Determination of chromium speciation in fumes prepared by a plasma metal sprayer as a model of actual welding fumes.

Chromium in fumes generated in work environments including sites of welding work appears in various and complex states. Determination of chromium speciation in samples is useful for estimating the toxicity of such fumes. In the present study, determination of chromium speciation in chromium fumes prepared using a plasma metal sprayer, which are regarded as a model of actual fumes, was carried out. Fumes were treated with heated sodium carbonate solution, ammonium chloride-ammonia buffer solution at pH 9.5, Tris-HCl buffer solution at pH 7.5, hydrochloric acid, heated dilute sulfuric acid, distilled water, and a boiling mixture of sulfuric acid and perchloric acid in various series of the tests. The amounts of chromium (III) and chromium (VI) dissolved in each solution were determined, and the dissolution rates in those solutions were examined. The fumes were concluded to contain dichromium trioxide with a corundum structure (25%), chromium (III) oxide (45%) and chromium (VI) oxide (27%) mixed at random in a nonstoichiometric state, and chromium trioxide (3%). The procedure presented could be applied to the determination of chromium speciation in various types of fumes with a few modifications. In addition, the sodium carbonate leaching method has been demonstrated to be available for the determination of chromium (VI) in such samples.