A simple method is described for the determination of trace metals (Cu, Mn and Mo) in seawater directly and simultaneously using a multi-element electrothermal atomic absorption spectrometer equipped with a transversely heated graphite atomizer. A mixture of Pd(NO3)2 and Mg(NO3)2 with the special gas (5% H2 and 95% Ar) was used as the chemical modifier. Matrix interferences were removed completely, so a simple calibration curve method could be used. The relative standard deviations (RSD) for the simultaneous determination of Cu, Mn and Mo in CASS-3 (near shore seawater) were 2–12% and the detection limits were 0.42 mg l for Cu, 0.68 mg l for Mn and 1.2 mg l for Mo. The accuracy of the method was confirmed by the analysis of certified reference saline waters (CASS-3, SLEW-2 and NASS-5). The analytical results were compared with those obtained using pure Ar as the purge gas. Scanning electron micrographs were used to investigate the physical form of Pd on the surface of the platform in the graphite furnace.