Electrochemical determination of paraquat in potato, lemon, orange and natural water samples using sensitive-rich clay carbon electrode

Paraquat and Diquat: Recent Updates on Their Pretreatment and Analysis Methods since 2010 in Biological Samples

Paraquat (PQ) and diquat (DQ) are quaternary ammonium herbicides which have been used worldwide for controlling the growth of weeds on land and in water. However, PQ and DQ are well known to be toxic. PQ is especially toxic to humans. Moreover, there is no specific antidote for PQ poisoning. The main treatment for PQ poisoning is hemoperfusion to reduce the PQ concentration in blood. Therefore, it is essential to be able to detect PQ and DQ concentrations in biological samples. This critical review summarizes the articles published from 2010 to 2022 and can help researchers to understand the development of the sample treatment and analytical methods for the determination of PQ and DQ in various types of biological samples. The sample preparation includes liquid-liquid extraction, solid-phase extraction based on different novel materials, microextration methods, and other methods. Analytical methods for quantifying PQ and DQ, such as different chromatography and spectroscopy methods, electrochemical methods, and immunological methods, are illustrated and compared. We focus on the latest advances in PQ and DQ treatment and the application of new technologies for these analyses. In our opinion, tandem mass spectrometry is a good choice for the determination of PQ and DQ, due to its high sensitivity, high selectivity, and high accuracy. As far as we are concerned, the best LOD of 4 pg/mL for PQ in serum can be obtained.

Analytical Performance of Clay Paste Electrode and Graphene Paste Electrode-Comparative Study

The analytical performance of the clay paste electrode and graphene paste electrode was compared using square wave voltammetry (SWV) and cyclic voltammetry (CV). The comparison was made on the basis of a paracetamol (PA) determination on both working electrodes. The influence of pH and SWV parameters was investigated. The linear concentration ranges were found to be 6.0 × 10^-7-3.0 × 10^-5 and 2.0 × 10^-6-8.0 × 10^-5 mol L^-1 for clay paste electrode (ClPE) and graphene paste electrode (GrPE), respectively. The detection and quantification limits were calculated as 1.4 × 10^-7 and 4.7 ×10^-7 mol L^-1 for ClPE and 3.7 × 10^-7 and 1.2 × 10^-6 mol L^-1 for GrPE, respectively. Developed methods were successfully applied to pharmaceutical formulations analyses. Scanning electron microscopy and energy-dispersive X-ray spectroscopy were used to characterize ClPE and GrPE surfaces. Clay composition was examined with wavelength dispersive X-ray (WDXRF).

Extraction and determination of flubendiamide insecticide in food samples: A review

Flubendiamide (FBD) is the first commercially available phthalic acid diamide that targets ryanodine receptors (RyRs) in insects, which play a major role in lepidoptera control. However, excessive use of FBD can influence the quality of treated products leading to toxic effects on human health. The availability of rapid and convenient methods for evaluating FBD amount in the environment is necessary. Therefore, analytical methods were developed for the determination of residues of FBD and its metabolite desiodo in different food matrices like tomato, cabbage, pigeon pea, apple, chilli and rice. The current review carries forward methods for FBD residues analysis in foods by using several chromatographic techniques including sample preparation steps. The comparison between the different methods employed for quantitative and qualitative analysis of food quality and safety is also discussed. Liquid chromatography (LC) is the predominant analytical method for assessing the quality of foods treated with FBD. Studies related to LC coupled multichannel detector (Ultraviolet (UV), Mass spectrometry (MS)) are also applied to detect pesticide residues. Extraction and clean up steps are essential to obtain reliable results. Moreover, this review reports the allowed limits of residues for the safety of consuming products treated with FBD.

New Trends in Nanoclay-Modified Sensors

Nanoclays are widespread materials characterized by a layered structure in the nano-scale range. They have multiple applications in diverse scientific and industrial areas, mainly due to their swelling capacity, cation exchange capacity, and plasticity. Due to the cation exchange capacity, nanoclays can serve as host matrices for the stabilization of several molecules and, thus, they can be used as sensors by incorporating electroactive ions, biomolecules as enzymes, or fluorescence probes. In this review, the most recent applications as bioanalyte sensors are addressed, focusing on two main detection systems: electrochemical and optical methods. Particularly, the application of electrochemical sensors with clay-modified electrodes (CLME) for pesticide detection is described. Moreover, recent advances of both electrochemical and optical sensors based on nanoclays for diverse bioanalytes’ detection such as glucose, H2O2, organic acids, proteins, or bacteria are also discussed. As it can be seen from this review, nanoclays can become a key factor in sensors’ development, creating an emerging technology for the detection of bioanalytes, with application in both environmental and biomedical fields.

