Dumas method for nitrogen

The residual platinum compound was analyzed for xenon by the conventional Dumas method for nitrogen and, for platinum and fluorine by the pyrohydro-lytic technique previously described [4]. Found F, 27.0 per cent 26.4 per cent Pt, 54.5 per cent and Xe, 14.7 per cent 14.7 per cent. XePt2Fio requires F, 26.7 per cent Pt, 54.8 per cent and Xe, 18.5 per cent. 

Although the Dumas method for nitrogen determination is seldom used in clinical chemistry, it is interesting to know that it seems to be well suited for automation. The apparatus described by Gustin (G7) can perform 6 determinations on samples of 1 to 10 mg in 1 hour. 

The Dumas method of nitrogen determination consists of an oxidation method in which a mixture of coal and copper oxide (CuO) is heated in an inert atmosphere to produce carbon dioxide (C02), water (H20), and nitrogen (N2). The carbon dioxide is absorbed, the water condensed, and the nitrogen determined volumetrically. Although the Dumas method has been employed for many years, various modifications have been made to increase accuracy and precision. 

Figure 1 Crude protein determination by the Dumas method for total nitrogen with the LECO apparatus. (Reproduced from O Keeffe M (1992) Chemical analysis of animal feed and human food. In Smyth MR (ed.) Chemical Analysis in Complex Matrices, pp. 241-287. Chichester Ellis Horwood.)...

Skepticism People don t trust NIR (yet). Management still tends to adhere to the tried and trusted methods, such as forms of the Kjeldahl test for nitrogen or protein. Even the extremely efficient Dumas (combustion) method for nitrogen has been slow in widespread adoption, although in good hands it is more efficient and precise than any Kjeldahl method. 

The two chief methods for estimating nitrogen in organic compounds are (i) the Dumas method, which can be applied to all organic compounds (ii) the Kjeldahl method, which is of more restricted application, but which is frequently used in biochemical and physiological work. Its limitations are indicated in the description of the method (p. 492). 

A universal procedure for combined nitrogen is the Dumas method. This gasometric procedure is applicable to any organic compd contg nitrogen in any form, such as amino, nitroso, nitro, azo, cyano, nitrate, nitrite, as well as N in heterocyclic compds. The procedure involves combusting the sample in a closed system in a C02 atm, with subsequent reduction of the oxides... 

TABLE FOR CALCULATIONS IN THE DETERMINATION OF NITROGEN BY DUMAS METHOD... 

The determination of nitrogen in petroleum products is performed regularly by the Kjeldahl method (ASTM D3228), the Dumas method, and the microcoulomet-ric (ASTM D3431) method. The chemiluminescence method is the most recent technique applied to nibogen analysis for petroleum and is used to determine the amount of chemically bound nitrogen in liquid samples. 

Dumas method analychem A procedure for the determination of nitrogen in organic substances by combustion of the substance. dti-ma. meth-od dunnite See ammonium picrate. da.nTt)... 

M.I. Fauth H. Stalcup, AnalChem 30,1670— 72(1958) Be CA 53, 2929(1959) [Evaluation of six methods for detn of nitrogen in NGu. (Nitro N methods tested are modified nitrometer — greatest precision of the six acetate-buffered titanous chloride transnitration with sulfuric acid and Bowman-Scott). Total N methods are modified Kjeldahl and micro-Dumas — better of these two. The titanous chloride and trans-nitration methods are satisfactory]... 

Drop volume tensiometer (DVT), for interfacial tension, 636-638 DSA. see Drop shape analysis Dumas method, nitrogen content... 

Nitrogen is determined by the micro Dumas method. Palladium is determined by ignition. The mixture of metallic palladium and its oxides is reduced with formic acid and dried at 200°. Anal. Calcd. for [Pd(NH3)2-(N02)2] Pd, 45.83 N, 24.07. Found Pd, 45.75 N, 23.70. 

Comment. The Dumas method, standard for nitrogen, requires little comment, results being very satisfactory, although it is necessary to make determinations on a substance of standard nitrogen content. 

The commonly used methods for the determination of total nitrogen involve variations of the Dumas or Kjeldahl techniques. The Dumas approach involves oxidation of the nitrogen to elemental or oxide form by combustion of the sample, reduction of nitrogen oxides, and determination of the elemental nitrogen. The Dumas oxidation is usually represented by the following example for acetanilide ... 

Figure 18.4 Instrument for nitrogen analysis. This instrument is a modern adaptation of the Dumas method, with the conventional detection hy means of a catharometer (He is the carrier gas).

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