Determination of felbamate concentration in pediatric samples by high-performance liquid chromatography

A simple and rapid procedure to determine felbamate (2-phenyl-1,3-propanediol dicarbamate) concentrations in human plasma/serum by high-performance liquid chromatography is described. The method employs a high-performance liquid chromatography unit equipped with a C18 reverse-phase cartridge (3-microliters particle diameter, 3.2 x 40 mm), an acetonitrile/water gradient, and detection at 210 nm. The sample is deproteinized with acetonitrile containing internal standard (2-methyl-2-phenyl-1,3-propanediol dicarbamate), and the resulting supernatant, after diluting 1:1 with water, is injected onto the column. The felbamate and internal standard are eluted with a linear gradient of 0% to 22% acetonitrile for 11 minutes at a flow rate of 0.8 ml/minute. Under these conditions, felbamate and the internal standard are eluted at 9.2 +/- 0.03 and 10.8 +/- 0.03 minutes, respectively. The assay is linear from 10 to 400 microgram/ml. It is highly reproducible; at 100 micrograms/ml felbamate, within-day and between-day coefficients of variation are less than 0.5% and 4.3%, respectively. Recovery is > or = 95%. No interferences from other common antiepileptic drugs and analgesics are observed. Advantages of this method include simple and fast sample preparation; use of a gradient to eliminate interferences; and use of a cartridge column, which is economical, provides good resolution, allows rapid equilibration and elution, and operates at low back pressures. The method requires samples of only 100 microliters and is ideal for pediatric samples.