Re: MS fragments 50 amu apart

50 amu is only caused by CF2 (to my knowledge), so you have a fluorocarbon or
fluorocarbon tail.  There are lots of surfactants that have the hydrophobic
portion that is fluorinated.  Typically, this portion is C8F17 to C3F7.  The
other end maybe ethoxylated (giving masses 44 apart).  If you're not separating
the surfactant, you'll get many different ethoxylations at once or if you are
separating them, you'll get a series of peaks that differ by 44 amu in the
spectra.