A composite consisting of microporous carbon and cobalt(III) oxide and prepared from zeolitic imidazolate framework-67 for voltammetric determination of ascorbic acid Microchim. Acta (IF 4.58) Pub Date : 2018-01-16 Yuvaraj Haldorai, Sang Rak Choe, Yun Suk Huh, Young-Kyu Han
A nanoporous carbon/cobalt oxide (NPC/Co3O4) composite was synthesized from a single-precursor (zeolitic imidazolate framework-67). Transmission electron microscopy showed that the Co3O4 nanoparticles with an average particle size of 10 nm (±2 nm) were well dispersed in the NPC matrix. However, in a few places, Co3O4 nanoparticles were aggregated. The composite shows outstanding performance in terms of electrooxidation of ascorbic acid (AA) in phosphate buffer of pH 7.0. The differential pulse voltammetric response of the composite electrode (at 0.12 V vs. SCE) is linear in the 2–240 μM AA concentration range, with a 20 nM detection limit. The electrode exhibits high sensitivity (0.13 μA·μM·cm−2), reliable reproducibility, and good selectivity. The method, when applied to the direct determination of AA in vitamin C tablets, gave recoveries between 98.0 and 102.0%.
A cationic conjugated polymer coupled with exonuclease I: application to the fluorometric determination of protein and cell imaging Microchim. Acta (IF 4.58) Pub Date : 2018-01-16 Yufei Liu, Liyun Gao, Huijuan Yan, Jingfang Shangguan, Zhen Zhang, Xia Xiang
A strategy is described for the detection of protein by using a cationic fluorescent conjugated polymer coupled with exonuclease I (Exo I). Taking streptavidin (SA) as model protein, it is observed that Exo I can digest single-stranded DNA conjugated with biotin and carboxyfluorescein (P1) if SA is absent. This leads to the formation of small nucleotide fragments and to weak fluorescence resonance energy transfer (FRET) from the polymer to P1. If, however, SA is present, the high affinity of SA and biotin prevents the digestion of P1 by Exo I. This results in the sorption of P1 on the surface of the polymer through strong electrostatic interaction. Hence, efficient FRET occurs from the fluorescent polymer to the fluorescent label of P1. Fluorescence is measured at an excitation wavelength of 370 nm, and emission is measured at two wavelengths (530 and 425 nm). The ratio of the two intensities (I530/I425) is directly related to the concentration of SA. Under the optimal conditions, the assay has a detection limit of 1.3 ng·mL−1. The method was also applied to image the folate receptor in HeLa cells, thus demonstrating the versatility of this strategy.
Selective adsorption and determination of hexavalent chromium ions using graphene oxide modified with amino silanes Microchim. Acta (IF 4.58) Pub Date : 2018-01-16 Paulina Janik, Beata Zawisza, Ewa Talik, Rafal Sitko
Novel adsorbents are described for the preconcentration of chromium(VI). Graphene oxide (GO) was modified with various amino silanes containing one, two, or three nitrogen atoms in the molecule. These include 3-aminopropyltriethoxysilane (APTES), N-(3-trimethoxysilylpropyl)ethylenediamine (TMSPEDA), and N1-(3-trimethoxysilylpropyl)diethylenetriamine (TMSPDETA). The resulting GO derivatives were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, and energy-dispersive X-ray fluorescence spectrometry (EDXRF). Adsorption studies show that these GO based sorbents are highly selective for Cr(VI) in the presence of Cr(III) at pH 3.5. Although the amino silanes applied in modification of GO contain different numbers of nitrogen atoms, the maximum adsorption capacities of GO derivatives are very similar (13.3–15.1 mg·g−1). Such results are in accordance with spectroscopy studies which show that the amount of amino silanes attached to GO decreases in the order of APTES > TMSPEDA > TMSPDETA. The APTES-modified GO was applied to selective and sensitive extraction of Cr(VI) ions prior to quantitation by low-power EDXRF using the Cr Kα line. The Cr(VI) ions need not be eluted from the solid adsorbent. The method has a 0.17 ng·mL−1 detection limit, and the recovery is 99.7 ± 2.2% at a spiking level of 10 ng·mL−1. The method was successfully applied to the determination of Cr(VI) in water samples.
Fluorescence polarization gene assay for HIV-DNA based on the use of dendrite-modified gold nanoparticles acting as signal amplifiers Microchim. Acta (IF 4.58) Pub Date : 2018-01-16 Shuping Liang, Guicheng He, Jianniao Tian, Yanchun Zhao, Shulin Zhao
The authors describe a fluorescence polarization assay for HIV-DNA. It is based on the use of gold nanoparticles (AuNPs) modified with DNA dendritic macromolecules that act as signal amplifiers. In the presence of HIV-DNA, the AuNP-DNA dendritic macromolecules and fluorescently labeled DNA probe combine with HIV-DNA in a sandwich format to form a conjugate. This reaction slows down the rotational speed of the labeled DNA probe because of the increase of molecular weight and volume. This increases fluorescence polarization and the sensitivity of the system. The relative fluorescence polarization values increase linearly in the 150 pM to 6 nM HIV-DNA concentration range, with a 73 pM detection limit. The results show this amplification strategy to be most useful for ultrasensitive determination of oligonucleotides by means of fluorescence polarization.
Cyclodextrin-modified nanodiamond for the sensitive fluorometric determination of doxorubicin in urine based on its differential affinity towards β/γ-cyclodextrins Microchim. Acta (IF 4.58) Pub Date : 2018-01-15 M. Laura Soriano, Carolina Carrillo-Carrion, Celia Ruiz-Palomero, Miguel Valcárcel
The manuscript reports on the preparation of β-cyclodextrin-modified nanodiamonds (βCD-ND) for the extraction and preconcentration of the fluorescent anticancer drug doxorubicin (DOX) from biological samples. The inclusion of DOX into the cavities of β- and γ-cyclodextrin (CD) confirms their utility for selective extraction and elution of the drug based on its good fit to the cyclodextrin cavity. Although both larger cyclodextrins (βCD and γCD) accommodate DOX, DOX clearly prefers the bigger γCD cavities. Dispersive micro solid-phase extraction using βCD-ND as sorbent enables the inclusion complexation of DOX. The elution of DOX from βCD-ND cavities occurs with a basic solution of γCD containing 10% acetonitrile owing to the preferential affinity (i.e. optimal fit) of DOX into the larger γCD cavity. DOX is quantified by monitoring its intrinsic fluorescence (exc/em = 475/595 nm). The method can determine DOX in urine with a limit of detection of 18 ng·mL−1. Recoveries (93.2% and 94.0%) and precision (RSDs of 5.9% and 4.7%) at 100 and 400 ng·mL−1 DOX levels in urine are satisfactory. The matrix effect is negligible even when working with undiluted urine samples.
Immobilization of horseradish peroxidase on amino-functionalized carbon dots for the sensitive detection of hydrogen peroxide Microchim. Acta (IF 4.58) Pub Date : 2018-01-15 Ya Su, Xuan Zhou, Yumei Long, Weifeng Li
The authors describe the preparation of amino-functionalized carbon dots (NH2-CDs) via a one-step hydrothermal process using silver nitrate and chitosan as the precursors. The NH2-CDs have a fairly consistent size distribution with an average size of 2.8 ± 0.5 nm. This is attributed to the introduction of Ag(I) both as a catalyst and a precipitant. The NH2-CDs are highly crystalline. Their surface carries amino groups and carboxy groups which is confirmed by transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy. Horseradish peroxidase (HRP) was immobilized in the NH2-CDs and then placed on a glassy carbon electrode (GCE). Spectroscopic and electrochemical analyses evidenced the stability and good bioactivity of the immobilized HRP. This reveals that NH2-CD is a desirable matrix for enzyme immobilization. The modified GCE exhibits enhanced electro-catalytic activity towards hydrogen peroxide (H2O2) reduction as compared to that of plain CDs. The effects of pH value and loading on the performances of the modified GCEs were studied. Under optimized conditions, the biosensor has a linear response in the 5 to 590 nM H2O2 concentration range, with a 1.8 nM defection limit (at an S/N ratio of 3). The sensor is stable, reproducible and selective. Finally, the sensor was applied to determine H2O2 in real samples, and satisfactory recoveries were achieved.
Selective extraction of theophylline from plasma by copper-doped magnetic microspheres prior to its quantification by HPLC Microchim. Acta (IF 4.58) Pub Date : 2018-01-12 Peihong Chen, Jiwei Shen, Chaozhan Wang, Yinmao Wei
The authors describe the preparation of copper-doped magnetic microspheres (Cu-Fe3O4) by a solvothermal method. Due to their good magnetic property and high affinity for compounds containing an imidazole moiety (containing N-H), they are excellent adsorbents for such compounds as tested by eighteen compounds. Specifically, a method has been developed for magnetic solid-phase extraction (MSPE) of theophylline (TP) from plasma. The method enables selective enrichment of TP over many potential interferents that can occur in plasma. Following elution with alkaline methanol, TP was quantified by HPLC-UV at a detection wavelength of 272 nm. Under the optimized conditions, a linear response is found for the 0.02 to 20 μg·mL−1 concentration range, and the limit of detection is as low as 3 ng·mL−1. Recoveries from spiked samples range from 91.2 to 100.4%, and the repeatabilities are between 2.9 and 12% (for n = 6). The method was successfully applied to the determination of TP in rabbit and rat plasma.
