Thiacalix[4]arenetetrasulfonate as specific pre-column chelating reagent for nickel(II) ion in kinetic differentiation mode high-performance liquid chromatography Original Research Article

Thiacalix[4]arenetetrasulfonate (TCAS) has been examined as a pre-column chelating reagent for the determination of trace metal ions by kinetic differentiation mode (KD) ion-pair reversed-phase high-performance liquid chromatography (HPLC) with spectrophotometric detection. Among 14 kinds of common metal ions tested here, viz. Al(III), Ca(II), Cd(II), Co(II), Cr(III), Cu(II), Fe(III), Hg(II), Mg(II), Mn(II), Ni(II), Pb(II), V(V), and Zn(II) ion, only Ni(II) ion was detected as the TCAS chelate in the HPLC separation stage in spite of TCAS forming the chelates with various metal ions except for Al(III), Ca(II), and Mg(II) at the pre-column chelation stage. The undetected metal–TCAS chelates seemed to be dissociated on an HPLC column where no added TCAS was present in the mobile phase because of their kinetic unstability. The calibration graph for Ni(II) ion gave a wide linear dynamic range (40–20,000 nM) with the very low detection limit (DL) (3σ base-line fluctuation) to be 5.4 nM (0.32 ng ml−1). The practical applicability of the KD-HPLC method with TCAS was demonstrated with the determination of trace Ni in coal fly ash.