running heavier compounds through low-temp columns

[JHZR2]

Hi,

My varian system is set up with columns that cant take over ~320C.

If I want to run heavier stuff - heavier than diesel, but lighter than a motor oil, whats the best way to do it? Can I do it at all?

Ive found that if I cut stuff in octane, I get my octane peak, and then a constant, elevated hump with no peaks at all, at the top end, when I approach and sit at 320C. This is more or less the same in the FID and PFPD.

Is it a matter of using the right solvent, diluting it enough, or can I plain not do it due to the boiling points of this stuff (which is advertised as 'greater than 370C)?

Thanks!

JMH

[CE Instruments]

Try doing a search on SIMDIS, this allows determination op oils up to 600C boiling point and beyond with the right conditions of GC, column etc. You may however not be able to resolve them into individual peaks as there are too many isomers to separate.

[chromatographer1]

I once did an analysis looking at C16 to C37 content of a matrix (low levels) dissolved into hexane. (1µL to 5µL slow injection rate)

I used a 3m 0.53mm 0.5µm film 50% phenyl methyl silicone capillary using 10 to 20cc/min, direct injection, and a ramp rate of 20°C/min starting at 40°C oven 2 min. initial hold (injector 250°C detector 325°C )

I got a fairly flat baseline and a spikey chromatogram.

It is something you could try. I was trying to keep carbon number isomers together rather than to separate them. A 100% methyl silicone or 5% Phenyl could be a better choice but will require a higher end temperature or a thinner film.

The analysis was over in 15 min.

best wishes,

Rod

[Tony_Montanari]

I have been doing long chain alcohols and an aluminized column produced by this company. It can go up to 400C and I think is included for use with biodiesel.


http://www.quadrexcorp.com/new/

[Consumer Products Guy]

Similar to Tony, I use a high temperature capillary from Quadrex, only mine is stainless steel.