Amperometric nonenzymatic sensing of glucose at very low working potential by using a nanoporous PdAuNi ternary alloy Microchim. Acta (IF 4.58) Pub Date : 2018-01-12 Lu Lu, Jianli Kang
The authors present a nonenzymatic sensor for glucose that has an exceedingly low working potential which makes the sensor highly selective over other electroactive species. The sensor is based on the use of a glassy carbon electrode (GCE) that was modified with a nanoporous PdAuNi alloy (np-PdAuNi). The PdAuNi alloy nanostructure displays enhanced electrocatalytic activity for glucose oxidation (compared to PdNi alloys). The modified GCE enables amperometric sensing of glucose at a typical working electrode potential of 0.0 V vs. SCE in solutions of pH 13 containing 0.1 M NaCl. Response is linear in the 5 to 100 μM concentration range, with a 1.7 μM detection limit (at an S/N ratio of 3). For higher concentrations deviations from linearity were found. The method is selective and reproducible. The modified electrode was applied to the determination of glucose in human serum.
Advances in the use of carbonaceous materials for the electrochemical determination of persistent organic pollutants. A review Microchim. Acta (IF 4.58) Pub Date : 2018-01-12 Shanli Yang, Yingru Li, Shaofei Wang, Ming Wang, Mingfu Chu, Binyuan Xia
Persistent organic pollutants (POPs) are key pollutants due to their persistence, refractory biodegradation, high toxicity and bioaccumulation in the food chain. This review (with 93 refs.) covers the progress made in the past decades in the application of carbonaceous materials for electrochemical detection of POPs as listed in the Stockholm Convention. Following an introduction into the field, typical carbonaceous materials for use in electrodes are discussed, with subsection on carbon nanotubes, graphene, reduced graphene oxide, graphitic carbon nitride and carbon dots. This is followed by a section on application of carbonaceous materials in electrochemical detection, with subsections on the use of carbon nanotubes, of (doped-) graphene, of reduced graphene oxide, of graphitic carbon nitride, and of carbon dots. The review concludes with conclusions and future perspectives. The detection mechanisms of POPs are also discussed.
A lateral flow assay for the determination of human tetanus antibody in whole blood by using gold nanoparticle labeled tetanus antigen Microchim. Acta (IF 4.58) Pub Date : 2018-01-11 Juanzu Liu, Junyan Wang, Zhaohui Li, Hongmin Meng, Lin Zhang, Hongqi Wang, Jianjun Li, Lingbo Qu
The authors describe a lateral flow assay (LFA) for the antibody against the infectious bacterium Clostridium tetani. Gold nanoparticles (AuNPs) were linked to tetanus antigen and are captured in the test line via the formation of a sandwich structure composed of AuNP-labeled tetanus antigen, tetanus antibody, and tetanus antigen. This leads to the formation of a characteristic red line due to the accumulation of AuNPs. The formation of the color line allows for a highly sensitive and selective detection of tetanus antibody, both with bare eyes and by smartphone-based quantitative analysis. This assay offers a wide detection range from 0 to 0.5 IU·mL−1 and has a linear relationship from 0.01 to 0.1 IU·mL−1 with an experimental detection limit of 0.01 IU·mL−1. This assay is simple, fast, inexpensive and highly selective. When applied to the detection of tetanus antibody in spiked whole blood, it provided reliable results that compared well to those obtained with a commercial ELISA kit.
Determination of the activity of alkaline phosphatase by using nanoclusters composed of flower-like cobalt oxyhydroxide and copper nanoclusters as fluorescent probes Microchim. Acta (IF 4.58) Pub Date : 2018-01-10 Hai-Bo Wang, Yang Li, Ying Chen, Zi-Ping Zhang, Tian Gan, Yan-Ming Liu
The authors describe a sensitive fluorometric method for the determination of the activity of alkaline phosphatase (ALP). It is based on the use of a composite prepared consisting of flower-like cobalt oxyhydroxide (CoOOH) and copper nanoclusters (CuNCs). On formation of the CuNC-CoOOH aggregates, the fluorescence of the CuNCs is quenched by the CoOOH sheets. If, however, the CoOOH sheets are reduced to Co(II) ions in the presence of ascorbic acid (AA), fluorescence recovers. AA is formed in-situ by hydrolysis of the substrate ascorbic acid 2-phosphate (AA2P) as catalyzed by ALP. Thus, the ALP activity can be detected indirectly by kinetic monitoring of the increase in fluorescence, best at excitation/emission wavelengths of 335/410 nm. The assay allows ALP to be determined in 0.5 to 150 mU·mL−1 activity range and with a 0.1 mU·mL−1 detection limit. The method was successfully applied to the determination of ALP activity in (spiked) human serum samples. The assay has attractive features in being of the off-on type and immune against false positive results.
Branched silver nanowires on fluorine-doped tin oxide glass for simultaneous amperometric detection of H 2 O 2 and of 4-aminothiophenol by SERS Microchim. Acta (IF 4.58) Pub Date : 2018-01-10 Ying-Chu Chen, Jui-Hung Hsu, Yu-Kuei Hsu
This study introduces a two-step method for the deposition of branched silver nanowires (AgNWs) on fluorine-doped tin oxide (FTO) glass. This material serves as both an active surface-enhanced Raman-scattering (SERS) substrate and as an enzyme-free electrochemical sensor for H2O2. This dual functionality is systematically studied. The AgNWs as the main trunk were first deposited on FTO by spray-coating. Silver branches were then electrochemically produced on the preformed NWs. Scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectrometry were employed to characterize morphology, composition and microstructure. SERS experiments show that the branched AgNW/FTO substrate exhibits excellent performance in detecting 4-aminothiophenol at an ultra-low concentration of 0.1 fM. Simultaneously, this material displays an excellent electrocatalytic response to H2O2 reduction at a concentration as low as 1 μM. The sensor has a rapid response and two linear analytical ranges that extend from 0.25 to 300 μM, and from 0.3 to 2.6 mM of H2O2, respectively. The ultrahigh sensitivity and satisfactory reproducibility highlights the merit of this hierarchical AgNW dendritic structure for sensing applications.
Fluorometric determination of nucleic acids based on the use of polydopamine nanotubes and target-induced strand displacement amplification Microchim. Acta (IF 4.58) Pub Date : 2018-01-10 Jia Ge, Dong-Mei Bai, Xin -Geng, Ya-Lei Hu, Qi-Yong Cai, Ke Xing, Lin Zhang, Zhao-Hui Li
The authors describe a fluorometric method for the quantitation of nucleic acids by combining (a) cycled strand displacement amplification, (b) the unique features of the DNA probe SYBR Green, and (c) polydopamine nanotubes. SYBR Green undergoes strong fluorescence enhancement upon intercalation into double-stranded DNA (dsDNA). The polydopamine nanotubes selectively adsorb single-stranded DNA (ssDNA) and molecular beacons. In the absence of target DNA, the molecular beacon, primer and SYBR Green are adsorbed on the surface of polydopamine nanotubes. This results in quenching of the fluorescence of SYBR Green, typically measured at excitation/emission wavelengths of 488/518 nm. Upon addition of analyte (target DNA) and polymerase, the stem of the molecular beacon is opened so that it can bind to the primer. This triggers target strand displacement polymerization, during which dsDNA is synthesized. The hybridized target is then displaced due to the strand displacement activity of the polymerase. The displaced target hybridizes with another molecular beacon. This triggers the next round of polymerization. Consequently, a large amount of dsDNA is formed which is detected by addition of SYBR Green. Thus, sensitive and selective fluorometric detection is realized. The fluorescent sensing strategy shows very good analytical performances towards DNA detection, such as a wide linear range from 0.05 to 25 nM with a low limit of detection of 20 pM.
A cascade amplification strategy of catalytic hairpin assembly and hybridization chain reaction for the sensitive fluorescent assay of the model protein carcinoembryonic antigen Microchim. Acta (IF 4.58) Pub Date : 2018-01-10 Wenting Yang, Xingxing Zhou, Jianmin Zhao, Wenju Xu
A cascade nucleic acid amplification strategy is presented for fluorometric aptamer based determination of the model protein carcinoembryonic antigen (CEA). Amplification is accomplished by combining catalytic hairpin assembly (CHA) and hybridization chain reaction (HCR). In this assay, a specially designed single-stranded DNA containing the aptamer sequence (AS) specific for CEA is hybridized with an inhibitor strand (IS) to form a double-stranded DNA (IS@AS). In the presence of CEA, it will recognize and bind to the AS strand which causes the release of IS. By introducing two DNA hairpins (H1 and H2; these containing complementary sequences) CHA will be activated via the hybridization reactions of H1 and H2. This is accompanying by the formation of a double-stranded DNA (H1-H2) and the release of CEA@AS. The liberated CEA@AS further drives successive recycling of the CHA, thereby generating further copies of H1-H2. The resultant H1-H2 hybrids act as primers and trigger HCR with the help of other two DNA hairpins (H3 and H4) containing G-rich toehold at the 5′-terminus and 3′-terminus of H3 and H4, respectively. The fluorescent probe N-methyl mesoporphyrin IX (NMM) is finally intercalated into the G-rich domains of the long DNA nanostructures due to formation of G-quadruplex structures. This generates a fluorescent signal (best measured at excitation/emission wavelengths of 399/610 nm) that increases with the concentration of target (CEA). This aptamer-based fluorescence assay is highly sensitive and has a linear range that covers the 1 pg·mL−1 to 2 ng·mL−1 CEA concentration range, with a 0.3 pg·mL−1 detection limit.
3-Dimensional hollow graphene balls for voltammetric sensing of levodopa in the presence of uric acid Microchim. Acta (IF 4.58) Pub Date : 2018-01-10 Xin Gao, Hongyan Yue, Shanshan Song, Shuo Huang, Bing Li, Xuanyu Lin, Erjun Guo, Bao Wang, Enhao Guan, Hongjie Zhang, Pengfei Wu
The development of novel nanomaterials brings new opportunity and challenge for high sensing detection of biomolecules. The authors describe the preparation of 3-dimentional hollow graphene balls (3D HGBs) using nickel nanoparticles (Ni-NPs) as the template. The Ni-NPs were synthesized by chemical reduction of nickel chloride and then graphene was coated onto their surface via carburization and carbonization. After etching Ni-NPs, 3D HGBs with few layers and a typical size of 100 nm were obtained. They were sprayed onto indium tin oxide glass to obtain a working electrode for electrochemical determination of levodopa in the presence of uric acid. Due to the unique hollow porous structure of the 3D HGBs, the electrode exhibits a sensitivity of 0.69 μA·μM−1·cm−2 and a 1 μM limit of detection. It is selective, reproducible and stable. It was applied to the determination of levodopa in spiked human plasma samples and it is of potential use in clinical research.
