1100 Degassers dropping like Flies!!

[tatep]

Within the last 2 weeks I have had 4 Agilent 1100 Degassers go bad - that is - to the point where the back-pressure fluctuates about 30-40% and flow is not stable. These degassers have had the red lights lit up for quite some time now but they hadn't visibly affected performance until now, all at the same time??

The solvents are from different dates/batches so there's no correlation there, my Waters 2795/Acquity systems aren't showing any symptoms. I have tried flushing with IPA in case it was bacterial growth but the problems persist. There is one prep system (waters) that shows flow irregularities as well but the prep systems don't have degassers.

I can only assume there has been some atmosphere change in our lab to have triggered this. Has anyone seen this before? We are in Boston and the Agilent instruments are mostly the same age so I wonder if Autumn is to blame somehow?

Any ideas?
Thanks,
-pete

[tom jupille]

I don't have an Agilent system, but I would assume that on most degassers the innards (fiber membranes) have a finite lifetime and should be changed periodically as part of preventive maintenance. You didn't say how old yours were, but they may just have died of old age.

[Consumer Products Guy]

We've got two 1100 degassers here, for several years now; we've never had an issue with either. We did have one 1050 degasser which lost its little vacuum pump, which is no longer available, and also before that had to replace some cracked black vacuum tubing (auto parts vacuum tubing worked fine). We still have four operating 1050 degassers going.

[LCbob]

Hi

A red light on a Agilent 1100 means it cannot get down to vacuum and so errors. Agilent tend to exchange units on these modules as they are a pain to fix in the field, although its usually the vac pump. Do check the tubing though as on old systems this can fray...just snip it with a pair of cutters.

As to why you are suddenly getting problems now i cannot answer. I always go on the assumption if your HPLCs have been working whats changed, clearly if the degassers were not working before they may not be the problem.

[mbicking]

As LCbob said, the red light indicates a problem. During training I always tell my students to remember the Agilent rule: "Green is good; red is bad!" Do you hear the vacuum pump running? (It's a faint fluttering sound.) If it is always running, or never running, then you need service.

The fact that you haven't had problems suggests that maybe you don't really need degassing. Most people actually don't need it.

You said the "back pressure" was higher. Do you mean how easy it is to flush out the degasser? Is this using a syringe at the front connections? If so, then maybe you do have something plugging the lines. But first remove the solvent inlet frits in the mobile phase reservoir. They may be the problem. If that doesn't do it, then try a series of solvents to try flushing. It will depend on what has been going through the system. I have had to resort to diluted bleach on some occasions, but that is an extreme case. Hopefully your system isn't that bad.

[tatep]

Tom, you are right about the lifetime and these degassers are all about 7-9 years and are all dead or dying. They probably haven't been performing for quite some time but didn't affect the chromatography (noticably) before. It's the fact that they all gave up the ghost at the same time that perplexes me.

I agree with you Merlin that we probably don't really need degassing that much and therefore the "red-light" degassers haven't been a problem even though they weren't working. A slight change in the lab atmosphere may have just brought to light the problems that the degassers already had.

As for the back-pressure, it wasn't higher, but fluctuating due to air getting into the pistons and creating irreproducible flow. The correct operating pressures have been about 80 bar (4.6x100mm 5um column -gradient depending) and currently they float around 60-30 bar and cycle.

I should have Agilent here today and will question them about the coincidence in timing as well.

Thanks for all the replies,
-peter

[mbicking]

If you are getting air in the lines before the pump head, that may be due to a simple leak or loose connection in one of the fittings. The other possibility is the solvent inlet frits, as I mentioned.

To check them, disconnect the mobile phase tubing where it goes into the degasser. Hold it over a waster container. You should see a steady drip - organic solvents will be faster than water, but it should drip at least one drop per second. If not, then the frits are bad/plugged.

Let us know what happens.

[tatep]

Well, after having Agilent look at them, 3 of the 4 needed new tubing to the vacuum pump and now those work fine and the systems have no pressure ripple. The 4th seems to have a leak in the degassing block and needs to be exchanged.

Still no explanation as to how or why they all went at the same time but I'll live without an explanation as long as they work!

Thanks everyone,
-peter

[Consumer Products Guy]

We've had to replace some cracked black vacuum tubing (auto parts vacuum tubing worked fine).

See, take it from the former mechanic: tubing !!!

[DR]

Better late than never -

My understanding is that not all 1100 degassers are created equal. The older ones with the higher internal volume (>10mL, I think) - are pretty tough. The newer ones with much lower internal volumes are not so robust - you can break their blocks by using a (large) syringe to pull MP into them (so try to prime them with your pumps or a gentle pressure push from the MP bottle).

[Flop]

Are your failures truly synchronised?

We have a tendency to use Unit A because it is in better condition than Unit B - until it isnt.

The result is that at some point all Units are poorly or non- functioning. And it is time to do something about it.

Hence all units have failed at the same time.

[Bruce Hamilton]

My understanding is the same as DR's. The later systems are more fragile. I don't vacuum prime mine, on the advice of the local service support person.

Also, it is possible to set the unit internally for the pump to run all the time for high volatility solvents, and mine's been set at that for the last 2.5 years. I assume the pump life will be shortened, but it eliminated the high pressure error with some very volatile solvents I use.

Please keep having fun,

Bruce Hamilton

[LCbob]

Better late than never -

My understanding is that not all 1100 degassers are created equal. The older ones with the higher internal volume (>10mL, I think) - are pretty tough. The newer ones with much lower internal volumes are not so robust - you can break their blocks by using a (large) syringe to pull MP into them (so try to prime them with your pumps or a gentle pressure push from the MP bottle).

Hi

Very true they are not created equally, the newer G1379 degasser chamber have a lower dead volume and involve a membrane in contact with the solvent. The G1322 degasser chamber splits the solvent into approx 30 very narrow semi perm tubes (for the high surface interface ). The membrane examples do split and are not as good as the G1322 escpecially for methanol / water mixes. Agilent released a service note a few years ago with reference to degassing problems with methanol water.

[jaytee]

Jaytee Biosciences have designed some new degassers for the HP/Agilent 1100 systems. These degassers are more advanced than the current models from Agilent and include Teflon AF chambers, NEW Vacuum Pump and control PCB. Continuous slow speed Vacuum Pumping to maintain the perfect quiet degassing performance with dead volumns of less than 500ul.
The degassers are offered on a swap out basis, you send your dead degasser and we send an exchange unit with a full year warranty. All this for less than the price of a chamber swap by Agilent.