Alternative to DCM for source cleaning

Abrasive cleaning does not mean removing metal.  Think of it like doing the dishes. Scrub the parts, wash off the stuff, and leave the parts clean.

How careful you need to be sort of depends on the application and usage.  If the instrument is used for ppt or lower levels and the system must be ultra-clean, then thoroughly cleaning very often and using every way of removing the adhered residue from the sample, column, and gas is important.  If the instrument is used for peaks that are too big all the time anyway, or sees hundreds of samples a day, being extra cautious may be unnecessary.  Since everything that comes out of the column goes into the MS, cleaning the source is one part of managing the overall instrument contamination.  The cleaner you keep it the longer time between cleanings and the longer time before remedial cleaning is required. 

If you've abrasively cleaned it the solvent washes are mostly for removing residue that isn't stuck on the parts.  Of course it's difficult to get every bit clean enough to ensure that the invisible residue is removed.  As little as 200 angstroms of stuff negatively affects the source's performance and you can't see 200 angstroms.

Knowing both the best way and also the most workable way considering the circumstances is important.  Cleaning videos can be seen here: (+) Videos - GC/MS Portal - Agilent Community

Some say any soap is bad even though it does help remove the alumina and swarf (metal residue).  There have been instances where soap residue caused contamination peaks. To that I say rinse longer with more changes of water.  I do the soapy water step with the smallest amount of detergent I can use, barely a drop of liquid or a tiny dash of powder in a large beaker full of water.  I swirl the parts in that and then put the beaker at the bottom of the sink and run tap water over it, letting it spill into the sink and swirl it more there. Then I use a tweezers to remove the parts from that beaker into a new clean beaker before continuing.  Fresh beakers at every step is a best practice.

Metal finishers and painters have the water drop or water break test. Water beads up, or doesn’t flow as a continuous sheet, on a surface with hydrophobic residues.  This test can help identify surfaces contaminated with an adhered organic layer like all parts inside of a GCMS vacuum chamber.  There are two ways to do this test.  Set a flat part down on a flat surface and use a dropper or pipette to place a single drop of water on the substrate. Look at how it behaves. If the droplet sits still beaded up, the surface is contaminated. If it spreads out, it’s clean. That’s difficult since it’s quite subjective and the source parts are mostly curved.   The second way is easier to do, but maybe even harder to evaluate.  Hold the part in a tweezers, submerge it in water, and withdraw the part. As the part is withdrawn, does the water flow off as a continuous sheet or is it broken up?   Again, this is a bit hard to evaluate.

Clean the source parts thoroughly and often.  Replace the consumables - repeller insulators, transferline tip seal, and extractor lens insulator often and the lens stack insulator every few years.