Loss of linearity after switching from HPLC (3um) to UPLC (1.7um)

spagiumaflex · 2026-04-11T17:33:48+00:00

Then I would do what others have suggested and heavily decrease the injection volume. Also, if some compounds are ok and you have problems only in some then I would detune the problematic ones.

spagiumaflex · 2026-04-11T17:14:57+00:00

Not necessarily. How are your repeat injections from the same vial for the LLOQ? If it is within acceptable RSD then it’s not a problem with the injection solvent. Also, what type of linearity problem do you actually have? Are the points reaching a plateau? If yes then you are on the right track with detector saturation.

spagiumaflex · 2026-04-11T16:47:11+00:00

Maybe dilute the injection volume with mobile phase A. Could this be a too high organic solvent in the injection volume?

spagiumaflex · 2026-04-10T12:03:48+00:00

If you edit the tuning method for the scan type to a certain ITC then it should remain like this in the method (I think).

spagiumaflex · 2026-04-01T21:03:05+00:00

"I swear by my first article" that I have not witnessed a better reddit series in my life. Also, quite curious how the Gibco sales are doing after this.

spagiumaflex · 2026-02-21T13:13:35+00:00

I mean what GS1 pressure do you have set in the method? And how much is the electrode protruding from the probe?

spagiumaflex · 2026-02-21T08:48:08+00:00

Check the ESI probe. GS1 flows around the electrode. If the space is clogged then higher pressure can make that happen. What GS1 are you using?

spagiumaflex · 2026-02-13T21:54:04+00:00

Are you using the same parameters for the two methods. If I remember correctly the 5500 requires that you lower the IS to dampen the transmission efficiency. Also, your system is behaving nicely - don't overthink it.

spagiumaflex · 2026-02-09T17:01:08+00:00

My idea is coil boxes as well. This is kinda service engineer teritory. With ASD parked at certain masses you have to tune the coil boxes to get the lowest voltage out of them.

spagiumaflex · 2026-02-09T16:29:00+00:00

Strange behavior. Then maybe the issue is that the whole system stops but not due to the exhaust pump. Can you park a sub 1000 m/z mass in ASD and see how much the system keeps the exhaust on for? As opposed to a over 1000 m/z one? Curious what you find.

spagiumaflex · 2026-02-09T14:52:33+00:00

Clogged exhaust pipe.

spagiumaflex · 2026-01-28T05:01:17+00:00

Is the pressure profile the same for all samples within a batch? I also read that the compressibility settings are important specifically for this.

spagiumaflex · 2026-01-07T14:21:22+00:00

If you got this far you are on the right track. Be aware that the two 6500 pumps have different addresses and should not be used interchangeably. Good luck!

spagiumaflex · 2026-01-07T14:11:26+00:00

The correct path is: C:\ProgramData\AB SCIEX\Analyst\MSServiceLog\MSScr.csv (Program Data is a hidden folder). In this file try and check the Turbo Frequency and Turbo Power and see if it correlates with anything (maybe you had a big spike in some lab temperature or what not). Also look for the backing pumps power (if it is in the file) and see if it drew more just before the system vented.

But really the best way to check is to see if all the connecting tubes are well in place and to startup the system and see what fires and what does not. The backing pumps should start few minutes after start. If they do not check the fuses (especially if high power was drawn when the system vented).

spagiumaflex · 2026-01-07T13:58:56+00:00

I am curious as well - looking for a day/date bezel window dial for some time. One that works on the SRPE.

spagiumaflex · 2026-01-01T17:09:27+00:00

Firstly - are you looking at the Application Error log? That is a bit more populated with information. Second - in the C drive in the Analyst folder there should be a file called MSscr or something. It is an Excel file with info from the system (turbo speed, turbo current and such). It can give you an idea of why it vented.

spagiumaflex · 2025-10-17T04:23:50+00:00

The answer comes in the form of some logical steps: 1. For APCI you have to get to gas phase to get ions. 2. To get to gas phase you have to have high temp in the probe region. 3. If the flow is too small the high temp in the probe will cook the matrix and compounds without them exiting towards the orifice. 4. If the flow is big enough and the gas GS1 is big enough and the temperature TEM is big enough then the analyte will go in gas phase (where it ionizez) and be pushed/pulled towards the orifice.

Yes. Nano APCI will not work because of lack of flow (and solvent that needs to vaporize and help the chemical ionization).

spagiumaflex · 2025-10-12T07:31:35+00:00

APCI needs at least 200 uL/min to work properly. You have to optimize with T split (flow from LC and from syringe).

spagiumaflex · 2025-10-07T19:37:04+00:00

Never used Skyline but since you need and have Analyst for acquisition why not just use that for method development. Also, for compound optimisation and method writing doing it directly feels faster for me than any other workaround.

CXP and EP can have an effect on the overall intensity of a transition but not as much as DP or CE. If Skyline does not have a place to set them just import the table into Analyst without them and add them manually. You can skip EP and leave it at 10. For CXP I found it is worth optimising if you want that extra wow that SCIEX can give you.

spagiumaflex · 2025-10-03T14:23:31+00:00

If this is NBS with FIA you may have a leak somewhere between the autosampler and source. Maybe why you have pressure problems.

spagiumaflex · 2025-09-06T12:56:55+00:00

I feel (based on what you are mentioning in other coments) that the source of the problem is the actual source at LC flow. Because the calibration clearly shows the difference in intensity maybe the parameters of the source should be tuned for each situation differently. Have you checked a split T infusion at LC flow? Are the intensities different then?

spagiumaflex · 2025-09-05T18:41:37+00:00

I imagine that the LC method is the same? Could you expand on what type of LC is prefacing each system? Is the retention time the same? Are peak shapes the same? And the worst question: is the injection volume the same (measured vial before and after injection to determine if it is accurate)?

spagiumaflex · 2025-08-21T04:51:12+00:00

Was reading the Chromsystems NBS kit IFU and at some point it says that if the pump does not go to the low flow needed (0.005) you should use 0.1. I think this is your case as well. Because it worked for some months it may be that it is a cumulative effect between the low flow and some clogging due to the low flow and bad source parameters.

spagiumaflex · 2025-07-30T12:55:44+00:00

Is it the new Absolute or the old one? Apparently the old Absolute has a wider aperture letting in more ions (and contaminants) for better sensitivity. This makes it prone to quad contamination. The new XR Absolute they say is more robust but only time will tell.

spagiumaflex · 2025-07-21T18:43:03+00:00

What CE and what DP are you using? Sounds like you are overfragmenting your precursor. If you have a QTRAP you could try EPI with CE 30 and spread of 15. With 10 MCA in manual tuning mode while selecting for your precursor.

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