Development of an analytical method for the determination of pesticides in tropical fruits by LC-QTOF-MS/MS after QuEChERS extraction sample cleanup and DLLME preconcentration

In this study, QuEChERS extraction was combined with dispersive liquid-liquid microextraction (DLLME) to extract pesticides from tropical fruits for determination by a highly accurate and sensitive liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-QTOF-MS/MS) system. The QuEChERS method served as a matrix clean-up tool and the DLLME method preconcentrated the analytes for their determination at trace levels. All parameter variables of the DLLME method were optimized to improve the extraction output and lower the limits of detection and quantification (LOD and LOQ) for all the analytes. Under the optimum experimental conditions, the LOD and LOQ values were found in the range of 0.004-0.013 and 0.27-0.61μg l-1, respectively. The detection limits achieved by direct LC-QTOF-MS/MS analysis were increased by about 10-260 folds using the optimized DLLME method. To assess the accuracy and applicability of the developed method, spike recovery experiments on tropical fruits were carried out. The matrix matching calibration method was used to enhance the quantification accuracy of the analytes in kiwi, pineapple, and mango matrices, with percent recoveries ranging between 89 and 117%.

A method for determining valproic acid in human whole blood and urine via gas chromatography-mass spectrometry and small-scale inter-laboratory trial

A simple and cost-effective method for analyzing valproic acid (VPA) in biological samples was developed. VPA was extracted in methyl tertiary-butyl ether (MTBE) and derivatized using trimethylsilyldiazomethane. The MTBE extract was analyzed by gas chromatography-mass spectrometry (GC-MS). The extraction recovery in human whole blood and urine was over 90 %, with good linearity in the range of 1.0 to 250 µg/mL of VPA. The RSD for 2.0, 20, and 200 μg/mL VPA in whole blood ranged from 0.9 to 4.7 % for intra-day and 1.5 to 5.9 % for inter-day. The RSD for 2.0, 20, and 200 μg/mL VPA in urine ranged from 1.9 to 2.6 % for intra-day and 1.2 to 2.9 % for inter-day. As a preliminary cross-validation study, a cross-check was conducted using blinded concentration samples. The results demonstrated that the assay data of the two laboratories were comparable.

Comparison of the short-chain fatty acids in normal rat faeces after the treatment of Euphorbia kansui, a traditional Chinese medicine for edoema

Context: As a toxic traditional Chinese medicine for edoema, Euphorbia kansui S.L. Liou ex S.B. Ho (Euphorbiaceae) (EK) stir-fried with vinegar for detoxification was associated with alterations of gut microbiota. However, the evidence of correlation between short-chain fatty acids (SCFAs) and toxicity of EK has not been confirmed.Objective: In order to study the biological basis of detoxification of EK stir-fried with vinegar (VEK), a rapid, sensitive and validated GC-MS method was developed to determine SCFAs in normal rat faeces after given EK and VEK.Materials and methods: Sprague Dawley rats were orally administered 0.5% CMC-Na (control group), EK (EK-treated group) and VEK powder (VEK-treated group) at 680 mg/kg for six consecutive days (eight rats each group). Fresh faeces samples were promptly collected, derivatized and then analyzed by GC-MS.Results: The ranges of LOD and LOQ were within 0.13-1.79 and 0.45-5.95 μg/mL, respectively. The RSD values of intra-day and inter-day precisions were less than 15%. Four SCFAs were generally stable under four storage conditions. The extraction recoveries were ranged from 53.5% to 97.3% with RSD values lower than 15%. The concentrations of four SCFAs in EK and VEK were decreased significantly compared with those not administered (EK-treated, p < 0.01; VEK-treated, p < 0.05 and p < 0.01). After being stir-fried with vinegar, the concentrations were all increased (p < 0.05 and p < 0.01).Discussion and conclusions: The negative correlation between SCFAs and toxicity of EK may provide evidence for biological mechanism and toxic Chinese medicine.

Simultaneous Determination of Valproic Acid and Its Major Metabolites by UHPLC-MS/MS in Chinese Patients: Application to Therapeutic Drug Monitoring

A specific and sensitive Ultra-high Performance Liquid Chromatography-tandem Mass spectrometry (UHPLC-MS/MS) method was developed for the simultaneous determination of the concentrations of valproic acid (VPA) and its clinically relevant metabolites (4-ene-VPA, 2,4-diene-VPA and 2-ene-VPA) in human serum. After solid-phase extraction, VPA, its metabolites and the internal standard were subjected to chromatographic separation by gradient elution of acetonitrile and 10 mM ammonium acetate as mobile phase at a flow rate of 0.6 mL/min on an EC-C18 column. The method was validated over the concentration ranges of 1-200 μg/mL for VPA, 0.5-10 μg/mL for 2-ene-VPA, 10-500 ng/mL for 4-ene-VPA and 25-500 ng/mL for 2,4-diene-VPA. The inter-day and intra-day accuracy and precision were within the acceptable limits of <15 %. The recoveries and matrix effects met the requirement for the analysis of biological samples. No obvious degradation was observed under various storage conditions including room temperature for 12 h, three freeze-thaw cycles and -80°C for 1 month. The assay method was successfully applied to monitor the concentration of VPA and its three metabolites in epileptic patients. The UHPLC-MS/MS method demonstrated a good analytical performance essential for therapeutic drug monitoring, which would potentially lead to clinically relevant improvements in VPA dosage and patient management.

Current state of bioanalytical chromatography in clinical analysis

Chromatographic methods have become popular in clinical analysis in both routine and research laboratories.