EPA 525.2 Calibration Issues

[James_Ball]

I have been doing some SIM runs of 525.3 for some different compounds, mostly the OP Pest like Simazine, Atrazine, Metolachlor, ect. I have found they behave similar, some perfectly linear others quadratic in fit. I did notice if I increase the gain they become less curved in the responses. With the 5973, 5975 I find the opposite to be true, using the least amount of gain gives more linear curves. I wonder if this is something that is related to the extractor source in the 7000 or the triple axis detector?

Having responses in the 10^7 or 10^8 counts on the 7000 seems to be well within its working range where on the older models it would be giving saturation problems. Maybe if you increase the gain it will help? Can't hurt to try, then we will all know a little more about what works and what doesn't on the 7000s.

[Bigbear]

I was told by Agilent not to use the extractor lens for 525.

[Ostravaczech]

I was told by Agilent not to use the extractor lens for 525.

My service engineer / app chemist said the opposite. I will try just EI next week but I need to ask you about collision gas. Do you turn it off when running MS1 or do you keep it at default value? I run 525 with N2 at 0.5 mL/min and all was fine until the PM was done by Agilent. I am really scratching my head.

[James_Ball]

Unless doing MRM turn the collision and quench gas off, you will get much better sensitivity. Those are only needed for the fragmentation in the collision cell.

[Ostravaczech]

Unless doing MRM turn the collision and quench gas off, you will get much better sensitivity. Those are only needed for the fragmentation in the collision cell.

Thanks James. I still do not have answers why the instrument performed the EPA 525 method well for almost 2 years, until mid October 2017. I am running a curve today in EI (no EIEX) mode, with He@2.25, N2@0.5 (as I have run it in the past), cycloliner, splitless for 1.25 min at 300C. I have 2 methods setup, one 1uL injection, and the other one 0.5uL. I will report tomorrow. I am also thinking about creating MRM method for the problem compounds like metribuzin, butachlor, adipate, phthalate and methoxychlor to check. So you don’t have to read the entire thread - curve for the above mentioned compounds is convex (or concave up) and therefore the linear fit will not pass. I have made the curves so many times and in different ways. I would like to think that I am not the problem re: the curve prep.
I also ordered some new source parts to see if the cleaning had anything to do with it (just a reminder: the source was cleaned 3 times since early October, once during the annual PM by Agilent, second cleaning was done a different Agilent engineer about a week later, and the third cleaning by me few weeks ago).

[Bigbear]

I don't think you can do MRM with 525.2.

[James_Ball]

I don't think you can do MRM with 525.2.

Not legally by the method, but could use it as a check. But you will lose some sensitivity at the same gain when doing MRM.

I would still turn off the collision cell gasses and see if that helps. I wonder if the Agilent rep turned them on when doing tests after the PM and that is what is throwing you off. They only cause problems with MS1 Scan or SIM analysis.

[Ostravaczech]

I don't think you can do MRM with 525.2.

Yes, I am aware of that. This would be just for the lab info only to see if the problematic compounds behave the same in MS1 and MRM.

[Ostravaczech]

I don't think you can do MRM with 525.2.

Not legally by the method, but could use it as a check. But you will lose some sensitivity at the same gain when doing MRM.

I would still turn off the collision cell gasses and see if that helps. I wonder if the Agilent rep turned them on when doing tests after the PM and that is what is throwing you off. They only cause problems with MS1 Scan or SIM analysis.

I did run a method today with quench/collision gasses off. Same results, little bit worse because most of the targets exhibited quadratic curves. Right now, I am running the same method I used in August - October with He 2.25, N2 at 0.5 mL/min, and same setup as far as guard column, same liner and same injection technique. I will report tomorrow. I didn’t have time to mess around with developing MRM method today, though. Also, waiting for new source parts to be delivered so I can swap the old parts for brand new ones.

[Ostravaczech]

I had to switch gears today because I have a NDMA project that I need to start working on (instrument had to be configured for CI work). I received the brand new EI parts today which I will put in as soon as I am done with CI project. Hopefully, I will get good results with new EI source parts. Anyway, the curve that I ran last night is no good for the same compounds reported previously.

[Ostravaczech]

I have been tied up with different projects in the past year or so, but I finally got some information about the linearity issues. Apparently, you must or should use 9 mm draw out plate for the full scan methods. We ordered one and I was finally able to reconfigure the instrument from NH3 CI to EI with 9 mm lens last Friday. I put on a curve today and hopefully I will have good news tomorrow.
(I am running 7890/7000C combo)

CHEERS!

[James_Ball]

I have been tied up with different projects in the past year or so, but I finally got some information about the linearity issues. Apparently, you must or should use 9 mm draw out plate for the full scan methods. We ordered one and I was finally able to reconfigure the instrument from NH3 CI to EI with 9 mm lens last Friday. I put on a curve today and hopefully I will have good news tomorrow.
(I am running 7890/7000C combo)

CHEERS!

I switched to the 9mm lens a few months ago and it is really nice. I can't see that I lost any sensitivity and doing EPA8270 semivolatiles I don't have linearity issues with the late eluting PAH compounds now, and it stays cleaner longer.

[Ostravaczech]

I have been tied up with different projects in the past year or so, but I finally got some information about the linearity issues. Apparently, you must or should use 9 mm draw out plate for the full scan methods. We ordered one and I was finally able to reconfigure the instrument from NH3 CI to EI with 9 mm lens last Friday. I put on a curve today and hopefully I will have good news tomorrow.
(I am running 7890/7000C combo)

CHEERS!

I switched to the 9mm lens a few months ago and it is really nice. I can't see that I lost any sensitivity and doing EPA8270 semivolatiles I don't have linearity issues with the late eluting PAH compounds now, and it stays cleaner longer.

As I mentioned I put on EPA 525 curve last night. All curves look great, no issues anymore, most RSDs well below 10%, so to conclude this topic: If you run 7000C in full scan mode, you should use 9mm draw out plate!