POTENTIOMETRIC MICROTITRATION OF VITAMIN-B-1 WITH PHOSPHOTUNGSTIC ACID BY USING A PHOSPHOTUNGSTATE-SENSITIVE ELECTRODE AND ITS APPLICATION TO THE ANALYSIS OF PHARMACEUTICAL PREPARATIONS

A method for the determination of micro-amounts of vitamin B-1 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 war 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 B-1, 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.