Aptamer-modified carbon nanomaterial based sorption coupled to paper spray ion mobility spectrometry for highly sensitive and selective determination of methamphetamine Microchim. Acta (IF 4.58) Pub Date : 2018-01-10 Tahereh Zargar, Taghi Khayamian, Mohammad T. Jafari
A cellulose paper was modified with an aptamer against methamphetamine on either carbon dots (CDs) or on multichannel carbon nanotubes (CNTs). The resulting sorbent was applied to the extraction of METH from blood or saliva. The METH-loaded paper than also was directly applied as a paper spray ionization source in ion mobility spectrometry. The carbon nanomaterial enhances sensitivity, and the aptamer enhances selectivity. The materials were covalently bound to the paper on one side, while the aptamer was immobilized on the other. After optimization of the extraction process and instrumental parameters, the limits of detection when using the aptamer-CNT modified paper are 0.6 ng·mL−1 for saliva, and 0.45 ng·mL−1 for plasma. The respective values when using aptamer-CD modified paper are 1.5 ng·mL−1 for saliva and 0.9 ng·mL−1 for plasma. Calibration plots are linear in the 2 to 150 ng·mL−1 METH concentration range for saliva, and in the 1.5 to 200 ng·mL−1 concentration ranges for blood when using the aptamer-CNT based method. When using the aptamer-CDs, the dynamic ranges extend from 5 to 200 ng·mL−1 and from 3 to 250 ng·mL−1, respectively. The method was applied to the determination of METH in real samples of saliva and blood, and the accuracy of the method was confirmed by comparison of the results with data analyzed by GC-MS.
A conventional chemical reaction for use in an unconventional assay: A colorimetric immunoassay for aflatoxin B 1 by using enzyme-responsive just-in-time generation of a MnO 2 based nanocatalyst Microchim. Acta (IF 4.58) Pub Date : 2018-01-10 Wenqiang Lai, Qiao Zeng, Juan Tang, Maosheng Zhang, Dianping Tang
The authors describe a colorimetric immunoassay for the model nalyte aflatoxin B1 (AFB1). It is based on the just-in-time generation of an MnO2 nanocatalyst. Unlike previously developed immunoassay, the chromogenic reaction relies on the just-in-time formation of an oxidase mimic without the aid of the substrate. Potassium permanganate (KMnO4) is converted into manganese dioxide (MnO2) which acts as an oxidase mimic that catalyzes the oxidation 3,3′,5,5′-tetramethylbenzidine (TMB) by oxygen to give a blue colored product. In the presence of ascorbic acid (AA), KMnO4 is reduced to Mn(II) ions. This results in a decrease in the amount of MnO2 nanocatalyst. Hence, the oxidation of TMB does not take place. By adding ascorbate oxidase, AA is converted into dehydroascorbic acid which cannot reduce KMnO4. Based on these observations, a colorimetric competitive enzyme immunoassay was developed where ascorbate oxidase and gold nanoparticle-labeled antibody against AFB1 and magnetic beads carrying bovine serum albumin conjugated to AFB1 are used for the determination of AFB1. In presence of AFB1, it will compete with the BSA-conjugated AFB1 (on the magnetic beads) for the labeled antibody against AFB1 on the gold nanoparticles. This makes the amount of ascorbate oxidase/anti-AFB1 antibody-labeled gold nanoparticles, which conjugated on magnetic beads, reduce, and resulted in an increase of ascorbic acid. Under optimal conditions, the absorbance (measured at 652 nm) decreases with increasing AFB1 concentrations in the range from 0.1 to 100 ng mL−1, with a 0.1 ng mL−1 detection limit (at the 3Sblank level). The accuracy of the assay was validated by analyzing spiked peanut samples. The results matched well with those obtained with a commercial ELISA kit. Conceivably, the method is not limited to aflatoxins but has a wide scope in that it may be applied to many other analytes for which respective antibodies are available.
Colorimetric determination of the activity of alkaline phosphatase based on the use of Cu(II)-modulated G-quadruplex-based DNAzymes Microchim. Acta (IF 4.58) Pub Date : 2018-01-10 Zhenwei Tang, Huifang Zhang, Changbei Ma, Pan Gu, Gehou Zhang, Kefeng Wu, Mingjian Chen, Kemin Wang
A colorimetric detection scheme is introduced for the determination of alkaline phosphatase (ALP) activity based on Cu(II)-modulated G-quadruplex-based DNAzymes. It is exploiting the strong affinity of Cu(II) for pyrophosphate (PPi) upon which the cofactor PPi is trapped by Cu(II). Hence, the activity of the DNAzyme is inhibited. ALP catalyzes the hydrolysis of PPi, causing the release of Cu(II). DNAzyme, in turn, is activated and catalyzes the cleavage of the DNA probe substrate. The released G-rich sequence folds into the G-quadruplex, which can bind hemin and catalyze the oxidation of 2,2′-azinobis (3-ethylbenzothiozoline)-6-sulfonate (ABTS), and this leads to an increase in absorbance at 420 nm. Absorbance increases linearly with increasing ALP activity in 0.07 to 300 U.L−1 range, with a 70 mU.L−1 detection limit. The method was applied in ALP inhibition tests and to the determination of ALP activity in spiked serum samples where it gave satisfactory results.
Colorimetric and visual determination of Au(III) ions using PEGylated gold nanoparticles Microchim. Acta (IF 4.58) Pub Date : 2018-01-10 Kunhao Yang, Long Pan, Lingling Gong, Qingju Liu, Zhongqiu Li, Li Wu, Yujian He
A highly selective method is described for the colorimetric determination of Au(III) ions in acidic solution using gold nanoparticles (AuNPs) functionalized with thiolated methoxy poly(ethylene glycol) (mPEG). The presence of Au(III) induces the aggregation of the PEG-AuNPs, and this is accompanied by a color change from wine red to blue, and a decrease in absorbance at 525 nm. This can be monitored spectrophotometrically and visually. Absorbance at 525 nm linearly drops in the 0.50 to 1.75 mg·L−1 Au(III) concentration range, with a 0.25 mg·L−1 detection limit. The method is surprisingly selective over other metal ions. It was successfully applied to the analysis of ore samples.
Simultaneous determination of captopril and hydrochlorothiazide by using a carbon ionic liquid electrode modified with copper hydroxide nanoparticles Microchim. Acta (IF 4.58) Pub Date : 2018-01-10 Ghodratollah Absalan, Morteza Akhond, Raziye Karimi, Amir M. Ramezani
A carbon electrode modified with the ionic liquid octylpyridinium hexafluorophosphate and copper hydroxide nanoparticles was employed in an electrochemical assay for simultaneous determination of captopril (CPT) and hydrochlorothiazide (HCT). The electrode showed two well-defined oxidation peaks for CPT (at 0.22 V) and HCT (at 0.73 V, both vs. Ag/AgCl) at pH 8.0 using square wave voltammetry. Calibration plots are linear in the concentration ranges of 0.7–70 µM (CPT) and 3–600 μM (HCT), with detection limits of 12 and 60 nM, respectively. The electrode was repeatedly applied to simultaneous determination of CPT and HCT in pharmaceutical formulation without showing any fouling.
A gold nanoparticle based fluorescent probe for simultaneous recognition of single-stranded DNA and double-stranded DNA Microchim. Acta (IF 4.58) Pub Date : 2018-01-10 Haiyan Ma, Zongbing Li, Ning Xue, Zhiyuan Cheng, Xiangmin Miao
A fluorescent method is described for simultaneous recognition of single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA). It is based on the quenching of the fluorescence of fluorophore labeled DNA probes by gold nanoparticles (AuNPs). To demonstrate feasibility, two DNA probes labeled with spectrally different fluorophores were designed. The first DNA probe (P1) was modified with 6-carboxyfluorescein (FAM; with green fluorescence, peaking at 518 nm), while the second (P2) was modified with carboxy-X-rhodamine (ROX; with yellow fluorescence, 610 nm). The fluorescence signals of the labels are quenched if P1 or P2 are adsorbed on AuNPs. Upon addition of ssDNA and dsDNA, hybridization occurs between P1 and ssDNA to form a dsDNA. In contrast, P2 hybridizes with dsDNA such that a triplex DNA is formed. As a result, the dsDNA and the triplex DNA, respectively, are desorbed from the surface of the AuNPs so that quenching no longer can occur and strong fluorescence can be observed. Under the optimal conditions, ssDNA and dsDNA can be detected simultaneously via the green and yellow fluorescence, respectively. The detection limits can be as low as 330 pM. In particular, the method has excellent selectivity for the target DNAs over control DNAs.
