Determination of As, Mn, Pb and Se in coal by slurry electrothermal vaporization inductively coupled plasma mass spectrometry

A method for the determination of trace elements in coal by electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS), int roducing the sample as a slurry, is proposed. The slurry was prepared by mi xing the powdered coal (< 45 mu m) with aqueous 5% v/v nitric acid solution in an ultrasonic bath. An ultrasonic probe was used to homogenize the slur ry in the autosampler cup just before its introduction into the graphite tu be. The best compromise conditions for the furnace temperature program, the amount of palladium used as modifier, the carrier gas flow rate, etc., wer e determined. By introducing 10 mu L of a 4.0 mg mL(-1) coal slurry, using 3 mu g of Pd as a modifier, and a pyrolysis temperature of 600 degrees C, m ost of the obtained values for four coal reference materials were well with in the certified range, using external calibration with aqueous solutions. No carrier had to be added in addition to the palladium modifier. Using a l ower slurry concentration of 1.3 mg mL(-1) and 2 mu g of Pd as the modifier , the values obtained for lead were significantly lower than the certified ones. This problem could be solved in part by adding NaCl as a physical car rier, in addition to the palladium, showing that this carrier reduces the d ifferences in the analyte transport from the sample and from the calibratio n solutions. However, results for most elements, except for arsenic, tended to be a little low even under these conditions, hence, preference was give n to the higher slurry concentration.