Determination of eflornithine enantiomers in plasma by precolumn derivatization with o-phthalaldehyde-N-acetyl-l-cysteine and liquid chromatography with UV detection

A bioanalytical method for indirect determination of eflornithine enantiomers in 75 microL human plasma has been developed and validated. L- and D-eflornithine were derivatized with o-phthalaldehyde and N-acetyl-L-cysteine to generate diastereomers which were separated on two serially connected Chromolith Performance columns (RP-18e 100 x 4.6 mm i.d.) by a isocratic flow followed by a gradient flow for elution of endogenous compounds. The diastereomers were detected with UV (340 nm). The between-day precisions for L- and D-eflornithine in plasma were 8.4 and 2.3% at 3 microm, 4.0 and 5.1% at 400 microm, and 2.0 and 3.7% at 1000 microm. The lower limit of quantification was determined to be 1.5 microm, at which precision was 14.9 and 9.9% for L- and D-eflornithine, respectively.