Microwave-assisted synthesis of highly luminescent N- and S-co-doped carbon dots as a ratiometric fluorescent probe for levofloxacin Microchim. Acta (IF 4.58) Pub Date : 2018-01-10 Huiyu Li, Yuan Xu, Jie Ding, Li Zhao, Tianyu Zhou, Hong Ding, Yanhua Chen, Lan Ding
Uniform N- and S-co-doped carbon dots (NSCDs) with fluorescence quantum yields of up to 64% were synthesized via a one-step microwave-assisted method. Ammonium citrate and L-cysteine act as precursors, and synthesis is completed in 2.5 min using a 750 W microwave oven to give a 62% yield. The NSCDs show bright blue fluorescence (with excitation/emission peaks at 353/426 nm) and have narrow size distribution. On exposure to levofloxacin (LEV), the emission maximum shifts to 499 nm. This effect was used to design ratiometric (2-wavelength) assays for LEV. The fluorometric method (based on measurement of the fluorescence intensity ratio at 499 and 426 nm) has a detection limit of 5.1 μg·L−1 (3σ/k) and a linear range that extends from 0.01 to 70 mg·L−1. The method was applied to the determination of LEV in three kinds of spiked water samples and has recoveries in the range from 98.6 to 106.8%. The fluorescent probe described here is highly selective and sensitive.
Electrochemical determination of dopamine using a glassy carbon electrode modified with a nanocomposite consisting of nanoporous platinum-yttrium and graphene Microchim. Acta (IF 4.58) Pub Date : 2018-01-10 Dandan Chen, Chunhuan Tian, Xiangyi Li, Zihan Li, Zhida Han, Chun Zhai, Ying Quan, Rongjing Cui, Genhua Zhang
A nanoporous platinum-yttrium alloy (NP-PtY) was fabricated by dealloying ribbons of a PtYAl alloy. Owing to the high porosity and the synergistic effect of Y in the Pt backbone, the NP-PtY exhibits superior structural stability, reproducibility and electrocatalytic activity. An electrochemical sensor was developed for the highly sensitive and selective detection of dopamine (DA) based on the use of a glassy carbon electrode modified with NP-PtY alloy and graphene. The sensor, best operated at 0.16 V vs. SCE, has a linear range covering the 0.9 to 82 μM concentration range, a 0.36 μM detection limit (at S/N = 3), and good selectivity over tyramine, tryptamine, phenethylamine, uric acid, and ascorbic acid. It gave satisfactory results in the determination of DA in spiked samples of urine.
A hyper-cross linked polymer as an adsorbent for the extraction of chlorophenols Microchim. Acta (IF 4.58) Pub Date : 2018-01-10 Yao Wang, Ruiyang Ma, Ruobai Xiao, Lin Hao, Qiuhua Wu, Chun Wang, Zhi Wang
A porous material (polytriphenylamine; PTPA) was synthesized by using triphenylamine as the monomer and dimethoxymethane as the cross-linker. PTPA was characterized by Fourier infrared spectrometry, X-ray diffraction measurements, scanning electron microscopy and N2 adsorption-desorption isotherms. The PTPA has a spherical-shape morphology and relatively high specific surface area. It is shown to be a viable adsorbent for solid phase extraction of 3-chlorophenol, 2,3-dichlorophenol, 2,4-dichlorophenol and 2,4.6-trichlorophenol prior to their determination by high performance liquid chromatography-mass spectrometry. Under the optimized conditions, recoveries from spiked samples are in the range from 92.5% to 106.3%. The limits of detection range from 0.03 to 0.3 ng mL−1 (at an S/N ratio of 3) in case of bottled juice, and from 0.03 to 0.1 ng g−1 in case of tomato samples. The enrichment factors for the four analytes are in the range of 127–183 for bottle juice, and from 110–150 for tomatos. Response is linear in the range of 1.0 to 40.0 ng mL−1 for juice, and 0.3–40.0 ng g−1 for tomatos. The relative standard deviations for the determination of the chlorophenols at 20 ng mL−1 in bottled beverage, and 20 ng g−1 in tomatos are lower than 5.7%.
Simultaneous voltammetric determination of guanine and adenine by using a glassy carbon electrode modified with a composite consisting of carbon quantum dots and overoxidized poly(2-aminopyridine) Microchim. Acta (IF 4.58) Pub Date : 2018-01-10 Shaoying He, Ping He, Xiaojuan Zhang, Xingquan Zhang, Faqin Dong, Lingpu Jia, Licheng Du, Hong Lei
A composite consisting of carbon quantum dots (CQDs) and overoxidized poly(2-aminopyridine) (PAPox) was deposited on a glassy carbon electrode (GCE) through electrochemical polymerization and electrochemical oxidation. The modified GCE was used for the simultaneous determination of guanine and adenine. Electrochemical responses to guanine and adenine were investigated by cyclic voltammetry and differential pulse voltammetry. Owing to the synergistic effect of CQDs and PAPox, two oxidation peaks can be observed, with peaks at 0.81 and 1.13 V (vs. SCE) for guanine and adenine, respectively. The current at the respective peaks has a linear dependence on the concentrations of guanine in the range from 1.0 to 65 μM, and of adenine in the range from 2.0 to 70 μM. The respective detection limits are 0.51 and 0.39 μM (at an S/N ratio of 3). The modified GCE is selective, reproducible and stable.
Graphitic carbon nitride nanosheets as a fluorescent probe for chromium speciation Microchim. Acta (IF 4.58) Pub Date : 2018-01-10 Nadereh Rahbar, Zeinab Salehnezhad, Amir Hatamie, Ahmad Babapour
A fluorometric method was developed for simultaneous determination of Cr(VI) and Cr(III) ions using graphitic carbon nitride nanosheets (g-C3N4 NS) as a nanosized fluorescent indicator probe. The g-C3N4 NS were prepared using high-temperature carbonization of melamine followed by ultrasonication-assisted liquid exfoliation. The g-C3N4 NS display fluorescence with excitation/emission peaks located at 320 and 450 nm. The chromium speciation is based on the quenching of g-C3N4 NS fluorescence. The total concentration of chromium is determined after oxidation of Cr(III) to Cr(VI). The Cr(III) content was then calculated by subtracting the concentration of Cr(VI) from that of total chromium. The effects of pH value, probe amount, and contact time are optimized. Under optimum conditions, calibration plots are linear in the range in the 0.01 to 100 μM chromium concentration range. The limit of detection is 3 nM for for Cr(VI). The intra- and inter-day relative standard deviations (RSD) of the assay are 3.6–7.5% and 4.1–8.5%, respectively. The indicator probe was applied to the determination of chromium species in spiked water and food samples, and recoveries were satisfactory (93.9–107.0%).
Macroemulsion-based dispersive magnetic solid phase extraction for preconcentration and determination of copper(II) in gasoline Microchim. Acta (IF 4.58) Pub Date : 2018-01-10 Francisco Antônio S. Cunha, Danilo Tadeu S. Ferreira, Willy C. R. Andrade, Julys Pablo A. Fernandes, Wellington S. Lyra, Amália G. G. Pessoa, Mario Cesar Ugulino de Araujo
A new method referred to as microemulsion-based Dispersive Magnetic Solid-Phase Extraction (MDM-SPE) is presented for use in the extraction and preconcentration of metal ions from complex organic matrices. MDM-SPE combines the features of magnetic nanoparticles (MNPs) and microemulsions. It was successfully applied to the extraction of copper(II) from gasoline prior to its determination by Graphite Furnace Atomic Absorption Spectrometry (GF-AAS). The material for use in MDM-SPE was obtained by first functionalizing MNPs of the type Fe3O4@Al2O3 with sodium dodecyl sulfate and the chelator 1-(2-pyridylazo)-2-naphthol (PAN) dispersed in 1-propanol. The resulting functionalized magnetic MNPs were dispersed in a microemulsion prepared from gasoline, buffer, and 1-propanol. After waiting for 5 s (during which the formation of the copper complex on the MNPs is complete), the MNPs are magnetically separated. The complex was then eluted with 2 mol L−1 HNO3, and the eluate submitted to GF-AAS. Various parameters were optimized. Copper(II) can be quantified by this method over a linear range that extends from 2.0 to 10.0 μg·L−1. Other figures of merit include (a) a 37 ng·L−1 detection limit, (b) a repeatability of 1.1%, (c) a reproducibility of 2.1%, and (d) an enrichment factor of nine. The high surface-to-volume ratio of the microemulsion containing the dispersed magnetic sorbent warrants an efficient contact for reaction between copper(II) and the complexing agent, and this results in fast (about 40 s) extraction and pre-concentration of copper(II). MDM-SPE is accurate, precise and efficient. Microemulsions do not break down, and phase separation, heating, laborious, and time-consuming sample preparation, and incorporation of impurities into the graphite furnace (which can generate inaccuracies in GF-AAS analysis) are not needed.
Ce doped ZnO/f-MWCNT moss ball like nanocomposite: a strategy for high responsive current detection of L-tryptophan Microchim. Acta (IF 4.58) Pub Date : 2018-01-10 Dhanalakshmi Naganathan, Priya Thangamani, Thennarasu Selvam, Thinakaran Narayanasamy
An electrochemical sensor is described for the determination of L-tryptophan (TRP). The method is based on the use of a glassy carbon electrode (GCE) modified with a nanocomposite consisting of moss ball-like cerium-doped ZnO and functionalized multiwalled carbon nanotubes (Ce-ZnO/f-MWCNT). Ce-doped ZnO was synthesized by a low temperature hydrothermal method. The Ce-ZnO/f-MWCNT nanocomposite was characterized by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, FTIR and field emission scanning electron microscopy. The nanocomposite was drop cast on a GCE for use in electrochemical detection of TRP via cyclic voltammetry and differential pulse voltammetry. The oxidation peak current (0.76 V vs. Ag/AgCl) is strongly improved compared to a bare GCE. The experimental parameters such as solution pH value, scan rate, stability, concentration, reproducibility and repeatability were optimized. Response is linear in the 10 to 100 nM TRP concentration range, the limit of detection is 1.2 nM, and the sensitivity is 2.59 μA·nM−1·cm−2. The electrode was applied to the determination of TRP in spiked real samples and gave satisfactory results.
