Simultaneous enantiomeric determinations of acid and ester imidazolinone herbicides in a soil sample by two-dimensional direct chiral liquid chromatography.

A two-dimensional HPLC method for the simultaneous direct chiral enantiomeric determination of acid and ester IMI herbicides has been described. Difficulties arising from differences in polarity were overcome. Firstly, the imazaphyr, imazethapyr and imazamethabenz methyl herbicides were separated in a C18 achiral column. Then, their respective enantiomers were separated using a protein chiral AGP(TM) column; a heart-cut mode was used. Mobile phases of the two systems were compatibilized, after optimizing by factorial design using multiple response analysis. The proposed method has been validated by recovery studies from an enriched soil sample. Important enantiomer parameters such as enantioresolution higher than 1.12, enantiomeric ratio (ER) close to 1 and enantiomeric fraction (EF) around 0.5 were obtained for standards, confirming that herbicides are present as racemates.