The determination of nitrogen in nickel

Even for nitrogen concentrations of the order of 1 g/g good agreement was found between the above methods and activation analysis. It can therefore be assumed that, under the conditions mentioned, both reducing fusion and 

For reaction 1 nuclear interferences do not occur for proton energies below 21.7 MeV. In addition, spectral interferences are not very probable, if the 7-ray at 2313 keV is measured. A disadvantage is the high threshold energy of the N(p,n) 0 reaction, so that for low Z matrices it is not possible to use an incident energy below the coulomb barrier of the matrix to avoid activation of the matrix. 

The N(p,a) C reaction is interfered with by boron for all proton energies. This interference was discussed in detail in Chapter IV, section 2.1. In general, the boron concentration in industrial metals is lower than the 

Nitrogen concentration (ng/g) in an aluminium sample that yields at the end of an irradiation I intensity, irradiation time = one half-life) at the indicated energy an activity of 100 desintegra-tions/min. 

Reaction 3 also has a high sensitivity and, for energies below 10.6 MeV, 

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A number of workers have studied the development of methods for the determination of nitrogen in compounds separated in a GC column. Coulson [138, 139] devised a special coulometric detector that only detects ammonia. After separation, the compounds under investigation were hydrogenated in a flow of hydrogen over a nickel catalyst. As a result of hydrogenation, nitrogen-containing compounds formed ammonia, which was detected by the coulometric detector. A similar method was developed by Martin [140]... 

In 1970 Friedrich et al. (24) reached the following conclusion "The determination of nitrogen in tantalum using the nickel-magnesium-cerium technique is possible if the nickel. -tantalum ratio is above 8 1. It has still not been possible to find a method suitable for the determination of nitrogen in niobium". 

The coarse copper oxide is not previously heated in the nickel crucible as in the determination of nitrogen, but this is done later in the tube itself. If the nature of the substance to be analysed is such that it is necessary to mix it with fine copper oxide, the latter is ignited for a quarter hour in the porcelain crucible and allowed to cool in a desiccator. 

Lee [524] described a method for the determination of nanogram or sub-nan ogram amounts of nickel in seawater. Dissolved nickel is reduced by sodium borohydride to its elemental form, which combines with carbon monoxide to form nickel carbonyl. The nickel carbonyl is stripped from solution by a helium-carbon monoxide mixed gas stream, collected in a liquid nitrogen trap, and atomised in a quartz tube burner of an atomic absorption spectrophotometer. The sensitivity of the method is 0.05 ng of nickel. The precision for 3 ng nickel is about 4%. No interference by other elements is encountered in this technique. 

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