Is solvent sparging absolutely necessary?

[ChristofferBR]

Hi!

I'm in the progress of reviving some old Waters 600 gear, and the manual specifies how to set up solvent sparging with helium.

Is sparging "just" the older alternative to an actual degasser, and can it be omitted if a degasser is used?

Would it be possible (with reduced effectivity) to skip both sparging and degassing?

Thanks in advance!

[Rndirk]

Yes it's possible. Monitor the baseline/pressure to check if you need to degas.

Edit: I should specify I have no experience with that particular LC. Just replying to the general question of "it is possible to not degas my mobile phase".

[ChristofferBR]

Thanks a lot!

I'll try without, but I guess I'll look for the vacuum degasser as well. Could never hurt.

[benhutcherson]

I have done either/or-sparging both on HP 1050s and old Waters(600 series) instruments, and vacuum on the HP/Agilent 1100 and on the PE 200s I have now and detest. I've never done both.

My experience with sparging has been poor-it uses a lot of helium(which isn't exactly cheap these days) and in my experience doesn't always do the best job of degassing. IIRC, I did like the implementation somewhat better on the Waters 600 than I did on the HP 1050-if I'm remembering right the Waters actually let you set a flow rate in the menus and keep it somewhat consistent, while the 1050 just gave you four knobs across the front of the solvent tray and you set them until it looked "about right." Even sparging both at low and high flow rates, though, I'd still get occasional bubbles. When I was running a 1050 daily(which I used a lot more than the Waters 600, even though the HP/Agilent fanboy in me has to acknowledge the Waters as overall a better unit), I'd usually drop the solvent bottles in the ultrasonic bath and stopper them while connected to house vac to do gross degassing before loading them up in the solvent tray, and then just sparge for "maintenance."

By contrast, the in-line vacuum degassers I've used just work, and work well enough that I forget they're even there. My PE 200s are used infrequently these days, and when I first power one on I generally spend a few minutes chasing out bubbles just in the process of getting things primed. Once I've spent a few minutes doing that, the systems will run days at a time without the slightest worry about bubbles. I'll only see one if I dally in solvent refills and let solvent evaporate out of the frit/start of the line. In fact, the degasser is the single most trouble-free part of the otherwise miserable Perkin Elmer HPLCs

[Consumer Products Guy]

Our early Agilent 1050 units used helium sparging; yes, cumbersome and expensive. That was before vacuum degassers were available.

Get a decent vacuum degasser instead.

[ChristofferBR]

Thank you for the replies,

I'll skip the sparging and try without, and look for a vacuum degasser. Vacuum degassers are pretty isolated from the rest of the system, and I could likely use one from another manufacturer, isn't that right?



--Chris

[benhutcherson]

The ones I've used are what I'd consider a "dumb" device-they're a box with an in and out connection for the PTFE solvent hoses on the low pressure side of the system. The only control I have on the ones I use now is an on-off switch, and it has no electrical tie-in to the rest of the HPLC stack.

[janoshik]

1. If you are doing low sensitivity analysis or isocratic analysis, you probably don't need to bother with degassing at all.

2. If you figure you have issues, then setting up damper and mixer to the biggest possible value helps.

3. If you still have issues with it, then you can try boiling/vacuum filtering/sonicating the solvent before use. You can also try continually sonicating the bottles with solvent during analyses. (start at least 15 minutes before).

You might want to try switching Methanol and Acetonitrile in your analysis. ( too late at night to remember which one gives more trouble, but I think it's methanol, so stick to using MeCN).


If all else fails, gets a flow through degasser from ebay for pocket money.

[Multidimensional]

You should absolutely set up and use a degasser with your HPLC system. Degassing ALL mobile phases types is beneficial to reducing pump cavitation and check valves from getting stuck (from air bubbles). Helium sparging (degassing) is superior to all degassing techniques because it both displaces most of the gas from the solution in a continuous manner and is chemically compatible with all mobile phase types (which inline vacuum degassers are not). Their are only two negatives associated with using high purity helium to degass the liquids. Helium sparging is inconvenient due to the heavy gas cylinders which must be exchanged every few months and the gas is expense.

Setting up continuous helium sparging is very simple (never set it up for ON and OFF use as that defeats the purpose!). Use a secondary pressure regulator off of the high pressure tank and set it for about 3-4 psi. Run the gas to SS or Teflon perforated solvent pickup frits for delivery to the MP bottles and make sure you position them higher than and away from the MP solvent pickups (to prevent them from sucking gas into the system). You will end up with a mobile phase that is thoroughly degassed and has the lowest oxygen levels (great for low UV work).

Inline vacuum degassers were created for convenience, but there are downsides to their use too. They do not provide the level of degassing that helium sparging does (few need that level), but if setup and used correctly will work great for many applications. Limited chemical compatibility of the vacuum chambers and the fact that they must be regularly flushed (wastes solvent) are two drawbacks which must be attended to. Also, never leave a degassing channel empty, always run with them ALL filled with liquid (per the manufacturer's spec). They also wear out and degrade inside over time so need to be serviced every 4 to 5 years (or your mobile phase may become contaminated).

Based on your request: If you want convenience and your mobile phase solutions are compatible with the vacuum degasser you selected, then use it. The easy plug-in convenience is great and if properly serviced will provide good degassing improving your baselines and freeing you from spending all of your time getting the pump to work. If you have easy access to high purity helium, then sparging with He will work with everything well and you will have no need to buy or use a vacuum degasser.

Here is a link where it was discussed: https://www.researchgate.net/post/What_ ... g_for_HPLC

[ChristofferBR]

Thank you for all your replies, that's a lot of info!

I'll skip sparging for now, go with the in-line degasser, which looks in pretty good shape.

- I'm not sure i have fitting hardware enough for all 4 channels on it, and I only plan on using 2 solvents at first. Each degassing "channel" has its own vacuum chamber all connected to one pump - couldn't I just remove the two surplus ones and plug the tubing?

--Chris

[Consumer Products Guy]

I'm not sure i have fitting hardware enough for all 4 channels on it, and I only plan on using 2 solvents at first. Each degassing "channel" has its own vacuum chamber all connected to one pump - couldn't I just remove the two surplus ones and plug the tubing?

Yes.

[Multidimensional]

Whatever you do, please do not run the inline vacuum degasser with empty or unused chambers. Either, as you say, remove the unused chambers and plug the vacuum tubing ports where they used to be connected OR .... Use what we call "C-Tubes" (short lengths of low pressure tubing with fittings) to connect one or more vacuum chambers together, in-series, for improved vacuum degassing efficiency and at the same time use the 'extra' channels. This last option is the best way to keep all of the vacuum chambers in use and improve overall degassing. You can interconnect one or two extra vacuum solvent channels in this way to easily improve performance.

[lmh]

just remember that if you interconnect multiple channels so that they're working in series, you've got a bit more dead volume between the solvent bottles and the pump, so you'll have to purge a little longer when you change solvent. But yes, it will give you a more efficient degassing. Helium sparging is almost unethical in these days of helium being so much a limited resource. It should only be used as an absolute last resort in event of total failure of all other methods! If we blow all our helium out the window, our GC colleagues are going to be most upset in a few years - not to mention those who need NMR magnets.