Graphite spectrographic analysis

Ultrapure (triple distilled) mercury is commonly tested by evaporation or spectrographic analysis. In the former, a composite sample is evaporated and the residue weighed. In spectrographic analysis, a sample is dissolved and evaporated, the residue mixed with graphite [7782-42-5] and the emission spectmm determined with a spectrograph. 

In this study, a spectrographic analysis of the by-products of the decomposition of methane revealed the presence of large amounts of acetylene, ethylene, and benzene, plus a variety of compounds consisting mostly of the polyaromatic hydrocarbons (PAH) such as naphthalene, anthracene, phenantrene, acenaphthylene, pyrene, and fluoranthene, in addition to the deposited pyrolytic graphite. Some of these compounds form the soot and tar-like deposits which are often observed on the wall of CVD reactors during carbon deposition. 

The combination of hydrofluoric acid and nitric acid vapor as a digestion agent has proven effective in the preparation of samples for spectrographic determination of trace impurities in open systems. Zilbershtein et al. [113] used this approach to dissolve silicon and to concentrate impurities on a PTFE sheet. The residue and PTFE sheet were transferred to a graphite electrode that subsequently served as one electrode of the DC arc for spectrographic trace analysis. 

Samples of various stoichiometries were prepared by reacting in an arc furnace fully analysed thorium metal rods (99.7% purity) with spectrographic quality graphite rods, followed by remelting processes. From the full analysis of the samples given in Table A-31 hereunder their molecular composition could be calculated. 

The analysis of solid materials by their direct insertion into an ICP has been utilized as a method for compositional determination without the need for sample dissolution. The technique involves the packing of 10—30 mg of finely pulverized and homogenized (to ensure satisfactory subsampling statistics) sample into a depression or cavity in the end of a high-purity graphite rod. Often conventional direct current arc emission spectrograph-ic electrodes can be used for this purpose. 

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