UHPLC method using high pH buffer (pH 10)

[peiliny]

Hi, we are running an UHPLC method on Agilent 1290 LC. We are using pH 10 ammonium acetate buffer and max pressure is 800 bar. We had a lot of problem with rotor seals, both on the autosampler and purge valve. Looks like corrosion to me (channels on the seal are completely rusted). We also had pump reliability issues (leaking from pump seal). We had replaced entire pump head assembly twice within a year. We were told by Agilent that we are running out of their specified pH range for 1290 LC. Anyone has any experience with high pressure high pH method on Waters or Dionex UPLC systems? pH 10 is not that high to me....

[Gaetan Glauser]

Hi,

I have episodically worked at pH 10 on Waters UPLC. I assumed that since their BEH columns have a pH range of 1-11 or 12, their machine should also be compatible over that pH range. I haven't had any issue, but worked too rarely under these conditions to draw any definite conclusion.

[bisnettrj2]

The 1290 specifications say the recommended pH range is 1-12.5, but they do specify in their system manual and quick reference guide that you should avoid the use of pH greater than 9.5 with the UV detector, as you could damage the flow cell. Also, the link below has pH range specs for the different valves supplied with the various 1290 configurations. Most are maximum pH 12, but all the 1200-bar valves have a max pH of 10. So, you might have issues with the valves or the flow cell at 10, but the pump heads should have been fine, so I'm not sure I buy Agilent's reason for the corrosion (unless your pH is way off).

http://www.chem.agilent.com/Library/use ... USR_EN.pdf

At my last job I had to have a brand new 1290's pump drive replaced within a month because it was defective, so maybe they had some production difficulties or installation issues with some of the drives, and the two problems are unrelated? Just a thought.