Chromatography Forum

Hi!
This might sound like a strange question, but I read about some experiments using toluene and ethylbenzene as probes and pure water as mobile phase, and a "home made/packed" column. Now, someone suggested to try this on a commercial C18 column, but I wonder if it is really possible to elute toluene from that type of column with only water in the mobile phase? If it comes out, will I see a peak, or will it come out spread over such a long time that it will not be an obvious peak?

Wasn´t there something like this on April 1? Just wonder how far to the center of earth one would have to move to get enough heat and pressure to make H2O and toluene miscible? Or someone might be able to foam up those two liquids and invent foam chromatography?

Actually, it is not a completely crazy idea (just a mostly crazy one!).

Selerity sells an oven for LC systems that allows you to do temperature programming in LC, just like you would in GC. The idea is that you can get the same type of gradient separations, but under isocratic mobile phase conditions. The idea is that you could use less, or even no, organic solvent, and still get things to elute. Of course, your column has to be stable at higher temperatures, and most C18's may not stand up to this much abuse.

Or, Zirchrom sells columns designed to go to 200 C in a special oven. Again, at high temps you can speed up the analysis and/or reduce the amount of organic solvent needed.

So, yes, you could elute toluene from a C18 column using water, but not at room temperature.

Check this out:

LC-GC LC Column Technology Supplement June 2004
"Stationary Phases for High-Temperature LC Separations"

Yu Yang and Donald R. Lynch, Jr.

http://chromatographyonline.findpharma. ... p?id=12064

Sorry, I read the original question wrong, I thought that a toluene/H2O mobile phase was mentioned. Considering toluene as analyte, one can see that there could be an equilibrium of toluene between the stat. phase and mobile phase which may be be useful under some conditions.
Nevertheless, I had read the LC.GC column, as well as other papers on high temp. applications, . . maybe some specialty applications?
(For instance, how green is something that needs a lot more energy? Or use earth´s core energy after all?).

Hans,

not sure how "green" this technology is in global terms. It is sort of "green" since the lab doesn't have to deal with hazardous waste disposal etc. and to cite a German joke from the 80s: "Atomkraft-nein danke! Bei uns kommt der Strom sowieso aus der Steckdose" (" Nuclear power? No thanks! We get electricity from our wall outlets...") most labs (as far as I know) don't really count their kWh...

Hi,

It may have been my article referred to in the first post:

Reversed Phase Liquid Chromatography of Organic Hydrocarbons with Water as the Mobile Phase
Foster, M. D.; Synovec, R. E.
Anal. Chem.; (Article); 1996; 68(17); 2838-2844.

Basically, if you reduce the phase volume ratio by 2 or 3 orders of magnitude you also reduce the capacity factor for a given solute/mobile phase composition/stationary phase system. You might expect a cap factor of around 1000 for toluene with a commercial reversed phase column using only water as the mobile phase. I reduced the phase volume by ~ 100 and used a more polar stationary phase and got cap factor of around 1 for toluene and water as the mobile phase. Some other authors (and Selerity) have used high temperature water as well. Once you get up around 200 celcius or so the dielectric constant of water is similar to methanol and similar in eluting power. The solubility of toluene in water is around 1% which is plenty for UV detection.

Thank you for answers everyone, that was really helpful. I don't think I will do this after all but the articles mentioned are really interesting, thanks!