The addition of hydrogen fluoride to a seawater sample in a graphite tube atomizer makes possible the removal of the major matrix components in an optimized pre-heating step, thus a near interference free determination of copper and manganese trace metals is achieved. The optimization studies were supported by a priori calculation of limit of detection (LOD) data. For optimized conditions, the experimentally determined LOD values (3σ, n=20) were 0.11 and 0.03 μg l-1 for Cu and Mn, respectively, for 20 μl applied seawater volume. With the use of calibration with standard addition, determined concentrations of Cu and Mn in CASS-2 seawater and in SLEW-1 estuarine water were in good agreement with certified values at the 95% confidence level (n=10). © 2002 Elsevier Science B.V. All rights reserved.