分光光度法快速测定酱油中半胱氨酸

Rapid Determination of Cysteine in Soy Sauce by Spectrophotometry

基于半胱氨酸与阳离子染料碱性品红发生加成反应,首次提出碱性品红加成反应褪色分光光度法测定半胱氨酸含量的新方法。在硼砂-氢氧化钠缓冲溶液中,半胱氨酸与碱性品红发生加成反应形成无色的硫醚衍生物,溶液褪色,吸光度减小,加成产物最大吸收波长在542 nm处,据此建立了分析方法。半胱氨酸的浓度C与吸光度差值ΔA呈现良好的线性关系,线性范围为1.00~10.00 mg/L,相关系数r=0.9993,表观摩尔吸光系数为1.525×10^(4) L/(mol·cm)。方法成功应用于市售酱油样品中半胱氨酸含量的测定,酱油样品加标回收试验平均回收率为97.1%和98.3%,相对标准偏差为0.85%、1.23%,不同酱油样品测定值的相对标准偏差(n=6)均小于3%。建立的方法操作简单,专属性强,检测成本低,结果准确可靠,可用于酱油中半胱氨酸的快速测定。

Based on the addition reaction of cysteine with the cationic dye basic fuchsin,a new method for the determination of cysteine content by fading spectrophotometry of basic fuchsin addition reaction is proposed for the first time.In borax-sodium hydroxide buffer solution,the addition reaction between cysteine and basic fuchsin forms a colorless thioether derivative,the solution fades,the absorbance decreases,and the maximum absorption wavelength of the addition product is at 542 nm.Based on this,the analytical method is established.The concentration C of cysteine shows a good linear relationship with the absorbance difference ΔA,with a linear range of 1.00~10.00 mg/L,the correlation coefficient r=0.999 3 and the apparent molar absorbance coefficient of 1.525×10^(4) L/(mol·cm).The method is successfully applied to the determination of cysteine in commercially available soy sauce samples.The average recovery rates of the spiked recovery tests of soy sauce samples are 97.1% and 98.3% with the relative standard deviations of 0.85% and 1.23%,and the relative standard deviations(n=6) of the determined values of different soy sauce samples are all less than 3%.The established method is simple to operate,has strong specificity,low cost,accurate and reliable results,and can be used for the rapid determination of cysteine in soy sauce.