甲基橙褪色光度法快速测定食品中亚硝酸根含量

RAPID PHOTOMETRIC DETERMINATION OF NITRITES IN FOODSTUFFS BY ITS COLOR-FADING REACTION WITH METHYL ORANGE

基于在室温下HOAc介质中亚硝酸能使甲基橙褪色的原理,建立了测定亚硝酸根的快速褪色光度方法.通过正交试验优化了方法的测定条件,在最佳条件下,方法的表观摩尔吸光系数分别为ε416=1.1×104L·mol-1·cm-1,ε506=5.2×104L·mol-1·cm-1;线性范围及回归方程分别为5.0～600.0 mg·L-1、△A416=0.000344 6 c+0.002 23、r=0.999 6(416 nm);1.0～300.0 mg·L-1、△A506=0.000 147 c+0.021 02、r=0.985 3(506 nm);检出限为5.0 mg·L-1(416 nm)、1.0 mg·L-1(506 nm).用于食物中亚硝酸根的测定,RSD为0.2%～4.2%,加标回收率在98%～103%.经t检验,其测定结果与国标GB/T 5009·33-1996方法的测定结果一致.

It was found that in a dilute acetic acid solution, fading of the color of methyl orange was observed due to its reaction with nitrite ion under room temperature. The optimum condition of this color-fading reaction was tested and a new photometric method for the determination of nitrites in foodstuffs was proposed. The photometric measurements made either at 416 nm or at 506 run gave consistent analytical results. Linear relationships between the decrease of color intensity of methyl orange （~4,） and the concentration of nitrite ion were found in the range of 5.0-600. 0 mg· L^-1 with its molar absorptivity of （ε416） 1.1× 10^4L· mol^-1· cm^-1 and in the range of 1.0- 300. 0 mg· L^-1 with its molar absorptivity of （ε506） 5.2 × 10^4L · mol^-1· cm^-1. The linear regression equations and correlation coefficients were found as follws ： △A416 =0.000 344 6 c＋0. 002 23, r=0. 999 6, △A506 =0. 000 147 c＋ 0.021 02, r=0. 985 3. Detection limits were found to he 5. 0 mg ·L^-1 and 1.0 mg ·L^-1 at 416 nm and 506 nm respectively. In its application to the analysis of 5 foodstuff samples, results obtained were in consistency with the results obtained by the standard method given in GB/T 5009. 33- 1996, and the RSD＇s and recoveries found were in the ranges of 0. 2 %-4. 2%and 98%-103% respectively