Extraction and Preconcentration of Some Triazole Pesticides in Grape Juice by Salting Out Homogeneous Liquid–Liquid Extraction in a Narrow-Bore Tube Prior to Their Determination by Gas Chromatography–Flame Ionization Detection

Trace-Level Determination of Triazole Fungicides Using Effervescence-Assisted Liquid-Liquid Microextraction Based on Ternary Deep Eutectic Solvent Prior to High-Performance Liquid Chromatography

A simple and sensitive preconcentration method, namely, effervescence-assisted liquid-liquid microextraction based on the ternary deep eutectic solvent method, was developed for enrichment of triazole fungicide residues prior to their determination by high-performance liquid chromatography coupled with UV detection. In this method, a ternary deep eutectic solvent (as extractant) was prepared by combination of octanoic acid, decanoic acid, and dodecanoic acid. The solution was well dispersed with sodium bicarbonate (as effervescence powder) without using auxiliary devices. In order to obtain relatively high extraction efficiency, analytical parameters were investigated and optimized. Under optimum conditions, the proposed method showed good linearity within the range of 1-1000 μg L^-1 with a coefficient for determination (R²) greater than 0.997. The low limits of detection (LODs) were in the range of 0.3-1.0 μg L^-1. The precisions were assessed from the relative standard deviations (RSDs) of retention time and peak area obtained from intra- (n = 3) and inter-day (n = 5 × 5) experiments, which were greater than 1.21 and 4.79%, respectively. Moreover, the proposed method provided high enrichment factors ranging from 112 to 142 folds. A matrix-match calibration method was used for analysis of real samples. Finally, the developed method was successfully applied for determination of the triazole fungicide in environmental water (near agricultural area), honey, and bean samples, and it represents a promising alternative method for analysis of triazoles. The recoveries of the studied triazoles were obtained in the range of 82-106% with an RSD less than 4.89.

Magnetic dispersive solid-phase extraction of some pesticides from fruit juices using monodisperse nanosorbent combined with dispersive liquid-liquid micro-extraction

In this study, the new synthesized magnetic nanoparticles based on amorphous carbon have been used as a sorbent in magnetic dispersive solid-phase extraction prior to dispersive liquid-liquid micro-extraction. The developed method was applied for analysis of ten pesticides from different fruit juice samples by gas chromatography-flame ionization detection. In this work, a few mg of the sorbent is added into an aqueous solution containing the analytes. Adsorption and desorption of the compounds of interest are accelerated by vortexing and sonication, respectively. To achieve high enrichment factors, a suitable organic solvent (iso-propanol) is used to elute the target analytes from the nanosorbent. The obtained iso-propanol is phased and 1,1,2-trichloroethane are employed as the disperser and extraction solvents, respectively, in the following micro-extraction procedure. The synthesized magnetic nanoparticles were characterized by scanning electron microscope, X-ray diffraction, vibrating sample magnetometer, and Fourier-transform infrared spectrophotometer. To achieve the high extraction efficiency and optimum conditions, all parameters that could affect the extraction yield were investigated. Under optimum conditions, the method had broad linear ranges with a proper linearity (r² ≥ 0.9987). Limits of detection and quantification for analysis of the selected pesticides were found in the ranges of 0.5-1.0 and 1.7-3.3 µg L^-1, respectively. High enrichment factors and extraction recoveries were obtained in the ranges of 321-438 and 64-88%, respectively. To evaluate repeatability of the method, it was performed on two sets of standard solutions at the concentrations of 10 and 50 µg L^-1 (each analyte). Relative standard deviations varied in the ranges of 2-6% and 4-7% for intra- (n = 6) and inter-day (n = 5) precisions, respectively.

Covalent organic framework in situ grown on Fe3O4 hollow microspheres for stir bar sorptive-dispersive microextraction of triazole pesticides

Based on covalent organic framework (COF) 1,3,5-tris-(4-formylphenyl)benzene-benzidine (TFPB-BD) in situ grown on Fe₃O₄ hollow microspheres and combined with gas chromatography-flame thermionic detector, a rapid and simple stir bar sorptive-dispersive microextraction method was developed for the determination of five triazole pesticides (paclobutrazol, hexaconazole, flusilazole, propiconazole, and tebuconazole). The synthesized TFPB-BD/Fe₃O₄ microspheres were characterized by transmission electron microscope, vibrating sample magnetometer, and thermogravimetric analysis, which showed that the material has strong magnetism and higher load capacity of COF. Under optimal conditions, the extraction equilibrium could be achieved within 9 min with detection limits of 0.17-1.48 μg L^-1 (S/N = 3) and a linear range of 5-1000 μg L^-1. The developed method was applied to the determination of trace triazole pesticides in apples, pears, and cabbages with recoveries from 81 to 117%.

