Abstract: Generally, an oxygen blank and a memory effect interfere with the isotopicanalysis for organic substance. Futhermore the study of δ~(34)S in some sulphidehas as well suggested that sampling process of inorganic substance affects onthe results of mass spectrometry. Author suggests to eliminate the effects men-tioned above with following steps: 1) Preheating the sampling system in vacua and repetitive processing ofsamples prior to the analysis can reduce and neutralize memory effects. 2) The reduction reactor is thin nickel-plated to minimize the reactionbetween carbon and silica which results in the blank.