DETERMINATION OF TRACE AMOUNTS OF THALLIUM AND TELLURIUM IN NICKEL-BASE ALLOYS BY ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY

A method is described for determining trace amounts of Tl in nickel-ba se alloys using pre-treatment with ammonia solution and electrothermal atomic absorption spectrometry. Thallium was coprecipitated when the sample solution of a nickel-base alloy was treated with ammonia soluti on. Background absorption was effectively eliminated in the new matrix . Nickel worked effectively as a chemical modifier for Te, and raised the charring temperature from 500 to 1000-degrees-C. Therefore, it was possible to determine sub-nanogram levels of Te without any complicat ed pre-treatment. The accuracy and precision of the proposed method we re elucidated through the analysis of two nickel-base alloys: spectros copic standard certified reference material 346A IN100 Alloy and Stand ard Reference Material 899 Tracealloy C. There was good agreement betw een the expected values and the results obtained. For Tl, the results found for IN100 and Tracealloy C were 1.94 +/- 0.09 mug g-1 (Sr = 5%) and 0.251 +/- 0.005 mug g-1 (s(r) = 2%), respectively, the reference v alue for IN100 being 2 and certified value for Tracealloy C being 0.25 2 +/- 0.003 mug g-1. The recoveries for these alloys were 100 +/- 4 an d 102 +/- 3%, respectively. The detection limit was 15 pg g-1. For Te, the certified values for IN100 and Tracealloy C were 9 +/- 1 and 5.9 +/- 0.6 mug g-1, respectively. The Te contents determined by the propo sed procedure were 9.03 +/- 0.09 mug g-1 (s(r) = 1%) and 5.93 +/- 0.26 mug g-1 (s(r) = 4%), with recoveries of 98 +/- 4 and 97 +/- 4%, respe ctively. The detection limit was 35 pg g-1. Although the addition of P d modifier gave a better detection limit (18 pg g-1), it led to poorer results in terms of accuracy, precision and recovery.