A lateral flow immunoassay for straightforward determination of fumonisin mycotoxins based on the quenching of the fluorescence of CdSe/ZnS quantum dots by gold and silver nanoparticles Microchim. Acta (IF 4.58) Pub Date : 2018-01-10 Laura Anfossi, Fabio Di Nardo, Simone Cavalera, Cristina Giovannoli, Giulia Spano, Elena S. Speranskaya, Irina Y. Goryacheva, Claudio Baggiani
A lateral flow immunoassay (LFIA) was developed for the determination of fumonisin mycotoxins. The fluorescence of CdSe/ZnS quantum dots (QDs), observed at excitation/emission wavelengths of 365/525 nm, is suppressed by the addition of silver nanoparticles (SNPs) or gold nanoparticles (GNPs) because SNPs overlap the excitation bands of the QDs, and GNPs overlap the emission bands. The fluorescence of the QDs is recovered upon addition of fumonisins, allowing for the sensitive detection in “positive mode” of the target mycotoxin by monitoring the changes of the QDs fluorescence intensity. The SNPs are found to be the most effective quenchers, while the use of GNPs allows for an efficient recovery of fluorescence and can be employed in the LFIA. The method was successfully applied to the fluorometric determination of fumonisins in spiked maize flour samples. The visual detection limit is at the ng·mL−1 level. This is four times lower compared to the colorimetric LFIA based on the use of the conventional gold NPs.
Determination of nickel(II) at nanomolar levels using iodide-responsive gold-copper nanoparticles as colorimetric probes Microchim. Acta (IF 4.58) Pub Date : 2018-01-08 Hongyan Xi, Qingyun Liu, Zhengbo Chen
The authors present a colorimetric method for the quantification of Ni(II) at nanomolar levels. It is based on the use of iodide-responsive copper-gold nanoparticles (Cu-Au NPs) combined with the Ni(II)-catalyzed glutathione (GSH)-oxygen reaction system. In the presence of Ni(II), the catalytic reaction between GSH and oxygen is can triggered. This leads to the formation of GSSG which is bulky and hinders the access of iodide to the surface of the Cu-Au NPs. Concomitantly, the color of the solution containing the Cu-Au NPs changes from gray to red. Based on these findings, a method was developed for the quantitation of Ni(II) that has a detection limit as low as 0.54 nM. This is 1–3 orders of magnitude lower than that of previously reported optical methods. The assay has excellent selectivity for Ni(II), is rapid, cost-effective, portable, and allows for bare eye observation. Conceivably the method is suitable for field detection of Ni(II) in biological, food, and environmental samples.
Aptamer based electrochemiluminescent thrombin assay using carbon dots anchored onto silver-decorated polydopamine nanospheres Microchim. Acta (IF 4.58) Pub Date : 2018-01-08 Yuanyuan Liu, Yanhua Zhao, Qi Fan, Malik Saddam Khan, Xiaojian Li, Yong Zhang, Hongmin Ma, Qin Wei
An electrochemiluminescent (ECL) aptamer based assay is described for thrombin. It is based on the use of carbon dots (C-dots) placed on polydopamine nanospheres loaded with silver nanoparticles (PDANS@Ag) and with probe DNA (pDNA). The PDANS possess high specific surface and can load a large number of C-dots. The AgNPs, in turn, enhance the ECL emission of the C-dots. Platinum functionalized graphene (Gr-Pt) can connect capture DNA (cDNA). The ECL nanoprobe consisting of PDANS@Ag/C-dots was placed on a glassy carbon electrode modified with Gr-Pt/cDNA/BSA via hybridization between cDNA and pDNA. On applying voltages from −1.8 V to 0 V, a strong ECL signal is generated. If thrombin is added, it will bind to cDNA. This leads to the release of pDNA from the electrode surface and a decrease in ECL intensity. Response to thrombin is linear in the 1.0 fmol·L−1 to 5.0 nmol·L−1 concentration range, with a 0.35 fmol·L−1 detection limit. The assay is stable, repeatable and selective, which demonstrates its clinical applicability.
A glassy carbon electrode modified with N-doped carbon dots for improved detection of hydrogen peroxide and paracetamol Microchim. Acta (IF 4.58) Pub Date : 2018-01-08 Li Fu, Aiwu Wang, Guosong Lai, Cheng-Te Lin, Jinhong Yu, Aimin Yu, Zhong Liu, Kefeng Xie, Weitao Su
Nitrogen doped carbon dots (NCDs) were synthesized using a low temperature approach and used to modify a glassy carbon electrode (GCE) via dipping. The oxygen groups on the surface of the NCDs, and the charge delocalization of the NCDs warrant an excellent electrocatalytic activity of the GCE toward oxidation of paracetamol (PA) and reduction of H2O2. PA and H2O2 were detected at 0.34 V and −0.4 V (both vs. Ag/AgCl) using differential pulse voltammetry and amperometric I-T measurement, respectively. The modified GCE has a linear response to PA in the 0.5 to 600 μM concentration range, and to H2O2 in the 0.05 μM to 2.25 mM concentration range. The detection limits are 157 nM and 41 nM, respectively. In our perception, the modified GCE holds promise for stable, selective and sensitive determination of PA and H2O2 in pharmaceutical analysis.
Direct determination of the tumor marker AFP via silver nanoparticle enhanced SERS and AFP-modified gold nanoparticles as capturing substrate Microchim. Acta (IF 4.58) Pub Date : 2018-01-08 Chenmeng Zhang, Yukun Gao, Nan Yang, Tingting You, Huaxiang Chen, Penggang Yin
The authors describe a rapid and direct SERS-based immunoassay for the determination of AFP, an important marker for diagnosis of hepatocellular carcinoma. Silver nanoparticles (AgNPs; 36 nm i.d.) serve as a support to immobilize antibody and as a SERS intensifier, and AFP-modified gold nanoparticles are employed as capturing substrate. Direct and quantitative detection of AFP is accomplished with a limit detection as low as 5 ng·mL−1. Compared to assays based on the use of metal nanoparticles, the use of gold-silver nanoparticle heterodimers as an active SERS substrate can save costs because only a single antibody is required. Moreover, the high selectivity and good linear relationship of detecting AFP in fetal bovine serum indicates its potential applicability for the direct analysis of clinical samples.
3D nitrogen-doped graphite foam@Prussian blue: an electrochemical sensing platform for highly sensitive determination of H 2 O 2 and glucose Microchim. Acta (IF 4.58) Pub Date : 2018-01-08 Yu Zhang, Bintong Huang, Feng Yu, Qunhui Yuan, Meng Gu, Junyi Ji, Yang Zhang, Yingchun Li
A platform is described for voltammetric sensing of hydrogen peroxide (H2O2). It is based on the use of nitrogen-doped graphite foam modified with Prussian Blue particles (PB/NGF). Graphite foam was synthesized by chemical vapor deposition, and doping with nitrogen was realized via dielectric barrier plasma discharge. PB particles were grown on the NGF through electrodeposition. SEM images of NGF verified the porous and interconnected structure of graphite foam, and XPS and Raman spectroscopy verified the successful doping with N. The performance of the PB/NGF electrode was characterized by CV and EIS which showed it to possess outstanding properties in terms of sensing H2O2. H2O2 was quantified in a range of 0.004 to 1.6 mM with a detection limit of 2.4 μM. The PB/NGF electrode also is shown to be a viable substrate for loading glucose oxidase (GOx). The GOx-functionalized electrode responds to glucose over the 0.2 to 20 mM concentration range at a potential of −50 mV (vs. Ag/AgCl), with a sensitivity of 27.48 mA M−1 cm−2 and a 0.1 M detection limit (at an S/N ratio of 3). The glucose sensor is selective, stable, and reproducible. The biosensor was successfully applied to the determination of glucose in spiked human serum samples, and this confirmed it practicability.
Voltammetric sensing based on the use of advanced carbonaceous nanomaterials: a review Microchim. Acta (IF 4.58) Pub Date : 2018-01-08 Ankita Sinha, Dhanjai, Rajeev Jain, Huimin Zhao, Priyanka Karolia, Nimisha Jadon
This review (with 210 references) summarizes recent developments in the design of voltammetric chemical sensors and biosensors based on the use of carbon nanomaterials (CNMs). It is divided into subsections starting with an introduction into the field and a description of its current state. This is followed by a large section on various types of voltammetric sensors and biosensors using CNMs with subsections on sensors based on the use of carbon nanotubes, graphene, graphene oxides, graphene nanoribbons, fullerenes, ionic liquid composites with CNMs, carbon nanohorns, diamond nanoparticles, carbon dots, carbon nanofibers and mesoporous carbon. The third section gives conclusion and an outlook. Tables are presented on the application of such sensors to voltammetric detection of neurotransmitters, metabolites, dietary minerals, proteins, heavy metals, gaseous molecules, pharmaceuticals, environmental pollutants, food, beverages, cosmetics, commercial goods and drugs of abuse. The authors also describe advanced approaches for the fabrication of robust functional carbon nano(bio)sensors for voltammetric quantification of multiple targets.
