Mechanism of the action of palladium and palladium- magnesium nitrate modifiers used in the determination of tellurium by electrothermal atomic absorption spectrometry

A study was made of the possible mechanism of tellurium atomization with th e use of palladium and palladium-magnesium nitrate as chemical modifiers in electrothermal atomic absorption spectrometry (ETAAS). The experiments wer e performed by adding various masses of Pd and Pd-Mg( NO3)(2) to the standa rd solution of tellurium and then injecting them into an ETAAS for the dete rmination of tellurium. Absorbance profiles of Te peaks were found to be se nsitive to the mass of Pd present. Slightly positive shifts in the temperat ure of peak appearance were observed, while a higher level of Pd caused inc reasing shifts in the peak appearance temperature and a significant tailing . However, these phenomena can be avoided by adding a large amount of Mg( N O3)2. The effect of various amounts of modifiers on the analytical signal o f tellurium was also investigated by electrothermal vaporization inductivel y coupled plasma mass spectrometry (ETV-ICP-MS) for monitoring the analyte behavior through a heating cycle from 120 to 2650 degreesC. The positive sh ift in the peak appearance temperature was also observed on increasing the mass of Pd. Several marked signal pulses at temperatures between 1500 and 2 650 degreesC were observed and assumed to result from the different migrati on rate of tellurium out of the droplets of Pd and the desorption of the va por condensation for [Te, Pd] coupling. The typical distribution of Te and Pd onto the surface of the graphite tube after the atomization step was als o investigated by laser ablation inductively coupled plasma mass spectromet ry (LA-ICP-MS) and scanning electron microscopy (SEM).