DETERMINATION OF NICKEL IN ROCKS BY USE OF A CONTINUOUS PRECIPITATIONPRECONCENTRATION SYSTEM COUPLED ONLINE TO A FLAME ATOMIC-ABSORPTION SPECTROMETER

A rapid, accurate and precise method is described for the determinatio n of Ni at the microgram per gram level in silicate rocks. The method is based on the continuous precipitation of Ni with 1-nitroso-2-naphth ol and dissolution of the complex formed in ethanol. The sensitivity o f Ni determination is greatly enhanced by the presence of hydrogen per oxide. The metal can be preconcentrated 50-fold using a 10 ml volume o f sample, with a sampling frequency of 15-20 h-1 and a relative standa rd deviation of 3.2% at 50 mug l-1 of Ni. Tiron was used to increase t he tolerated amount of Fe up to an Fe:Ni ratio of 7500:1. Six referenc e silicate rocks were analysed fr Ni to test the accuracy of the propo sed method; the results were all consistent with the compiled values.