DETERMINATION OF TRACE-METALS IN SEAWATER BY GRAPHITE-FURNACE ATOMIC-ABSORPTION FOLLOWING ONLINE SEPARATION AND PRECONCENTRATION

A discontinuous microscale preconcentration system, based on the chelation of trace metals by a 20 mul column of silica-immobilized 8-hydroxyquinoline, was interfaced with a graphite furnace atomic absorption spectrometer. Volume-based loading of 835-5000 mul sample loops, followed by elution of the sequestered elements directly into the furnace in 48 mul of acid, provided quantitative recovery of Fe, Cd, Zn, Cu, Ni, Mn and Pb from open ocean seawater with a frequency of 10-20 per hour. Absolute detection limits were 0.3, 6.9, 4.2, 1.8, 10.2, 5.7 and 1.8 pg for Cd, Cu, Fe, Mn, Ni, Pb and Zn, respectively. The sensitivity of the graphite furnace technique is enhanced up to 250-fold compared to a standard 20 mul injection volume. Results are presented for the analysis of these elements in NRCC seawater Reference Materials NASS-3 and CASS-2 using simple calibration curves for quantitation.