Studyonthephotolysisandhydrolysischaracteristicsofprocymidone

In order to study the photolysis characteristics of procymidone, a gas chromatography with electronic capture detection (GC-ECD) method for the determination of procymidone residue on rape leaves was developed by extraction with acetonitrile and purification through florisil column. Under indoor simulation conditions, the photodegradation behavior of procymidone on rape leaves, and the effects of different initial concentration of procymidone, pH buffers, concentrations of NO₃^-, NO₂^-, Fe²⁺ and Fe³⁺ on the photodegradation of procymidone in aqueous solution were studied. The photolysis products of procymidone in methanol, acetone and acetonitrile were identified by gas chromatography-electron impact ionization mass spectrometry (GC-EIMS). Besides, the effects of different pH buffers, anionic and cationic surfactants on the hydrolysis of procymidone were investigated. The results showed that the recoveries of procymidone from rape leave samples at the spiked concentrations of 0.05, 0.2, 2 and 12 mg/kg were 80%-100% with the relative standard dissipation of 2.3%-7.8%. The dissipation dynamics of procymidone on the leaf surface of rape accorded with the first-order kinetic equation, and the dissipation half-life of procymidone under UV lamp was 1.03 h. The photodegradation rate of procymidone was decreased with the increase of the initial concentration. Procymidone was stable under acidic conditions, while it easily photolyzed under alkaline conditions. NO₃^-, NO₂^-, Fe²⁺ and Fe³⁺ inhibited the photodegradation of procymidone in aqueous solution. Therefore they were the photoquenching agents of procymidone. Two photolysis products of procymidone in methanol, acetone and acetonitrile were identified as monochlorination C₁₃H₁₂ClNO₂ and demethylation C₁₂H₉Cl₂NO₂, respectively. The hydrolysis of procymidone was easier under alkaline conditions, but slowly under acidic conditions. The anionic surfactant sodium dodecyl sulfate (SDS) had no effect on the hydrolysis of procymidone. However, the cationic surfactant cetyl trimethyl ammonium bromide (CTAB) promoted the hydrolysis. This study provides a reference for the reasonable application and environmental safety evaluation of procymidone.