Bestimmung von Nicotinsäure in Fruchtsäften durch HPLC mit elektrochemischer Detektion an einer stationären Quecksilbertropfelektrode

Purification procedure for the determination of niacin vitamers in gastrointestinal contents and blood

A solid phase extraction procedure for subsequent simultaneous HPLC analysis of free nicotinic acid (NIA) and nicotinamide (NAM) in dried or liquid rumen and gastrointestinal contents from sheep is described. Twenty-five mg dried samples were suspended in 1.0 ml of 0.1 mol/l Li2SO4 and centrifuged. The supernatants were passed through two 500 mg solid phase extraction columns (Bond Elut NH2 and Sep Pak C18), mounted in series, and eluted by a four step pH gradient procedure. Recoveries of the two vitameres were between 70 and 75%. Purification was satisfactory when the method was applied to different fractions of rumen content (e.g. to food residues, to a microbial preparation and to rumen fluid), to intestinal contents of sheep and to blood. In rumen fluid no free NIA and NAM was found. Food particles and rumen microbes contained no free NAM.

Evaluation of elution parameters in reversed phase HPLC for the determination of niacin vitamers and metabolites

A procedure for separation of nicotinic acid (NIA), nicotinamide (NAM), nicotinuric acid (NUR) and N1-methyl-nicotinamide (NMN) from biological samples by isocratic HPLC is described. The effects a) of different buffer systems (citrate, acetate, propionate), b) of different pH values (between pH 2.4 and 3.35), c) of different ionic concentrations of the eluents (between 10 and 100 mM) and d) of different methanol concentrations added to the eluent on retention times of the four compounds were tested. Results were described by multiple regression equations which allow selection of suitable analytical conditions according to the specific composition of different biological materials. The procedure yielded satisfactory separation of NIA and NAM from various purified fractions of rumen and intestinal contents and blood.

[An automated photometric method for determining niacin and niacinamide content in grain and cereals]

The subject of this report is an automated photometric method for the determination of the content of total niacin in grain and cereal food. The customary coupling reagent sulfanilic acid has been replaced by 1,3-dimethylbarbituric acid; CNCl is produced in the flow through system directly from KCN and chloramine T. The composition of reagents, the procedure and the analytical manifold are specified. 30 analyses/h can be performed. The accuracy and reproducibility of the automated method is good. In a range of 0.5-4.0 micrograms/ml niacin and a total content of 10-135 mg niacin/kg dry matter an average variation coefficient of vk = 0.74% (n = 10) was obtained. When lack of homogeneity of samples and variation in alkaline hydrolysis are included average vk to +/- 2.43% at the same range of niacin. The content of total niacin in various kinds of grain and in enriched ready to eat cereal foods was determined.