INVESTIGATIONS ON THE PHOTOLYSIS OF IMAZETHAPYR IN AQUEOUS SOLUTIONS UNDER DIRECT SUNLIGHT BY HPLC UV AND LC-MS/MS-ESI - APPLICATIONS OF GREEN ALGA AS A POTENTIAL BIOMARKER

Abstract

Photolysis of Imazethapyr was studied in Milli-Q water, in acidic (pH 5.0), neutral (pH 7.0) and basic (pH 7.0) buffer solutions at two concentration levels 1.0 µg/ml and 2.0 µg/ml under direct sunlight. Aliquots of water samples were collected, filtered and analysed by HPLC-UV detection at different predetermined intervals. The results showed a limit of quantification (LOQ) 0.01 µg/ml and the recovery was 96 to 105%. The degradation of Imazethapyr under direct sunlight was considerably more rapid than hydrolysis in dark with a half-life of 2.2, 2.4 and 2.6 days for acidic, neutral and basic buffer solutions respectively. The estimated DT50 value of Imazethapyr in hydrolysis study was 22.7 days in acidic, 24.5 days in neutral and 26.4 days in basic buffer solutions. The dissipation followed first order kinetics. The influence of cations - Fe2+, Cu2+, Co2+, Ni2+, Mn2+, Zn2+and anions - SO42- , Cl- , ClO4- , CO3- , HCO3- and aeration of oxygen was studied. Major photo transformation products were identified in water using liquid chromatography electrospray tandem mass spectrometry (LC-MS/MS-ESI). The data was compared with similar hydrolysis study conducted at 25°C. The impact of residues if any, present in the aqueous samples after the quantitative indication of residues to below the detectable level was studied by alga bioassay test. Residues dissipated to below detectable level on 15th day. The growth inhibition at this occasion was 65%. Observations on 40th day showed no sign of inhibition in the growth of green alga.