SILVER AND LANTHANUM AS EFFECTIVE MODIFIERS IN TRACE DETERMINATION OFCADMIUM IN NICKEL-BASE ALLOYS BY ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY

Trace cadmium in nickel-base superalloys was determined by a stabilize d temperature platform furnace using atomic absorption spectrometry wi th a deuterium are background correction system. The volatility of cad mium limits the pyrolysis temperature. This prevents the removal of th e interfering alloy matrix at the thermal pretreatment step. Hence, an enormously high background signal has been observed. Chemical modifie rs including ammonium citrate, 1-(2-pyridylazo)-naphthol, 4-(2-pyridyl azo)resorcinol, 2-(5-bromo-2-pyridylazo)-5-(diethylamino)-phenol, Trit on-X 100, EDTA, potassium nitrate, palladium nitrate, magnesium nitrat e, aluminum chloride, ammonium dihydrogen phosphate, lanthanum oxide, lanthanum chloride and silver nitrate have been studied. Matrix interf erences were effectively reduced by silver and lanthanum. The 100-300 degrees C increase in the pyrolysis temperature effectively reduced th e non-specific absorption from the alloy matrix. Interferences from fo reign ions were also investigated. The merit of the proposed method wa s increased by the excellent agreement between the certified and the e xperimental values of Cd in the standard reference material, IN100, an d the recovery obtained (100-104%). The precision of six successive re plicate measurements was 4.9% with Ag modifier and 2.5% with La modifi er, respectively. The results of analysing Tracealloy B were also sati sfactory. (C) 1997 Elsevier Science B.V.