Determination of ultra-trace amounts of nickel in environmental samples by atomic absorption spectrometry with in-situ trapping of volatile species in an iridium-palladium coated graphite furnace

A sensitive and accurate method is described for the determination of ultra-trace nickel in environmental samples with in-situ trapping of volatile species in iridium-palladium coated graphite furnace atomic absorption spectrometry. The effects of the conditions for the generation and collection of volatile nickel species, such as medium acidity, potassium borohydride concentration, enhancement reagent concentration, reaction temperature, as well as graphite tube coating, carrier gas flow rate and trapping time were investigated. Phenanthroline was selected as the enhancement reagent due to its good enhancing effect, and iridium-palladium coating was used for the in-situ trapping of volatile nickel species at 300C. Under the optimal conditions, the calibration curve was linear from 0.21 up to 30.0 ng mL-1 with correlation coefficient of 0.9991, the detection limit (S/N = 3) was 0.21 ng mL-1 for 4 mL sample volumes and the relative standard deviation for 11 determinations of Ni at 10 ng mL-1 was 3.5%. The results found by the proposed methods are accordant with the certified values of water, soil and tea certified reference materials. The proposed methods have been applied for the determination of ultra-trace Ni in tap, river and wastewater, as well as rice and soil samples, with recoveries ranging from 97.3 to 100.5%.