Dissipation kinetics and degradation mechanism of amicarbazone in soil revealed by a reliable LC-MS/MS method

A sensitive and reliable analytical method was developed for simultaneous determination of amicarbazone (AMZ) and its two major metabolites including desamino amicarbazone (DA) and isopropyl-2-hydroxy-DA-amicarbazone (Ipr-2-OH-DA-AMZ) in soil for the first time. Targeted analytes were extracted and purified using a modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) procedure, and then analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) with a total run time of 9 min. The established approach was extensively validated by determining the linearity (R-2 >= 0.99), recovery (84-96), sensitivity (limits of quantification at 5-10 mu g kg(-1)), and precision (RSDs <= 12 %). Based on the methodological advances, the subsequent dissipation kinetics and degradation mechanism of amicarbazone in soil were thoroughly investigated in an illumination incubator. As revealed, AMZ was easily degraded with the half-lives of 13.9-19.7 days in soil. Field trial results of AMZ (40 g a.i. ha(-1)) in Shanghai showed that the residues of AMZ and its metabolite Ipr-2-OH-DA-AMZ decreased from 0.505 mg kg(-1) (day 50) to 0.038 mg kg(-1) (day 365) and from 0.099 mg kg(-1) (day 50) to 0.028 mg kg(-1) (day 365), respectively, while the content of DA increased from 0.097 mg kg(-1) (day 50) to 0.245 mg kg(-1) (day 365). This study provided valuable data to understand the toxicity of AMZ and substantially promote its safe application to protect environment and human health.