Trace analysis of rimantadine in human urine after dispersive liquid liquid microextraction followed by liquid chromatography-post column derivatization.

The first dispersive liquid liquid microextraction scheme followed by liquid chromatography-post column derivatization for the determination of the antiviral drug rimantadine in urine samples is demonstrated. The effect of the type and volume of organic extraction solvent, type and volume of disperser solvent, sample pH, ionic strength, extraction time, and centrifugation speed on the extraction efficiency were studied. Rimantadine and the internal standard (amantadine) were chromatographed using a reversed phase monolithic stationary phase with a mixture of equal volumes of methanol and phosphate buffer (pH = 3) as mobile phase. On-line post-column derivatization of the analyte was performed using a "two-stream" manifold with o-phthalaldehyde and N-acetyl-cysteine at alkaline medium. Under the optimized extraction conditions, the enrichment factor of rimantadine was 58. The linear range was 5-100 µg/L with correlation coefficient r of 0.9984 while the limit of detection achieved was 0.5 µg/L. The within-day and between-day precision for the tested concentration levels were less than 14.3% and the mean recoveries obtained from the spiked samples were ranged between 87.5 and 113.9%. The main advantages of the proposed method are the simplicity of operation, rapidity, low cost, and low limit of detection of the analyte.