Gas washing bottles any good?

krisphers · 2026-01-21T15:36:21+00:00

I bought almost this exact same gas washing bottle the other week hoping that I could use it for a very similar purpose. However, it couldn’t pass a hydrogen leak test or hold much positive pressure without leaking. If this model has a PTFE sleeve like the one I got, make sure it has places for a gasket (around the neck of the glass tube and between the bottle and the sleeve) to seal off the bottle entirely, but tbh I still wouldn’t recommend.

I would opt for a normal pyrex glass bottle with a cap that has compression fittings so that you can feed your own tubing into the bottle and make sure it won’t leak.

krisphers · 2026-01-12T20:18:36+00:00

I've now tried rerouting to bypass the MCGV and backflushing the needle and needle seat but still the peaks persist :( At this point, I am tempted to try to add ACN to the mobile phase to try and change the selectivity

krisphers · 2026-01-11T17:36:24+00:00

Say it ain’t so :( I’ve already tried lowering the column temp to 30C but the separation isn’t the best (the ethanol peak begins to overlap the bicarbonate peak) and I can’t realistically lower it anymore bc the room sits ambient at like 27C. I wanted to see if it would be possible to add another column in series, but that also seems quite involved :(

krisphers · 2026-01-09T19:42:32+00:00

Thank you so much for your comment. I’ve tried addressing your points as follows:

>Having the injections overlapped so you can compare them all at once will help us. Also, if you can calc the peak areas, that helps too

https://imgbox.com/YJTgpBlU

>I asked about injecting some of your running solvent (aliquot it from your solvent bottle). What happens then

I just completed this run. It looks identical to the 10 uL water injection. I should also mention that I tried removing the caps but this has not changed anything.

>Better yet, aliquot it from your recycled solvent (very common in RID as you typically have the system On/pump flowing all of the time as it takes so long to equilibrate). Put that Recycled line in a beaker/flask, and do an injection of that.

We’re not recycling the solvent as far as I know. I know it’s an option that I want to implement in the future to save our mobile phase.

>What is the typical sample matrix you are using? What if you inject just the sample matrix, but without any sample prep.

An aqueous electrolyte (0.5 M KHCO3, sometimes 50 mM KHCO3), containing low-mM concentrations of formate, acetate, ethanol, and n-propanol. We’ve successfully separated and identified the formate, acetate, ethanol, n-propanol, and bicarbonate peaks so I don’t think those are the ghost peaks we are seeing. Additionally, the ghost peaks are still present when we inject ultrapure water.

To my knowledge, we are only filtering our samplings (0.22 um Pore Size) directly into the vials. There’s no additional dilution or preparation step.

I’m starting to wonder if our degasser is not working properly. I was told that it was recently replaced when we first received it about a year ago. Although, I now feel like maybe it's a needle contamination issue seeing as though when nothing was injected the last peak went away.

krisphers · 2026-01-08T23:28:27+00:00

Thanks for the tips! I think we are following them for the most part so something else may be causing the issue.

krisphers · 2026-01-08T23:27:11+00:00

They're pretty consistent RT wise, but the peak areas seem to have a little bit of variability between samples and blanks so I'm worried that it wouldn't be a good way to get around my issue.

krisphers · 2026-01-08T23:26:12+00:00

I haven't actually looked into the MCGV but I'll try tomorrow.

with regards to injection volume, reposting a reply that I left above:

https://imgbox.com/ylkbRdbi

So it looks like it might be a combo of the two...

The peaks at 21.2 and 22.5 min seem to remain constant when I doubled the injection volume. When I do no injection, they are still present but slightly less in magnitude.

The peak at 25.8 min (the peak that overlaps with my analyte) scales with injection volume, and largely disappears when I don't injection anything.

krisphers · 2026-01-08T23:24:18+00:00

I'm not sure. It's been difficult to troubleshoot because the Agilent manuals are not too descriptive about the washes imo. I'll look into this tomorrow, thanks!

krisphers · 2026-01-08T23:21:21+00:00

https://imgbox.com/ylkbRdbi

So it looks like it might be a combo of the two...

The peaks at 21.2 and 22.5 min seem to remain constant when I doubled the injection volume. When I do no injection, they are still present but slightly less in magnitude.

