HPLC determination of D and L moxalactam in human serum and urine

A high‐pressure liquid chromatographic procedure was developed to determine the D and L isomers of moxalactam in human plasma and urine. After protein precipitation with hydrochloric acid the sample was extracted with ethyl acetate. It was then back extracted into tromethamine buffer (pH 8.0) and washed with octanol. Extraction recovery from plasma ranged from 73–81%. An aliquot of the tromethamine buffer was then injected onto a C₁₈‐μBondapak column. The mobile phase was 3% acetonitrile in 0.05 M ammonium acetate pH 6.5 buffer. Samples were quantitated by UV detection at 275 nm and 0.01 aufs. The lower limit of detection was 0.5 μg/ml for each isomer. Preliminary stability studies were performed to assess proper sample handling and storage conditions. The procedure was evaluated in a clinical setting to demonstrate its applicability to the study of moxalactam pharmacoki‐netics in critically ill patients.