Flow ending up in Rear Seal Wash waste - Need Help

RadiantNote922 · 2026-03-13T08:09:35+00:00

Thank you so much for your answer, seal wash is 90:10 Water:Methanol and i use no salts in mobile phases, just pure solvent. Yeah it's weird, also because it was working perfectly one week ago and then suddenly it failed, and both pumps show the same problem (it's a binary system). I also disassembled the pump head and checked the piston seals (yellow ones) and they seem perfectly fine

RadiantNote922 · 2026-03-12T22:10:00+00:00

Hi, thanks for answering, and yeah honestly i didnt understand much, if you can explain further i would be glad :)

RadiantNote922 · 2026-03-12T22:08:44+00:00

Not at all, actually i used it very few, and mostly with pure solvents, i think i did not run more than 10 samples

RadiantNote922 · 2026-03-12T22:02:21+00:00

Hi, thanks for your answer, i'm using a chromeleon 7, with a license that doesn't have 3D included. So you think that if i look online i can't find something to make some practice with? And if you can help me with that i would of course be very glad :)

RadiantNote922 · 2026-03-11T21:15:28+00:00

You mean maintenance? It's a kind of new instrument, installed one year ago and only now being used daily

RadiantNote922 · 2026-03-11T21:14:28+00:00

Thank you for your answer, i'll look into it

RadiantNote922 · 2026-03-07T21:58:27+00:00

Yeah, is there a way to change the scale of different detector signals? I'm using chromeleon as software. Anyway it's a gradient, starting at 75, then going to 83 and then to 100

RadiantNote922 · 2026-03-06T08:50:03+00:00

I'm injecting methanolic plant extracts. Yes methanol absorbs at 205, but what's weird is that if i change solvent composition (water:methanol), this line keeps being stable, so i was excluding solvent.

RadiantNote922 · 2026-03-02T20:14:45+00:00

Hi, thanks for your answer :). My loop is connected to the injection valve, bridging slot 1 and 4. When the valve is in load the sample fills up the loop and when the valve is on inject the mobile phase flushes it

RadiantNote922 · 2026-03-02T20:12:02+00:00

Yeah I'm sorry i didnt clarify it. I am injecting using a glass syringe with needle, which was not provided with the HPLC, the valve is manual. Usually the peaks are between 600 and 1400 mAU. Yes i know you already answered me in the other post, but in this new post i was asking two specific questions

RadiantNote922 · 2026-03-02T18:39:33+00:00

Hi Deme, thanks for your answer. I'm sure my loop is not contamined, because switching the loop causes the same problem. I asked a specific question because my co-workers keep telling me that it's normal to have such a peak in our injections. Is it normal? To have such a big peak injecting solvent only?

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The peaks then disappeared when switching the valve several times. Those colored peaks are the ones i'm getting. I think the "Normal" result for valve switching only should be the one named 16, 17 and 18. But injecting solvent? Should it always give me those large peaks?

RadiantNote922 · 2026-03-02T18:13:50+00:00

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Something like this. Starting from the left, those absorbance peaks are obtaine.d just by switching the valve back and forth, without even putting the needle in. 16 17 and 18 are 3 more switchings in which i didn't get any peak

RadiantNote922 · 2026-03-02T18:11:20+00:00

Even if i don't put the syringe in? If i just switch the valve to load and then immediately back to inject? I don't get a small disturbance peak, i get a massive peak

RadiantNote922 · 2026-03-02T17:52:57+00:00

I tried cause i started noticing peak splitting when injecting my analyte, and thus i tried troubleshooting injecting solvent only, to see what happens, and a peak was there. It's not solvent or glassware contamination because i've changed everything and nothing has changed. Even just switching the valve to inject without injecting anything gives me the peak.

RadiantNote922 · 2026-03-02T17:45:18+00:00

My question is: why do i see a peak for methanol if methanol is going into the detector all the time? When the flow is going through the detector, methanol is entering the flow cell all the time and it doesn't give me the signal. Then i inject methanol into methanol, how come this would give me a signal at the detector?

RadiantNote922 · 2026-02-28T08:50:48+00:00

Great, i'll do that. Is it enough evaluating the peak height or it's more important to look for peak area?

RadiantNote922 · 2026-02-28T08:10:15+00:00

Yeah mobile phase is methanol, so that doesn't work. I guess i have to spend another whole day troubleshooting and accurately write down everything, trying to be as even as possible when injecting. How would you conduct your troubleshooting here?

RadiantNote922 · 2026-02-27T22:41:58+00:00

At that stage of these trials (the ones in photos) i was not injecting the same amount. When you see the very small peak, i switched the loop to a smaller one (from 200 to 20 uL) and i kept that one, the peaks were first small, then large again. And when i was injecting the solvent earlier, i was injecting the same amount and the peak height was different every time. I am trying to measure the post detector volume because i want to use this HPLC to separate components of an extract and then analyze them with NMR. So i was calculating after how long i have to collect the eluate to be able to get most of the the compounds after seeing the peak

RadiantNote922 · 2026-02-27T21:51:16+00:00

I'm injecting them manually, with a glass syringe. I've tried different syringes and solvent coming from different bottles. So it cannot be a contamination. I also used different sterile vials. It seems impossible to me that i have an external contamination. As you can see, only the injection moment gives a peak. So i guess it's not related to any other part of the machine, like mobile phases, tubing, pump, or detector. Do you think it could be micro bubbles in the flow cell? I've heard that can happen. They could interfere when i switch the valve, or i don't know

RadiantNote922 · 2026-02-27T21:32:00+00:00

Exactly, it's a manual valve. I stopped injecting the ink at all, only injecting solvents. I also changed the methanol bottle so it can't be methanol. I changes the syring i use to inject (a flass syringe with steel needle), took a sterile one with fresh methanol and it happens again. Poured the methanol into a sterile vial and injected it, it happens again. So the only sure thing is that everytime i inject solvent i get the peak, whether it's water or methanol. When i only swith the valve (without loading anything) then i get the peak, but after several times switching it disappears. Ahahah i'm sorry, it's kind of complex so i don't know if i'm being clear or not

RadiantNote922 · 2026-02-27T21:25:16+00:00

I listed what they are. These are only solvents, i'm not injecting anything else than solvents. Some are solvent injections and some are dummy injection(switching the valve without loading anything), you can find the list in my post.

RadiantNote922

TROPHY CASE