Combination of a dispersive solid phase extraction method based on octadecylamine modified magnetic nanoparticles with dispersive liquid-liquid microextraction for the extraction and preconcentration of pesticides

In the present work, a new and efficient sorbent has been prepared using the co-precipitation method for magnetic dispersive solid phase extraction followed by dispersive liquid-liquid microextraction. This method was used for the extraction and preconcentration of some widely-used pesticides (chlorpyrifos, haloxyfop-R-methyl, oxadiazon, diniconazole, clodinafop-propargyl, fenpropathrin, and fenoxaprop-P-ethyl) from fruit juices prior to their determination by gas chromatography-flame ionization detection. The sorbent was prepared by octadecylamine co-precipitation with Fe₃O₄. In the first step, mg amount of the magnetic sorbent was spread into an aqueous sample solution including the selected analytes and vortexed. Then the analytes were eluted with acetonitrile from the surface of the nanoparticles separated with an external magnetic field from the aqueous solution. In the second step, the obtained eluent was mixed with an extraction solvent (chloroform) at the μL-level and rapidly injected into deionized water. After centrifugation, an aliquot of the sedimented phase was injected into the separation system. Experimental parameters which control the performance of both steps were investigated and optimized. Using optimum extraction conditions, the proposed method provided low limits of detection (0.23-0.41 μg L^-1) and quantification (0.81-1.3 μg L^-1), high enrichment factors (353-443), acceptable extraction recoveries (70-88%), and satisfactory relative standard deviations (≤6%) for intra- (n = 6) and inter-day (n = 4) precisions at a concentration of 30 μg L^-1 of each pesticide.

An In Situ Formation of Ionic Liquid for Enrichment of Triazole Fungicides in Food Applications Followed by HPLC Determination

An in situ formation of ionic liquid was used for preconcentration of four triazole fungicides in food samples. The microextraction method was used for the first time in the literature for preconcentration of triazole fungicides. In the developed method, tributylhexadecylphosphonium bromide ([P₄₄₄₁₂]Br) and potassium hexafluorophosphate (KPF₆) were used for the formation of hydrophobic ionic liquid. After centrifugation, the fine microdroplets were produced in one step, providing the extraction step in a quick and environmentally friendly manner. The functional group of the hydrophobic ionic liquid was investigated using FT-IR. Various extraction parameters were studied and optimized. In the extraction method, 0.01 g of [P₄₄₄₁₂]Br and 0.01 g of KPF₆, centrifugation at 4500 rpm for 10 min were used. The optimized technique provided a good linear range (90-1000 μg L^-1) and high extraction recovery, with a low limit of detection (30-50 μg L^-1). Methods for the proposed in situ formation of ionic liquid were successfully applied to honey, fruit juice, and egg matrices. The recoveries were obtained in a satisfactory range of 62-112%. The results confirmed the suitability of the proposed microextraction method for selective extraction and quantification of triazole fungicides.

Preparation of magnetic MOFs for use as a solid-phase extraction absorbent for rapid adsorption of triazole pesticide residues in fruits juices and vegetables

Detection of low levels of triazole fungicides in agricultural product matrices is important. Although several detection methods have been developed, all have some drawbacks, such as being time-consuming, requiring complex sample pretreatment, and consuming large volumes of organic solvents. There is an urgent need for a simple and rapid detection method for triazole fungicides. In this study, the adsorbent composite material magnetic MOFs based on Fe₃O₄-MWCNT was synthesized by in-situ polymerization at room temperature, and was applied to extract triazole pesticides from fruits and vegetables. High-performance liquid chromatography-tandem mass spectrometry was used for quantification. Under optimized conditions, the constructed detection method showed a low detection (LOD) of 0.52-1.83 μg/L (S/N = 3) and wide linear range of 5.00-500.00 μg/L for triazole fungicides in the fruit and vegetable samples. The method recovery for spiked fungicides (10, 50, and 100 μg/L) in cabbage, spinach, orange juice, and apple juice ranged from 62.80% to 94.20%. The constructed detection method has a lower detection limit than previously reported methods and has a higher sensitivity for triazole pesticide residues in complex matrices.

Multi-residue analysis of pesticides in blood plasma using hollow fiber solvent bar microextraction and gas chromatography with a flame ionization detector

The challenges faced on pesticide extraction from biological samples are finding a method that allows a multi-residue extraction, pre-concentration, clean-up, and isolation of analytes in just one step. In this sense, the hollow fiber - liquid phase microextraction method (HF- LPME) in the "solvent bar" mode was used to optimize and validate a method for pesticide multi-residue analysis in blood plasma at trace levels, through gas chromatography coupled with a flame ionization detector (GC-FID). Hollow fiber solvent bar microextraction HF-SBME was carried out with octanol immobilized into the pores of hydrophobic polypropylene fiber and disposed within a matrix of blood plasma, spiked with a mixture of pesticides (monocrotophos, lindane, aldrin, methyl parathion, endosulfan, dieldrin, DDD, DDT, and endrin). The optimization parameters evaluated were: extraction temperature and time, stirring speed, and salt concentration. A principal component analysis was performed to visualize the analytes' behaviour based on their explained variance, and then, a Box-Behnken analysis was generated to identify the optimum parameters. According to the PCA, all pesticides showed similar responses to the extraction method and the response of dieldrin exhibit the lowest variance. Moreover, the stationary points selected from the Box-Behnken analysis were 25.5 °C for the extraction temperature, 870 rpm for stirring speed, 16 min for extraction time, and 8.3 % w/v of salt concentration. Moreover, the validation results proved that HF-SBME is an alternative technique for pesticide multi-residue extraction in blood plasma. The analytes were able to concentrate, reaching 46 fold enrichment. The solvent type, sample and solvent volume were narrowed down without changing the method's precision or accuracy. The relative standard deviation was under 10 %, and the recovery was between 55 % and 105 % for the different analytes excepting lindane, which had lower recovery (27 %). The detection limits were 0.02 until 0.13 μg mL^-1 for most of the pesticides used. Finally, HF-SBME is a good alternative for pesticide multi-residue extraction in complex matrices like plasma.