Evaluation of Stability Constant for Vitamin B1 Depending on Stoichiometric Curves by Visible Spectroscopy

Abstract

The measurement of vitamin B₁ in pure and pharmaceutical formulations was proposed by using a straightforward and sensitive spectrophotometric approach. Sulfacetamide (SFA) is diazotized, then coupled with vitamin B₁ in alkaline media to produce a colored azo dye complex with a stability constant of 5.597 × 10⁵ L/mol. The product is stable, with a maximum absorption wavelength of 489.5 nm, molar absorptivity of 10108 L/mol∙cm, Sandell's sensitivity of 0.0334 μg/cm², detection limit of 0.0135 μg/mL, and Beer's law being observed over the concentration range of 0.2–20.0 μg/mL. The stability constant and stoichiometry of the produced azo dye were calculated using the continuous variation (Job's) and mole ratio methods. The suggested approach was used successfully in the determination of vitamin B₁ in its pharmaceutical formulations.