Determination of nickel in saliva by electrothermal atomic absorption spectrometry using various chemical modifiers with Zeeman-effect background correction

The profile of nickel signals using electrothermal atomic absorption spectrometry with deuterium and Zeeman-effect background correction is presented. The Zeeman effect system of background correction offered definitive advantages and therefore was used for the determination of nickel in saliva in the presence of various isomorphous metals. The highest nickel absorbance values corresponded to 200, 300, 300, 300, 600, and 200 ng of Tb, Mg, Sm, Lu, Tm, and Pd, respectively. On the other hand, the addition of Eu, Er, and Ho decreased the nickel signal. The presence on each modifier alone does not eliminate the matrix interference. However, the use of 200 ng of Pd in conjuction with 300 ng of Lu has a higher sensitivity, offers an advantage against interference from the background of saliva matrix and produces good recoveries (98 to 102% from unspiked and spiked saliva samples). The limit of detection was 0.11 mu g/L for a characteristic mass of 16.6 pg of nickel using Pd-Lu as modifier. The within-batch precision varied between 0.8 and 1.5% relative standard deviations. The analysis of thirty samples of whole saliva gave an average of 0.81 +/- 0.30 of mu g/L of Ni (range from 0.5 to 2.0 mu g/L of Ni). The agreement between the observed and certified values obtained from a Seronorm Blood Serum Standard Reference Material was good.