探讨了快速测定食品中还原型抗坏血酸的检验方法,在0.9 mol·L-1盐酸介质中,以甲苯胺蓝为动力学指示剂,抗坏血酸还原甲苯胺蓝染料并产生褪色反应,其褪色速度与抗坏血酸浓度呈正比.采用固定时间法测定,抗坏血酸浓度在100 μg/10 mL以内与吸光度ΔA值间呈线性关系,线性回归方程ΔA=0.010 C-0.009(r=0.999).检出限为2.0 μg/10 mL,表观摩尔吸光率为1.8×104L·mol-1·cm-1.应用此方法测定了6种试样中抗坏血酸含量,所得结果与国标法测得结果相一致.

In an acidic medium of 0.9 mol·L-1 HCl,toluidine blue (TB) (λmax=585 nm) was reduced by ascorbic acid leading to decoloration of the thiazine dye. Speed of the decoloration reaction was directly proportional to the concentration of ascorbic acid. Linear relationship beteen the magnitude of decrease in absorbance (ΔA) due to redective decoloration and concentration of ascorbic acid in its reductive species was obtained under fixed time intervals as shown by the linear regression equation ΔA=0.010 C-0.009 (r=0.999) where C is the concentration of ascorbic acid in μg (10 mL)-1,with molar absorptivity of (ε585) 1.8×104L·mol-1·cm-1,and detection limit of 2.0 μg/10 mL. In the application of the proposed method to the determination of ascorbic acid in 6 different samples,the results obtained were in consistency with those obtained by the GB standard method.