Fabricated Electrochemical Sensory Platform Based on the Boron Nitride Ternary Nanocomposite Film Electrode for Paraquat Detection

Hexagonal boron nitride (BN), an effective diffusion material for mass transport, was functionalized with molybdenum disulfide (MoS₂) and Au nanoparticles (Au NPs). Then, the working electrodes with developed nanomaterials were applied to construct an electrochemical paraquat sensor. BN was prepared using a solid-state synthesis method combined with solvent-cutting. The electrochemical properties of the BN/MoS₂/Au NP-based glassy carbon electrode (GCE) were investigated using differential pulse voltammetry and cyclic voltammetry. An excellent response signal to paraquat was found from 0.1 to 100 μM with a limit of detection of 0.074 μM, and it had acceptable reproducibility (relative standard deviation = 2.99%, n = 5) and good anti-interference ability. The modified GCE showed superior performance owing to the synergistic effects among all three given nanomaterials. With the proposed method, paraquat in grass samples from an orchard was then investigated. The results of the electrochemical analysis agreed with those of experiments and obtained a 96.28% confidence level via high-performance liquid chromatography, exhibiting relatively high stability. Therefore, the fabricated sensor can be a candidate for the determination of paraquat.

A novel electrochemical sensor based on Au nanoparticles/8-aminoquinoline functionalized graphene oxide nanocomposite for paraquat detection

In this paper, a novel electrochemical sensor based on Au nanoparticles/8-aminoquinoline functionalized graphene oxide (AuNPs/GAQ) nanocomposite was developed and tested for the first time for detection of paraquat (PQ). The morphology and composition of AuNPs/GAQ nanocomposite were characterized by various techniques, including transmission electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and x-ray photoelectron spectroscopy. Cyclic voltammetry and differential pulse voltammetry were utilized to investigate the electrochemical performances of AuNPs/GAQ nanocomposite modified glassy carbon electrode. The obtained modified electrode exhibited excellent electrocatalytic activity towards detection of PQ. Under the optimized conditions, the proposed sensor showed low detection limit (6 nM, S/N = 3), wide linear range (0.02-24 μM), high selectivity and good stability. In addition, it was successfully applied for detection of PQ in natural water samples with satisfactory results.

Preparation of Methyl Viologen-Kaolinite Intercalation Compound: Controlled Release and Electrochemical Applications

This work reports the preparation of novel kaolinite nanohybrid material obtained by intercalation of methyl viologen (MV) in the interlayer space of kaolinite, using methoxykaolinite (K-M) as starting material. Characterization of the resulting material (K-MV) confirmed the presence of MV units in the interlayer space of K-M with lateral orientation, associated with a high amount of water molecules due to the hydrophilic nature of MV. The resulting structural formula of this organoclay based on thermogravimetric analysis was Si₂Al₂O₅(OH)_3.72(OCH₃)_0.28(MV)_0.17(H₂O)_0.82. The release of MV from the K-MV composite was studied in order to evaluate the advantages of using this material for pesticide formulation with MV as active ingredient. The localization of MV in the interlayer space of K-M significantly slows its release in water. However, the interactions that retain MV in the interlayer space remain sufficiently less intense to ensure a complete release of MV in a relatively short time (2 h). On the basis of the interactions that ensure MV intercalation in methoxykaolinite, K-M was used as electrode modifier and applied for the electrochemical determination of MV. The electrochemical signal of MV on the K-M modified electrode was 2 times more intense compared to the pristine kaolinite modified electrode. After optimization of experimental parameters, a sensitivity of 3.91 μA M^-1 and a detection limit of 0.14 nM were obtained at the K-M modified electrode. This performance represents one of the most important reported so far in the literature during the electrochemical determination of MV. The sensor was also found very efficient for MV determination in real water systems (well, spring, and tap water) despite the decrease of sensitivity due to the presence of interfering species.