FENG Jun, LAN Mingguo, SHI Youchang, DUAN Wen, WANG Quancai, HE Xiuhui
The accurate determination of key target elements such as sulfur, boron, arsenic and gallium in geological samples is crucial to mineral exploration and comprehensive utilization of resources. In the conventional acid dissolution methods, boron easily reacts with acid to form volatile compounds (such as BF3), resulting in significantly lower determination results. In this study, nitric acid-hydrogen peroxide-hydrofluoric acid-mannitol digestion system was adopted. The digestion temperature (150 ℃), mannitol solution dosage (2.0 mL, 5.0 g/L) and analytical line (S 182.034 nm, B 208.959 nm, As 189.042 nm, Ga 294.364 nm) were systemically optimized. The method for the determination of sulfur, boron, arsenic and gallium by inductively coupled plasma atomic emission spectrometry (ICP-AES) was established. The linear correlation coefficients of calibration curves were all not less than 0.999, The limit of detection (LOD) for sulfur, boron, arsenic and gallium in this method was 0.07, 0.25, 0.05, and 0.005 μg/g, respectively. The contents of sulfur, boron, arsenic and gallium in the certified reference materials (CRMs) of soil (GBW07980), stream sediment (GBW07311) and rock (GBW07103) were determined according to the experimental method, and the relative standard deviation (RSD, n=12) of determination results were all less than 10%. The measurement results were all within the range of uncertainty of certified values. The contents of sulfur, boron, arsenic and gallium in geological samples, including the soil survey sample 1#, geological mapping stream sediment sample 2# and general rock sample 3#, were determined according to the experimental method, and compared with the standard methods (DZ/T 0279.28-2016 for sulfur, DZ/T 0279.11-2016 for boron, DZ/T 0279.13-2016 for arsenic, and GB/T 14506.30-2010 for gallium). The results indicated that the determination values of this method were in good agreement with those obtained by the standard methods. The performance index of proposed method could meet the requirements of The Specification of Testing Quality Management for Geological Laboratories. The mannitol chelating agent effectively inhibited the volatilization of boron, which was suitable for the efficient analysis of multi-elements in geological samples.