Using the high velocity helium jet and the cold finger simultaneously, the anticontamination of the sample in vacuum chamber of the probe can be achieved for at least the first 12 min. A limit of detection (LOD) of carbon of 0.03 wt % in steel samples has been achieved. Further, it has been shown that the anticontamination technique extends the general usefulness of the electron probe for obtaining the carbon concentration profile of carburized steel.