Some problems concerning signal fluctuation, matrix effect and internal standard in ICP-MS technique have been studied. Experiments show that besides the instability of the instrument itself, space-charge effect will exert an influence on the signal fluctuation as well. Spacecharge effect and ambipolar diffusion would play on important role on matrix effect. According to the variation of signal fluction and matrix effect, the mass number of internal standard should be close to analyte.Better than signal-internal standard,a double-internal standard method has been proposed.
