Direct determination of theophylline in human serum by high-performance liquid chromatography using zwitterionic micellar mobile phase. Comparison with an enzyme multiplied immunoassay technique

Abstract

A liquid chromatographic procedure is reported for the direct determination of theophylline in human serum. It includes the use of a micellar zwitterionic mobile phase [10^–3 mol l^–1 3-(dimethyldodecylammonio)] propanesulfonate (also known as C₁₂ DAPS)z–propanol (97 + 3, v/v) and a µBondapak phenyl column. Detection is based on ultraviolet absorption at a wavelength of 273 nm. After dilution with the mobile phase, the serum is injected into the chromatography; no solvent extraction or deproteinization is performed. The linearity of the method described was excellent over the range 0.5–20 mg l^–1. The within-run precision was better than 2%, and the recovery of the theophylline approached 98%. Two hundred direct injections of serum samples did not affect the column life. The total analysis time, including chromatography, was approximately 15 min. As little as 0.5 mg l^–1 of theophylline could be detected, and the results were in good agreement with those of an enzyme multiplied immunoassay technique.