用凯氏法和杜马斯法测定植物样品中的全氮

作者对比了凯氏定氮法与杜马斯定氮法的特点，用两种方法分别检测24种植物样品的氮含量，并对两种方法的测得结果进行了比较，发现杜马斯法测定的全氮总是略高于凯氏定氮法的结果，其原因是凯氏法不便检测硝态氮，所以认为杜马斯定氮法更适用于植物样品全氮的测定。     

TOTAL NITROGEN CONTENT IN SINGLE KERNEL MALTING BARLEY SAMPLES

It was demonstrated that the Dumas method is suitable to analyse single kernel barley samples for their total nitrogen content directly without milling. The method was compared to the nitrogen analysis in milled samples over a range of 1.5-3.0%N. These samples consisted of kernel size grading fractions from barley cultivated at different N-dressings and using a shading regime. A good correlation was found between milled and whole barley kernels (r²=0.852). The method was used to determine the nitrogen content of individual kernels in the barley grading fractions. The nitrogen content in these fractions decreased with increasing kernel size depending on growth conditions. A large variation in nitrogen content between individual kernels was found for all grading fractions. In a study of barley main spikes the variation in kernel nitrogen content within spikes was smaller than the variation between spikes, especially when the barley was grown at a 60% light reduction regime during the kernel filling period. The average kernel total nitrogen content under the latter condition was about two times as high as in the control experiment. The kernel position along the spike did not clearly affect its nitrogen content. Acid and SDS polyacrylamide gel electrophoresis (PAGE) revealed similar banding patterns for proteins from kernels at different positions of both low and high N barley spikes. The single kernel method for nitrogen may be used by the breeder as a quality criterion for new barley varieties to test their spike development at different cultivation conditions. It can suit the maltster to screen rapidly the homogeneity in nitrogen (protein) content of barley batches.     

杜马斯燃烧法测定钒氮合金中氮

氮含量是钒氮合金质量的重要技术指标之一,目前国内主要采用湿法分析氮,结果可靠但效率低,因此有必要建立快速测定钒氮合金中氮含量的方法。实验探讨了采用杜马斯燃烧法测定钒氮合金中氮的方法,对样品粒径、称样量、燃烧时间、助熔剂用量进行了优化。实验选定条件为:样品粒径不大于0.074mm,称样量0.0400~0.0600g,燃烧时间270s,采用0.1g纯镍和0.1g纯钨作助熔剂。结果表明:在优化实验条件下,氮含量为13.14%~16.64%(质量分数,下同),氮的质量分数与对应的峰面积呈线性关系,校准曲线的线性相关系数r为0.9996。按照实验方法测定钒氮合金有证标准物质中氮,测定值与标准值的相对误差为0.21%~0.38%。方法用于实际样品中13.55%~15.56%氮的测定,结果的相对标准偏差(RSD,n=10)为0.42%~0.50%。     

杜马斯燃烧法测定食品中总氮含量

以各类食品为试验材料,分析了各种参数对杜马斯燃烧法测定含氮量结果的影响,并比对了杜马斯法和凯氏法的测定结果。结果表明,当通氧量为110~200 mL/min,反应炉温度设定900℃以上,样品量在100~150 mg时,测定结果理想。大部分食品样品杜马斯和凯氏法无显著性差别。但杜马斯法结果RSD较凯氏法稍大。另改进前处理方法,杜马斯法还可以用于测定液体食品中的氮含量,结果准确。     

杜马斯燃烧法测定牛奶中的蛋白质含量

目的通过对杜马斯燃烧法和凯氏定氮法测定牛奶中的蛋白质含量的比较,建立杜马斯燃烧法测定牛奶中蛋白质的方法。方法杜马斯燃烧法检测条件:称样量100 mg,通氧量80 m L/min,通氧时间80 s;结果选用合适的燃烧条件用杜马斯燃烧法可以准确测定牛奶中的蛋白质含量。结论此方法具有结果准确、精密度高、易于操作的优点,适用于大批量牛奶样品的检测。     

Comparison of combustion and Kjeldahl methods for determination of nitrogen in oilseeds

The recent development of combustion-type nitrogen analyzers capable of handling relatively large samples with semi automatic operation offers a potential replacement for the Kjeldahl method for direct determination of nitrogen. Nitrogen analyses for canola seed, flaxseed, sunflower seed, mustard seed and soybeans on a LECO (St. Joseph, MI) FP-428 Nitrogen Analyzer were evaluated against results from the Grain Research Laboratory's (GRL) Kjeldahl system. The nitrogen analyzer gave significantly higher values than the Kjeldahl method, resulting in a correction of low values in the GRL Kjeldahl, caused by the inability to use mercury as catalyst. The standard error for results from the analyzer was comparable to that for the Kjeldahl method. The nitrogen analyzer also was faster than the Kjeldahl method and had less environmental impact. The combustion method has replaced the Kjeldahl method for routine nitrogen determinations in oilseed surveys conducted by the GRL. Presented at the 84th AOCS Annual Meeting & Expo, April 27, 1993, Anaheim, California.     

杜马斯燃烧法测定煤炭中氮含量

采用杜马斯燃烧法,利用氮分析仪对煤炭中的氮含量进行测定。试样在一个分析周期中分为3个阶段：冲洗、燃烧和分析。结果表明,用杜马斯燃烧法测定煤炭中氮含量与传统湿法分析相比,操作方法简便容易掌握,快速分析的同时确保了准确性,符合工业生产与试验分析的要求。     

Alfred Binet and higher education.

At the beginning of the 20th century, Alfred Binet sought teaching positions at the Colfte de France and the Sorbonne. Binet wanted to develop experimental psychology in France, but the strong psychopathological orientation of French psychology blocked his ambition. The 1st part of this article relates the history of the introduction of psychology, via Théodule Ribot, to the Sorbonne and the Coll6ge de France. Ribot's premature retirement from the Collège de France in 1901 triggered a battle that led to Binet's repeated failure to gain access to these institutions of higher education and the success in 1902 of Ribot's students: Pierre Janet at the Colfte de France and Georges Dumas at the Sorbonne. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Non‐destructive determination of nitrogen in malting barleys by instrumental photon activation analysis and its comparison with the Dumas method

Instrumental photon activation analysis (IPAA) was used to measure the nitrogen content of malting barleys used in brewing and breeding in the Czech Republic. The study compares the fast and non‐destructive IPAA method with the classical Dumas method requiring combustion of the sample. The IPAA procedure for nitrogen assay is based on measuring the positron–electron annihilation γ line at 511 keV from the photoactivation product ¹³N, which is interfered with by other positron emitting nuclides. Interference from ¹⁵O can be eliminated by counting after a sufficient decay time. Interferences from ^34mCl and ³⁸K can be corrected via measuring their specific γ lines at 146.4 and 2167.7 keV, respectively. The IPAA procedure has been verified by analysis of several biological reference materials and is suitable for nitrogen measurement in cereals and other plant materials with a detection limit down to 10^?2 wt%. Nitrogen contents in malting barleys ranged from 1.4 to 2.2 wt% and were dependent on the cereal variety and growth conditions (fertilizer use and chemical protection). Copyright © 2018 The Institute of Brewing & Distilling