Chromatography Forum

Hello everybody,

Is it possible to use different solvent for calibration standards (for example DCM or iso-octane) than for the samples (for example in hexane)? Can different solvents cause shifts in retention times?

Can we inject dichloromethane (DCM) with micro-ECD with appropriate solvent delay?

I will appreciate your input regarding these very basic questions.

regards,

Words are so important:

"Can we inject dichloromethane (DCM) with micro-ECD with appropriate solvent delay? "

Yes.

but SHOULD you? With a packed column I would say NO. With a capillary, I would say yes.

I would use the same solvent for samples and standards, why differ?

"Can different solvents cause shifts in retention times?"

It is possible, but not likely.

best wishes,

Rod

Words are so important:

"Can we inject dichloromethane (DCM) with micro-ECD with appropriate solvent delay? "

Yes.

but SHOULD you? With a packed column I would say NO. With a capillary, I would say yes.

I would use the same solvent for samples and standards, why differ?

"Can different solvents cause shifts in retention times?"

It is possible, but not likely.

best wishes,

Rod

Hi Rod,

Thank you so much for the reply. Yes, I have asked that in context of capillary column chromatography. Sorry for not being so explicit. The reason for using different solvents is in fact to reduce some steps in term of solvent switching. . Some of solvents are not compatible with the PDMS chips which I am using for the sorption studies of hydrophobic compounds. Making stock solutions of PCB and PAHs powder in DCM can make life easy because later on I can use the same to spike the methanol which i am using to load PCBs and PAHS on these PDMS chips. For the back extractions of these chips, I will use hexane/iso-octane.

regards,

Have you considered using methyl formate or ethyl acetate instead of DCM?

best wishes,

Rod

Changes in retention times with different solvents are unlikely, but changes in peak area are quite likely, depending on the inlet and injection conditions.

Peter

Thanks Rod and Peter.

Yes, I can even use ethyl acetate but from Peter's reply it seems it is important that I use the same solvents for calibration standards and sample standards. I will be using typical splitless mode with purge valve open after 60 sec and temperature 270 degree C and injection volume of 1 microliter.

regards

If you do use different solvents you will have to run a series of comparisons between solvents to demonstrate what, if any,difference the solvent makes. That extra work may be more trouble than the solvent exchanges.

Peter

Peter,

Yes, I see your point. Thanks for your valuable input.

regards