Prod.
- J. CO2 UTIL.
- J. Colloid Interface Sci.
- J. Comput. Chem.
- J. Cryst. Growth
- J. Dairy Sci.
- J. Electroanal. Chem.
- J. Electrochem. Soc.
- J. Environ. Manage.
- J. Eur. Ceram. Soc.
- J. Fluorine Chem.
- J. Food Drug Anal.
- J. Food Eng.
- J. Food Sci.
- J. Funct. Foods
- J. Hazard. Mater.
- J. Heterocycl. Chem.
- J. Hydrol.
- J. Ind. Eng. Chem.
- J. Inorg. Biochem.
- J. Magn. Magn. Mater.
- J. Mater. Chem. A
- J. Mater. Chem. B
- J. Mater. Chem. C
- J. Mater. Process. Tech.
- J. Mech. Behav. Biomed. Mater.
- J. Med. Chem.
- J. Membr. Sci.
- J. Mol. Catal. A Chem.
- J. Mol. Liq.
- J. Nat. Gas Sci. Eng.
- J. Nat. Prod.
- J. Nucl. Mater.
- J. Org. Chem.
- J. Photochem. Photobiol. C Photochem. Rev.
- J. Phys. Chem. A
- J. Phys. Chem. B
- J. Phys. Chem. C
- J. Phys. Chem. Lett.
- J. Polym. Sci. A Polym. Chem.
- J. Porphyr. Phthalocyanines
- J. Power Sources
- J. Solid State Chem.
- J. Taiwan Inst. Chem. E.
- Macromol. Rapid Commun.
- Mass Spectrom. Rev.
- Mater. Chem. Front.
- Mater. Des.
- Mater. Horiz.
- Mater. Lett.
- Mater. Sci. Eng. A
- Mater. Sci. Eng. R Rep.
- Mater. Today
- Meat Sci.
- Med. Chem. Commun.
- Microchem. J.
- Microchim. Acta
- Micropor. Mesopor. Mater.
- Mol. Biosyst.
- Mol. Cancer Ther.
- Mol. Catal.
- Mol. Nutr. Food Res.
- Mol. Pharmaceutics
- Mol. Syst. Des. Eng.
- Nano Energy
- Nano Lett.
- Nano Res.
- Nano Today
- Nano-Micro Lett.
- Nanomed. Nanotech. Biol. Med.
- Nanoscale Horiz.
- Nat. Catal.
- Nat. Chem.
- Nat. Chem. Biol.
- Nat. Commun.
- Nat. Energy
- Nat. Mater.
- Nat. Med.
- Nat. Methods
- Nat. Nanotech.
- Nat. Photon.
- Nat. Prod. Rep.
- Nat. Protoc.
- Nat. Rev. Chem.
- Nat. Rev. Drug. Disc.
- Nat. Rev. Mater.
- Natl. Sci. Rev.
- Neurochem. Int.
- New J. Chem.
- NPG Asia Mater.
- npj 2D Mater. Appl.
- npj Comput. Mater.
- npj Flex. Electron.
- npj Mater. Degrad.
- npj Sci. Food
- Pharmacol. Rev.
- Pharmacol. Therapeut.
- Photochem. Photobiol. Sci.
- Phys. Chem. Chem. Phys.
- Phys. Life Rev.
- PLOS ONE
- Polym. Chem.
- Polym. Degrad. Stabil.
- Polym. J.
- Polym. Rev.
- Powder Technol.
- Proc. Combust. Inst.
- Prog. Cryst. Growth Ch. Mater.
- Prog. Energy Combust. Sci.
- Prog. Mater. Sci.
- Prog. Photovoltaics
- Prog. Polym. Sci.
- Prog. Solid State Chem.