Speciation of chromium in Australian fly ash

The concentrations of chromium (III) and (VI) in fly ash from nine Australian coal fired power stations were determined. Cr(VI) was completely leached by extraction with 0.01 M NaOH solution and the concentration was determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). This was confirmed by determining Cr(III) and Cr(VI) in the extracts of fly ash that had been spiked with chromium salts. These analytical measurements were done using a combination of ion-exchange chromatography and ICP-AES. The elutant was 0.05 M HNO3 containing 0.5%-CH3OH. When the column was operated at a flow rate of 1.2 ml min−1 and samples were injected by use of a sample loop with a volume of 100 μl, Cr(III) and Cr(VI) in sample solution was exclusively separated within approximately 10 min. The detection limits (3σ) were 5 ng for Cr(III) (0.050 mg l−1) and 9 ng for Cr(VI) (0.090 mg l−1), respectively. A relative standard deviation of 1.9% (n = 6) was obtained for the determination by IC–ICP–AES of 0.25 mg l−1 Cr(III) and Cr(VI).