对基于同时用高锰酸钾氧化及光化学反应的荧光分光光度法测定复杂试品如奶粉及人尿中叶酸的条件作了系统的试验并予以优化.对奶粉试样的预处理方法也作了详细叙述.试样溶液在作荧光光度检测之前,须经硅藻土填充的层析柱进行纯化.含有叶酸的试液在0.01 mol·L-1盐酸介质中,用1×10-3mol·L-1高锰酸钾溶液氧化,并置于波长为254 nm的紫外灯下照射30 min,经如此处理后叶酸的荧光强度明显增大,并测得其激发波长及发射波长分别为280 nm及448 nm.在5.0×10-8~2.0×10-6mol·L-1叶酸浓度范围内,与相应的荧光强度之间保持线性关系,相关系数为0.999 1.方法的检出限为6.5×10-9mol·L-1,所提出的方法曾用于奶粉及人尿中叶酸的测定.测定结果的RSD值(n=7)为3.2%~4.9%,方法的回收率为97.0%~102.0%.

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.