This is a question that I wish people would ask me more.
The question: Is there really a difference between HPLC and LC-MS grade solvents?
The answer? YES!!!!! And please please stop putting HPLC grade solvents into your mass spectrometer!
Over the course of this summer I went on a whole lot of trips where I helped people restore their mass specs performance. While the situations were all different, I can say with a high degree of certainty that every lab I visited that was using HPLC grade solvents in their mass spectrometers came to regret it and that we got better performance when we switched it...and an engineer cleaned everything to get all the junk out....
To make an HPLC solvent you need nice clean water. No doubt. But the biggest determinant of what is clean water is that it isn't going to react to UV. Lots and lots of things in this world will have zero effect on chromatography and will also not show up on UV. ALL of these things have mass. A lot will ionize. Many will end up putting undo stress on your nanoLC components, source, quads, lenses and other shiny things in your MS. Some will even screw up the charges of your peptides and proteins.
Sorry this is a rant. I Googled: HPLC vs LC-MS grade solvents and came up with very little. I hate you to take my words just because they are my words, but I swear that if you are using HPLC grade solvents in your mass spectrometer you are going to have problems. Maybe not today, maybe not tomorrow, but soon...
My experience is actually the total opposite: I systematically tested methanol, acetonitrile and water in different grades (Ultrapure MS grade vs. HPLC grade or milliQ grade 3 in the case of water) and found no detectable background difference. The only difference I found was on the formic acid modifyer, where ultrapure formic acid gave around 25% lower baseline on mass transition in the lower mass range compared with crude formic acid of unknown grade.
ReplyDeleteIt may of course be that other analysts will find differences using their instr/methods, but my point is: test the solvents systematically using the same instrument (and of course the same timepoint) before making a choice of what to use as mobile phase.
Cathrine, NTNU
We've had issues with some ultrapure MS grade containing too high levels of sodium, potassium, calcium etc. - was very easy to see as peptide adducts in an LCMS run of BSA where peptides often elute as pure peptides (only 1 precursor mass should be present).
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