Determination of Selenium by Single-Drop Microextraction and Diffuse Reflectance Infrared Spectroscopy

ABSTRACTA simple and convenient assay based on single-drop microextraction with infrared spectroscopy is reported for the determination of selenium. The extraction conditions were carefully optimized and selenium was preconcentrated through single-drop microextraction in 1,2-dichloroethane containing N-hydroxy-N-phenyl-N′-(o-tolyl) benzimidamide. The method is selective and almost all common ions including molybdenum(VI), chromium(VI), and tungsten(VI) did not interfere with the isolation protocol. The selenite band at 875 ± 2 cm−1, which is assigned to the asymmetric vibrational stretch (υ3), was used for the quantification of selenium. Low limits of detection and quantification of 2.0 and 6.6 µg L−1 demonstrate the sensitivity of the method. Good precision was evaluated by the standard deviation (2.0 µg L−1) and relative standard deviation (0.5%) for 8 µg L−1 was achieved for 10 measurements. The method was used to analyze human blood, urine, and water for selenium.