Detection of herbicide clopyralid at nanogram per gram level in agricultural products using easy-to-use micro liquid–liquid extraction followed by analysis with ultraperformance liquid chromatography–tandem mass spectrometry

•We developed a sample preparation method to analyze clopyralid in crop samples.•Micro liquid–liquid extraction was used effectively for sample extract cleanup.•No matrix effect was found to interfere with the analysis of clopyralid.•The proposed analytical method showed good recovery, accuracy, and sensitivity. A new sample preparation method was developed for auxin-like herbicide clopyralid residue in agricultural products. The method uses extraction with sulfuric acid – acidified acetonitrile, with cleanup of sample extracts using solid-phase extraction (diatomaceous earth) and micro liquid–liquid extraction, followed by ultraperformance liquid chromatography–tandem mass spectrometry (UPLC–MS/MS). This sample preparation method greatly reduces the influence on ionization during determination with UPLC–MS/MS. Quantification was achieved using external calibrators prepared in matrix-free 0.1% formic acid. The proposed analytical method supported good recovery of 73.7–91.4% with less than 8% relative standard deviation. Method quantification limits (MQL) of samples were 0.6–1.0 ng g–1. The method was applied to determine clopyralid residue in several crop samples. The herbicide was detected as near the MQLs in all samples.