Determination of Toxic and Low-Temperature Elements As, Sb, Cd and Tl in Rapeseeds by Inductively Coupled Plasma-Mass Spectrometry with Slurry-emulsion System Sampling

BACKGROUND The quality of rapeseed and the degree of heavy metal pollution are directly related to human health. Monitoring the content of toxic elements such as As, Sb, Cd, and Tl in rapeseed is helpful for early monitoring of raw materials for edible oil production. OBJECTIVES To avoid the cumbersome pretreatment of strong acid digestion, quickly determine the accurate content of volatile toxic elements such as As, Sb, Cd, and Tl in rapeseed, and to solve the challenge of pretreatment due to the heavy fat content of grains, oils, and foods. METHODS A suspension-emulsion synergistic sample preparation technique was used to investigate conditions affecting suspension-emulsion, and a homogeneous and stable slurry-emulsion solution (SES) system was prepared. In the electrothermal vaporizer (ETV) with high sampling efficiency, the temperature-programmed parameters and the dosage of improver palladium nitrate were all optimized. SES was directly injected, and inductively coupled plasma-mass spectrometry (ICP-MS) was used to determine As, Sb, Cd and Tl. RESULTS The overall reproducibility (relative standard deviation, RSD) of the suspension-emulsion sampling-ETV-ICP-MS detection method were 10.1%, 8.8%, 8.9% and 6.4% [c=0.5% (m/V), n=5] for As, Sb, Cd and Tl, respectively. Under the optimum conditions, the limits of detection (3σ) were 40.0ng/L, 20.0ng/L, 50.0ng/L and 10.0ng/L for As, Sb, Cd and Tl, respectively. Accordingly, the limits of detection for the original solid samples were 8.0ng/g, 4.0ng/g, 10.0ng/g and 2.0ng/g for As, Sb, Cd and Tl, respectively. The contents of As, Sb, Cd and Tl in tested rapeseed samples were 50.4-90.5ng/g, 28.0-59.9ng/g, 51.3-69.1ng/g and 91.3-216.6ng/g, respectively. CONCLUSIONS The suspension-emulsion synergistic treatment of rapeseed with high oil content is simple, fast, and cost efficient. It utilizes the advantages of ETV sampling and promotes the application of ETV-ICP-MS solid sampling analysis.