Chiral Separation of Lorazepam on Ovomucoid-Bonded Columns: Peak Coalescence Due to Racemization

Abstract

Racemic lorazepam (LZ) was separated on an ovomucoid (OVM)-bonded column by changing the column temperature. Chromatographic peak coalescence, appearing as a plateau between the resolved peaks, was observed above column temperatures of 15°C. Each LZ enantiomer was isolated on another chiral column using a non-aqueous eluent. Racemization of each LZ enantiomer in two different solutions and peak coalescence on these chiral columns were investigated. These results revealed that the peak coalescence should be due to racemization of LZ on the OVM-bonded column. By reducing the column temperature to 7°C, the enantiomeric composition of LZ before chromatography could be determined on the OVM-bonded column.