Some examples of contamination by mass interference are studied in this work, specifically the molybdenum contamination in indium and boron implantations. This contamination is detected by Elymat and DLTS analyses, whereas it is missed by SPV, which is commonly used for routine line monitoring. Both Elymat and DLTS analyses consistently show molybdenum contamination clearly related to indium implantation conditions and to high dose boron implantations.