Chromatography Forum

Hi,

I am writing a validation plan for a GC method and was wondering what robustness parameters you would usually validate for such a method?

The chromatographic conditions are as follows:


Column: DBWAX column of 30 m x 0.32 mm i.d., 0.5 µm film thickness
Carrier gas: Nitrogen
Flow rate: 1 ml/min, with 1:35 split ratio
Purge: 4.0 ml/min
Detection: FID at 250 ºC
Gas used for detection: Hydrogen at a flow rate of 44 ml/min
Air at a flow rate of 275 ml/min
Nitrogen at a flow rate of 20/min
Injection method: Split flow, maintained at 200 °C, with 1 µl injection volume
and unpacked insert
Temperature: Isotherm at 60 °C
Run time: 20 minutes

So far I would change the injector, detector and column temperature by +/- 10%.

But some of the parameters above do not make sense to me, such as the 4ml/min purge. Does anyone know if this is a headspace method and can I run this on an Agilent system too?

Thanks for any help in advance!

Max

Sounds like a std split injection method with a 4mL per min septum purge to remove contaminants from the sample from the septum area.

One other parameter to consider for robustness would be the carrier flow.

Rod

Sounds like a std split injection method with a 4mL per min septum purge to remove contaminants from the sample from the septum area.

One other parameter to consider for robustness would be the carrier flow.

Rod

Hey chromatographer1,

thanks a lot for your reponse as it was very helpful. Would you say it makes sense to consider the 1:35 split ratio as a robustness parameter?

Yes. Good catch.

Perhaps 25-45 to one.

best wishes,

Rod

Is this FID? Why are you running air so low? The default FID flows are 30 H2, 400 air, 25 make up. I've seen people run at 45/450/25 but never lower air.

You want to keep the H2/air ratio approximately the same to keep the same richness/leanness of the flame.

This is a rich flame but some run this way if they have issues with flameout when performing large injections of air in HS analysis and fast or variable carrier flows. But it is a bit rich, I agree.

Rod

Rod is (as always) right. The S/SL injector on the 86.10 is extremely prone to contamination as the purge and split lines are unheated and uninsulated starting directly at the injector.

Therefore I run my 86.10 with similar purge flow rates.

Hello.

First - written "delirium" in the method . 1:35 and 1 ml /min not equivalent 4 ml/min. Mistake error in write text or text translation, such as " Forgot to put a point digit 1.0 => 10"
Conclusion: "spit (on paper) and forget (to score for the method)" , work in accordance with common sense. And then look for the author's methodology and e-e-e..."apply it face down on the table" for inattention
Second - Norms EC Pharmacopeia "is not a law, but a recommendation. "
If you get the correct result and [url]can prove it[/url](validated method in some way) - then you will not condemn it.
In the U.S., a different approach, but I think the FDA a written notice of non-compliance you insure yourself out of trouble.
But here in Russia.
Saltykov Shchedrin wrote "severity of the law it is offset by not performing" (c)