119 Rapid Method for the Determination of Thiamine in Enriched Flours and Enrichment Mixtures

Methods Type: Generic Methods
Key data
Number: 119
Analyte: Thiamine
Matrix: Enriched Cereal Flours and Enrichment Mixtures
Year of Approval: 1974
Scope: The following method is applicable to enriched cereals flours as well as to enrichment mixtures.
Principle: Thiamine is extracted with a 25 % solution of KCl in 0.1 M HCl at room temperature. This extraction is found to be complete even in those instances in which an absorbent for the vitamin is present or is produced in the sample during extraction. The thiochrome resulting from oxidation of the filtrate with potassium ferricyanide in alkaline solution is extracted with isobutyl alcohol. The intensity of the blue fluorescence of the isobutyl alcohol extract is compared with that of a standard solution. The intensity of fluorescence is measured photoelectrically and the fluorescence value of a blank test is subtracted from that of the sample extract. The use of the HCl blank results in a considerable saving in time required for analysis. There is little or no interference from sample material and no indication that the samples contain substances capable of quenching thiochrome fluorescence under the conditions of the method. There it is sufficient for measurement and calculation to outline in the assay directions the use of one external or outside standard.


The method serves for the determination of free thiamine, which is extractable with acid KCl-solution without digestion. The actual process of measurement is based on the thiochrome method.


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