Chromatography Forum

Dear all,

I am encountering a problem when using HPLC-MS/MS recently. The instrument I am using is HPLC (Agilent)- MS/MS (ABSciex 3200 Q Trap). I notice that when I run 100% methanol (with 10 mM ammonium formate and 0.005% formic acid), the pressure elevated and go over the maximum pressure which my column could bear. Then I standby the instrument and did not connect the mass spec, let the mobile phase ran through the column and went to the waste beaker and the pressure was fine. But every time I tried to equilibrate the instrument and connect the tubes to the mass spec, the pressure elevated at once.
Then I thought it may because the ion source was clogged (but actually we just replaced the ion source pulp with a new one recently), but when I used the syringe to tune compounds, the TIC was very stable which indicated that the ion source pulp was OK. So what would the problem be?
Thanks a lot for your attention

Best regards,
Kenny

If you connect everything, but divert the flow to waste using the divert valve, do you have the same problem?

If yes, there is something clogged in the tubing between the column and the divert valve, or the divert valve itself.

If no, the clogging is after the divert valve: the tubing between the valve and the probe, or the inside of the probe (silica or a metal needle depending on your instrument).

I'm not sure what the "pulp" is you refer to.

If you connect everything, but divert the flow to waste using the divert valve, do you have the same problem?

If yes, there is something clogged in the tubing between the column and the divert valve, or the divert valve itself.

If no, the clogging is after the divert valve: the tubing between the valve and the probe, or the inside of the probe (silica or a metal needle depending on your instrument).

I'm not sure what the "pulp" is you refer to.

Thanks for your answer. Yes, it should be the probe. I just changed another probe from another instrument and the pressure is OK. Any method to solve the clogging of the probe? Sonicate with what kind of solvent would be better?

If you connect everything, but divert the flow to waste using the divert valve, do you have the same problem?

If yes, there is something clogged in the tubing between the column and the divert valve, or the divert valve itself.

If no, the clogging is after the divert valve: the tubing between the valve and the probe, or the inside of the probe (silica or a metal needle depending on your instrument).

I'm not sure what the "pulp" is you refer to.

Thanks for your answer. Yes, it should be the probe. I just changed another probe from another instrument and the pressure is OK. Any method to solve the clogging of the probe? Sonicate with what kind of solvent would be better?

For the LCMS systems I work with (Thermo and Waters), the inside of the probe can be replaced easily, and is not very expensive. If it can be replaced for your type of probe, i'd advice to do that. Check which part number you need with Sciex, I haven't worked with their instruments.

Alternatively, I guess you could try passing different solvents trough it, going from polar (water with formic acid) to MeOH, to iPrOH, to apolar (dichloromethane, hexane) and then back, hoping that something unclogs it. I would never put the whole probe including electronics in an ultrasone bath!

Backflush your probe; most of the time you will be able to dislodge whatever is caught there. Sounds like you might have an issue with solutes dropping out of solution post-column.

Backflush your probe; most of the time you will be able to dislodge whatever is caught there. Sounds like you might have an issue with solutes dropping out of solution post-column.

ABSciex uses a very thin needle inside the probe, not so easy to backflush. If you can't get solvent to flow through it, best to just replace.

To flush try connecting without the column in place, if it builds up past 500-1000 psi, it is probably plugged completely and needs replacing.