Determination of 23 Elements in Ground Substrate Samples of Plain Areas by ICP-OES with Three Mixed Acid Digestion and Aqua Regia Extraction

The ground substrate is mainly agricultural tillage layer, with high organic matter content and significant differences in composition, which affects the accuracy of detection results. The industry standard DZ/T 0279.2—2016 adopts four acid dissolution, and there is a difference between the standard curve established by the standard solution and the processed sample, which is affected by the matrix. On the basis of this standard method, this article optimizes and establishes a method for the determination of 23 elements in ground substrate samples in plain areas using three acid digestion aqua regia extraction and inductively coupled plasma-optical emission spectroscopy (ICP-OES). In order to solve the problems of complete sample digestion and matching with the matrix, the strong decomposition ability of hydrofluoric acid on silicates was utilized to form a three acid system with perchloric acid and nitric acid (hydrofluoric acid nitric acid perchloric acid volume ratio of 5:3:1), which completely digested the sample under heating; The effective extraction efficiency of 5 different dosages of aqua regia was investigated, and it was determined to select 10mL of aqua regia. A standard curve was established using national standard substances with different content gradients to ensure consistency between the matrix in the standard series and the sample to be tested, eliminating matrix interference. The results showed that the measured values of each element in the standard reference material were basically consistent with the standard values. The precision (n=12) of the method was less than 10%, and the accuracy (ΔlogC) was not greater than 0.1. The detection limit of the method was higher than DZ/T 0258—2014, and the difference with XRF and ICP-MS detection results was not significant. Through actual sample verification, this method can improve the efficiency of simultaneous detection of multiple elements in surface matrix survey samples in plain areas and reduce analysis costs.