Determination of 33 Elements in Ground Substrate of Black Soil by ICP-MS/OES with Alkali Melting Digestion

The organic matter content in black soil samples is high, typically ranging from 3% to 10%. Traditional pretreatment methods such as open acid dissolution digestion, microwave acid dissolution and digestion, high-pressure closed acid dissolution and digestion, and ashing method cannot completely digest the sample, and different elements need to adopt different digestion and determination methods, resulting in long experiments, complex operation processes, high analysis costs, and are not suitable for the simultaneous determination of multiple elements. Sodium carbonate, lithium tetraborate and lithium metaborate were selected as mixed fluxes to digest the samples, and a method of adding tartaric acid to the acid extractor was proposed to extract the samples. 33 elements in the ground substrate of black soil were determined by inductively coupled plasma-mass spectrometry/optical emission spectrometry (ICP-MS/OES). The traditional method for analyzing black-soil samples is not suitable for the simultaneous determination of rare earth and other multiple elements, nor for elements prone to hydrolysis such as tantalum and hafnium, while ICP-MS/OES is suitable. The effects of different extraction systems on the extraction of tantalum and hafnium were studied, and the optimal ratio of 30mL of hydrochloric acid and 10mL of 100g/L tartaric acid was determined. On this basis, the detection limit of the samples was 0.01−41.04μg/g by the experimental method of control samples, and the results satisfied the requirements of soil analysis and detection. At the same time, different kinds of soil reference materials were selected for practical testing, and the measured values of each element were basically consistent with the standard values, with the relative standard deviations (RSDs) between 0.48%−4.36% and the relative errors between −5.23%−4.85%. In addition, to further verify the feasibility of the method, the relative standard deviations were all between 0.16%−4.97% when applied to actual samples.