Simultaneous Determination and Separation of Several Barbiturates and Analgesic Products by Ion-Pair High-Performance Liquid Chromatography

Abstract

A sensitive, rapid, and accurate high-performance liquid chromatographic method for the simultaneous determination of several barbiturates and analgesic drugs is described. Reversed-phase ion-pair chromatography, using 1-decanesulfonic acid sodium salt as the counterion, was used. The method is rapid because no sample extraction is involved. Internal standards were used for the quantification. A μ Bondapak C₁₈ column with a mobile phase of 0.01M KH₂PO₄ and acetonitrile (7:3) pH 3.2 for barbiturates and (1:1) pH 7.9 for propoxyphene HCl or napsylate was used at a flow rate of 1.0 mL/min. The barbiturates and propoxyphene compounds were monitored at 214 nm and 220 nm respectively. Precision and ruggedness (relative standard deviation) were below 1.0%. The detection limit ranged from 0.05 μ/mL to 0.1 ng/mL, depending on the compound. The method is stability indicating and can be applied to bulk pharmaceutical chemicals.