Niacin assay methods

Chemical and microbiological methods for niacin assay are now generally used rather than animal assays. 

Both nicotinic acid and nicotinamide have been assayed by chemical and biological methods. Owing to the fact that niacin is found in many different forms in nature, it is important to indicate the specific analyte in question. For example, if biological assay procedures are used, it is necessary to indicate whether the analysis is to determine the quantity of nicotinic acid or if niacin activity is the desired result of the analysis. If nicotinic acid is desired, then a method specific for nicotinic acid should be used. If quantitation of niacin activity is the desired outcome, then all compounds (bound and unbound) which behave like niacin will assay biologically for this substance (1). 

The microbiological method using Lactobacillus phntarum, originally described by Snell and Wright (49), has been widely used for the determination of niacin in urine, serum, blood, foods, and tissues (16, 48,50,51,52). This organism is able to detect minute amounts of niacin (1-30 ng/mL) using a turbidimetric or titrimetric assay. 

Several B vitamins, including folic acid, niacin, pyridoxine, and pantothenic acid, are routinely determined using microbiological assays, details of which can be found in the AOAC Official Methods of Analysis. Standard methods for thiamine determination using fluorimetric detection are also detailed in the AOAC methods in addition, LC techniques are now being used routinely for thiamine and other B vitamins, e.g., riboflavin. 

Coverage includes B vitamins and folate in the context of a historical background, disease, cardiovascular effects and the importance of vitamins in biochemistry as illustrated by a single vitamin. Thereafter there are chapters on the chemistry and biochemistry of thiamine, riboflavin, niacin, pantothenic acid, pyridoxine, biotin, folate and cobalamin. Methodical aspects include characterization and assays of B vitamins and folate in foods of all kinds, dietary supplements, biological fluids and tissues. The techniques cover solid-phase extraction, spectrofluorimetry, mass spectrometry, HPLC, enzymatic assay, biosensor and chemiluminescence. In terms of fimction and effects or... 

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