Carrier gas hot extraction

Carrier gas hot extraction - the sample is heated to more than 2000 °C in the presence of carbon and an auxiliary bath of metal such as platinum and in a stream of a carrier gas such as He. Nitrogen is liberated as N2 and is usually measured in a thermoconductivity cell. Oxygen combines with C to give CO and can thus be analyzed. Because of the high temperatures involved, the method is suitable for powder samples with larger grain size or even for small sohd pieces. The accuracy of the method is on the order of 1-2 rel %N. 

A common technique is vacuum or carrier-gas hot extraction where CO is formed and measured with an IR spectrometer or with a thermal conductivity... 

Also vacuum or carrier-gas hot extraction such as for the carbides can be applied. If carbon is present the CO is absorbed after IR measurement and the remaining nitrogen is measured usually in a thermoconductivity cell. Temperature-controlled furnaces can yield a fractional nitrogen analysis which resolves nitrogen differently bonded or different nitride phases. 

Ion extraction. The aspirated or laser ablated sample is transported from the sample introduction system into the center of the torch by a 1 1/min flow of Ar carrier gas where it is immediately dissociated and ionized by energy transfer with the hot -6000 K temperature of the surrounding Ar plasma. Ionization efficiencies are >95% for U and Th (Jarvis et al., 1992). For laser ablation sampling, helium may be employed as the carrier... 

The total hydrogen content is defined for the present purposes as the sum of the diffusible and residual contents, the latter being determined by hot extraction at 650 °C under vacuum or in a carrier gas as described below. The results may be expressed in terms of the hydrogen content per unit weight of either deposited metal (i.e. the weld metal deposited on to the test specimen during the test) or fused metal (i.e. the metal deposited plus the parent metal in the test sample which has been melted by the welding operation). 

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