Determination of impurity elements in graphite by acid decomposition–inductively coupled plasma atomic emission spectrometry

A simple acid decomposition procedure was developed for the determination of impurity elements in graphite by ICP-AES. A high-purity graphite sample of 0.5 g was completely decomposed with a mixture of 5 ml of H2SO4(98% m/v), 3 ml of HClO4(70% m/v) and 1 ml of HNO3(70% m/v) in a 100 ml silica Erlenmeyer flask fitted with an air condenser at 200 °C for 30 min. Any excess of HClO4 and HNO3 in the solution was removed by heating on a hot-plate at 150 °C. The remaining solution was diluted to 100 ml with water. The major impurity elements (Ca, Fe, Ni, Sr, Ti and V) in the solution were determined by ICP-AES. Relative standard deviations were 2–10% at 5–200 µg g–1 levels for each element determined.