Organophosphate (OP) compounds impose significant strains on public health, environmental/food safety and homeland security, once they have been widely used as pesticides and insecticides and also display potential to be employed as chemical warfare agents by terrorists. In this context, the development of sensitive and reliable chemical sensors that would allow in-situ measurements of such contaminants is highly pursued. Here we report on a free-enzyme impedimetric electronic tongue (e-tongue) used in the analysis of organophosphate pesticides comprising four sensing units based on graphene hybrid nanocomposites. The nanocomposites were prepared by reduction of graphene oxide in the presence of conducting polymers (PEDOT:PSS and polypyrrole) and gold nanoparticles (AuNPs), which were deposited by drop casting onto gold interdigitated electrodes. Impedance spectroscopy measurements were collected in triplicate for each sample analyzed, and the electrical resistance data were treated by Principal Component Analysis (PCA), revealing that the system was able to discriminate OPs at nanomolar concentrations. In addition, the electronic tongue system could detect OPs in real samples, where relations between the principal components and the variation of pesticides in a mixture were established, proving to be useful to analyze and monitor mixtures of OP pesticides. The materials employed provided sensing units with high specific surface area and high conductivity, yielding the development of a sensor with suitable stability, good reproducibility, and high sensitivity towards pesticide samples, being able to discriminate concentrations as low as 0.1nmolL. Our results indicate that the e-tongue system can be used as a rapid, simple and low cost alternative in the analyses of OPs pesticide solutions below the concentration range permitted by legislation of some countries.
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The increasing demand for food production has necessitated
the
development of sensitive and reliable methods of analysis, which allow
for the optimization of storage and distribution while ensuring food
safety. Methods to quantify and monitor volatile and biogenic amines
are key to minimizing the waste of high-protein foods and to enable
the safe consumption of fresh products. Novel materials and device
designs have allowed the development of portable and reliable sensors
that make use of different transduction methods for amine detection
and food quality monitoring. Herein, we review the past decade’s
advances in volatile amine sensors for food quality monitoring. First,
the role of volatile and biogenic amines as a food-quality index is
presented. Moreover, a comprehensive overview of the distinct amine
gas sensors is provided according to the transduction method, operation
strategies, and distinct materials (e.g., metal oxide semiconductors,
conjugated polymers, carbon nanotubes, graphene and its derivatives,
transition metal dichalcogenides, metal organic frameworks, MXenes,
quantum dots, and dyes, among others) employed in each case. These
include chemoresistive, fluorometric, colorimetric, and microgravimetric
sensors. Emphasis is also given to sensor arrays that record the food
quality fingerprints and wireless devices that operate as radiofrequency
identification (RFID) tags. Finally, challenges and future opportunities
on the development of new amine sensors are presented aiming to encourage
further research and technological development of reliable, integrated,
and remotely accessible devices for food-quality monitoring.
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