Development of an Isotope Dilution Mass Spectrometry Method for Accurate Determination of Thiamine in Diverse Food Matrices

Many foods contain thiamine as a natural or fortified nutrient. In order to realize accurate measurement of thiamine in various food matrices, analytical methods should be developed on the basis of careful examination of the matrix and the analytes in the matrix. An isotope dilution liquid chromatography–mass spectrometry (ID-LC-MS/MS) method was developed for the analysis of thiamine in various samples such as multivitamin tablets, infant formula, rice, and wheat flour. After using spiked isotope-labeled thiamine HCl (13C4-thiamine HCl) as an internal standard, samples were analyzed by LC/MS in a selected reaction monitoring mode to detect ions at m/z 265 → 122 and m/z 269 → 122 for thiamine and 13C4-thiamine, respectively. To improve the accuracy and precision of this method, the preparation procedure was optimized depending on the chemical form of thiamine present in each sample. Thiamine in multivitamin tablets, infant formula, rice, and wheat flour was analyzed after buffer extraction, acid hydrolysis, and continuous acid and enzyme hydrolyses, respectively. The instrumental analyses were also optimized for individual samples, facilitating excellent repeatability (0.16–0.81%) and reproducibility (0.1–4%). The accuracy of the developed method was verified by comparing the experimental data with the certified values of certified reference materials. Thus, optimization of the preparation procedures and ID-LC-MS/MS method allowed the accurate determination of thiamine in diverse food matrices.