Manganese dioxide based electrochemical sensor for the detection of nitro-group containing organophosphates in vegetables and drinking water samples
Graphical abstract
Introduction
Acute and chronic toxicity associated with organophosphates which are widely used in vegetable and fruit farms all over the world for pest control has serious impacts on human health [1]. Irreversible phosphorylation of the carboxylic ester hydrolase, acetylcholinesterase by organophosphates at its serine residue accounts for their severe toxicity posed to the humans. The acetylcholinesterase inhibition disrupts acetylcholine metabolism resulting in the accumulation of acetylcholine in synapses and neuromuscular junctions causing the acetylcholine receptors to get over-stimulated and eventually get damaged [2]. The stability of the phosphorylated acetylcholinesterase against hydrolysis depends upon the alkoxy groups attached to the phosphorus [3]. Therefore, the level of toxicity varies from one organophosphate to another. With the exception of fenitrothion (moderately toxic), all nitro-group containing organophosphates such as methyl parathion, parathion, EPN (O-Ethyl O-(4-nitrophenyl) phenylphosphonothioate) are classified under “Class Ia (extremely hazardous)” category by the ‘WHO Recommended Classification of Pesticides by Hazard’ [4]. Apart from their extreme inherent toxicity, wide spread usage of them, especially methyl parathion and parathion at considerable levels by the farm owners and availability of multiple routes of entry for these into the human system (dermal contact and inhalation and ingestion of organophosphate contaminated food and water) [3] further aggravates the problem of pesticide poisoning.
Number of electrochemical [[6], [7], [8], [9]] and optical sensing [[10], [11], [12], [13]] strategies that employs biological recognition elements for organophosphate has been reported till now. Many have developed electrochemical organophosphate sensors based on electrocatalysis that does not make use of a biological recognition element such as an enzyme. The reported electrocatalyst materials include silicon carbide nanoparticles [14], zirconia nanoparticles [15,16] gadolinium-prussian blue–graphene composite [17], polyacrylamide-MWCNTs composite [18], nano-platinum intercalated Ni/Al layered double hydroxides [19], nanosilica-graphene composite [20], SWCNTs with ionic liquid composite [21], ionic silsesquioxane film immobilized on silica [22], polyaniline nanofibers-SWCNTs composite [23], gold nanoparticles-MWCNTs composite [24,25], gold nanoparticles-graphene nanocomposite [26], gold nanoparticles-nafion film composite [27], palladium-MWCNTs composite [28] and cerium oxide-reduced graphene oxide composite [29]. Yet the number of electrocatalyst materials explored remains relatively lower than the non-electrocatalysis based works such as enzymatic sensors and molecularly imprinted polymer based sensors [30].
Metal oxides are well known for their affinity towards phosphate groups. This affinity is seen to be utilized in “Metal Oxide Affinity Chromatography (MOAC)” as many metal oxides such as titanium dioxide, zirconium dioxide aluminium oxide, gallium oxide, iron oxide, niobium oxide, tin oxide, hafnium oxide and several others have been used as stationary states in liquid chromatography [31]. Good absorption rates of organophosphates ensure efficient electrocatalysis by reducing the adsorption component of the activation energy [30]. Some of the aforementioned metal oxides such as ZrO2 [15,33], CeO2 [29,34,35] and TiO2 [36,37] have already been used to develop electrochemical organophosphate sensors. To the best of our knowledge, the ability of manganese dioxide in behaving as an electrocatalyst for organophosphate detection has not been studied yet. This is probably because unlike many other metal oxides such as clay minerals, hydrous iron(III) oxides and hydrous aluminium oxides, that develop a positive surface charge at near-neutral pH, manganese dioxide develops a negative surface charge [[38], [39], [40]]. Thus manganese dioxide has low adsorption rates at neutral pH. Interestingly, the manganese oxide attains a positive surface charge in the presence of alkaline earth metal cations (Ba2+, Sr2+ Ca2+, Mg2+) and transition metal cations (Mn2+, Co2+ and Ni2+) and therefore exhibits strong phosphate adsorption rates in the pH range 6–9 [41]. Synthesis of manganese dioxide having a high population of Mn2+ ions is therefore an appropriate strategy to allow high rates of organophosphate adsorption onto the oxide surface at neutral pH.
