Sweeney R A, Rexroad P R
University of Missouri, Experiment Station Chemical Laboratories, Columbia 65211.
J Assoc Off Anal Chem. 1987 Nov-Dec;70(6):1028-30.
The LECO FP-228 "Nitrogen Determinator" was compared with the AOAC copper catalyst Kjeldahl method, 7.033-7.037, for the determination of crude protein in feed materials. The completely microprocessor-controlled instrument determines nitrogen by measuring the nitrogen gas following combustion of the sample; it was easy to operate and broadly applicable. A wide variety of feed materials of various nitrogen levels were analyzed in one mixed sequence. Results were precise, accurate, and rapid. Analysis time for one sample was approximately 3 min. Fourteen samples containing 2.5-15.5% N were selected for study and consisted of meals, grains, forages, and standard organic materials. The overall mean for the 14 samples by the LECO combustion method was 8.61% N compared with an overall mean of 8.58% N for the AOAC Kjeldahl method. Within-sample standard deviations for the LECO combustion method ranged from 0.013 to 0.052% N with a pooled standard deviation (SD) of 0.033% N for the 14 samples. Standard deviations for the AOAC Kjeldahl method ranged from 0.006 to 0.035% N with a pooled SD of 0.022% N. Combined average recovery of nitrogen from tryptophan, lysine-HCl, and EDTA determined by the LECO combustion method was 99.94% compared to 99.88% determined by the AOAC Kjeldahl method.
将LECO FP - 228“定氮仪”与美国官方分析化学师协会（AOAC）的凯氏定氮法（方法7.033 - 7.037）进行比较，以测定饲料原料中的粗蛋白。这台完全由微处理器控制的仪器通过测量样品燃烧后产生的氮气来测定氮含量；它操作简便，适用性广。对各种氮含量水平的多种饲料原料按一个混合序列进行了分析。结果精确、准确且快速。一个样品的分析时间约为3分钟。选取了14个含氮量为2.5 - 15.5%的样品进行研究，这些样品包括粕类、谷物、草料和标准有机物质。采用LECO燃烧法对这14个样品测定的总平均氮含量为8.61%，而AOAC凯氏定氮法测定的总平均氮含量为8.58%。LECO燃烧法的样品内标准偏差范围为0.013至0.052%氮，14个样品的合并标准偏差（SD）为0.033%氮。AOAC凯氏定氮法的标准偏差范围为0.006至0.035%氮，合并标准偏差为0.022%氮。LECO燃烧法测定色氨酸、盐酸赖氨酸和乙二胺四乙酸（EDTA）中氮的综合平均回收率为99.94%，而AOAC凯氏定氮法测定的为99.88%。
