Determination of selenium using the hydride AAS technique

1 Determination of selenium using the hydride AAS technique Principle 

Using sodium borohydride, selenium ions are reduced to selenium hydride, transferred to a heated quartz cuvette with the aid of a current of inert gas, decomposed thermally, and the absorption of the atoms is measured in the beam of an atomic-absorption spectrometer. In the hydride technique, the element which is to be determined is volatilized as a gaseous hydride and separated off from the matrix. Interferences may occur if there is a considerable excess of elements such as antimony, arsenic, tin, bismuth, mercury, or tellurium, which may also be volatilized using this technique. Above all, heavy metals such as copper and nickel have a disturbing effect during the hydride formation itself. These interferences may be diminished by adding 300 mg of solid 2-pyridine aldoxime to the solution for measurement. 

Since the hydride technique only permits quantitative detection of selenium (IV), selenium (VI) must be converted to selenium (IV) by prereduction (boiling in a strongly hydrochloric solution at the reflux). 

Treat 100 ml of the sample for investigation with 50 ml hydrochloric acid (1.17 g/ml) and boil for 15 minutes at the reflux. Treat blanks and calibration solutions in the same way. 

Atomic-absorption spectrometer with hydride attachments 

---