全自动凯氏定氮仪测定婴幼儿奶粉中的粗蛋白含量

Determination of Crude Protein Content in Infant Milk Powder by Automatic Kjeldahl Nitrogen Analyzer

优化了全自动化凯氏定氮仪测定婴幼儿奶粉粗蛋白含量的前处理条件。探究了样品含量、催化剂配比、浓硫酸投加量、消化温度、消化时间等因素对粗蛋白质含量测定的影响。实验得到了最好的前处理条件:样品量1.0 g,催化剂质量配比为8∶0.5,浓硫酸加入量为12.0 mL,消化温度/时间为200℃(20 min)、300℃(20 min)、420℃(80 min)。平行测定结果的标准偏差为0.54%,加标回收率超过99%。奶粉中粗蛋白含量经优化前处理条件测定,精密度高、稳定性好,测定结果与外包装标注接近一致,达到国家乳制品蛋白含量标准。

The pretreatment conditions for the determination of crude protein content in infant milk powder by automatic Kjeldahl nitrogen analyzer were optimized.The effects of sample size,catalyst ratio,concentration of sulfuric acid,digestion temperature and digestion time on the determination of crude protein content were investigated.The optimal pretreatment conditions were as follows:sample size 1.0 g,catalyst mass ratio 8∶0.5,concentration sulfuric acid addition amount 12.0 mL,digestion temperature and time:200℃(20 min),300℃(20 min),420℃(80 min).The standard deviation of parallel determination results was 0.54%,and the recovery rate was over 99%.The content of crude protein in milk powder was determined by optimized pre-treatment conditions with high precision and good stability.The results were close to the content marked on the outer package,which was in line with the national dairy protein content standard.