Chemical Forums
Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: confusedstud on February 08, 2020, 03:56:11 AM
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In an experiment we are supposed to analyse a series of standards to get their retention times for identification purposes. But before that we needed to obtain the optimal linear flow rate by using ethylbenzene as the analyte. We were using nitrogen gas carrier gas. However I don't understand the rationale for this choice since compared to the other components it has the 2nd highest boiling point and one of the lowest polarities.
The other standard samples include o-xylene, toluene, ethanol, n-propanol, n-butanol, n-pentanol, cyclohexane and ethylbenzne itself, which have a spread of boiling points from 78C to 144C and the polarity range is also relatively large. However ethylbenzene does not have the intermediate properties of these analytes so I'm not very sure why it was chosen for this experiment. Does anyone have any insight for this?
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Do you know the retention order of all of the analyses? I am not sure whether or not this helps, but it might.
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Yes, I have identified the following details:
Boiling point Dielectric constant Retention times
Toluene 110.6 2 – 2.4 4.714
Ethylbenzene 136 3 6.806
Cyclohexane 80.74 2 1.793
o-xylene 144 2.6 8.875
Ethanol 78.37 24.3 2.632
n-propanol 97 20.1 3.761/3.805
n-butanol 117.7 17.8 5.900
n-pentanol 138 13.9 9.484
So ethylbenzene has one of the latest retention times, but it isn't the biggest so I'm not very sure what makes us choose it for the optimal linear flow rate for all the other compounds. Thanks in advance for the *delete me*