In this work, cyclic voltammetry is employed to deposit α-manganese dioxide nanorods on a platinum disk electrode in a three-step electrodeposition process. Potentiodynamic nature of the electrodeposition process and the stabilization steps involved are assumed to introduce a number of Mn2+ ions in the deposited oxide rendering its surface positively charged at neutral pH, thereby aiding in providing high adsorption rates. Cyclic voltammetry is exclusively employed in this work for the determination of 4-NPP to ensure that Mn2+ ions on the oxide surface are preserved.
Section snippets
Chemicals
4-Nitrophenyl phosphate disodium salt hexahydrate [4-NPP] was purchased from sigma-Aldrich (USA). Manganese acetate (tetrahydrate) [Mn(CH3CO2)2·4H2O], magnesium chloride (hexahydrate) [MgCl2·6H2O] ferrous chloride (hydrated) [FeCl3·xH2O], aluminium sulphate [Al2(SO4)3], sodium sulphate (anhydrous) [Na2SO4], sodium phosphate dibasic (dihydrate) [NaH2PO4·2H2O] and zinc sulphate (heptahydrate) [ZnSO4·7H2O] were purchased from Loba chemie Pvt. Ltd. (Mumbai, India). Potassium chloride [KCl],
Electrodeposition of manganese dioxide on platinum disk electrode
Fig. 1 represents the CV recorded on Pt electrode for the electrodeposition of α-manganese dioxide. The peak observed at around 0.8 V corresponds to the oxidation of Mn(II) ions present in the solution to manganese dioxide. The increase in peak currents with successive cycles in Fig. 1 could be attributed to an increase in the rate of electrodeposition as the surface area available on the electrode for deposition increases at the end of each cycle [32,44]. The increase in surface area owes to
Conclusion
The MnO2/Pt sensor electrode developed in this work shows a good linear response to 4-NPP with a high sensitivity and Limit of Detection (LOD). The sensor also exhibits appreciable selectivity against common interfering species present in the vegetable washings prepared with water of drinking quality. Interference was observed from nitro-group bearing aromatics such as nitrobenzene and 4-nitrotoluene. Manganese dioxide, being a relatively cheap, water-insoluble, non-toxic material with high
CRediT authorship contribution statement
Amogh K. Ravi: Data curation, Writing - original draft, Investigation, Supervision, Writing - review & editing. Navaneeth Punnakkal: Data curation, Investigation, Supervision, Writing - review & editing. Suneesh Punathil Vasu: Formal analysis, Writing - review & editing. Bipin G. Nair: Formal analysis, Writing - review & editing. Satheesh Babu T.G.: Conceptulization, Funding acquisition, Project administration, Supervision, Writing - review & editing.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
The authors thank the Department of Biotechnology (DBT), Govt of India for financial support (Sanction No. 102/IFD/SAN/2238/2016-17 dated 30-08-2016).
References (47)
- et al.
Facile synthesis of zirconia nanoparticles-decorated graphene hybrid nanosheets for an enzymeless methyl parathion sensor
Sensors Actuators B Chem.
(2012) - et al.
Efficient stripping voltammetric detection of organophosphate pesticides using NanoPt intercalated Ni/Al layered double hydroxides as solid-phase extraction
Electrochem. Commun.
(2010) - et al.
A nanosilica/exfoliated graphene composite film-modified electrode for sensitive detection of methyl parathion
Chin. Chem. Lett.
(2016) - et al.
Sensitive voltammetric response of methylparathion on single-walled carbon nanotube paste coated electrodes using ionic liquid as binder
Sensors Actuators B Chem.
