Postcolumn fluorimetric HPLC procedure for determination of niacin contentof cereals

Analytical procedures for determining niacin or vitamin B3 content of foods are tedious, require large quantities of toxic chemicals, and are time-con suming. In addition, food matrices are difficult as samples because of thei r complex nature. A selective, sensitive HPLC technique was developed with postcolumn derivatization as well as fluorescence and spectroscopic detecti on systems. Niacin was separated and retained for 6.5 min on a polymeric co lumn with an aqueous mobile phase containing sodium acetate buffer. A postc olumn system consisting of a stainless-steel pump and reaction coil allowed detection and quantitation of niacin. An acid-enzyme sample-extraction met hod was most compatible with HPLC and postcolumn derivatization with 5% eac h of acidified p-aminophenol and cyanogen bromide. Lower detection limit an d mean recovery were 3.6 ng and 99.43%, respectively. Fluorescence response for nicotinamide was half that of nicotinic acid. A lower response for nic otinamide was also noted with conventional spectroscopy. However, the new m ethod yielded comparable values for six of eight ready-to-eat commercial ce real samples. No significant difference was observed between the AACC refer ence and HPLC fluorimetric methods. Chemical derivatization was done within a reaction coil with reagents at half strength, limiting exposure to hazar ds and minimizing waste-disposal problems.