Separation of alkanes using HPLC

Discussions about HPLC, CE, TLC, SFC, and other "liquid phase" separation techniques.

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My sample is an oil consisting of aliphatic as well as aromatic components. The HPLC instrument we have is RP-HPLC. Is there any way to convert RP-HPLC to NP-HPLC which would help me in the separation of the heavier fractions for easier analysis?
In short, yes. You'll need a different column and to be mindful of mobile phase solubilities but it can be done after a careful flushing of the system. Most people use either IPA or MeOH after flushing whatever's there out of the system to switch from NP or RP or back to RP. Either way, make sure it's a new (dry) bottle.
Thanks,
DR
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Thank you so much for your reply DR. My product is soluble with DCM and it is made from plastic pyrolysis. Do you have any suggestions in the type of column that might work?
Maria97 wrote:
Thank you so much for your reply DR. My product is soluble with DCM and it is made from plastic pyrolysis. Do you have any suggestions in the type of column that might work?


How are your samples prepared for the instrument? Are you doing an extraction into a solvent (like DCM) or is it a direct application of your sample into the system?
"Have you tried explaining it to the rubber duck?"
The oil is extracted into DCM and I was thinking to use the DCM extract for the analysis. Or is there any other way to use more suitable solvent. Apologies if I sound stupid, I am a newbie trying to learn this technique.
Some LC systems need different pump seals for normal phase solvents (especially true of UHPLC systems; the normal-phase seals often aren't rated to quite such high pressures, and the reverse-phase seals will start leaking pretty quickly if run in normal phase solvents).
If your system is regularly used with salty buffers, I'd recommend keeping a set of the filters that sit on the ends of the tubes in the solvent bottles specifically for normal phase applications. It can be hard to wash out every last trace of anything salty from these filters, depending on their design, and you may find that if you use one from a salty buffer even after copious aqueous rinses and then changing over via isopropanol, about 3 runs later, your check-valves start to complain because some tiny bit of salt has diffused its way out of some deeply buried pore, met a load of hexane coming the other way and precipitated, and whisked its way pumpwards...
6 posts Page 1 of 1

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