GC-MS Method Development Question

[dblux_]

... Incase if I have to use carbondisulphide, how can I rinse carbondisulphide thoroughly between injections and what wash solvent can I use?

Please let me know.
Thank you,
Srikanth.S

It's a solvent. You don't need special procedures. Just use CS2 as wash solvent.

[tangaloomaflyer]

In general extracted ion chromatography has no benefit when analysing hydrocarbons as they tend to fragment in the same way (so all have similar spectra) and it is difficult to resolve isomers.

If you are looking at several individual isomers then quantitaion by an extracted ion is OK - run a calibration using standards (internal or external calibration)

If you are expecting hydrocarbon products then TIC is better and you should quantitate fractions of the chromatogram. the fractions represent hydrocarbons of different chain length and you can set the boundaries using n-alkane standards. You can either calibrate using a product of known concentration or use individual hydrocarbons and assume that the response factor applies to the whole fraction. External calibration is better for TIC. If you are adding internal standards you need to subtract them from the fraction that is being quantitated.

[Bigbear]

The method using CS2 will work as I ran it decades ago. If you have tha resources I feel it would be better to purchase a thermal desorber, then you could collect the samples on tubes packed with VOCARB 3000. The thermal desorber is similar to a purge and trap in that there is no solvent to worry about nor loss of volatiles when preparing with CS2.

[srikkanth4somarouthu]

Hi all, thank you very much for responses. We don't have a purge and trap capability. We have a split and splitless inlet with liquid autosampler. So, I cannot use thermal desorption procedure. Do any one have any idea how to semiquant quantitation using four or five standards?

I am thinking to go with semiquant procedure.

Please let me know.

Thank you,
Srikanth.S

[tangaloomaflyer]

I believe to semi-quant (quantitate multiple analytes from one standard) then you just set up your calibration as normal, but integrate the same peak for the different analytes in the calibration.

[srikkanth4somarouthu]

Hi thank you for the reply. Your suggestions are very helpful.

Srikanth.S