Troubles with analysis of acetonitrile with GC-FID

[Sfverhae]

Hello

I have some questions about my method for testing acetonitrile in an aqueous sample. I use a GC-FID

First my GC settings (GC 6890N):
inlet temperature: 200 °C
Detector temperature: 250 °C
Splitless injection: 1 microliter was injected with autosampler

Temperature program:
0-3 min: 60°C
after that it rise with 80°C/min to 220 °C then it holds that temperature for 2min.

Hydrogen and nitrogen: 40 mL/min
Air: 400 mL/min

Column: HP FFAP 30 m * 320 μm * 0.25 μm


1) I don't get consistent results. I've read that it's hard to get good results with a GC-FID for testing acetonitrile. But it's not impossible I hope? Because I don't really have an alternative. I found another method with GC-NPD but the upper range of this method is 5 mg/L and my range of concentration lies between 5 mg/L and 250 mg/L so that's also not an option.

2) maybe my column is broken. On the picture you see that at the end there're a lot of peaks and the baseline gets higher. I searched this and maybe this is columnbleed? Can I fix this or will the results be better with a new column?



Thanks in advance

[Sfverhae]

Here's a link to the picture I'm talking about.

https://imgur.com/a/UINKxvP

[James_Ball]

It may be the FFAP column. Reading about it, the stationary phase contains acid, and acetonitrile can be broken down by acid. Maybe you need a column such as a normal Wax column or even one of the 624 phase columns https://www.agilent.com/en/product/gc-c ... cb-columns

The other option is to use either Headspace sampling or Purge and Trap, since acetonitrile is volatile enough to use those methods.

[Consumer Products Guy]

USP assay for ethanol uses ACN as the internal standard (instead of the more-commonly utilized n-propyl alcohol) and FC-FID, so my supervisor wanted us to do and validate our procedure using ACN. We used water as solvent, and didn't have any reproducibility issues.

No - we did not use FFAP.

[Sfverhae]

USP assay for ethanol uses ACN as the internal standard (instead of the more-commonly utilized n-propyl alcohol) and FC-FID, so my supervisor wanted us to do and validate our procedure using ACN. We used water as solvent, and didn't have any reproducibility issues.

No - we did not use FFAP.

Which column did you use then?

[Sfverhae]

It may be the FFAP column. Reading about it, the stationary phase contains acid, and acetonitrile can be broken down by acid. Maybe you need a column such as a normal Wax column or even one of the 624 phase columns https://www.agilent.com/en/product/gc-c ... cb-columns

The other option is to use either Headspace sampling or Purge and Trap, since acetonitrile is volatile enough to use those methods.

Thanks for the answer. The column that I use is made for analyzing organics acids. But if I inject acetic acid (400 ppm) in a water sample than I don't get any peak. Only the peaks at the end like I always have. So that's not normal I guess?