interferences from titanium and zirconium during calcium determination by flame spectrometry

Titration methods based on an inhibition effect were used to investigate the interferences from Ti and Zr in the determination of Ca by atomic absorption and flame emission spectrometry using an air–acetylene flame. Changes either in the absorption or emission signal of Ca was continuously registered on a computer display and characteristic titration curves were obtained. The mole ratios between Ti or Zr and Ca at characteristic points on titration curves were used to explain the quantitative changes occurring in the solution being titrated and aspirated into the flame. In order to investigate procedures for eliminating these interferences, a method of atomic absorption inhibition release titration was used. For this purpose, a solution of La, as a releasing agent with a very low Ca concentration, used as an indicator, was continuously titrated with the solution of Ti as inhibitor. A comparative study of the activity of Ba, Sr and La as releasing agents was investigated during titration of Ca with Zr solution. Based on the calculated mole ratios between Zr and Ba, Sr or La, the effectiveness of these agents in eliminating the interferences was determined. Possible reactions occurring during evaporation of the aerosol in the air–acetylene flame are represented by chemical equations.