PVC Membrane and Coated Graphite Sensors for the Determination of Vitamin B1

Vitamin B1, also known as thiamine or thiamin or "thio-vitamine" is used by all living organisms. The compound is synthesized by bacteria, fungi, and plants, and hence animals have to obtain it from external sources. Vitamin B1 is an essential nutrient for human beings too. The present work focuses on the development of symmetric and asymmetric PVC membrane sensors for the selective determination of Thiamine. The membranes were prepared through the incorporation of thiamine-tetraphenyl borate ion-pairs, as the ionophore, in PVC membranes, based on different plasticizers (i.e. dibutyl phthalate (DBP), benzyl acetate (BA) and nitrobenzene (NB)). Based on the results of the optimization experiments, the best sensor performance was found in the case of DBP-based membranes. The optimal symmetric electrodes were found to produce fast and stable Nernstian responses from in thiamine solution in the concentration window of 5.0×10-6-1.0×10-1 mol L-1, while the asymmetric sensors (the graphite coated electrodes) led to linear responses in the range of 5.0×10-7 – 1.0×10-2 mol L-1. The electrodes revealed pH independent responses in the pH range of 2.0-5.0. The validation of the methods, based on the application of the developed sensors, revealed the devices to be suitable for application in the analysis of the target species in pharmaceutical formulations.