Simultaneous determination of trace amounts of nickel, copper and mercury by liquid chromatography coupled with flow-injection on-line derivatization and preconcentration Original Research Article

Reversed phase liquid chromatography (LC) combined with flow-injection (FI) on-line derivatization and preconcentration resulted in a sensitive technique for analyses of multi-metals at trace levels. A new home-designed micro-preconcentration column containing RP-C18 material as solid sorbent, accommodated in a pressure-tight housing of stainless steel, combined with an LC six port valve was used to interface the flow-injection on-line derivatization and preconcentration system to the LC equipment. This preconcentration column, which can be used for on-line derivatization and preconcentration with use of peristaltic pump, proved to be strong enough to bear the high pressure of the LC eluent. Based on this FI-LC system, a method for the determination of Ni(II), Cu(II), and Hg(II) in water samples as their diethyldithiocarbamate (DDC) complexes has been developed. A methanol/water mixture (80:20 v/v) as LC eluent and intelligent UV detector programmed in time for absorption measurement at the maximum absorption wavelength of the respective metal–DDC complexes were used. The detection limits were (signal : noise=3) 0.16, 0.41 and 1.1 μg l−1 for Ni, Cu and Hg, respectively; and the relative standard deviations were 3.6, 4.5 and 3.9% for Ni(II)(0.10 mg l−1), Cu(II) (0.10 mg l−1) and Hg(II)(0.40 mg l−1)(n=6), respectively. The developed method was successfully applied to wastewater samples from an electric power station and a machine tool factory and the results agreed with values determined by atomic absorption spectrometry.