The influence of non-spectral matrix effects on the determination of twenty-two trace elements (Rb, Sr, Y, Cs, Ba, lanthanides, Pb, Th and U) in rock samples using ICP-MS was investigated. Three types of multi-element solutions were synthesised containing the twenty-two trace elements, In, Tl and ten major rock-forming elements with varying mass fractions mimicking the compositions of basalt, peridotite and dolomite. The synthetic solutions were conditioned to have dilution factors (DF) of 1000-10000. The extent of sensitivity suppression relative to the DF = 10000 solution became more significant for smaller DF solutions, which was not constant across different elements in a single solution but displayed general dependence on m/z. This indicates that at least two internal standards (e.g., In and Tl) are required for the correction of sensitivity variation. On the basis of the results, a new isotope dilution-internal standardisation method for the determination of twenty-two trace elements with ICP-MS was developed, in which the sensitivity variation was corrected by monitoring two enriched isotopes, In-113 and Tl-203. This method, coupled with the quantitative correction of interference from oxides and hydroxides, achieved precise determination of twenty-two trace elements in some rock reference materials with reproducibilities of +/- 2% for basaltic to andesitic samples.