A SERS-based multiple immuno-nanoprobe for ultrasensitive detection of neomycin and quinolone antibiotics via a lateral flow assay Microchim. Acta (IF 4.58) Pub Date : 2018-01-06 Qiaoqiao Shi, Jie Huang, Yaning Sun, Ruiguang Deng, Man Teng, Qingmei Li, Yanyan Yang, Xiaofei Hu, Zhijun Zhang, Gaiping Zhang
The authors describe an ultrasensitive method for simultaneous detection of neomycin (NEO) and quinolones antibiotics (QNS). It is based on the use of (a) two immuno-nanoprobes (a probe for NEO and a probe for QNS), (b) surface-enhanced Raman scattering (SERS) detection, and (c), a portable lateral flow assay (LFA). The two probes consist of gold nanoparticles (AuNPs) conjugated to the Raman active molecule 4-aminothiophenol (PATP), and to monoclonal antibody against NEO (NEO mAb) or against NOR (NOR mAb). Quantitative detection of NEO and QNS was realized via SERS of the PATP-coated AuNPs captured in the test line of a LFA. Under optimized condition, the visual limits of LFA are 10 ng·mL−1 for NEO and 200 ng·mL−1 for NOR, and with LODs down to 0.37 pg·mL−1 and 0.55 pg·mL−1 by using SERS. The NEO test line is not interfered by the NEO analogues gentamycin, streptomycin and tobramycin, but the NOR test line suffers from different degrees of cross-reactivity (CR) to 12 common other QNS, the CRs ranging from 1.5% to 136%. The recoveries of NEO and NOR from spiked milk samples ranged between 86% and 121%, with relative standard deviations (RSD) from 3% to 6%. The method is highly sensitive, accurate and effective. It may be applied to simultaneous detection of NEO and 8 QNS, including NOR, enoxacin, ciprofloxacin, ofloxacin, fleroxacin, marbofloxacin, enrofloxacin, and pefloxacin.
Red emitting and highly stable carbon dots with dual response to pH values and ferric ions Microchim. Acta (IF 4.58) Pub Date : 2018-01-04 Yuanqing Sun, Xiaojie Wang, Chan Wang, Dingyi Tong, Qian Wu, Kaili Jiang, Yingnan Jiang, Chuanxi Wang, Minghui Yang
The authors describe strongly red-emitting carbon dots (CDs) which were obtained via microwave synthesis using phenylenediamine as the carbon source. The structural and optical properties of the resultant CDs are studied in some detail. The CDs possess (a) longwave emission (peaking at 620 nm under 470 nm excitation), (b) a quantum yield of ~15%, (c) a size of typically 3.8 nm; and (d) good photostability. The CDs have a pH-dependet response that covers the pH 5 to 10 range, and their fluorescence is quenched by ferric ions. The CDs can detect ferric ions in aqueous samples in the 0 to 30 μM concentration range with a lower detection limit of 15 nM. The CDs were also used to image pH values and ferric ions in E. coli bacteria.
A chromium(III) oxide-coated steel wire prepared by arc ion plating for use in solid-phase microextraction of aromatic hydrocarbons Microchim. Acta (IF 4.58) Pub Date : 2017-12-29 Hongmei Liu, Fanpeng Ran, Xiaoqi Wang, Nairu He, Yong Guo
An arc ion plating method was introduced for the deposition of chromium oxide (Cr2O3) on a steel wire substrate, and its use as a coating for solid phase microextraction with high mechanical strength, stability, and long operational lifetime.
Correction to: Loop-mediated isothermal amplification for visual detection of Vibrio parahaemolyticus using gold nanoparticles Microchim. Acta (IF 4.58) Pub Date : 2017-12-28 Cong Kong, Yuan Wang, Essy Kouadio Fodjo, Guang-xin Yang, Feng Han, Xiao-sheng Shen
Abstract The published version of this article, unfortunately, contained error. Modifications have been made to the Abstract, Introduction, Results and discussion, and Acknowledgements section. The original article has been corrected.
Wireless electrochemical preparation of gradient nanoclusters consisting of copper(II), stearic acid and montmorillonite on a copper wire for headspace in-tube microextraction of chlorobenzenes Microchim. Acta (IF 4.58) Pub Date : 2017-12-26 Marzieh Enteshari Najafabadi, Habib Bagheri
A gradient coating of organoclay–Cu nanoclusters was fabricated on a copper wire by wireless electrofunctionalization. The oxidation of copper takes place at the anodic pole (red) while dissolved oxygen in ethanol solution is reduced at the cathodic pole (blue).
Electrochemical immunosensor for the breast cancer marker CA 15–3 based on the catalytic activity of a CuS/reduced graphene oxide nanocomposite towards the electrooxidation of catechol Microchim. Acta (IF 4.58) Pub Date : 2017-12-26 Jafar Amani, Alireza Khoshroo, Mehdi Rahimi-Nasrabadi
The authors report on an electrochemical immunosensor for the tumor marker carbohydrate antigen 15–3 (CA15–3). It is based on the use of a composite consisting of reduced graphene oxide (RGO) and copper sulfide (CuS) that was placed on a screen-printed graphite electrode. The electrode shows excellent activity towards the oxidation of catechol acting as an electrochemical probe, best at a working potential of 0.16 V. The electrode was modified with antibody against CA15–3. Once the analyte (CA15–3) binds to the surface of the electrode, the response to catechol is reduced. The assay has a linear response in the 1.0–150 U mL−1 CA15–3 concentration range, with a 0.3 U mL−1 lower detection limit and a sensitivity of 1.88 μA μM−1 cm−2. The immunosensor also shows good reproducibility (2.7%), stability (95% of the initial values after storing for four weeks). The method was successfully applied to the determination of CA15–3 in serum samples, and results were found to compare well to those obtained by an ELISA. Conceivably, this nanocomposite based detection scheme has a wider scope and may be applied to numerous other immunoassays.
Voltammetric lidocaine sensor by using a glassy carbon electrode modified with porous carbon prepared from a MOF, and with a molecularly imprinted polymer Microchim. Acta (IF 4.58) Pub Date : 2017-12-26 Junjie Zhang, Jiang Liu, Yang Zhang, Feng Yu, Fu Wang, Zhengchun Peng, Yingchun Li
The work describes a hybrid electrochemical sensor for highly sensitive detection of the anesthetic lidocaine (LID). Porous carbon (PC) was synthesized from an isoreticular metal-organic framework-8 (IRMOF-8) and drop cast onto a glassy carbon electrode (GCE). A layer of a molecularly imprinted polymer (MIP) layer was then fabricated in situ on the modified GCE by electro-polymerization, with LID acting as the template and resorcinol as the functional monomer. Hexacyanoferrate is used as an electrochemical probe. The electrical signal (typically acquired at 0.335 V vs. SCE) increases linearly in the 0.2 pM to 8 nM LID concentration range, with a remarkable 67 fM detection limit (at an S/N ratio of 3). The sensor is stable and selective. Eventually, rapid and accurate detection of LID in spiked real samples was successfully realized.
Colorimetric determination of ferrous ion via morphology transition of gold nanorods Microchim. Acta (IF 4.58) Pub Date : 2017-12-22 Simin Lu, Xiao Zhang, Ling Chen, Ping Yang
A colorimetric method is described for the determination of ferrous ion (Fe2+) with high sensitivity and selectivity. The method is based on catalytic etching of gold nanorod (NR). In an acid condition, Fe2+ reacts with H2O2 to produce superoxide radical (O2•−) that etches gold NRs from the low energy surface along the longitudinal direction preferentially. As a result, the changes in the absorption spectrum and color of gold NR can be measured and also can be detected visually. Under the optimal conditions, the assay has very low detection limit (13.5 nM) and a linear response in a concentration range of 75 to 1 μM. The method was applied to the determination of Fe2+ in spiked samples of fetal bovine serum and also transferred to a kind of test stripe for use in fast practical applications. A unique colorimetric sensing method is demonstrated for the colorimetric detection of Fe2+, again based on the oxidation of gold nanorods which leads to the blue-shift of the absorption.
Aptamer-functionalized magnetic and fluorescent nanospheres for one-step sensitive detection of thrombin Microchim. Acta (IF 4.58) Pub Date : 2017-12-22 Cong-Ying Wen, Jia-Hui Bi, Ling-Ling Wu, Jing-Bin Zeng
A one-step sandwich method is described for detecting proteins with magnetic nanospheres (MNs) and fluorescent nanospheres (FNs). Thrombin is selected as a model analyte to validate the method. Two DNA aptamers (Apt 29 and Apt 15 targeting two different exosites of thrombin) are chosen as recognition elements to modify MNs and FNs. The superparamagnetic MN-Apt 29 conjugate is used to separate and concentrate thrombin. The FN-Apt 15 conjugate encapsulates hundreds of fluorescent quantum dots and is used as reporter to provide a stable signal. Magnetic capture and fluorescence identification are performed simultaneously to form a sandwich complex (MN-Apt 29-thrombin-FN-Apt 15) for fluorescence determination (at excitation/emission wavelengths of 380/622 nm). The method is convenient, time saving, and gives a strong signal (compared to the two-step method where capture and identification are performed in two steps). The one-step method presented here is completed within 30 min and has a 3.5 ng·mL−1 (97 pM) detection limit. The method is reproducible, has an intra-assay variability of 1.5%, and an inter-assay variability of 4.9%. Other serum proteins (HSA, CEA, PSA, and AFP) do not interfere. The method was also applied to analyze serum samples. Almost the same fluorescence intensity was measured when analyzing 1% serum samples (compared to buffer samples).
Colorimetric detection of genetically modified organisms based on exonuclease III-assisted target recycling and hemin/G-quadruplex DNAzyme amplification Microchim. Acta (IF 4.58) Pub Date : 2017-12-21 Decai Zhang, Weijia Wang, Qian Dong, Yunxiu Huang, Dongmei Wen, Yuejing Mu, Yong Yuan
An isothermal colorimetric method is described for amplified detection of the CaMV 35S promoter sequence in genetically modified organism (GMO). It is based on (a) target DNA-triggered unlabeled molecular beacon (UMB) termini binding, and (b) exonuclease III (Exo III)-assisted target recycling, and (c) hemin/G-quadruplex (DNAzyme) based signal amplification. The specific binding of target to the G-quadruplex sequence-locked UMB triggers the digestion of Exo III. This, in turn, releases an active G-quadruplex segment and target DNA for successive hybridization and cleavage. The Exo III impellent recycling of targets produces numerous G-quadruplex sequences. These further associate with hemin to form DNAzymes and hence will catalyze H2O2-mediated oxidation of the chromogenic enzyme substrate ABTS2− causing the formation of a green colored product. This finding enables a sensitive colorimetric determination of GMO DNA (at an analytical wavelength of 420 nm) at concentrations as low as 0.23 nM. By taking advantage of isothermal incubation, this method does not require sophisticated equipment or complicated syntheses. Analyses can be performed within 90 min. The method also discriminates single base mismatches. In our perception, it has a wide scope in that it may be applied to the detection of many other GMOs.
