CHAPTER 17: The Assay of Thiamine in Food

The assays of thiamine in food, fortified food and infant formulas are based on the microbiological, chemical and animal methods. The microbiological methods for thiamine analysis are the most frequently used for low-level naturally occurring vitamins in food whereas the official methods of thiamine analysis are based on chemical procedures using fluorimetry and high-performance liquid chromatography (HPLC) which are now the first methods of choice. Reverse-phase high performance liquid chromatography (RP-HPLC) on a C18 column support with an isocratic mobile phase works efficiently for the resolution of thiamine. The animal assays for thiamine are hardly ever used because they are time-consuming and poorly reproducible. Recently elaborated multivitamin methods for B vitamin assays using liquid chromatography-tandem mass spectrometry (LC-MS/MS), micellar liquid chromatography (MIC), liquid chromatography/diode array detection-mass spectrometry (LC-DAD/MS), liquid chromatography/electrospray ionization-mass spectrometry (LC/ESI-MS) or liquid chromatography-isotope dilution mass spectrometry (LC-IDMS) systems offer better sensitivity and selectivity, and can be potentially used for thiamine determination in fortified foods and infant formulas. These methods, as well as other techniques based on electrochemical methods (mainly voltammetry) have the potential to improve the performance of thiamine analysis in the future.