Abstract: Sample was digested by microwave. Potassium iodide is oxidized by Se (Ⅳ) in medium of 0.2 mol/L hydrochloric acid，the product I3－ reacts with rhodamine B to form ion complex. Potassium iodide of 1 mL at 10 g/100mL and rhodamine B of 3 mL at 0.005 g/100mL were used. The formed ion complex was extracted into the 0.5 mL ionic liquid phase (C4MIM)PF6. The quenched fluorescence was observed for rhodamine B in the presence of Se (Ⅳ). The linear determination range of Se (Ⅳ) was between 2 and 60μg/L. The limit of quantification of method (RSN＝10) for selenium was 20μg/kg, and the average recoveries were from 87.9% to 105%. The proposed method has the characteristics of easy operation, no pollution and high sensitivity, and it can be used for the analysis of trace selenium in zinc-selenium health food and fortified nutrient salt.

Key words: microwave digestion, room temperature ionic liquid, fluorescence quenching, selenium, food