DETERMINATION OF NICKEL IN SALIVA BY ELECTROTHERMAL ATOMIC-ABSORPTIONSPECTROMETRY USING VARIOUS CHEMICAL MODIFIERS WITH ZEEMAN-EFFECT BACKGROUND CORRECTION

The profile of nickel signals using electrothermal atomic absorption s pectrometry with deuterium and Zeeman-effect background correction is presented. The Zeeman effect system of background correction offered d efinitive advantages and therefore was used for the determination of n ickel in saliva in the presence of various isomorphous metals. The hig hest 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 interfer ence. However, the use of 200 ng of Pd in conjuction with 300 ng of Lu has a higher sensitivity, offers an advantage against interference fr om 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 wh ole saliva gave an average of 0.81 +/- 0.30 of mu g/L of Ni (range fro m 0.5 to 2.0 mu g/L of Ni). The agreement between the observed and cer tified values obtained from a Seronorm Blood Serum Standard Reference Material was good.