Determination of theophylline in serum by a simple enzyme method and by liquid chromatography.

Theophylline in serum was estimated by three methods. Two of them are based on high pressure liquid chromatography. A reversed phase method was chosen as reference method. Liquid chromatography on a straight phase was compared with this method. A third method was based on inhibiting alkaline phosphatase enzyme activity. Samples of test serum and patients' serum were analysed. The precision and accuracy of the methods were estimated by linear regression analysis. Some other aspects like duration of analysis and cost were also investigated. Generally, straight phase liquid chromatography was the method of choice because of its simplicity, high selectivity and relatively low cost.