Abstract：The energy-dispersive X-ray fluorescence (EDXRF) method for detecting heavy metal Cd in soybeans faces challenges due to the complex composition of soybeans, difficulties in obtaining standard samples, and high production costs. Leveraging the sulfhydryl groups in soy protein that complex with Cd2+, we propose a mixed solid-liquid sample preparation method based on the standard addition method. This, combined with intensity correction for matrix correction, aims to improve the accuracy and reliability of EDXRF for Cd detection in soybeans. First, we optimized seven parameters affecting Cd excitation in soybeans through single-factor experiments. The optimized conditions were as follows: tube voltage of 70 kV, tube current of 700 μA, detection time of 1 200 s, sample mass of 12.00 g, sample mesh size of ≥100 mesh, tablet pressure of 25 MPa, and holding time of 20 s. Next, we prepared soybean powder samples with Cd spiked at concentrations of 0.000, 0.100, 0.200, 0.300, 0.400, and 0.500 mg·kg-1 by the standard addition method. Under the optimized conditions, a standard curve was established between the resolved spectral area and the spiked concentration of Cd in soybean. This curve exhibited excellent linearity with an R2 value of 0.996 22. This indicates a significant linear relationship between the fluorescence intensity of Cd in soybean and its elemental concentration, demonstrating that soybeans have an effective complexation effect on Cd2+. Finally, comparing the Cd content calculated by the standard addition and incremental methods revealed a deviation due to the absorption enhancement effect of other elements, particularly Sn, on Cd. Based on GFAAS results for Cd content in soybeans, a correction equation was derived using the intensity correction model. After intensity correction, the average deviation of the EDXRF method for four 100-mesh soybean samples decreased from 0.048 30 to 0.006 73. Testing ten randomly selected samples validated the universality of the calibration method, with the average deviation decreasing from 0.035 48 to 0.010 94 and the overall deviation reducing from 36.32% to 3.31%. The mixed solid-liquid sampling method proposed in this paper is simple to operate. It effectively overcomes the limitation of the lack of corresponding standard samples for EDXRF in soybean detection. Combined with the intensity correction mode, the correction effect is remarkable, providing a new and effective method for detecting cadmium (Cd) in soybeans.
Key words：EDXRF; Standard addition method; Condition optimization; Matrix correction
马嘉昊，杨剑波，李 锐，许 洁，李 辉，吴佳慧. 标准加入法固-液混合制样在EDXRF检测大豆中重金属含量的应用研究[J]. 光谱学与光谱分析, 2025, 45(06): 1639-1647.
MA Jia-hao, YANG Jian-bo, LI Rui, XU Jie, LI Hui, WU Jia-hui. Application of Solid-Liquid Mixing Sample Preparation With Standard Addition Method in EDXRF Detection of Heavy Metal Content in Soybeans. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2025, 45(06): 1639-1647.
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