Development and application of a porous cage carrier method for detecting trace elements in soils by direct current glow discharge mass spectrometry

The accurate and reliable determination of trace elements in soil still remains a big challenge for glow discharge mass spectrometry due to the poor conductive nature of soils. In the present work, a porous cage carrier was developed and applied into the analysis of soils. The investigation results suggested that the carrier with circular cross-section area in the range from 20 to 38 mm2, length from 15 to 17 mm and diameter of hole size from 1.5 mm to 2.0 mm could obtain good signals. Then the porous cage carrier method was systematically evaluated with analysing three types of soil reference materials. The discharge process was maintained stable more than 100 minutes, which was much longer than boric acid method and indium sheet method. The investigations suggested that the internal precision was obtained within 16%, the external precision was better than 20% and the relative error was in the range from 0.7% to 17%. The detection limit of Tb could reach 0.014 μg g-1, which made the new method qualified for the analysis of trace elements in soils. Compared to the traditional tablet-pressed methods, the porous cage carrier method was investigated not only convenient for sample preparation, but also indicated good stability, reproducibility and better detection limit for trace elements. Furthermore, this method was proved to have potential application of GD-MS in the environmental area.