Capillary electrophoresis of the imidazolinone herbicide imazamox and its metabolites in environmental matrices

Two residue methods were developed for the determination of imazamox in water as well as its two polar metabolites, the hydroxy imazamox and glucose conjugates, in soybean samples. One method utilizes Immunoaffinity Chromatography (IAC) combined with Capillary Electrophoresis, (CE) coupled to UV detection (CE-UV); the other method, uses CE coupled to Mass Spectrometry (MS) to quantitatively determine imazamox via Atmospheric Pressure Ionization in Electro Spray (API-ES) mode in various water samples.; For the soybean seed samples Solid Phase Extraction (SPE) was used as a preliminary cleanup step prior to the IAC. The development of this new and novel technology brings about the marriage of IAC with CE-UV for combined sample preparation, analyte determination and quantitation. In this method, residues are extracted from soybean samples with acidic aqueous-methanol. After preliminary cleanup using solid-phase extraction of imazamox and its metabolites, the analytes are concentrated onto an imidazolinone-specific antibody column. Samples were then desalted using another SPE column prior to analysis with CE. The limit of quantitation (LOQ) by the method was 0.05 ppm for each compound. Rates of recoveries from five spiked soybean seed extracts were 90% with 10.7% standard deviation (%SD), 99.8% with 10.1% SD, and 98.2% with 8.8% SD, for imazamox and its metabolites the hydroxy imazamox and glucose conjugate, respectively.; To determine imazamox residues in the water samples a separate CE-MS method was developed. This method utilizes reversed phase RP-102 SPE to concentrate the imazamox residues from 1-L volumes of water. Imazamox residues are eluted from RP-102 using methanol which is then evaporated. The residues are re-dissolved in appropriate amounts of 0.01% formic acid in water prior to analysis by CE-MS.; Overall mean recoveries of greater than 83% with less than 4% standard deviations (%SD) were achieved for imazamox in all water samples. A Limit of Detection (LOD) of 20 ppt was achieved. The selectivity of CE combined with high sensitivity and specificity of MS allowed analyte quantitation at sub ppb levels. This unique combination of selectivity, sensitivity and specificity offered by CE-MS dramatically reduced sample preparation complexity and time of analysis.