In situ growth of copper-based metal-organic framework on a helical shape copper wire as a sorbent in stir-bar sorptive extraction of fenthion followed by corona discharge ion mobility spectrometry.

In this paper, a helical copper wire, coated with copper-benzene-1,4-dicarboxylic acid metal-organic framework (Cu-BDC) was used as a sorbent for stir-bar sorptive extraction of fenthion from water and fruit samples. The homogenous coating was fabricated through two simple and fast steps. The chemical conversion of copper substrate to copper hydroxide nanotubes (Cu(OH)2 NTs) was performed in an alkaline solution and then Cu-BDC was formed through a neutralization reaction. Corona discharge ion mobility spectrometry in positive mode was applied for the detection of fenthion. To improve the sensitivity of the method, some synthesis and extraction parameters affecting the extraction efficiency such as benzene-1,4-dicarboxylic acid concentration, ionic strength, sample pH, stirring rate, extraction temperature, and extraction time were investigated. The linear dynamic range between 0.5 and 80 µg L-1 and detection limit of 0.1 µg L-1 were obtained under optimal conditions. The intra- and inter-day relative standard deviations were less than 6.4 and 8.6%, respectively. The applicability of the method was examined for the analysis of different samples (i.e., well water, agricultural wastewater, and orange). The recovery for the determination of fenthion in spiked samples varied from 88 to 111%.

Simultaneous Analysis of Fenthion and Its Five Metabolites in Produce Using Ultra-High Performance Liquid Chromatography-Tandem Mass Spectrometry.

A simultaneous analytical method for the organophosphorus insecticide fenthion and its five metabolites (fenthion oxon, fenthion oxon sulfoxide, fenthion oxon sulfone, fenthion sulfoxide, and fenthion sulfone) was developed based on ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Five matrices (brown rice, chili pepper, orange, potato, and soybean) were selected to validate the method. The target compounds were analyzed using positive electrospray ionization in the multiple reaction monitoring mode. For the best sensitivity in regard to the detector response, water and methanol containing formic acid (0.1%) were selected as the mobile phase. The optimum extraction efficiency was obtained through a citrate-buffered QuEChERS (quick, easy, cheap, effective, rugged, and safe) method. Recovery tests were carried out at three spiking levels (n = 3). At all fortification levels, the accuracy and precision results were between 70% and 120% with a relative standard deviation of ≤15%. The limit of quantitation was 0.01 mg/kg, and the correlation coefficients (r2) of the matrix-matched calibration curves were >0.99. Significant signal suppression in the detector responses were observed for all matrices, suggesting that a compensation method, such as matrix-matched calibration, is required to provide accurate quantitative results. The applicability of the presented method was confirmed for the simultaneous analysis of fenthion and its metabolites in various crops.

Detection of chemical residues in tangerine juices by a duplex immunoassay.

A rapid duplex ELISA for the simultaneous determination of two of the most widely used organophosphorous insecticides in tangerine juices is described. To accomplish this aim, two individual enzyme-linked immunosorbent assays for chlorpyrifos and fenthion pesticides were integrated into one ELISA test. The strategy uses 96-well plates with specific wells coated with the corresponding haptenized conjugate. The optimized duplex ELISA was accomplished within 40 min achieving a detection limit of 0.20±0.04 µg/L and 0.50±0.06 µg/L, for chlorpyrifos and fenthion, respectively in tangerine juice samples. The determination of residues of both pesticides was carried out by simple sample dilution, without any extra sample clean-up procedure. Results of testing precision, stability, and selectivity demonstrated that the assay provided reliable analytical performances for the simultaneous determination of residues of chlorpyrifos and fenthion in fruit juice samples below the established European maximum residue limits (MRL). In addition, the accuracy and reliability of this duplex bioanalytical method is demonstrated by analyzing blind spiked juice samples and the results, correlated well with those achieved using a well-established GC/MS method (recoveries between 95% and 106%).

Comparison of matrix solid-phase dispersion and liquid-liquid extraction for the chromatographic determination of fenthion and its metabolites in olives and olive oils.

Matrix solid-phase dispersion (MSPD) methodology has been developed to extract fenthion and its metabolites from olives and olive oils, and the technique compared with conventional liquid-liquid extraction (LLE). The method was applied to olives and olive oil samples obtained from olive groves treated with fenthion. Pesticide residues were analysed by gas chromatography (GC) using a nitrogen-phosphorus detector. Both extraction methods gave a linear response over the concentration range assayed (0.03-1 mg kg-1 for MSPD and 0.1-1 mg kg-1 for LLE). Recoveries and RSD (n = 6) values in olives were 85-112% and 2-6% for MSPD, and 68-108% and 4-16% for LLE, respectively. In the case of olive oil, recoveries and RSD (n = 6) values were 67-98% and 5-11% for MSPD, and 63-115% and 6-14% for LLE, respectively. When compared to LLE, the newly developed MSPD method was twice as sensitive and required 10 times less sample weight.