EPA Method 625.1 difficulties.

[MLS2227]

Simply put, the issue is getting the system to show suitability.

Running the DFTPP mix everything looks good (DFTPP tune passes, Pentachlorophenol and DDT have good response and tailing) but the problem child, Benzidine, is showing a lot of degradation and therefore a lot of tailing.

Here is our setup:
Agilent 9000 GC and 5977B MSD
We run it exactly like this application not from Agilent https://www.agilent.com/cs/library/appl ... 7256EN.pdf

What has been done: Source has been cleaned. new inlet liner, septum, guard chip and column (only had 250 injections on it) and was replaced with one that had only 150 injects. I also cleaned the split vent port and replaced the line.

Any suggestions on what else I can do to get the system suitable?

[Jake]

Right off I should say I do not and never have run the method. But looking at the structure and your issues passing suitability, first thing I thought of was liner deactivation. The App Note you're using is from 2018. In 2019, there was a presentation by Agilent using a fritted liner for passing suitability testing for EPA method EPA 8270D/E, which includes a tailing factor requirement for benzidine. Granted, this was on a 7890, but based on everything you've tried, I'd be inclined to give this glass wool-free, fritted liner a shot:

https://nemc.us/docs/2019/presentations ... 0Henry.pdf

[MLS2227]

Right off I should say I do not and never have run the method. But looking at the structure and your issues passing suitability, first thing I thought of was liner deactivation. The App Note you're using is from 2018. In 2019, there was a presentation by Agilent using a fritted liner for passing suitability testing for EPA method EPA 8270D/E, which includes a tailing factor requirement for benzidine. Granted, this was on a 7890, but based on everything you've tried, I'd be inclined to give this glass wool-free, fritted liner a shot:

https://nemc.us/docs/2019/presentations ... 0Henry.pdf

I had seen these fritted liners, but I am not familiar with them. I am going to have to give them a try, because even on a completely new liner I am still getting a good deal of breakdown. I was also hesitant to switch liners, because we have about 50 of them; luckily I have another instrument that runs a method where I can use them.

Thanks, I will try to remember to respond once I have given them a try to update you on how it worked.

[itspip]

I noticed in the app note that they use an inert source. Is your source also inert? If so, how did you clean it? I've had people from Agilent tell me that you can't clean the inert source the same way, or it doesn't require cleaning.

[MLS2227]

I noticed in the app note that they use an inert source. Is your source also inert? If so, how did you clean it? I've had people from Agilent tell me that you can't clean the inert source the same way, or it doesn't require cleaning.

Yeah it is an inert EI source like they have. I followed the manual they provided with the MSD. Which was cleaning the source with a slurry of Aluminum oxide and MeOH. Rinsing with MeOH. Then sonicated in MeOH for 15 minutes. Then dried for overnight.

[MLS2227]

Just an update, but I switch the column from one with a 0.5 μm thick phase to a 0.25 μm thick phase (it was all I had on hand) and replaced the inlet chip. Now my benzidine looks better than it ever did. The only thing I regret is that I did both at the same time. If I had the time to spare I would have done it one at a time to more accurately find the root of the problem.