Single-Laboratory Validation of a Multi-residue Method for Simultaneous Analysis of Multi-class Pesticides in Turmeric by Liquid Chromatography Tandem Mass Spectrometry.

Background: For years, turmeric has been used in several cuisines worldwide because of its proven health benefits. However, as its cultivation often involves applications of polar and semi-polar pesticides, their residues might cause health hazards to consumers. The dearth of a validated LC-MS/MS method for the residue analysis of these pesticides in turmeric has warranted the present study.

Objective: The aim was to develop and validate a multi-residue method for simultaneous determination of multi-class pesticides in turmeric (both rhizome and powder) by LC-MS/MS.

Method: Both the rhizome and powder samples (1 kg) were soaked in water for 30 min, followed by homogenization. Each homogenate (2 g) was mixed with 10 mL water, and extracted with acetonitrile (10 mL) in the presence of acetic acid and NaCl. The extract was cleaned by using dispersive solid phase extraction (dSPE) with graphitized carbon (5 mg/mL) sorbent. The cleaned extract was measured by LC-MS/MS with a runtime of 20 min. The method was validated on 211 multi-class pesticides.

Results: The method performance was satisfactory at 10 ng/g and higher levels, in compliance with the SANTE/12682/2019 guidelines. The dSPE cleanup was effective in minimizing the matrix effects. The use of matrix-matched calibrations specific for turmeric powder and rhizome corrected all recoveries within the satisfactory range of 70-120%. The precision -RSDs were <20% for all test pesticides. The Horwitz ratio and measurement uncertainty results were satisfactory as well.

Conclusions: As the method was convenient, selective, accurate, and repeatable, it is recommended for regulatory and commercial testing purposes.

Highlights: For the first time, this study reports a validated LC-MS/MS method for the multi-residue analysis of pesticides in turmeric. The method provided a high throughput analysis of multi-class pesticides in turmeric rhizome and powder matrices with satisfactory selectivity, sensitivity, accuracy, and precision. The method performance satisfied the requirements of the SANTE/12682/2019 guidelines, and the method sensitivity complied with the EU-MRL requirements.