Fluorospectrophotometric Determination of Folic Acid in Milk Powder and Urine Based on Simultaneous Potassium Permanganate Oxidation and Photochemical Reaction

Conditions of fluorospectrophotometric determination of foilc acid by simultaneous oxidation with potassium permanganate and photochemical reaction,and its application to the analysis of some complex sample were studied and optimized.Method of pretreatment for samples of milk powder and urine was described.Purification of sample solution by passing through a chromatographic column (250 mm×18 mm),packed with diatomite suspended in methanol,was necessary.Folic acid,in the sample solution of 0.01 mol·L-1 HCl,was oxidized with 1.0×10-3mol·L-1 KMnO4 and irradiated for 30 min with UV-lamp at 254 nm.The fluorescence intensity of folic acid was remarkably enhanced by this treatment,and the maximum excitation and emission wavelength were found at 280 nm and 448 nm respectively.Linear relationship between the fluorescence intensity of folic acid and its concentration was kept in the range of 5.0×10-8-2.0×10-6mol·L-1 (r=0.999 1) with detection limit of 6.5×10-9mol·L-1.The proposed method has been applied to the determination of folic acid in samples of milk powder and human urine,giving values of RSD′s (n=7) and average recovery in the ranges of 3.2%-4.9% and 97.0%-102.0% respectively.