Use of liquid chromatography–tandem mass spectrometry for quantitative analysis of clopyralid in compost and forage

In this study, we first developed a technique to quantify clopyralid using liquid chromatography–tandem mass spectrometry (LC/MS/MS) and tested its performance for compost and corn plant samples. Then, we measured the uptake of clopyralid by forage corn grown on two types of soil mixed with clopyralid-contaminated compost, in order to investigate the potential of ingestion of compost clopyralid by animals through forage crops. Because of the high recovery ratios (80–82% for compost and 98% for corn), sufficient theoretical quantification limits (5.0 and 1.7 μg kg−1 fresh matter, respectively) and close agreement with the bioassay method (73 μg kg−1 for LC/MS/MS and 80 μg kg−1 for bioassay), the LC/MS/MS method was considered to be of potential value for determining clopyralid in compost and plant materials. Corn plants took up clopyralid from soil (compost), with the amount and rate of uptake varying with soil types and application of activated carbon to soil. There is a need for quantifying clopyralid uptake by a range of forage crops under a range of cultivation conditions (e.g. climate, soil, management) to estimate clopyralid fluxes through the manure–forage–animal–manure pathway.