A selective optosensor for UV spectrophotometric determination of thiamine in the presence of other vitamins B Original Research Article

A flow-through UV-photometric sensor for the rapid, sensitive and selective determination of thiamine in the presence of riboflavin, pyridoxine and hydroxocobalamine was developed. The active solid phase of the optosensor was the cationic resin Sephadex CMC-25 placed in a quartz flow cell of 1 mm of optical path length. Thiamine was transitorily retained on this active microzone and its intrinsic absorbance monitored at 247 nm. Three calibration lines were constructed by using 300, 600, and 1000 μl, respectively of injected sample volume. Their linear dynamic ranges were 2.0–33.0, 1.0–20.0 and 0.6–12.0 μg ml−1 and their RSD (%) 0.8, 0.9 and 1.8 for the determination of 28, 15 and 9 μg ml−1, respectively, with sampling frequency of 18, 16 and 14 h−1. The chemicals of the B-complex commonly found along with thiamine were tolerated at w/w ratios higher than 10, so they did not cause interference at the usual concentrations. The sensor was successfully applied to the determination of thiamine in pharmaceuticals containing only thiamine or other B vitamins as well.