DETERMINATION OF ENANTIOMERIC PURITY OF PACLOBUTRAZOL AND FLUAZIFOP-P-BUTYL USING A DIODE-LASER-BASED POLARIMETRIC HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY DETECTOR

Enantiomeric purities of resolved enantiomers of the agrochemicals paclobutrazol (I) and fluazifop-P-butyl (II) have been determined using a diode-laser-based polarimetric high-performance liquid chromatography detector. Reversed-phase achiral chromatography was used with polarimetric and absorbance detectors in series to measure optical rotation, α, and absorbance, A. In blind trials enantiomer mole fractions in unknowns, xu, were calculated from a standard, xs, and α/A values using the equation (α/A)u/(α/A)s = (2xu - 1)/(2xs - 1). The method always gave xu within 1% of actual values. 95% confidence limits were roughly twice those from chiral chromatography and better than conventional polarimetry. The linear range of the polarimetric detector was 0.02 - 10 mg ml-1 for I and 0.1 - 10 mg ml-1 for II (20 μl injection). Limits of detection for I and II of 0.19 and 1.0 μg correlate with specific rotations of the compounds. © 1990.