Simultaneous Determination of Arsenic, Phosphorus and Sulfur in Coal by Inductively Coupled Plasma Atomic Emission Spectrometry with Fusing Sample by Eschka Reagent

As to solve the problem that arsenic, phosphorus and sulfur in coal sample could not be determined simultaneously by standard methods, the method mentioned by the title was proposed. With reference to the sample treatment method specified in the standard of GB/T 3058-2019, about 1 g of coal sample together with 1.5 g of Eschka reagent (produced by light magnesium oxide and anhydrous sodium carbonate at mass ratio of 2∶1) was mixed in the ceramic crucible, and extra 1.5 g of Eschka reagent was covered evenly on the above mixture. The crucible was heated to 500 ℃ for 1 h in the muffle furnace, and then heated to (800±10)℃ for 3 h. The burning residues were dissolved by 30 mL of hot water, and washed several times with 20 mL of hydrochloric acid. All the solutions were collected, transferred to a 100 mL-volumetric flask, diluted by water, and analyzed by inductively coupled plasma atomic emission spectrometer. In order to reduce the effect of salinity and viscosity of sample solution on intensities of spectral lines, working parameters of the instrument were set as to 1 350 W of RF power, 0.45 L·min^-1 of nebulization gas flow, 0.2 L·min^-1 of auxiliary gas flow, 13 L·min^-1 of cooling gas flow, and 60 r·min^-1 of analytical pump speed. The working curves were made by the standard addition method with the coal standard substances of GBW 11115a (arsenic and phosphorus) and GBW 11101y (sulfur) as the matrix, and calibrated by the software of the instrument, and the calibration curves were used for determination of arsenic, phosphorus and sulfur in standard substances and actual samples. It was shown that linear ranges of the calibration curves of arsenic, phosphorus and sulfur were found within 1.20, 20.0, 28.3 mg·L^-1, with detection limits (3s) of 0.004, 0.005, 0.170 mg·L^-1, respectively. The proposed method was applied to the analysis of coal standard substances, and determined values were within uncertainty ranges of certified values, with RSDs (n=7) of the determined values less than 5.0%. The results obtained by the proposed method were basically the same with determined values gained by the standard methods of GB/T 3058-2019 (arsenic molybdenum blue spectrophotometry used for determination of arsenic), GB/T 216-2003 (phosphorus molybdenum blue spectrophotometry used for determination of phosphorus) and GB/T 214-2007 (infrared spectrometry used for determination of sulfur).