水杨酸-靛酚蓝显色法测定芹菜中蛋白质含量

Determination of protein in celery by salicylic acid-indophenol blue spectrophotometry

目的：建立水杨酸-靛酚蓝光度法间接测定芹菜中蛋白质含量的新方法。方法：样品经过浓硫酸消化后生成的NH4＋,在亚硝基铁氰化钠催化作用下,与水杨酸等试剂在30℃水浴中反应1 h,生成蓝色的靛酚蓝物质在636 nm处有最大吸收,以吸光度A对NH4＋浓度进行线性回归,间接测定芹菜样品中蛋白质的含量。结果：显色产物最大吸收波长为636 nm,NH4＋浓度在2.82×10^-6-0.21×10^-3mol/L范围内,A与其浓度呈良好线性关系,回归方程为：A=4.32C＋0.0024,相关系数r=0.9999。方法检出限为0.739μg（以蛋白质计）,相对标准偏差为1.34%。用此方法测得芹菜杆中蛋白质含量为6.66 mg/g（以湿重计）,芹菜叶中蛋白质含量为7.73 mg/g（以湿重计）。结论：该方法简便、快速、灵敏度高、易于掌握。应用于芹菜中蛋白质测定,结果令人满意。

Objective：A new method of indirect determination of protein in celery was developed by salicylic acid-indophenol blue spcetrophotometry.Methods：The protein in celery sample was digested into NH＋4 by the use of concentrated sulfuric acid.NH＋4 reacted with the reagent of salicylic acid when sodium nitroferricyanide dihydrate was present as a catalyst,with water bath of 30℃ for 1h to form blue product.The absorption spectra of the blue product was scanned and it showed that it had the maximal absorption at 636 nm.Results：The linear regress equation of the method was A=4.32C＋0.0024 and the correlation coefficient was 0.9999 when NH＋4 concentration were between 2.82×10^-6 and 0.21×10^-3 mol/L.And the detection limit was 8.45×10^-7 mol/L 0.739 μg.The method has been applied to the determiantion of the contents of protein in celery leaf and celery shot.Conclusion：The proposed method is simple,fast and sensitive and it is suitable for the determination of protein in celery sample.