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Gas mixture components identification
Posted: Mon Jan 06, 2014 3:23 am
by offroad
Dear Chromato experts,
please allow me to ask a newbie question:
While observing technicians determine the composition of a gas mixture, I couldn't help wondering why they needed one single injection of standard to build the 'curve', which obviously, will always be a line. I have never seen this 'trick' being applied to liquid mixtures.
Could you shed some light on this?
Very much appreciated.
Offroad
Re: Gas mixture components identification
Posted: Mon Jan 06, 2014 12:40 pm
by Don_Hilton
What you do for calibration depends on how well characterized your chromatographic system is (or you believe it to be) and the accuracy you need for your result. Even if you assume that the linearity and precision of a system is stable, it is a good idea to check it every now and again. It is possible that the performance of the chromatographic system is checked for linearity and precision, but on a less frequent basis - and perhaps by other people than the technicians who run the one-point calibrations and samples.
Re: Gas mixture components identification
Posted: Mon Jan 06, 2014 1:28 pm
by offroad
What you do for calibration depends on how well characterized your chromatographic system is (or you believe it to be) and the accuracy you need for your result. Even if you assume that the linearity and precision of a system is stable, it is a good idea to check it every now and again. It is possible that the performance of the chromatographic system is checked for linearity and precision, but on a less frequent basis - and perhaps by other people than the technicians who run the one-point calibrations and samples.
So, when you are running the first analyses - supposing you haven't even run the GC yet - you'll need a muiltiple-point calibration for the gas?
Thank you
Re: Gas mixture components identification
Posted: Mon Jan 06, 2014 6:08 pm
by Steve Reimer
Yes, you need a calibration at multiple concentrations to determine detector response vs concentration as it may not be linear. Also a single injection at a single concentration gives you no information on reproducibility.
Re: Gas mixture components identification
Posted: Mon Jan 06, 2014 6:57 pm
by offroad
Exactly what I didn't want to hear as I have one cylinder (standard) only. I will see if I can copy their 'technology' and ask why they usually do a single injection.
Thank you very much.
Offroad