The preliminary partial factorial design (orthogonal test) and modified simplex optimization as well as univariate method were used to investigate the effects of small amounts of hydrogen added to three gas flows of an argon plasma on the signal and background intensities as well as their ratios for fourteen elements. According to the behaviour in such a plasma these fourteen elements can be divided into five groups. By the addition of hydrogen signal and background intensities were increased. The signal-tobackground ratio is not the only criterion to judge the performance of a plasma. Comparing with the pure argon plasma, also the signal-to-background ratios of all elements except for Ca and Mg decreased under the optimum parameters for Ca which was the extreme case in this study. The detection limits of Fe, Cd, Cr, V, Ni and Be were improved due to the increased signal intensity and more stable plasma. Ca can easily be used as an indicator to judge the performance of an argon-hydrogen plasma especially in the determination of heavy metals. Altogether, the behaviour of the following elements was studied: Al, Be, Ca, Cd, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Ti, V, Zn.