Square wave voltammetric determination of methiocarb insecticide based on multiwall carbon nanotube paste electrode

Breaking boundaries: Artificial intelligence for pesticide detection and eco-friendly degradation

Pesticides are extensively used agrochemicals across the world to control pest populations. However, irrational application of pesticides leads to contamination of various components of the environment, like air, soil, water, and vegetation, all of which build up significant levels of pesticide residues. Further, these environmental contaminants fuel objectionable human toxicity and impose a greater risk to the ecosystem. Therefore, search of methodologies having potential to detect and degrade pesticides in different environmental media is currently receiving profound global attention. Beyond the conventional approaches, Artificial Intelligence (AI) coupled with machine learning and artificial neural networks are rapidly growing branches of science that enable quick data analysis and precise detection of pesticides in various environmental components. Interestingly, nanoparticle (NP)-mediated detection and degradation of pesticides could be linked to AI algorithms to achieve superior performance. NP-based sensors stand out for their operational simplicity as well as their high sensitivity and low detection limits when compared to conventional, time-consuming spectrophotometric assays. NPs coated with fluorophores or conjugated with antibody or enzyme-anchored sensors can be used through Surface-Enhanced Raman Spectrometry, fluorescence, or chemiluminescence methodologies for selective and more precise detection of pesticides. Moreover, NPs assist in the photocatalytic breakdown of various organic and inorganic pesticides. Here, AI models are ideal means to identify, classify, characterize, and even predict the data of pesticides obtained through NP sensors. The present study aims to discuss the environmental contamination and negative impacts of pesticides on the ecosystem. The article also elaborates the AI and NP-assisted approaches for detecting and degrading a wide range of pesticide residues in various environmental and agrecultural sources including fruits and vegetables. Finally, the prevailing limitations and future goals of AI-NP-assisted techniques have also been dissected.

A portable smartphone-assisted digital image fluorimetry for analysis of methiocarb pesticide in vegetables: Nitrogen-doped carbon quantum dots as a sensing probe

The increasing use of pesticides in the agriculture fields strengthen the crop production to meet the needs of increasing population. The residues in water and food materials cause several health hazards. Herein, nitrogen-doped carbon quantum dot (N-CQDs) is designed for determination of methiocarb pesticide in vegetables by fluorescent paper sensor and compared the results with fluorimetry. The fluorescent paper-based detection is performed by recording the change in fluorescence of N-CQDs with introduction of methiocarb using smartphone and ImageJ software. Good linear range was acquired for analysis of methiocarb from 10 to 1000 μgL^-1 with a low detection limit (LOD) of 3.5 μgL^-1 in fluorimetry; and 700-10,000 μgL^-1 with a LOD of 500 μgL^-1 in fluorescent paper sensor. A better recovery from 92.0 to 95.4% illustrating the selectivity of both methods for analysis of methiocarb in vegetables. Thus, the advantage of using N-CQDs as a fluorescent sensor for analysis of methiocarb in vegetables is instrument free, portable and user-friendly.

2D Ti3C2Tx flakes prepared by in-situ HF etchant for simultaneous screening of carbamate pesticides

Present work reports preparation of colloidal single/few layer Ti₃C₂T_x MXene flakes using minimally intensive layer delamination (MILD) method for rapid electroanalytical screening of carbamate pesticides. Lithium fluoride salt and hydrochloric acid (7.5 M LiF/9M HCl) was used to produce in-situ generated HF as etchant to remove Al successfully from Ti₃AlC₂ MAX phase. Unlike the clay method (5 M LiF/6M HCl), this methodology simplified Ti₃C₂T_x synthesis protocol resulting in Li⁺ ions intercalated Ti₃C₂T_x which was delaminated without further sonication. The delaminated Ti₃C₂T_x flakes were found to be single/few layered sheets with mostly -OH and -O terminated surface groups. The characteristic 002 peak observed in X-ray diffraction (XRD) at 2θ = 6.4° with interplaner distance of 1.1137 nm suggested broadening of the peak attributed to the presence of Li⁺ ions between Ti₃C₂T_x flakes. Delaminated Ti₃C₂T_x flakes were utilized as working electrode which demonstrated simultaneous and selective detection of carbamate pesticides methiocarb and diethofencarb by voltammetry. The oxidation peaks of the two pesticides were well separated by a potential difference of 0.35 V in 0.5 M H₂SO₄ and DPV detection limits were calculated as 0.19 μg mL^-1 and 0.46 μg mL^-1 for methiocarb and diethofencarb respectively. Ti₃C₂T_x flakes as electrochemical sensor exhibited long term stability and acceptable recoveries in real sample for environmental applications.

Voltammetric Pathways for the Analysis of Ophthalmic Drugs

Background:

This review investigates the ophthalmic drugs that have been studied with voltammetry in the web of science database in the last 10 years.

Introduction:

Ophthalmic drugs are used in the diagnosis, evaluation and treatment of various ophthalmological diseases and conditions. A significant literature has emerged in recent years that investigates determination of these active compounds via electroanalytical methods, particularly voltammetry. Low cost, rapid determination, high availability, efficient sensitivity and simple application make voltammetry one of the most used methods for determining various kinds of drugs including ophthalmic ones.

