Determination of trace metal impurities in graphite powders by acid pressure decomposition and inductively coupled plasma atomic emission spectrometry

Abstract

The complete decomposition of graphite powders by an acid pressure decomposition method was investigated. A 0.5 g amount of graphite powder was completely decomposed by pressure decomposition with a mixture of 20 ml of nitric acid and 4 ml of sulfuric acid at 250 °C for 72 h. Excess of nitric acid in the solution was removed by heating on a hot-plate, then the remainder was diluted to 50 ml with water. Lithium, Na, K, Mg, Ca, Al, Fe, Ni, Cr, Sr, Ti and V in the solution were determined by inductively coupled plasma atomic emission spectrometry. The analytical results agreed with collaborative analytical values and the values obtained using an oxygen plasma etching method. The accuracy of the proposed method was superior to that of the ashing method, because the graphite powder is decomposed in a closed system without contamination from the environment or vessels used. The relative standard deviations (n= 5) were lower than 10% at the 1 µg g^–1 level of metal impurities.