In this paper, in the presence of Li+, Na+, K+, Ca2+ and Mg2+, determinations of Pd, Pt and Au by microwave plasma torch atomic emission spectrometry (MPT-AES) using an on-line clean-up were studied. It was shown from the experiments that these interfering matrix elements might be removed with the strong acidic cation exchange resin. The method was applied to the analysis of some practical samples and the results obtained were satisfactory.