Carbide-Treated Graphite Cuvettes for Electrothermal Atomization Prepared by Impregnation with Metal Chlorides

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Abstract
In order that carbide coatings could be prepared, graphite cuvettes were (1) placed in liquid TiCl4, MoCl5, or WCl6 under reduced pressure to fill the void space in the graphite with metal chloride; (2) allowed to soak for 24 h in water to hydrolyze the metal chloride; (3) heated for 1200 s at 120°C and 10 s at 500°C in an electrothermal atomizer to dry the metal hydroxide and form the oxide; and (4) heated to 1800°C for 30 s to form the carbide. The formation of metal carbide was confirmed by gravimetry and x-ray diffraction. X-ray diffraction also indicated the presence of oxide on Ti- and W-treated cuvettes and of multiple metal carbide species on Mo- and W-treated cuvettes. Scanning electron microscopy of Ti-treated cuvettes showed the presence of small particles of a discrete carbide phase. The carbide-treated cuvettes last longer than conventional graphite and show enhanced sensitivities for carbide-forming elements determined by graphite furnace atomic absorption. Their analytical characteristics do not differ significantly from carbide-treated cuvettes prepared by other procedures. It is hypothesized that the primary effect of the metal carbide is to seal the graphite, causing it to be less porous.