Determination of thiamine using continuous flow molecular emission cavity analysis

Abstract

A continuous flow method for the determination of thiamine hydrochloride (20.0–240.0 µg ml^–1, 5.9 × 10^–5–7.1 × 10^–4M) is described. The sample was mixed with an excess of sodium hydroxide and remained in the delay coil for 20 min at 90 °C. The solution was then mixed with an excess of orthophosphoric acid and the hydrogen sulphide evolved was transferred continuously into the cavity to generate a molecular emission of S₂. The analysis is completely automated, requires no sample pre-treatment and samples can be analysed at a rate of 30 samples h^–1 with a relative error of 1–2%. The method was evaluated by carrying out an interference study with common excipients and other water-soluble vitamins, a recovery study and by the analysis of commercial formulations. Results compared well with those obtained using the official method. The method was also applied to content uniformity tests.