MECHANISMS CONTROLLING ATOMIZATION OF STRONTIUM AND ASSOCIATED INTERFERENCES BY CALCIUM IN ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY

Real-time mass spectra of gas-phase species, produced in a graphite furnace containing strontium and calcium as an interferent, were obtained and used for elucidating mechanisms that control vaporisation, atomisation and interferences. The results suggest that strontium atoms were produced by desorption of the strontium created by dissociative chemisorption of the oxide. Strontium precursors included the carbide, oxide and hydroxide. During atomisation, strontium was lost by carbide and cyanide formation. The low- and high-temperature carbide losses imply two different formation mechanisms. Calcium interferes by increasing low-temperature strontium carbide and hydroxide losses and in shifting the appearance of free strontium to a lower temperature.