Abstract：The sample was digested with HNO3, HClO4 and HF. A new method of determining sulphur in coal by high resolution atomic absorption spectrometry with continuum light source based on the measurement the absorption of CS diatomic molecule formed in fuel-rich air and ethyne flame was proposed. The instrumental conditions were optimized using sulphur-bearing standard solution and certified reference materials of coal. The digestion methods of coal sample with different acid mixtures were compared. The possible existing spectral and chemical interference and the influence of organic solvent on the absorption of CS were studied. The results showed that, except that the wavelength difference between Fe 258.045 nm and CS 258.056 nm was smaller than 0.015 nm, the wavelength differences between the interference lines of other elements and CS line were all larger than 0.015 nm. There for,these interference lines could be separated from CS line by the high resolution of instrument, overcoming the interference. Although Fe 258.045 nm line could not be totally separated from CS 258.056 nm, its absorption strength in fuel-rich air and ethyne flame was very low and had no true interference. The generated PbSO4 precipitates from Pb and SO42- in solution reduced the absorption of CS, so ammonium acetate was added into solution to release the SO42- from PbSO4 precipitates to eliminate the interference of lead. The effect of HNO3 and HClO4 on the absorption of CS was not obvious. In five organic solvents including methanol, ethanol, acetic acid, acetonitrile and acetone, only ethanol showed obvious inhibition on the absorption of CS, and acetone and acetonitrile could significantly enhance the absorption of CS. For three absorption lines of CS （257.594 nm, 258.056 nm and 257.961 nm）, the linear ranges of calibration curves of sulphur were all 50-1 000 mg/L. The detection limits were 34 mg/L, 21 mg/L and 12 mg/L, respectively. The proposed method was applied to the determination of sulphur in certified reference material of coal and coal seam sample. The found results were consistent with the certified values, and the relative standard deviation （RSD, n=5） of determination results were 0.053 %-0.082 %.
