Determination of nickel and cobalt in reference plant materials by carbon slurry sampling GFAAS technique after their simultaneous preconcentration onto modified activated carbon

A novel method, in which dimethylglyoxime impregnated activated carbon (DMGC*) has been applied for preconcentration and further simultaneous determination of Ni(II) and Co(II) ions in the reference plant materials by the carbon slurry sampling graphite furnace atomic absorption spectrometry technique (GFAAS), is presented. Moreover, for comparison and evaluation, the activated carbons modified in different ways, e.g. oxidized with concentrated HNO3 solution (OC*) and outgassed at high temperature (OGC*), were prepared and carefully characterized, especially in terms of their selectivity. The method after preconcentration on DMGC* carbon has been successfully tested by the analysis of certified reference materials (spinach leaves: NIST 1570a and NCS ZC73013, mixed Polish herbs INCT-MPH-2, tea leaves INCT-TL-1), using carbon slurry sampling GFAAS and the standard calibration method. The obtained detection limits for nickel and cobalt were 0.02 and 0.001 μg/g, and quantification limits were 0.06 and 0.004, respectively. The precision (RSD% about 7%) and accuracy of nickel and cobalt determination by the described method were acceptable.