Why 371,445 and 519 in my LCMS system?

So sweet question, today, remind me 2005 Fall, The First Question I asked at Tech.
All the optimal conditions were set up, where were they from?

One reasons could be they are from Contaminant Peaks from C18 Column Bleed. The contaminant ions, at M/Z 371, 445, and 519, when seen on the LC/MSD and LC/MSD Trap systems in positive ion mode, are believed to be C18 column bleed peaks of polysiloxane [O-Si(CH3)2-]n