Enantiomer resolution and assay of propionic acid-derived herbicides in formulations by using chiral liquid chromatography and achiral gas chromatography

Enantiomers of 6 propionic acid-derived herbicides in the form of their esters were resolved using liquid chromatography with a chiral column. Free acids are converted to methyl esters by means of a BF3-catalyzed reaction. Chromatographic resolutions for 6 of 8 herbicides investigated were in the range of 2 to 4. The method was applied for the simultaneous determination of mecoprop and 2,4-D content and individual mecoprop enantiomers in 2 formulations containing racemic and R-mecoprop in mixture with 2,4-D. Precision and accuracy of content determination was comparable to standard methods, and enantiomer contents were in good agreement with declared values. The enantiomers of dichlorprop and mecoprop were also resolved as diastereomeric menthyl esters by achiral high resolution gas chromatography (HRGC). HRGC data on enantiomer composition were in good agreement with those from the LC method and other data.