Chromatography Forum

We ended up switching out the Pfeiffer Duo 2.5 and installing an Edwards E2M2 and inspected the turbo pump (which had a loose bolt). The pressure is now at 3.5x10-5 with a 1.2mL/min flow, the filaments are lighting up and we can get a proper tune. H20<2% and N2 < 0.5%, however I'm still getting over 600 peaks in a scan between m/z 10-700. Am I pretty much looking at an HED failure now or could something else be causing this?

E2M2 is what I am using, they work great still for such old pumps.

600 peaks but what is your Threshold set to?

You can clean the HED, I have had to do it myself before. Just remove the two screws holding the ceramic part in and pull the connector wire out, should just slide out. Wipe down the metal button with a kemwipe and some IPA. If it is not working at all you should be getting less signal not more I would think since it would not be making the ions take the 90* turn into the multiplier.

@James-Definitely a fan of the Edwards so far. Seems to be holding the pressure really well. Threshold is set to 150, scanning 35-250amu with 3.31 scans/sec. Everything looks great except for the "noise". Tried running a BFB but the baseline was elevated. Grass had a response of about 2500 across the board.

Is your source temperature above 230C? If so you will see higher background. Good to bake it out at higher temps but I have found if you lower it to 180-210C during analysis you get lower background and for running volatiles you are not going to have to worry about contamination very much since most of what you will desorb will cook off at those temps.

After so long with bad vacuum you may want to let it sit a day or two then retune. You will probably find that you EM will need less voltage and you can get rid of some of the noise that way. Once I get a tune to pass, I go to manual tune and adjust the EM voltage so that I have about 750,000 counts for m/z 69, when running a 40:1 split from the purge and trap that gives me enough sensitivity to get around 1-10ppb detection limits. If I am up to about 1,000,000 counts for m/z 69 I have too much response on high calibration standards of 200-400ppb. If you are using direct on column with cryofocusing you can probably get by with even lower counts on 69.

Can an E2M2 be plugged into the MSD safely? I was told anything more than a 1.5 has to much power draw.

BTW it was stated in an earlier thread the pfieffer duo turbo's have a lubricating resivour that needs periodic replacement (1 year). Have you ever done that. I am afraid to remove my quickswap and separate the MSD otherwise I would have done it.

Can an E2M2 be plugged into the MSD safely? I was told anything more than a 1.5 has to much power draw.

BTW it was stated in an earlier thread the pfieffer duo turbo's have a lubricating resivour that needs periodic replacement (1 year). Have you ever done that. I am afraid to remove my quickswap and separate the MSD otherwise I would have done it.

I plug my E2M2 directly into the wall outlet just in case. If you don't want to rewire I have found that a power cord from a laser printer works great as an adapter, just don't use a regular PC power cord because those are not heavy enough and become quite warm while in operation. It will also allow you to evacuate the analyzer before the turbo ever spins up which should make it easier on the turbo when first pumping down.

I have run one directly from the MSD, but I don't like putting that much load on it.