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 μL 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 × 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 μ m , 4.0 and 5.1% at 400 μ m , and 2.0 and 3.7% at 1000 μ m . The lower limit of quantification was determined to be 1.5 μ m , at which precision was 14.9 and 9.9% for L‐ and D‐eflornithine, respectively. Copyright © 2009 John Wiley & Sons, Ltd.