Simultaneous determinations of fluorine, chlorine, and sulfur in rock samples by ion chromatography combined with pyrohydrolysis

We present a simplified method for simultaneous determinations of fluorine (F), chlorine (Cl), and sulfur (S) contents and isotopic abundances in rock samples. After using pyrohydrolysis to extract F, Cl, and S from a sample and transfer it into a sodium hydroxide (NaOH) solution, concentrations of F, Cl, and S as sulfate are measured by ion chromatography. The method is applicable to a variety of rock materials, including peridotite, basalt, gabbro, andesite, rhyolite, sulfide minerals, and possibly to sea salt, with F, Cl, and S contents of several mu g g(-1) to several tens of weight percent in 40 to 250 mg of rock powder. F, Cl, and S contents obtained by 5-7 repeated analyses of each of nine geological reference materials were in good agreement with previously reported values. In certain reference materials, sulfite peaks were observed, indicating incomplete oxidation to sulfate during S extraction by pyrohydrolysis. However, total S contents in those samples analysed by ICP-AES were also in good agreement with previous reported values. The RSDs of F, Cl, and S contents in reference materials were <6%, except for samples with F content <10 mu g g-1 (similar to 20%) or S content