Simultaneous determination of paclobutrazol and myclobutanil enantiomers in water and soil using enantioselective reversed-phase liquid chromatography

Abstract

A sensitive reversed phase-liquid chromatography (RP-LC) method for the simultaneous separation and determination of paclobutrazol and myclobutanil enantiomers in water and soil was developed. The method involved a solid phase extraction of paclobutrazol and myclobutanil enantiomers from water and soil by using C₁₈ Bond-Elut column. The LC system consisted of a reversed phase cellulose tris-3,5-dimethylphenyl carbamate (CDMPC) chiral stationary phase (CSP) with a mobile phase of methanol–water with UV detection. The calibration curve for each enantiomer was linear from 0.5–20 μg mL⁻¹. Under suitable conditions, recoveries for all enantiomers were above 75% at two concentration levels in water and soil. Within-day and day-to-day assay precisions (RSDs, %) were below 9% for each enantiomer at concentrations of 0.5, 1.0, 5.0 μg mL⁻¹. The method precisions (RSDs, %) were in the range of 3.83–11.5%. The limit of quantification (LOQ) of each enantiomer was 0.0025 μg mL⁻¹ using 200.0 ml of water and 0.020 μg g⁻¹ using 25.0 g of soil. The limit of detection (LOD) for each enantiomer in water was 0.0015 μg mL⁻¹ and in soil 0.012 μg g⁻¹ (S/N = 3). In addition, circular dichroism (CD) and UV spectra were obtained by stopped flow scanning.