Summary - niacin
EN 15652:2009 Foodstuffs - Determination of niacin by HPLC:
This European Standard specifies a method for the determination of the mass fraction of niacin in foodstuffs by high performance liquid chromatography (HPLC) by three different ways of hydrolysis, acid hydrolysis (A), enzymatic hydrolysis (B) or acid/alkaline hydrolysis (C).
The method has been validated in interlaboratory tests on fortified and non-fortified samples such as breakfast cereal powder, chocolate cereals, cooked ham, green peas, lyophilized green peas with ham, lyophilized soup, nutritive orange juice, milk powder and wheat flour, at levels from 0,5/100 g to 24 mg/100 g.
A and B give similar results for niacin. In options A and B niacin is calculates as the sum of nicotinamide and nicotinic acid, and expressed as nicotinic acid. Option C gives higher results than A and B for naicin with non-supplemented cereals, but similar results for other products. In option C, niacin is calculated and expressed as nicotinic acid after transformation of nicotinamide into nicotinic acid.
Option A is faster and cheaper than B and C.
Option B is used if an exact quantification of nicotinamide and nicotinic acid is needed. This cannot be done with option A, because there is a slight transformation of nicotinamide into nicotinic acid during the acid hydrolysis.
Option C quantifies total niacin. The alkaline hydrolysis is able to liberate other forms giving higher results for niacin, which in some foods such as maize and cereals are not normally biologically available.
Niacin vitamers are extracted from food by an acid (option A), an enzymatic (option B) or and acid/alkaline (option C) treatment and quantified by HPLC with a fluorometric detection after a post-column derivatisation with UV irradiation. For option A and option B, niacin is determined as the sum of nicotinamide and nicotinic acid. Niacin is expressed as nicotinic acid after correction of the molecular weights. For option C, niacin is determined and expressed as nicotinic acid. The alkaline treatment transforms all nicotinamide into nicotinic acid.