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

Synthesis of composite materials combining magnetic metal-organic frameworks and conjugated organic frameworks for selective extraction of carbendazim and thiabendazole residues from Chinese herbal medicine samples

A magnetic metal-organic framework MIL-68(Al) and a covalent organic framework were used as magnetic solid-phase extraction (MSPE) adsorbents in combination with high-performance liquid chromatography ultraviolet detection (HPLC-UV) to detect carbendazim (CBZ) and thiabendazole (TBZ). The main parameters affecting the extraction in the MSPE process were studied and optimized. Fe3O4@MIL-68(Al) coated with 1,3,5-tris(4-aminophenyl)benzene and terephthaldehyde (Fe3O4@MIL-68(Al)@TAPB-PDA-COF) was analyzed and verified. The material was proven to be suitable for adsorbing CBZ and TBZ. Various adsorption models were used to study its adsorption mechanism. The adsorption results were in good agreement with the pseudo-second-order kinetic model and Langmuir isotherm model. The maximum adsorption capacities of Fe3O4@MIL-68(Al)@TAPB-PDA-COF over CBZ and TBZ were 54.24 and 67.87 mg g-1, respectively, and the equilibrium adsorption time was 200 min. Fe3O4@MIL-68(Al)@TAPB-PDA-COF with excellent recyclability showed higher adsorption capacity and selectivity. A method based on Fe3O4@MIL-68(Al)@TAPB-PDA-COF combined with HPLC-UV was established under the optimal extraction conditions and used to separate and detect trace imidazole drugs in Chinese herbal samples, achieving a low limit of detection (0.65-1.30 μg L-1) with excellent linear correlation (r > 0.999). The recovery rate and relative standard deviation were 86.05-99.78 % and 0.15-4.90 %, respectively. Therefore, the Fe3O4@MIL-68@TAPB-PDA-COF can be regarded as an effective adsorbent for the pretreatment of CBZ and TBZ drugs in Chinese herbal samples.

Qualitative and quantitative analysis of four benzimidazole residues in food by surface-enhanced Raman spectroscopy combined with chemometrics

In this study, surface-enhanced Raman spectroscopy (SERS) combined with chemometric methods were developed for qualitative and quantitative analysis of four benzimidazole (BMZs) residues in corn. Sulfhydryl functionalized Fe₃O₄@SiO₂@Ag-SH magnetic SERS substrates were prepared to obtain the SERS spectra of four BMZs for chemometric analysis. The partial least squares regression discrimination analysis (PLS-DA) model performed best, with a recall rate upwards 99.17%, and could successfully distinguish four BMZs. Under the support vector machine regression (SVR) model, the detection limits of carbendazim, benomyl, thiophanate-methyl and thiabendazole were 0.055 mg/L, 0.056 mg/L, 0.067 mg/L and 0.093 mg/L, respectively; the average recovery was in the range of 85.6%-107.5%. Furthermore, the method verified by HPLC, and the results showed that there was no significant difference between two methods (p > 0.05). Therefore, the strategy based on SERS coupling chemometrics can be served as a promising tool for rapid determination of BMZs residues in food.

Nanographite-assisted matrix solid phase dispersion microextraction of active and toxic compounds from complex food matrices using cyclodextrin aqueous solution as elution solvent

In this study, a cyclodextrin aqueous solution was used as an environmentally friendly eluent to simultaneously extract active and toxic compounds from food matrices with the aid of nanographite-assisted matrix solid phase dispersion microextraction (NG-MSPDM). The NG-MSPDM procedure was optimized by single-factor experiments and response surface methodology to obtain optimum conditions. The proposed method achieved excellent linearity at 0.10-20 μg/mL for all target analytes with a coefficient of correction (R²) ≥ 0.9909, limits of detection < 52.01 ng/mL, satisfactory reproducibility below 3.21 %, and acceptable recoveries of 82.0-112 %. To accurately determine the target components in the complex matrix, collision cross-section values of the analytes were obtained using ion mobility quadrupole time-of-flight mass spectrometry (IM-Q-TOF/MS). Results indicated that the NG-MSPDM method successfully achieved the simultaneous extraction of flavonoids and phenoxyacetic herbicides from Alpinia officinarum.

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.

Silver ions involved fluorescence "on-off" responses of gold nanoclusters system for determination of carbendazim residues in fruit samples

Herein, a fluorescence "on-off" system was developed for monitoring carbendazim (CBZ) residues in fruit samples, based on glutathione-gold nanoclusters (GSH-Au NCs) and silver ions (Ag⁺). First, the fluorescence intensity of GSH-Au NCs was greatly enhanced (turn on) with aggregation-induced emission enhancement (AIEE) effect in the presence of Ag⁺, then fluorescence quenching occurred (turn off) with adding CBZ by the chelation between CBZ and Ag⁺. The quenching degree was well linearly dependent on CBZ concentration covering from 0.5 to 20 μM. Moreover, the GSH-Au NCs-Ag⁺ system exhibited superior selectivity towards CBZ and was sensitive for the determination of CBZ in apple and orange juices with a low detection limit of 0.12 μM. The recoveries of CBZ spiked in fruit samples ranged from 81.0 % to 111.4% with the relative standard deviations less than 6.6%, demonstrating its great potential for monitoring CBZ residues in fruit samples.