AUTOMATIC ONLINE PRECONCENTRATION SYSTEM FOR GRAPHITE-FURNACE ATOMIC-ABSORPTION SPECTROMETRY FOR THE DETERMINATION OF TRACE-METALS IN SEA-WATER

An automatic on-line preconcentration system for graphite furnace atomic absorption spectrometry (GFAAS) for the determination of trace metals in sea water was developed. This system was modified from a Perkin-Elmer AS-40 autosampler by mounting a silica gel C18 microcolumn near the tip of the automsampler capillary. The preconcentration procedure was performed by using the pumps of the AS-40 autosampler and a four-way valve and controlled by a programmable controller. The chelating agent ammonium tetramethylenedithiocarbamate [ammonium pyrrolidinedithiocarbamate (APDC)] was added to the sample solution and only 0.2-2 ml of sample was required to determine cadmium and copper in sea water. The calibration graph method was used and the detection limits of cadmium and copper were 1.26 and 6.5 ng l-1, respectively.