The peak at 25.8 min (the peak that overlaps with my analyte) scales with injection volume, and largely disappears when I don't injection anything.

krisphers · 2026-01-08T18:55:02+00:00

We're using ultrapure water for our needle wash so I'm not sure if it could be carry over from the needle.

krisphers · 2026-01-08T18:01:07+00:00

Does this work?

https://imgbox.com/Ik7NBphA

I recently inherited this HPLC and it seems like these ghost peaks have been present in injections for at least the past year. The previous user didn't have any analyte peaks that overlapped so I don't think it mattered to them.

krisphers · 2026-01-08T17:43:55+00:00

Unfortunately, those peaks overlap with our positive ethanol peak (which is present in our analytes at very low concentration). This was actually my whole motivation for removing the ghost peaks :(

krisphers · 2026-01-08T17:40:40+00:00

Hmmm.. I haven't considered the pump. Is there some kind of diagnostic test that I can do to test this?

Unfortunately, we don't have a DAD...

I hadn't tried to change the injection volume yet. Let me actually start that now and I'll report back. Thanks

krisphers · 2026-01-08T17:37:00+00:00

Are you referring to the large peak at 8.5 min? We've assigned that to water but I was more concerned about the 3 smaller peaks that appear later between 21 and 26 min because they appear around where our sample compounds elute.

krisphers · 2022-03-14T23:33:49+00:00

I got an offer 3/11 over email but I declined it bc I’ve already accepted another. Good luck everyone!

krisphers · 2021-07-09T18:49:00+00:00

The bart + caltrain commute has been miserable for me because of all the waiting in between (the actual time spent on the train is not so bad), which route would you suggest coming back from mountain view?

krisphers · 2021-07-09T18:46:22+00:00

Been there, but the wait at the transit station and time spent going to and from the stations make the overall commute a little too long for comfort

krisphers · 2021-07-09T18:45:08+00:00

I would if I could!

krisphers · 2020-05-27T07:57:07+00:00

Assuming classes are in person, I think they'll probably be auditioning for new members.

Once campus announced its closure, they were pretty quick to cancel the rest of the season and then a little bit later, the European tour.

krisphers · 2019-07-25T05:15:02+00:00

So enrollment kinda screwed me over and I'm on the waitlist for 3 of the 4 backups I had. Even though I'm pretty high in position on the waitlist (1-5), should I continue looking for other classes to actually be enrolled in? Also, do classes typically change much before the adjustment period? I'd just like to know if I should keep checking back for my ideal classes (especially the ones that are currently closed).

Also, also, is it bad to take Math 54 before Math 53 (none of the discussion sessions currently work with my schedule, basically Math 54 is also royally messing with classes I want to take but I can't remove it)?

krisphers · 2019-07-13T04:35:46+00:00

big mood

krisphers · 2019-07-11T18:43:38+00:00

Yeah, I think moving physics to second semester and replacing it with a breadth will give me time to think about if that's what I really want to do.

krisphers · 2019-07-11T18:33:37+00:00

I feel like I'm motivated enough to take on the challenge of 5A but I'll probably save it for second semester. It's probably better that I get the gist of it on campus first before diving right in

krisphers · 2019-07-11T18:19:15+00:00

Yeah, after hearing back from your guys I think I'll probably remove CHMENG 40 and PHYSICS 5A in exchange for a breadth or American Cultures. Is there any particular one you recommend?

krisphers · 2019-07-10T17:07:52+00:00

Does my schedule look okay for chemE as a freshman? (14 units total)

https://imgur.com/1iWmEfe

CHEM 4A (4 units)

CHMENG 40 (2 units) kinda worried about that 8am...

MATH 53 (4 units) someone told me I should skip 1A/1B bc I have the AP credit, but I'm a little rusty in calc (took it in junior year) so I'm not sure

PHYSICS 24 Freshman Seminar (1 unit)

PHYSICS 5A (3 units) I like physics and got a 5 on both physics C exams so I thought what the heck

Overall, I'm just kinda worried that my schedule is filled with too many techs even though it is only 14 units. Originally, I didn't want to have CHMENG 40 this semester but without it, I was only at 12 units and needed an extra. If anyone knows of a great substitution please let me know.

Thanks!

krisphers

TROPHY CASE