(2008) - et al.
Electrochemical sensor based on polyaniline nanofibers/single wall carbon nanotubes composite for detection of malathion
Synth. Met.
(2014) - et al.
An enzymeless organophosphate pesticide sensor using Au nanoparticle-decorated graphene hybrid nanosheet as solid-phase extraction
Talanta
(2011) - et al.
Highly sensitive electrochemical stripping analysis of methyl parathion at MWCNTs-CeO2-Au nanocomposite modified electrode
Sensors Actuators B Chem.
(2013) - et al.
ELP-OPH/BSA/TiO2 nanofibers/c-MWCNTs based biosensor for sensitive and selective determination of p-nitrophenyl substituted organophosphate pesticides in aqueous system
Biosens. Bioelectron.
(2016) - et al.
Nonenzymatic electrochemical sensor based on CuO-TiO2 for sensitive and selective detection of methyl parathion pesticide in ground water
Sensors Actuators B Chem.
(2018) The surface chemistry of hydrous manganese dioxide
J. Colloid Interface Sci.
(1974)
Phosphate adsorption onto hydrous manganese(IV) oxide in the presence of divalent cations
Water Res.
Nonenzymatic electrochemical glucose sensor based on MnO2/MWNTs nanocomposite
Electrochem. Commun.
Organophosphate poisoning
Semin. Neurol.
Extraction of chlorpyrifos and malathion from water by metal nanoparticles
J. Nanosci. Nanotechnol.
Organophosphate pesticides: biochemistry and clinical toxicology
Ther. Drug Monit.
The WHO Recommended Classification of Pesticides by Hazard and Guidelines to Classification 2009
Nanoparticle-based electrochemical immunosensor for the detection of phosphorylated acetylcholinesterase: an exposure biomarker of organophosphate pesticides and nerve agents
Chem. Eur. J.
Acetylcholinesterase-polyaniline biosensor investigation of organophosphate pesticides in selected organic solvents
J. Environ. Sci. Health B
Acetylcholinesterase voltammetric biosensors based on carbon nanostructure-chitosan composite material for organophosphate pesticides
A gold–platinum bimetallic nanoparticles modified glassy carbon electrode for the sensitive detection of organophosphate pesticides, carbamates and nerve …
Nanoparticle-based Optical Biosensors for the Direct Detection of Organophosphate Chemical Warfare Agents and Pesticides
Fluorescence-based sensing of p-nitrophenol and p-nitrophenyl substituent organophosphates
Anal. Chim. Acta
A fluorescence-based biosensor for the detection of organophosphate pesticides and chemical warfare agents
Cited by (17)
Functionalized nanoscale metal oxides for biosensing, bioimaging and cancer therapy
2024, TrAC - Trends in Analytical ChemistryRecent progress in design and surface modification of manganese nanoparticles for MRI contrasting and therapy
2023, Chemical Engineering JournalHighly sensitive determination of niclosamide based on chitosan functionalized carbon nanotube/carbon black scaffolds with interconnected long- and short-range conductive network
2022, Journal of Materials Research and TechnologyElectrochemical sensing platform based on graphitized and carboxylated multi-walled carbon nanotubes decorated with cerium oxide nanoparticles for sensitive detection of methyl parathion
2022, Journal of Materials Research and TechnologyUltra-sensitive electrochemical sensor for fenitrothion pesticide residues in fruit samples using IL@CoFe<inf>2</inf>O<inf>4</inf>NPs@MWCNTs nanocomposite
2021, Microchemical JournalCitation Excerpt :Organic contaminants are becoming a major concern globally due to the hazardous effect on animals, environment and human health [1,2]. Among such contaminants are organophosphorus compounds that are used in great quantities as pesticides and insecticides [3,4]. Organophosphorus pesticides such as methyl paraoxon and fenitrothion (FNT) have been detected in soil, water and in food stuff like fruits and vegetables based on previous work [5].