A simultaneous multi-elemental measurement of As, Bi, Ge, Sb, Se, and Sn was performed in this study by flow injection-hydride generation-inductively coupled plasma-time-of-flight mass spectrometry (FI-HG-ICP-TOFMS). An off-line pre-reduction treatment using a solution of 5% (m/v) KI and ascorbic acid for 15 min at 80 degreesC is described by presenting its advantages and disadvantages and compared with the results achieved without pre-reduction. Using optimised conditions the following figures of merit were achieved: limits of detection in the 0.08-0.54 ng ml(-1) range and relative standard deviations (RSD) of 1.7-6.7%, respectively. Applying the presented method, two certified reference materials (NIST 1643d freshwater and PACS-2 marine sediment) were analysed to demonstrate the suitability of the method for analysis of real samples. Results obtained from treated samples showed good agreement with certified values while the untreated ones considerably departed from them. (C) 2003 Elsevier B.V. All rights reserved.