Effect of nickel and palladium as chemical modifiers and influence of urine matrix on different chemical species of selenium in electrothermal atomic absorption spectrometry

Abstract

The effect of nickel and palladium nitrates on the main selenium species in human urine, selenite and trimethylselenonium, was studied with respect to thermal stabilization in the graphite furnace. Special attention was also paid to the use of reduced palladium, either thermally or chemically. In all instances, maximum charring temperatures of 1200–1300 °C were attained for both species in aqueous solution. Trimethylselenonium was partially stabilized by reduced palladium, showing a similar behaviour to that using typical reducing agents that are found in urine, such as urea. The influence of the urine matrix on the selenium signal, using nickel as chemical modifier, was studied and minimized by optimization of the amount of modifier and charring and atomization steps. A selenium response independent of the urine matrix (selenium recoveries of 96%) was obtained for urine samples diluted 1+4 with water by adding 100 µl of nickel, using 900 and 2300 °C as charring and atomization temperatures, respectively, and including a cool-down step between charring and atomization.