Remarkable Emission Intensity of Dimethyl Sulfide Form-Sulfur on the Determination of Sulfur in Biomass Ethanol by Inductively Coupled Plasma-Optical Emission Spectrometry

Inductively coupled plasma-optical emission spectrometry (ICP-OES) was applied for the determination of sulfur in biomass ethanol and compared with three conventional combustion-based methods of microcoulometry, ultraviolet fluorescence and oxyhydrogen flame combustion. The three combustion-based methods gave similar results. However, ICP-OES with standard solutions prepared from sulfate form-sulfur caused a serious overestimate due to the presence of dimethyl sulfide (DMS). The emission intensity of DMS form-sulfur was much higher than that of sulfate form-sulfur due to its high introducing efficiency to a plasma. Consequently, DMS form-sulfur caused a 6 to 21-times overestimate, depending on the ICP instruments used. In order to suppress this phenomenon, it was recommended to carry out PTFE closed-vessel acid decomposition with a mixture of hydrogen peroxide and acetic acid prior to an ICP-OES measurement.