Thiamine-reineckate liquid membrane electrode for the selective determination of thiamine (vitamin B1) in pharmaceutical preparations

Abstract

The construction and electrochemical response characteristics of a liquid membrane electrode for thiamine (vitamin B₁) based on the formation of an ion pair between the thiamine cation and the reineckate anion in nitrobenzene are described. The electrode showed a linear response for thiamine over the concentration range 10^–3–10^–6–M with a cationic slope of 31.6–mV per concentration decade and had a wide working pH range (4–8), fast response time (1–2–min), low detection limit (0.3–µg–ml^–1) good stability and reasonable selectivity. The direct potentiometric determination of vitamin B₁ in some pharmaceutical preparations using the proposed electrode gave an average recovery of 98.1% of the nominal values and a mean standard deviation of 1.3%, which compare fairly well with data obtained using the British and United States pharmacopoeial methods.