Purine metabolites are recognized disease biomarkers and food quality inspecting parameters. As such, reliable electro-analytical strategies for the quantification of purine bases are indispensable from a clinical point of view. We propose an efficient voltammetric sensor based on reduced graphene oxide and poly-L-Glutathione modified glassy carbon electrode (GCE) for determination of purine bases such as Uric acid (UA), Xanthine (XA), Hypoxanthine (HX), and Theobromine (TB). Surface characterization of the GCE has been carried out via surface area determination, scanning electron microscopy, atomic force microscopy, Raman spectroscopy, attenuated total reflection spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. For simultaneous determination, the sensor offers a limit of detection of 1.83×10-7, 6.70×10-8, 2.12×10-7, and 1.14×10-6 mol L-1 for UA, XA, HX, and TB respectively. The practical utility of the sensor has been ascertained via analysis in real samples and the findings are validated using conventional analytical methods. Mechanistic aspects involved in the electrooxidation of analytes have been derived using scan rate studies. A wide concentration linear range with low limit of detection and successful applicability studies in tea, coffee, cocoa, and artificial physiological samples points toward the efficacy of the analytical assay in real sample analysis.

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Background: Plant protecting agrochemicals have significant contribution to enhance the crop production to meet the food requirement of upsurging global population. Meanwhile their long persistence, rampant aerial transit, bioaccumulation and resistance to degradation ascribe it as a catastrophic toxicant. Therefore the availability of early-warning and sensing systems for these toxic compounds especially organic toxicants, is inevitable due to uncontrollable environmental pollution by anthropogenic activities. Method: The literature and published papers available for electrochemical sensing of plant protecting synthetic agrochemicals namely insecticides, herbicides and acaricides were collected, critically evaluated and reviewed. Result: Compared to the conventional methods of quantification of organic pollutants, electrochemical sensors offer prospects of real time analysis, miniaturization, rapid response and on-site monitoring. Considering the diverse electrochemical sensing strategies designed for certain agronomically relevant plant protecting synthetic organic pollutants comes under organophosphate insecticides, carbamates, organochlorine insecticides, acaricides and herbicides, most widely reported sensors include voltammetric, amperometric and impedimetric sensors. Moreover microfluidic devices are also employed very recently for onsite detection and real-time monitoring. organic pollutants, electrochemical sensors offer prospects of real time analysis, miniaturization, rapid response and on-site monitoring. Considering the diverse electrochemical sensing strategies designed for certain agronomically relevant plant protecting synthetic organic pollutants comes under organophosphate insecticides, carbamates, organochlorine insecticides, acaricides and herbicides, most widely reported sensors include voltammetric, amperometric and impedimetric sensors. Moreover microfluidic devices are also employed very recently for onsite detection and real-time monitoring. Conclusion: This review describes state-of-the-art in electrochemical sensors specifically voltammetric, impedimetric, amperometric and potentiometric sensing strategies for the quantification of agrochemical organic pollutants.The emergence of microfluidic paper-based analytical devices (µ-PAD) by utilizing microfabrication technology and different electrode modifiers like metal-carbon nanocomposites, biorecognition elements could provide easy and sensitive detection of pollutants.

Apart from the significant physiological roles of hormones and purine metabolites in higher level living organisms, these biomolecules act as recognised biomarkers for early disease detection and its periodical monitoring. Here we detail the development of a voltammetric sensor based on a copolymer of [L-Cystein (LCys) and 2-(N-morpholino)ethanesulfonic acid (MES)] modified glassy carbon electrode for the selective and sensitive determination of Epinephrine (EP), Uric acid (UA), Xanthine (XA), and Hypoxanthine (HX) individually as well as simultaneously. Different perspectives of electrocopolymer formation and involved reaction mechanisms have been investigated and substantiated via Cyclic voltammetry, ATR and Raman spectroscopy. This copolymer modification enables the formation of well-defined peaks for the analytes and under optimised conditions, the designed sensor possess wide linear range with limit of detection of 9.22×10-7 M, 5.147×10-7 M, 1.260×10-7 M, and 2.406×10-7 M for EP, UA, XA, and HX, respectively. Scan rate studies were well employed to derive the mechanistic aspects behind the electrooxidation reactions. The credibility in measurements were validated via repeatability, reproducibility, and stability studies. Also, the feasibility of the proposed sensor was examined in real samples and the results obtained were validated via traditional analytical techniques which demonstrates its practical utility in real time monitoring.