Methods:

In this particular review, we searched the literature via the web of science database for ophthalmic drugs which are investigated with voltammetric techniques using the keywords of voltammetry, electrochemistry, determination and electroanalytical methods.

Results:

We found 33 types of pharmaceuticals in nearly 140 articles. We grouped them clinically into seven major groups as antibiotics, antivirals, non-steroidal anti-inflammatory drugs, anti-glaucomatous drugs, steroidal drugs, local anesthetics and miscellaneous. Voltammetric techniques, electrodes, optimum pHs, peak potentials, limit of detection values, limit of quantification values, linearity ranges, sample type and interference effects were compared.

Conclusion:

Ophthalmic drugs are widely used in the clinic and it is important to determine trace amounts of these species analytically. Voltammetry is a preferred method for its ease of use, high sensitivity, low cost, and high availability for the determination of ophthalmic drugs as well as many other medical drugs. The low limits of detection values indicate that voltammetry is quite sufficient for determining ophthalmic drugs in many media such as human serum, urine and ophthalmic eye drops.

PC software-based portable cyclic voltammetry system with PB-MCNT-GNPs-modified electrodes for E. coli detection

PC software-based portable cyclic voltammetry (PCV) systems have the advantages of portability, high performance, and real-time detection. In this paper, the PCV system used cyclic voltammetry (CV) as the main detection and analysis method and contained the following components: a three-electrode unit, a portable potentiostat, and PC software. The PC software was used as the system control and display, and a dynamic peak position adjustment (DPPA) algorithm for E. coli measurements based on thick biofilm modification on electrodes was designed especially for this system to realize the real-time correspondence between the measured results and the modified electrodes. The performance test results obtained by setting different detection parameters in the PCV system were compared with those of commercial electrochemical workstations. The difference was less than 4.99%, with a relative standard deviation less than 0.20%. An electrochemical biosensor based on a Prussian blue-multiwalled carbon nanotube-gold nanoparticle composite was developed for E. coli detection. After constructing an antibody-BSA-E. coli electrode modification on the sensor, experimental data processed by the DPPA algorithm showed that the logarithm (lg Df_E.coli) of the E. coli dilution factor and the peak current response had a linear relationship. The PCV system could quickly and accurately detect E. coli concentrations with dynamic adjustment algorithms for biofilm-modified electrodes. Furthermore, the system could detect the electrochemical activities of various high-sensitivity biomolecules, showing great detection potential for on-site monitoring and meeting the requirements of real-time and portable detection in various food safety fields.

Larvicidal activity of synthetic tropane alkaloids against Ascia monuste orseis (Lepidoptera: Pieridae)

BACKGROUND

Tropane alkaloids are known to play a role in plant defence. By blocking acetylcholine receptors, they exert insecticidal and deterrent effects against herbivore insects. Carbamates are an important class of chemical insecticides that also inhibit acetyl cholinesterase. The objective of this work was to synthesise a series of tropane alkaloids bearing a carbamate group, and to evaluate their effects against the pest Ascia monuste. The effects of the most active compounds were evaluated on the A. monuste predator Solenopsis saevissima and on the pollinator Tetragonisca angustula.

RESULTS

The synthesis of carbamate-tropane alkaloids was accomplished in 4-5 steps from commercially available ketones. Results from bioassays showed that compounds 6a, 10a and 14a presented higher activities against second-instar larvae of A. monuste, with LD₅₀ values of 1.01, 3.76 and 1.92 µg substance mg^-1 insect, and TL₅₀ values of 7.0, 15.0 and 5.0 h respectively. These compounds were also tested for their selectivity in favour of S. saevissima and T. angustula. Compound 6a, which showed the highest activity against A. monuste, also showed lower toxicity against S. saevissima.

CONCLUSION

Tropane alkaloid derivatives bearing a carbamate group show potential for the development of novel insecticides against A. monuste. © 2017 Society of Chemical Industry.

Determination of carnosic acid in Rosmarinus officinalis L. using square wave voltammetry and electrochemical behavior

A new, fast, sensitive and simple voltammetric method is established for the direct determination of carnosic acid (CA). And the electroreduction of carnosic acid (CA) was studied using electrochemical methods. The number of electrons transferred in electrode mechanisms were calculated for reversible and adsorption-controlled electrochemical reduction of CA at 17 mV versus Ag/AgCl at pH 7.0 in Britton–Robinson buffer (BR) on a hanging mercury drop electrode. Square-wave voltammetry was developed and validated for direct determination of CA. Square-wave parameters were optimized as accumulation potential = 0.0 mV, accumulation time = 5 s, frequency = 50 Hz, pulse amplitude = 50 mV, and staircase step potential = 5 mV. The developed method displays three linear responses from 2 to 9 μM, 10 to 30 and 40 to 90 μM for carnosic acid with a correlation coefficient of 0.996, 0.999 and 0.999. The detection limits were found to be 1.5 μM, 4.0 μM and 40.1 μM, respectively. The interference effect of most common organic and inorganic species was investigated. Proposed method was successfully applied for determination of CA in natural extract of rosemary and the average content was determined as 11.9 ± 1.0 (μg CA/1 g rosemary). The results were in agreement with that obtained by HPLC-UV comparison method. The developed method can be widely used in routine quality control of herbal materials as well as other in foods, medicinal, pharmaceutical and environmental analysis.