Neonicotinoids with a 6‐chloropyridinyl group (e.g. imidacloprid, acetamiprid, thiacloprid, nitenpyram, boscalid) – Determination of 6‐chloronicotinic acid in urine by GC‐MS [Biomonitoring Methods, 2018]

Abstract

The working group „Analyses in Biological Materials“ of the Permanent Senate Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area verified the presented biomonitoring method. Neonicotinoids with a 6‐chloropyridinyl structure are metabolised in warm‐blooded organisms to 6‐chloronicotinic acid that is excreted in urine. This analytical method permits the specific quantification of 6‐chloronicotinic acid in urine. For determination, 2 mL of a urine sample are hydrolysed using 500 µL concentrated hydrochloric acid to cleave the conjugates, which are subsequently extracted with methyl tert‐butyl ether. The solvent is evaporated to dryness under a stream of nitrogen and the residue is dissolved in acetonitrile. Then 6‐chloronicotinic acid is derivatised with hexafluoroisopropanol (HFIP) in the presence of diisopropylcarbodiimide. In a subsequent washing and extraction step, the formed HFIP ester is extracted using isooctane and an aliquot is injected in the GC‐MS system for quantitative analysis. Calibration is performed using calibration standards that are prepared in pooled urine and processed in the same way as the samples to be analysed. The method was extensively validated and the reliability data were confirmed by an independent laboratory, which has established and cross‐checked the whole procedure.