Alternative solvent-based methyl benzoate vortex-assisted dispersive liquid-liquid microextraction for the high-performance liquid chromatographic determination of benzimidazole fungicides in environmental water samples: Sample Preparation

A simple co-precipitation sorbent-based preconcentration method for the analysis of fungicides in water and juice samples by high-performance liquid chromatography coupled with photodiode array detection

A magnesium hydroxide co-precipitation sorbent-based method in the presence of an anionic surfactant (e.g., sodium dodecylbenzenesulfonate) and high-performance liquid chromatography were used to preconcentrate and analyze fungicides in water and apple juice samples. The preconcentration procedure can be accomplished in a single step based on the co-precipitation of target fungicides and magnesium chloride in the presence of surfactant in a sodium hydroxide solution (pH 11) and a white precipitate gel was simply obtained after centrifugation. The property of precipitate phase was subsequently characterized using Fourier-transform infrared spectroscopy, scanning electron microscopy, and X-ray diffractometry. Under the optimum conditions, the developed method exhibited good sensitivity, with an enrichment factor of 11–18 and limits of detection of approximately 1–5 μg/L for water samples and 7–10 μg/L for apple juices. High reproducibility was achieved with a relative standard deviation of less than 11%, and a good recovery range of 72% to 120% was also obtained. The proposed method was shown to be a simple preconcentration procedure for concentrating fungicides in the samples investigated.

Determination of benzimidazoles in fruits by open-tubular capillary electrochromatography based on ionic liquids grafted covalent organic frameworks

A novel capillary electrochromatography method has been developed for the simultaneous quantification of ten benzimidazole fungicides in fruits. Herein, covalent organic frameworks (COFs) and ionic liquids (ILs) were successfully introduced to prepare open-tubular capillary column to improve the loading capacity and separation performance. The parameters effecting the analytical performance including pH and concentration of running buffer, separation voltage and the addition of organic solvent were investigated systematically. Under the optimized conditions, the method allowed the baseline separation of ten benzimidazole fungicides, and showed a good linearity in the range of 3.5-200 μg kg^-1 with the detection limits between 1.0 and 2.8 μg kg^-1. The intraday and interday precisions for recoveries were lower than 7.9% and 12.2%, respectively. Intraday and interday precisions for their retention times were lower than 3.2% and 6.6%, respectively. Satisfactory recoveries for grape, pear and orange samples at two concentrations were obtained ranging from 85.0 to 95.9% with RSDs lower than 7.8%, demonstrating the potential applications of the open-tubular capillary electrochromatography method for trace benzimidazole fungicides analysis in fruits.

Matrix solid-phase dispersion based on cucurbit[7]uril-assisted dispersive liquid-liquid microextraction coupled with high performance liquid chromatography for the determination of benzimidazole fungicides from vegetables

A new method involving matrix solid-phase dispersion (MSPD) and dispersive liquid-liquid microextraction (DLLME) was optimized with the aid of stoichiometry and applied to the extraction, purification, and determination of benzimidazole residues in vegetables. Carbendazim, thiabendazole, and thiophanate-methyl were selectively extracted from vegetables using cucurbit[7]uril as the MSPD extractant and transferred to an aqueous solution, then further enriched using DLLME with acetonitrile and chloroform as dispersive and extraction solvents, respectively. The optimal extraction conditions of MSPD and DLLME were selected by two-level full-factorial design and central-composite design (CCD). The developed method (MSPD-DLLME-HPLC-UV) showed good linearity in the range of 0.025-5 μg/g, with R² > 0.9984. Intra- and interday precisions were 5.3-10.9% and 10.6-12.4%, respectively, and the limit of detection was between 0.004 and 0.007 μg/g of fresh weight. This method was applied to the analysis of four different types of vegetables, and the recoveries ranged from 65.4% to 124.0%. The method was environmentally friendly, easy to operate, and sensitive.

Pretreatment and determination methods for benzimidazoles: An update since 2005

Benzimidazoles, commonly used as pesticides and veterinary drugs, have posed a threat to human health and the environment due to unreasonable use and lack of valid regulation. Therefore, an up-to-date and comprehensive summary of the pretreatment and analytical approaches in different substrates is urgently needed. The present review consequently updates and covers various newly developed pretreatment methods (e.g., cationic micellar precipitation, magnetic-solid phase extraction, hollow fiber liquid phase microextraction, disperse liquid-liquid microextraction-solidified floating organic drop, stir cake sorptive extraction, solid phase microextraction method, QuEChERS, and molecular imprinted polymer-based methods) since 2005. The review also elaborates and discusses different determination methods (e.g., newly developed HPLC and related methods, improved spectrofluorimetry methods, capillary electrophoresis, and the electrochemical sensor). Furthermore, some critical points and prospects are highlighted, to describe the trends in this area.

A preconcentration method for analysis of neonicotinoids in honey samples by ionic liquid-based cold-induced aggregation microextraction

A preconcentration approach based on ionic liquid-based cold-induced aggregation microextraction for determination of neonicotinoid insecticide residues in honey samples before high-performance liquid chromatographic analysis has been developed. Room temperature ionic liquid [C4MIM][PF6] (extraction solvent) and SDS (emulsifier) was used for extraction of the target analytes. The parameters affecting the extraction efficiency were optimized. The optimum microextraction conditions were 200µL room temperature ionic liquids [C4MIM][PF6] containing 0.05molL(-1) SDS, 0.75g sodium carbonate, vortex agitation speed of 1800rpm for 30s and centrifugation at 3500rpm for 10min. Under optimum conditions, the high enrichment factors of 200 could be obtained, leading to low limit of detection (0.01µgL(-1) for all analytes) with the relative standard deviations lower than 2.68% and 5.38% for retention time and peak area, respectively. Good recoveries for the spiked target neonicotinoids at three different concentrations of honey samples were obtained in 86-100% and relative standard deviations were lower than 8.1%. The results demonstrated that the proposed method can be used as an alternative powerful method for the simultaneous determination of the studied insecticides in real honey samples.

Experimental and density functional theory study of Raman and SERS spectra of 5-amino-2-mercaptobenzimidazole

Raman spectroscopy, surface-enhanced Raman spectroscopy (SERS) and density functional theory (DFT) simulations were employed to study 5-amino-2-mercaptobenzimidazole (5-A-2MBI) molecules. Ag colloids were used as SERS substrates which were prepared by using hydroxylamine hydrochloride as reducing agent. Raman vibration modes and SERS characteristic peaks of 5-A-2MBI were assigned with the aid of DFT calculations. The molecular electrostatic potential (MEP) of 5-A-2MBI was used to discuss the possible adsorption behavior of 5-A-2MBI on Ag colloids. The spectral analysis showed that 5-A-2MBI molecules were slightly titled via the sulfur atoms adhering to the surfaces of Ag substrates. The obtained SERS spectral intensity decreased when lowering the 5-A-2MBI concentrations. A final detection limit on the concentration of 5×10(-7) mol · L(-1) was gained. SERS proved to be a simple, fast and reliable method for the detection and characterization of 5-A-2MBI molecules.