一阶导数单扫描极谱测定食品中凯氏氮含量

Determination of Nitrogen in Foods by 1st Order Differential Coefficient Single Sweep Polarography

建立用一阶导数单扫描极谱法测定食品中凯氏氮含量的简单、快速的方法。方法:将样品用凯氏烧瓶消化,消化液经稀释后定量吸取到甲醛乙酸盐缓冲溶液中。铵盐与甲醛反应生成六亚甲基四胺,生成物在-824mV处产生极谱波,以标准曲线法定量。结果:本法测定的相对标准偏差(RSD)=3.3%(n=8),回收率为98.6%～102.6%,对奶粉等10种食品分析的结果与凯氏定氮法比较,没有显著性差异(p>0.1)。结论:该法简便、快速、检出限低、重现性好、结果准确可靠,适于食品中蛋白质含量的测定。

Objective: To establish a simple rapid method for determining Kjeldahl nitrogen content by 1st order differential coefficient single sweep polarography. Method: The digested liquid was diluted and pipetted into a solution of formaldehyde in an acetate buffer. The hexamethylenteramine produced by ammonium and formaldehyde reaction was determined electrochemi- cally at –824 mV. The nitrogenous quantity was obtained by the method of standard curve. Results: The polarographic wave of 1st order differential was determined. The relative standard deviation was 3.3%.The recovery rate of nitrogen was 98.6%～ 102.6%.10 different foods were analysed. There was no significant difference between the result by this method and Kjeldahl method (p>0.1). Conclusion: It is a simple, rapid and accurate method for determining Kjeldahl Nitrogen in foods.