Optimization and Validation of a Multiresidue Method for Screening of 126 Pesticide Residues in Herbal Raw Materials and Extracts Used as Ingredients in Ayurvedic Medicines and Dietary Supplements

BACKGROUND: Testing for pesticide levels in herbal products is an important aspect in determining product safety. Plants and their extracts are widely used as ingredients in botanical dietary supplements and traditional medicines. The extracts of plants, especially those prepared out of organic solvents, are rich in secondary metabolites and pigments, and adequate clean-up is required since the extracts completely dissolve in organic solvents. OBJECTIVE: The study aims at reporting a multiresidue analytical method for 126 different pesticides in raw material biomass as well as extracts of plants, which are widely used as ingredients in ayurvedic medicines as well as dietary supplements using LC-MS/MS and GC-MS/MS with a rugged sample preparation technique for accurate results. METHOD: QuEChERS (quick, easy, cheap,effective, rugged, and safe) procedure, gel permeation chromatography (GPC), GPC coupled with solid phase extraction (SPE), and liquid-liquid extraction (LLE) coupled with SPE sample preparation methods were compared against each other for suitability to test pesticides in selected herbal raw materials and their alcoholic and aqueous extracts. The standard addition method was used for quantifying the level of pesticides below 10 μg/kg. RESULTS: Single laboratory validation for sample preparation involving GPC and SPE resulted linearity in the range of 2.5-500 ng/mL, average intraday and interday precision of 6.6% RSD, and average recovery (spiked at 10 μg/kg) of 92% for all analytes tested. The method was repeatable with different analysts and days. CONCLUSIONS: The sample preparation technique combining GPC and SPE as well as LLE and SPE was the most suitable for the selected herbal alcoholic extracts, whereas any of the regular techniques involving LLE, SPE, and QuEChERS were suitable for raw material biomass as well as aqueous extracts. HIGHLIGHTS: The method was found to be capable of determining selected pesticides in the selected matrixes at 10 μg/kg concentration. Provision of recycling solvents used in the GPC+SPE method was adopted to make the method environmentally friendly.