邻二氮菲荧光分光光度法测定粉状食品中铁的含量

Determination of Iron in Powder Food by Fluorescence Spectrophotometry with Phenanthroline

基于在三羟甲基氨基甲烷溶液中,邻二氮菲与Fe^(2+)形成的络合物使邻二氮菲荧光强度减弱的原理,提出了题示方法。取1.0000 g样品,加入8.00 mL硝酸和5.00 mL 30%(质量分数)过氧化氢溶液,静置过夜后加热至近干,加入5.00 mL硝酸和5.00 mL高氯酸,继续加热至近干,加入2.50 mL 1.0 mol·L^(−1)硝酸溶液溶解,用水定容至25 mL。取一定体积上述溶液(蛋白质粉固态饮料样品取1.00 mL、婴儿配方奶粉样品取1.50 mL和面粉样品取2.00 mL),加入1.00 mL 50.0 g·L^(−1)盐酸羟胺溶液,静置2 min,加入4.00 mL 5.00×10^(-4)mol·L^(−1)邻二氮菲工作溶液,混匀后加入2.50 mL1.0 mol·L^(−1)三羟甲基氨基甲烷溶液(pH 8.5),用水定容至25 mL,静置10 min后在激发波长323 nm下,测量体系在363 nm处的荧光强度。结果表明:Fe^(3+)质量浓度在1.3440 mg·L^(−1)以内与邻二氮菲的荧光强度下降值呈线性关系,检出限(3s/k)为0.009 mg·L^(−1)。方法用于粉状食品中铁含量的测定,本底值的相对标准偏差(RSD,n=5)为1.7%~7.6%;按标准加入法进行回收试验,回收率为94.6%~99.9%,测定值的RSD(n=5)为1.5%~4.1%。经F检验和t检验分析,本方法与紫外-可见分光光度法、火焰原子吸收光谱法测定结果无显著性差异,但本方法的灵敏度更高。

Based on the principle that the complex formed by phenanthroline and Fe^(2+)weakens the fluorescence intensity of phenanthroline in tris(hydroxymethyl)methyl aminomethane solution,the method mentioned by the title was proposed.1.0000 g of the sample was taken,and 8.00 mL of nitric acid and 5.00 mL of 30%(mass fraction)hydrogen peroxide solution were added.The mixture was settled overnight,and then heated to near dryness.5.00 mL of nitric acid and 5.00 mL of perchloric acid were added,and the mixture was continuously heated to near dryness.After 2.50 mL of 1.0 mol·L^(−1)nitric acid solution was added for dissolution,the volume of the mixed solution was made up to 25 mL by water.A certain volume of sample solution was taken(1.00 mL for protein powder solid beverage sample,1.50 mL for infant formula milk powder sample,and 2.00 mL for flour sample),and 1.00 mL of 50.0 g·L^(−1)hydroxylamine hydrochloride solution was added.The mixed sample solution was settled for 2 min,and 4.00 mL of 5.00×10^(−4)mol·L^(−1)phenanthroline working solution was added.After mixing well,2.50 mL of 1.0 mol·L^(−1)tris(hydroxymethyl)methyl aminomethane solution was added and the volume of the mixed sample solution was made up to 25 mL by water,settling for 10 min.The fluorescence intensity of the system at 363 nm was measured at the excitation wavelength of 323 nm.It was shown that linear relationship between the decrease in fluorescence intensity of phenanthroline and mass concentration of Fe^(3+)was found within 1.3440 mg·L^(−1),with detection limit(3s/k)of 0.009 mg·L^(−1).The method was applied for the determination of iron in powder food,and RSDs(n=5)of background values ranged from 1.7%to 7.6%.Test for recovery was made by the standard addition method,giving results in the range of 94.6%-99.9%,with RSDs(n=5)of the determined values in the range of 1.5%-4.1%.After F-test and t-test analysis,there was no significant difference among these methods,including this method,UV-Vis spectrophotometry and flame atomic absorption spectrometry,but the sensitivity of this method was higher.