Elution Order Question

Basic questions from students; resources for projects and reports.

4 posts Page 1 of 1
Which will elute first on Rxi 624Sil MS column (GC), cis-ocimene or trans-ocimene?
624 has some different polarity than a straight methyl column but it's not that different. You might not get any separation between them.

If you have the standards, just shoot them and see what you get. Beware, your "pure standard" may have the other in it too.
rb6banjo wrote:
624 has some different polarity than a straight methyl column but it's not that different. You might not get any separation between them.

If you have the standards, just shoot them and see what you get. Beware, your "pure standard" may have the other in it too.


I see, thank you! My standard is a combination of cis and trans, so there is where my problem lays. Is there a way to predict which is supposed to elute first?
Is the standard a 50:50 mix? If not, the response factors for these materials are likely to be very similar so they'll respond the same way in your detector. For example, if your standard is 85% trans and 15% cis, then the bigger peak will be for the trans isomer, etc.

What is the reason you have to tell the two apart? I'm not aware of any real flavor difference between the 2 isomers. When I have these situations, especially with hydrocarbons like this, I'll just integrate the 2 together (standards and samples) and report out a "Total Ocimene" value.

You might try to look someplace like the Restek library (restek.com) of chromatograms. Focus on the 624 phase and look for application notes where cis- and trans- isomers are listed. Maybe you can discern some trend about which isomer tends to elute before the other.
4 posts Page 1 of 1

Who is online

In total there are 4 users online :: 0 registered, 0 hidden and 4 guests (based on users active over the past 5 minutes)
Most users ever online was 599 on Tue Sep 18, 2018 9:27 am

Users browsing this forum: No registered users and 4 guests

Latest Blog Posts from Separation Science

Separation Science offers free learning from the experts covering methods, applications, webinars, eSeminars, videos, tutorials for users of liquid chromatography, gas chromatography, mass spectrometry, sample preparation and related analytical techniques.

Subscribe to our eNewsletter with daily, weekly or monthly updates: Food, Environmental, (Bio)Pharmaceutical, Bioclinical, Liquid Chromatography, Gas Chromatography and Mass Spectrometry.

Liquid Chromatography

Gas Chromatography

Mass Spectrometry