The chemical measurement of vitamin B1 in foodstuffs and biological material by means of the thiochrome reaction

Abstract

WHEN vitamin B1 is oxidized in an alkaline medium it is converted into thiochrome [Barger et al. 1935]. This substance has a vivid blue fluorescence which can be detected in dilutions of 1: 2,000,000. Recently Jansen [1936] published a quantitative method for the measurement of vitamin B1 which was dependent on the conversion of the vitamin into thiochrome and the subsequent measurement of fluorescence by means of a photoelectric cell. When it was attempted in this laboratory to apply the method to the measurement of vitamin B1 in foodstuffs certain difficulties arose. The following paper indicates the limitations of the method and the means which were devised in order to overcome them.Since the completion of the work reported below, two papers have appeared in which the thiochrome reaction for the measurement of vitamin B1 has been used. Karrer & Kubli [1937] have used Jansen's method with very little modification for preparations of high activity (between 500 and 220,000 i.u. per g.) which had been prepared during the production of crystalline, natural and synthetic vitamin B1. With substances of this high activity, these workers found it more convenient to compare the intensity of fluorescence by eye rather than use the somewhat delicate fluorimeter of Cohen [1935] in which a photoelectric cell is employed. Where vitamin B1 in foodstuffs is being measured, however, comparison by direct observation is not sufficiently accurate.Another Tecent paper by Goudsmit & Westenbrink [1937] reports the use of a procedure almost identical with that devised by the author for the measurement of vitamin B1 in urine. EXPERIMENTAL(1) Standardization of the reaction with International Standard adsorbate The procedure of Jansen [1936] was carried out with very slight modification. 0-1 ml. of 1 % K3Fe(CN)6 was required to oxidize each 10 mg. of acid clay. This solution was mixed with 2 ml. redistilled methyl alcohol and 1 ml. 30 % NaOH, and the accurately weighed and finely powdered International Standard added. The reagents were shaken for a few moments and made up to 5 ml. with water, and 13 ml. of isobutylalcoholwere added. The mixture was again vigorously shaken and finally centrifuged.The measurement of fluorescence was carried out on the Cohen fluorimeter. The blank reading obtained with 10 ml. of the original isobutyl alcohol was subtracted from the galvanometer deflexion given by exactly 10 ml. of isobutyl alcohol solution. Compensation for any variation in the intensity of the ( 1958 )

A Portable, Low-Cost, LED Fluorimeter for Middle School, High School, and Undergraduate Chemistry Labs

“…Thiamine does not fluoresce, but can be detected indirectly by oxidizing thiamine to thiochrome, as shown in Scheme . To date, three oxidizing agents have been used: potassium ferricyanide, , cyanogen bromide, and mercuric chloride. ,, There is considerable fluorescence quenching and spectral interference by the ions in the ferricyanide method. − Cyanogen bromide is toxic and has a relatively short (3 h) serviceable life after preparation. Mercury salts are poisonous, but a 1% salt solution is much easier to handle than cyanogen bromide.…”

Thiamine in Beef Muscle. A Comparison of Values of the Thiochrome Reaction Applied with and without Adsorption

“…Nonadsorption methods of thiochrome determination^i n both animal and vegetable tissues, which vary in details of digestion, of the final oxidation reaction, and of the reading of the fluorescence, have been described in a few American reports (2, 16,22) and in an earlier German one (36), as well as in many British reports (7, 14, 19,[26][27][28][29]34). On the other hand, applications of the Hennessy and Cerecedo base-exhange technique have been widely reported in this country (1, 2, 9,10, 18, 21, 25) and a similar adsorption procedure was described in one earlier Dutch study (85).…”

Section D. The Nutritional value of milk and milk products

“…Methods based on the fluorescence of lactoflavin and of thiochrome, a derivative of vitamin B x , in ultra-violet light have been applied to the determination of these vitamins in various products (76,77) and these methods, suitably modified, can be applied to milk probably with satisfactory accuracy (78,79,80,81,82,83). A test using the growth of the micro-organism Phycmnyces Blakesleanus has also been suggested for the estimation of vitamin B x and has been applied to milk(84) but the results yielded so far for milk in the reviewer's laboratory have not been very encouraging (85).…”

“…of vitamin B x and 100-150y of lactoflavin per 100 ml. (78,81,82). The former figure agrees satisfactorily with biological measurements (5,86).…”