Analyzing PCNB with GC-MS?

[ebbed93]

Anyone who have experience of analyzing pentachloronitrobenzene (PCNB) using GC-MS? I need some tips and tricks. Thank you!

[Rndirk]

Yes, PCNB or quintozene on GC-MS is a common analysis (environmental).

Check the literature (application notes, EPA methods,..) and if you have more specific questions you can ask them here.

[ebbed93]

Hi!
I have been searching for articles regarding this topic, but I can't find anything that is much helpful.
I am developing a method in school for idenftyfing PCNB and PCA in samples but my temperature programs just wont work the way I thought.. It's also the first time I'm working with a pulsed splitless injector so I don't really know if I have messed up the injection part or if it's the temp.program that is the problem haha.
The analytes wont come out even when I have a "end" temperature at 340°C and hold time at 5 min, so I'm thinking that the analytes might have got stuck in the coulmn or transferline. Any thought or tips?

[HPLC chemist]

Use the same GC column and temperature program as listed on page 13. See attached. Don't reinvent the wheel!

https://www.epa.gov/sites/production/fi ... 6-01-w.pdf

[Rndirk]

Is there another analysis on that instrument that does work currently?

Start at the beginning, with a solution of a PCNB standard in full scan MS or SIM scanning for the fragments listed in literature if you use standard ionization (EI). Use a high concentration (like 500 µg/L).

If then you don't see a peak with your oven method to 340°C, there's something wrong with your injection.

In that case, post your parameters (injection volume, splitless time, inlet temperature, liner, .. ), and we can try to help.

[ebbed93]

Thank you very much for your answers!
The instrument I'm working with is only used very seldom, thats why I can play with it as much as I need to fix this method as quick as possible So I don't know if it's working properly when used with existing methods.

I did an autotune yesterday after changing the column, septum and liner. And my teacher said it looked normal so I could start with my work. So hopefully my instrument is in good condition..

The samples I'm working with have a concentration of 1 ng/ul so it would be suitable to work with, and I did an full scan analysis. The only peak I got was at 167 m/z, which doesn't make sense since I'm expecting peaks at around 270-290 m/z. Unless it's a fragment, but where is the rest of the compound?! Haha

I might need to check the injection-part of the instrument and try some other temperature programs I think.. It's difficult when things doesn't work how they "should" haha, but that's the fun part of chemistry and analytics I guess

[Rndirk]

Did you condition the new column? Did you verify if your system is leak-free?

Try approaching this step by step.

[ebbed93]

Thanks for input!
I conditioned the column, then I checked for leaks. I had a minor peak at m/z 18, so I tightened the different "screws" (or what they is called in english) at the septum, injector and lastly the MS. After the tightning, the peak was smaller and "approved" by my teacher and then I autotuned the instrument.