Potentiometric microtitration of vitamin B1 with phosphotungstic acid by using a phosphotungstate-sensitive electrode and its application to the analysis of pharmaceutical preparations

Abstract

A method for the determination of micro-amounts of vitamin B₁ by direct potentiometric titration in aqueous medium with a standard phosphotungstic acid solution is described. A graphite electrode coated with a PVC matrix membrane containing the benzyldimethyltetradecylammonium–phosphotungstate ion association complex as electroactive material and dioctyl phthalate as plasticizer was constructed and used in conjunction with a Ag–AgCl double-junction reference electrode to detect the end-point of the titration. This method gave very satisfactory results in the range 1–4 mg of vitamin B₁, also in comparison with other methods; the recoveries were 100.00 ± 0.25% and the mean relative standard deviation was 0.22%. The method was successfully applied to the analysis of pharmaceutical preparations.