1991 Volume 40 Issue 3 Pages T71-T75
A microwave digestion technique for trace element analysis of coals was examined. Each 0.25g of twelve coals and cork containing fixed carbon ranging from 43.0 to 88.8% was digested in a microwave oven using a borosilicate vessel with two type mixtures of nitric-sulfuric acids or nitric-perchloric acids. The complete digestion times were compared by referring to the fixed carbon contents. The digest was transferred to a 50ml of PTFE vessel and evaporated until white fume appeared. After hydrofluoric acid treatment, boric acid was added and the solution was diluted to 25ml. Matrix matching was made by adding corresponding amounts of major elements. Chromium, copper, manganese, nickel, lead and zinc were determined by AAS. The analytical data for the digests of Black Water and Smoky River coals showed satisfactory agreement with those obtained by a sealed PTFE bomb method. However, the recovery for chromium in NIST SRM 1632a and Smoky River coal was low.