Electrochemical quercetin sensor based on a nanocomposite consisting of magnetized reduced graphene oxide, silver nanoparticles and a molecularly imprinted polymer on a screen-printed electrode Microchim. Acta (IF 4.58) Pub Date : 2017-12-20 Zufu Yao, Xin Yang, Xiaobo Liu, Yaqi Yang, Yangjian Hu, Zijian Zhao
An electrochemical quercetin (QR) sensor is described that is based on the use of magnetic reduced graphene oxide (MrGO) incorporated into a molecularly imprinted polymer (MIP) on the surface of a screen-printed electrode (SPE). The MrGO consists of reduced graphene oxide (rGO), magnetite (Fe3O4) and silver nanoparticles (Ag). The analyte (QR) is electrostatically adsorbed on the surface of the MrGO. Finally, the MIP was deposited via in-situ polymerization. The composite was characterized by X-ray diffraction, Fourier transform infrared spectroscopy and Vibrating sample magnetometry. The morphologies and electrochemical properties of different electrodes were characterized by Field emission scanning electron microscopy, Electrochemical impedance spectroscopy and differential pulse voltammetry. Under optimal conditions, the modified electrode has a linear response in the 20 nM to 250 μM QR concentration range. The limit of detection is 13 nM (at an S/N ratio of 3). The electrode is selective, stable, regenerable and reliable. It was applied to the determination of QR in spiked pharmaceutical samples and gave satisfactory results.
An ultrasensitive conformation-dependent colorimetric probe for the detection of mercury(II) using exonuclease III-assisted target recycling and gold nanoparticles Microchim. Acta (IF 4.58) Pub Date : 2017-12-20 Minqiang Hong, Bihua Zeng, Mingyu Li, Xueqin Xu, Guonan Chen
An ultrasensitive conformation-dependent colorimetric assay has been developed for the detection of mercury(II) ions. It is based on the use of exonuclease III (Exo III)-assisted target recycling and gold nanoparticles (AuNPs). In the absence of Hg(II), the hairpin-shaped DNA probe (H-DNA) binds to AuNPs and stabilizes them in solutions of high ionic strength. In the presence of Hg(II), on the other hand, the sticky termini of the H-DNA form a rigid DNA duplex stem with a blunt 3′-terminus. Thus, Exo III is activated as a biocatalyst for selective and stepwise removal of mononucleotides from the 3′-terminus of the H-DNA. As a result, Hg(II) is released from the T−Hg(II)−T complexes. The guanine-rich sequences released from the H-DNA are then self-assembled with potassium ion to form a stable G-quadruplex conformation. In solutions of high ionic strength, this results in aggregation of AuNPs and a color change from red to blue which can be seen with bare eyes. The method is highly sensitive and selective. It has a linear response in the 10 pM to 100 nM Hg(II) concentration range, and the detection limit is as low as 3.2 pM (at an S/N ratio of 3). The relative standard deviation at a level of 0.5 nM of Hg(II) is 4.9% (for n = 10). The method was applied to the detection of Hg(II) in spiked environment water samples, with recoveries ranging from 92% to 106%.
Nanodiamonds conjugated to gold nanoparticles for colorimetric detection of clenbuterol and chromium(III) in urine Microchim. Acta (IF 4.58) Pub Date : 2017-12-20 Muthaiah Shellaiah, Turibius Simon, Parthiban Venkatesan, Kien Wen Sun, Fu-Hsiang Ko, Shu-Pao Wu
Nanodiamonds were modified such that they carry thiol groups (ND-thiol). Gold nanoparticles were reacted with ND-thiol to obtain a highly stable conjugate of the type ND@AuNPs. Both ND-thiol and the ND@AuNPs were characterized by SEM, TEM, AFM, DLS, zeta potential, XPS, XRD, UV-Vis, Raman, FTIR and cytotoxicity studies. Their biocompatibility was confirmed via an MTT assay with HeLa cells. At a pH value of 6, the ND@AuNPs represent a colorimetric probe that can be used to selectively detect the illegally used β-adrenergic drug clenbuterol (CLB) and the pollutant chromium(III). Detection can be performed visually by monitoring the color change from wine red to purple blue, or by colorimetric measurement of the so-called SPR peaks at 651 and 710 nm. The color changes are due to aggregation, and this is confirmed by TEM and DLS data. The involvement of surface functional groups that assist in analyte recognition was verified by FTIR. The detection limits are 0.49 nM for CLB, and 0.37 nM for Cr(III). The ND@AuNPs were successfully applied to the determination of Cr(III) and CLB in spiked human urine samples. Notably, the low interference by other ions in the detection of Cr(III) in tap and lake water is confirmed by ICP-MS analyses.
Aptamer based voltammetric determination of ampicillin using a single-stranded DNA binding protein and DNA functionalized gold nanoparticles Microchim. Acta (IF 4.58) Pub Date : 2017-12-20 Jun Wang, Kui Ma, Huanshun Yin, Yunlei Zhou, Shiyun Ai
An aptamer based method is described for the electrochemical determination of ampicillin. It is based on the use of DNA aptamer, DNA functionalized gold nanoparticles (DNA-AuNPs), and single-stranded DNA binding protein (ssDNA-BP). When the aptamer hybridizes with the target DNA on the AuNPs, the ssDNA-BP is captured on the electrode surface via its specific interaction with ss-DNA. This results in a decreased electrochemical signal of the redox probe Fe(CN)63− which is measured best at a voltage of 0.188 mV (vs. reference electrode). In the presence of ampicillin, the formation of aptamer-ampicillin conjugate blocks the further immobilization of DNA-AuNPs and ssDNA-BP, and this leads to an increased response. The method has a linear reposne that convers the 1 pM to 5 nM ampicillin concentration range, with a 0.38 pM detection limit (at an S/N ratio of 3). The assay is selective, stable and reproducible. It was applied to the determination of ampicillin in spiked milk samples where it gave recoveries ranging from 95.5 to 105.5%.
Room temperature LPG resistive sensor based on the use of a few-layer graphene/SnO 2 nanocomposite Microchim. Acta (IF 4.58) Pub Date : 2017-12-20 Solleti Goutham, Satish Bykkam, Kishor Kumar Sadasivuni, Devarai Santhosh Kumar, Mohsen Ahmadipour, Zainal Arifin Ahmad, Kalagadda Venkateswara Rao
A nanocomposite consisting of a few layers of graphene (FLG) and tin dioxide (SnO2) was prepared by ultrasound-assisted synthesis. The uniform SnO2 nanoparticles (NPs) on the FLG were characterized by X-ray diffraction in terms of lattice and phase structure. The functional groups present in the composite were analyzed by FTIR. Electron microscopy (HR-TEM and FE-SEM) was used to study the morphology. The effect of the fraction of FLG present in the nanocomposite was investigated. Sensitivity, selectivity and reproducibility towards resistive sensing of liquid propane gas (LPG) was characterized by the I-V method. The sensor with 1% of FLG on SnO2 operated at a typical voltage of 1 V performs best in giving a rapid and sensitive response even at 27 °C. This proves that the operating temperature of such sensors can be drastically decreased which is in contrast to conventional metal oxide LPG sensors.
Boletus edulis loaded with γ-Fe 2 O 3 nanoparticles as a magnetic sorbent for preconcentration of Co(II) and Sn(II) prior to their determination by ICP-OES Microchim. Acta (IF 4.58) Pub Date : 2017-12-20 Sadin Ozdemir, M. Serkan Yalcin, Ersin Kilinc, Mustafa Soylak
The fungus Boletus edulis loaded with γ-Fe2O3 nanoparticles is a viable biosorbent for magnetic solid phase extraction (MSPE) of trace levels of Co(II) and Sn(II). The surface structure of immobilized magnetized B. edulis was characterized by FT-IR, SEM and EDX. Experimental parameters were optimized.
An oligosorbent-based aptamer affinity column for selective extraction of aflatoxin B 2 prior to HPLC with fluorometric detection Microchim. Acta (IF 4.58) Pub Date : 2017-12-20 Hongmei Liu, Yunxia Luan, Anxiang Lu, Bingru Li, Meihua Yang, JiHua Wang
The article describes an aptamer affinity column for selective solid-phase extraction of aflatoxin B2 (AFB2). Amino-modified aptamer against AFB2 was immobilized on CNBr-activated Sepharose through a covalent bond. The effects of oligosorbents based on 3′- or 5′-amino-modified sequences with a C6 or a C7 spacer arm were evaluated by UV spectroscopy at 260 nm. The extraction recovery was evaluated by HPLC with fluorometric detection. The extraction of AFB2 was optimized. Under the optimum conditions, the aptamer affinity column has a linear response to AFB2 in the range of 0.5–80 ng, with a capacity of 84.6 ng. Control supports without immobilized aptamers and a nonspecific oligosorbent immobilized with a negative control oligonucleotide were studied in order to demonstrate selectivity. The method was tested with spiked peanut sample (0.5–50 μg·kg−1 AFB2) and gave average recoveries of 80.9% and a mean relative standard deviation of 1.9%. The limit of detection is 25 pg·mL−1. This is much lower than the maximum residue limits suggested by the European Union. The columns can be re-used up to five times without any loss of performance. The oligosorbent was also applied to clean-up of AFB2 from peanut sample extracts before HPLC analysis. Results were further confirmed by ultra-fast liquid chromatography with tandem mass spectrometry. Conceivably, the method may also be applied to other samples, such as food, agricultural products, and traditional Chinese medicines.
