Inorganic constituents metals determination methods

The presence and concentration of various metallic elements in petroleum coke are major factors in the suitability of the coke for various uses. In the test method (ASTM D5056), a sample of petroleum coke is ashed (thermally decomposed to leave only the ash of the inorganic constituents) at 525°C (977°F). The ash is fused with lithium tetraborate or lithium metaborate. The melt is then dissolved in dilute hydrochloric acid and the resulting solution is analyzed by atomic absorption spectroscopy to determine the metals in the sample. However, spectral interferences may occur when using wavelengths other than those recommended for analysis or when using multielement hollow cathode lamps. 

Instrumental neutron activation analysis (INAA) is an extremely sensitive method for the determination of metals and metal isotopes. INAA has been used successfully by Nadkarni et al. (20A73), Jenkins et al. (1934) and Kubota (2214) to determine numerous inorganic constituents (elements and several elemental isotopes) in both tobacco and tobacco smoke (1933). The use of INAA for tobacco and tobacco smoke analysis has been accepted worldwide (1933). Tobacco is ideally suited for INAA because of its large abundance and variety of inorganic components. Tobacco is a readily available, easy-to-handle solid, it produces little gas during irradiation, and is rapidly assayed by INAA. The literature on the use of INAA in tobacco is very large because tobacco is often used as a model in non-tobacco-oriented... 

The technique is used predominantly for the isolation of a single chemical species prior to a determination and to a lesser extent as a method of concentrating trace quantities. The most widespread application is in the determination of metals as minor and trace constituents in a variety of inorganic and organic materials, e g. the selective extraction and spectrometric determination of metals as coloured complexes in the analysis of metallurgical and geological samples as well as for petroleum products, foodstuffs, plant and animal tissue and body fluids. 

On the other hand, if the lubricating oil has been subjected to excessive heat, it might be wise to consider application of the test method for determining the toluene-insoluble constituents of tar and pitch (ASTM D-4072, ASTM D-4312). In these methods, a sample is digested at 95°C (203°F) for 25 min and then extracted with hot toluene in an alundum thimble. The extraction time is 18 h (ASTM D-4072) or 3 h (ASTM D-4312). The insoluble matter is dried and weighed. Combustion will then show whether the material is truly carbonaceous or it is inorganic ash from the metallic constituents (ASTM D-482, ASTM D-2415, ASTM D-4628, ASTM D-4927, ASTM D-5185, ASTM D-6443, IP 4). 

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