Determination of creatine in biological fluids

The colour reaction between diacetyl and creatine in the presence of a-naphthol can be used for the determination ofcreatine (Barritt, 1936).A number of inhibitory substances occur in urine, plasma and tissue extracts which interfere with the formation of the coloured product (Eggleton, Elsden & Gough, 1943).It was shown by Ennor & Stocken (1948) that sulphydryl compounds could produce marked inhibition of the diacetyl reaction and that the interference could be prevented by the addition of p-chloromercuribenzoic acid.On applying their method to urine, Ennor & Stocken (1953) found that