I wonder if anyone could help.

I have been analysing vitamin B1 in foods using HPLC using the method from Finglas and Faulks (1984). The method uses the derivatization of thiamine (as well as TMP/TDP/TTP) with potassium ferricyanide (0.03M) in alkaline conditions (3.75M NaOH). However, I have found that the product (thiochrome) degrades within 2 hours of the derivatization step - meaning I can only run few samples at a time.

I have tried to stop the reaction by the addition of 5M phosphoric acid, however, this has not increased the shelf life of the thiochrome more than the 2 hours.

Has anyone else found a protocol which is able to stabilise the thiochrome compound for at least 6-8 hours? Or have a protocol that forms a stable compound to analyses?

Many thanks in advance,

Robyn

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