Strong enhancement of the chemiluminescence of the Cu(II)-H 2 O 2 system on addition of carbon nitride quantum dots, and its application to the detection of H 2 O 2 and glucose Microchim. Acta (IF 4.58) Pub Date : 2017-12-19 Tooba Hallaj, Mohammad Amjadi, Zhenlun Song, Robabeh Bagheri
The authors report that carbon nitride quantum dots (CN QDs) exert a strong enhancing effect on the Cu(II)/H2O2 chemiluminescent system. Chemiluminescence (CL) intensity is enhanced by CN QDs by a factor of ~75, while other carbon nanomaterials have a much weaker effect. The possible mechanism of the effect was evaluated by recording fluorescence and CL spectra and by examining the effect of various radical scavengers. Emitting species was found to be excited-state CN QDs that produce green CL peaking at 515 nm. The new CL system was applied to the sensitive detection of H2O2 and glucose (via glucose oxidase-catalyzed formation of H2O2) with detection limits (3σ) of 10 nM for H2O2 and 100 nM for glucose. The probe was employed for glucose determination in human plasma samples with satisfactory results.
Amperometric myeloperoxidase immunoassay based on the use of CuPdPt nanowire networks Microchim. Acta (IF 4.58) Pub Date : 2017-12-18 Yilin Wen, Jianyong Yuan, Jun Chen, Yilin Zhao, Yazhen Niu, Chao Yu
This research describes a nanowire network-based method for detecting the activity of myeloperoxidase (MPO), a biomarker of acute coronary syndromes (ACS). Trimetallic CuPdPt nanowire networks (CuPdPt NWNWs) were prepared by a one-step chemical reduction method. The metallic precursors quickly form nanowire network structures without the need for additional capping agents or surfactants. This process creates a product with a clean surface. The NWNWs were dropped onto a glassy carbon electrode (GCE) to obtain a sensor with good catalytic activity towards the reduction of hydrogen peroxide (H2O2), which was used as an electrochemical probe working at −0.4 V (vs. SCE). It also provided a large surface for further modification. Next, an antibody against MPO was immobilized on the modified GCE via the stable conjunction between Cu, Pt, Pd and amino groups. Upon binding of MPO to the antibody on the GCE, the current response to H2O2 was reduced by 35 μA·cm−2. The immunosensor had a linear response within the 100 fg·mL−1 to 50 ng·mL−1 MPO concentration range and a 33 fg·mL−1 detection limit (at an S/N ratio of 3). The recovery of spiked serum samples ranged from 99.8 to 103.6%. This result suggests that the method can be applied to the quantitation of MPO in human serum samples.
An electrochemical aptamer-based assay for femtomolar determination of insulin using a screen printed electrode modified with mesoporous carbon and 1,3,6,8-pyrenetetrasulfonate Microchim. Acta (IF 4.58) Pub Date : 2017-12-18 Mahmoud Amouzadeh Tabrizi, Mojtaba Shamsipur, Reza Saber, Saeed Sarkar, Maryam Besharati
The surface of a screen printed electrode was modified with ordered mesoporous carbon-1,3,6,8-pyrenetetrasulfonate. The amino-terminated aptamer was then linked to the 1,3,6,8-pyrenetetrasulfonate. Then, the Methylene Blue was interacted into the aptamer. The modified electrode was applied to the determination of insulin.
N-Doped graphene quantum dot@mesoporous silica nanoparticles modified with hyaluronic acid for fluorescent imaging of tumor cells and drug delivery Microchim. Acta (IF 4.58) Pub Date : 2017-12-18 Wenying Gui, Jinrui Zhang, Xueqian Chen, Dahai Yu, Qiang Ma
The authors describe new bifunctional mesoporous silica nanoparticles (NPs) for specific targeting of tumor cells and for intracellular delivery of the cancer drug doxorubicin (DOX). Mesoporous silica nanoparticles (MSNPs) were coated with blue fluorescent N-graphene quantum dots, loaded with the drug DOX, and finally coated with hyaluronic acid (HA). Cellular uptake of the NPs with an architecture of the type HA-DOX-GQD@MSNPs enabled imaging of human cervical carcinoma (HeLa) cells via fluorescence microscopy. The cytotoxicity of the nanoparticles on HeLa cells was also assessed. The results suggest that the NPs are higher cytotoxicity effect and exert in living cell imaging ability. Compared to the majority of other drug nanocarrier systems, the one described here enables simultaneous DOX release and fluorescent monitoring.
Fluorometric graphene oxide-based detection of Salmonella enteritis using a truncated DNA aptamer Microchim. Acta (IF 4.58) Pub Date : 2017-12-18 Raja Chinnappan, Saleh AlAmer, Shimaa Eissa, Anas Abdel Rahamn, Khalid M. Abu Salah, Mohammed Zourob
The work describes a fluorescence-based study for mapping the highest affinity truncated aptamer from the full length sequence and its integration in a graphene oxide platform for the detection of Salmonella enteriditis. To identify the best truncated sequence, molecular beacons and a displacement assay design are applied. In the fluorescence displacement assay, the truncated aptamer was hybridized with fluorescein and quencher-labeled complementary sequences to form a fluorescence/quencher pair. In the presence of S. enteritidis, the aptamer dissociates from the complementary labeled oligonucleotides and thus, the fluorescein/quencher pair becomes physically separated. This leads to an increase in fluorescence intensity. One of the truncated aptamers identified has a 2-fold lower dissociation constant (3.2 nM) compared to its full length aptamer (6.3 nM). The truncated aptamer selected in this process was used to develop a fluorometric graphene oxide (GO) based assay. If fluorescein-labeled aptamer is adsorbed on GO via π stacking interaction, fluorescence is quenched. However, in the presence of target (S. enteriditis), the labeled aptamers is released from surface to form a stable complex with the bacteria and fluorescence is restored, depending on the quantity of bacteria being present. The resulting assay has an unsurpassed detection limit of 25 cfu·mL−1 in the best case. The cross reactivity to Salmonella typhimurium, Staphylococcus aureus and Escherichia coli is negligible. The assay was applied to analyze doped milk samples for and gave good recovery. Thus, we believe that the truncated aptamer/graphene oxide platform is a potential tool for the detection of S. Enteritidis.
Microwave-assisted synthesis of graphene modified CuO nanoparticles for voltammetric enzyme-free sensing of glucose at biological pH values Microchim. Acta (IF 4.58) Pub Date : 2017-12-18 Faranak Foroughi, Mansour Rahsepar, Mohammad Jafar Hadianfard, Hasuck Kim
The effect of graphene nanosheets on the glucose sensing performance of CuO powders was investigated. CuO and graphene-modified CuO nanoparticles (NPs) were fabricated by microwave-assisted synthesis and characterized by X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. The material was placed on a glassy carbon electrode (GCE) which then was characterized by cyclic voltammetry and chronoamperometry with respect to the capability of sensing glucose both at pH 13 and pH 7.4. The results revealed that the modified GCE has a fast and selective linear response to glucose at pH 13 that covers the 0.21 μM to 12 mM concentration range, with a 0.21 μM low detection limit. The presence of graphene nanosheets results in an improved sensitivity which is to 700 μA mM−1 cm−2. In solution of pH 7.4, the respective data are a linear analytical range from 5 to 14 mM; a 5 μM LOD and a sensitivity of 37.63 μA mM−1 cm−2 at working potential of −0.05 V (vs. Ag/AgCl) and scan rate of 50 mV s−1. Ascorbic acid, dopamine, uric acid, sucrose, maltose and fructose do not interfere.
A gold electrode modified with a nanoparticulate film composed of a conducting copolymer for ultrasensitive voltammetric sensing of hydrogen peroxide Microchim. Acta (IF 4.58) Pub Date : 2017-12-18 Rongli Zhang, Can Jiang, Xiaoxia Fan, Renchun Yang, Yanyan Sun, Cuige Zhang
Preparation of a conducting nanoparticle (NP) film on the gold electrode (GE) by self-assembly of poly(γ-glutamic acid) that was modified with electroactive 3-aminothiophene (ATh-γ-PGA). It served as a platform for the fabricationof an ultrasensitive voltammetric enzyme-based biosensor for H2O2.
A nanocomposite prepared from a zinc-based metal-organic framework and polyethersulfone as a novel coating for the headspace solid-phase microextraction of organophosphorous pesticides Microchim. Acta (IF 4.58) Pub Date : 2017-12-18 Hasan Bagheri, Hatam Amanzadeh, Yadollah Yamini, Mohammad Yaser Masoomi, Ali Morsali, Jamileh Salar-Amoli, Jalal Hassan
The authors describe a zinc-based metal-organic framework/polyethersulfone nanocomposite (TMU-4/PES) coating deposited on a stainless steel wire via a single-phase inversion method. The nanocomposite represents a novel fiber coating for headspace solid-phase microextraction of organophosphorous pesticides (OPPs) from environmental water and soil samples. The synergistic effects of the high surface area and unique porous structure of TMU-4 as well as the rich π electron stacking and mechanical attributes of the PES polymer result in a high affinity of the composite for OPPs. Following thermal desorption, the OPPS were quantified by gas chromatography with a nitrogen-phosphorus detector. The preparation of the coating is simple, and the coated fiber is highly stable and reusable in that it can be used in about 100 consecutive extractions/desorption cycles. A central composite design was used for assessing the effect of the experimental parameters on the extraction process. Under optimized conditions, the limits of detection are in the 5–8 ng mL−1 range for the OPPs diazinon, fenitrothion, malathion and chlorpyrifos. The average repeatability and fiber-to-fiber reproducibility are 6.5% and 8.7%, respectively. The method was applied to the trace determination of OPPs in (spiked) water and soil samples where it gave good recovery (88–108%) and satisfactory reproducibility (5.9–10.1%).
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