Determination of pentoxifylline in pharmaceutical formulations using iodine as oxidizing agent.

Simple, selective and sensitive spectrophotometric methods are described for the determination of pentoxifylline, based on the haloform reaction with a known and excess of standard iodine solution under alkaline conditions. The excess of iodine is determined at pH 3.0 with metol-isoniazid (lambda(max)=620 nm; method A) or wool fast blue BL (lambda(max)=540 nm, method B). All the variables have been optimised and the reaction mechanisms presented. Regression analysis of Beer's law plots showed good correlation in the concentration ranges 4.0-24.0 and 0.4-2.4 mg ml(-1) for methods A and B respectively. No interferences were observed from excipients and the validity of the methods was tested by analysing pharmaceutical formulations. Recoveries were 99.0-100.0%. The concentration measurements were reproducible within a relative standard deviation of 1.0%.