Abstract:Chromium (Cr) in plants tends to inhibit plant growth and interfere with plant physiological processes. Appropriate amounts of selenium (Se) can enhance plant stress resistance and improve yield, while molybdenum (Mo) plays a key role in promoting plant growth and development and strengthening stress resistance. The contents of Cr, Se, and Mo in plants are of great significance for the evaluation of the nutritional value of agricultural products and food safety assurance. Plant samples are high in organic matter, complex in composition, and suffer from matrix interference. This study compared and evaluated three sample pretreatment methods: dry ashing, wet digestion, and microwave digestion, and compared the determination effects of inductively coupled plasma optical emission spectrometry (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS). Meanwhile, a relative carbon concentration (RCC) of less than 13% was introduced as an evaluation index for digestion efficiency. Validation through the determination of three different types of certified reference materials (CRMs) for biological composition analysis showed that: dry ashing achieved an RCC of less than 13%, but selenium volatilizes severely and chromium is prone to contamination. For wet digestion, the RCC of some samples exceeded 13%, requiring extended digestion time to eliminate matrix interference, along with a large amount of acid consumption and high blank values. Microwave digestion resulted in an RCC of 10.1%~12.7% with the least organic residue. ICP-MS exhibited higher accuracy and lower limits of detection (LOD) than ICP-OES. Microwave digestion combined with ICP-MS was selected for the determination of Cr, Se, and Mo, with LODs of 0.0067, 0.0082, and 0.0038 μg/g, respectively. The accuracy (relative error, RE) was less than 20%, and the relative standard deviation (RSD) was less than 10%, meeting the requirements ofSTechnical Requirements for Sample Analysis in Eco-Geochemical Assessment (Trial Implementation)S(DD2005-03). There was no significant difference between the detection results and those obtained by literature methods such as ICP-MS, ICP-OES, and atomic fluorescence spectrometry (AFS). Verified by actual samples, the RCC index realizes the quantifiable evaluation of digestion effects, reduces reagent consumption and environmental pollution, providing a reference method for the determination of elements in plants.