I intend to analyze samples containing mainly ketones, carboxylic acids, aldehydes etc. What is the standard procedure for calibrating these compounds using an internal standard (for instance, 1,4, dioxane) in gas chromatography?
I'm assuming that you want to vary the injection volume / dilution and want to spike the sample with an internal standard of known concentration so that you can account for any GC sample prep or injection variability. You just need to select a compound that will separate from the others during elution in the GC and then spike that compound to a known concentration in the original sample. Note, the volume of the standard added changes the concentrations of everything in the sample, so you need to know how much volume was added as well as the concentration to correct all the way back to the original sample. The simple procedure is to divide all the peak areas of the compounds you want to know by the area of the internal standard.
This, however, does not tell you anything about the actual concentration of each component. The issue is the response factor of the detector which varies for each component. To calculate that you need to prepare standard curves with known concentrations of each of the component so that you can correlate peak areas with concentration for each component. If you do this right, you also get information about the limits of detection both lower and upper. You always want to operate in the linear region where the response factor is constant. This is why you dilute your samples to get them into the linear range of the GC assay.
Hi Opeyemi,
I agree with Luke Schneider. Moreover, the analysis of the compound to be used as an internal standard is important to ensure that it has similar physicochemical properties to the targeted compounds to ensure similar recovery.
Good luck!
Mr. Ojelade,
Consider section 'Discussion' of the following work. In particular, concentrate on the reference section, therein:
[https://www.sciencedirect.com/science/article/abs/pii/S002228602200374X]
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