I think you already know this, but you are using the wrong "tool" for the job. A GC/FID or GC/MSD system is the more appropriate type of instrument for the application you describe. You are trying to make a system which is not designed to provide you with everything you need (i.e. HPLC), work for this application. OK, so disclaimers aside...

Method Comments: A Hi-Plex Ca column with RID could be used to resolve many of the compounds you mention. Simple mobile phase, VERY temperature sensitive. RID = isocratic only methods. As such, detection will be limited and vary a lot with each compound. Isocratic analysis also means your peaks are going to be broad. The longer the run, the broader the peak. *A gradient would sharpen them up, but you can not use a gradient with an RID (and you do not have a gradient capable HPLC).

Short column = BAD idea. The more surface area (actually, active sites available to the compounds) the column has, the better to resolve things apart.

Not sure where you are going with the 6-port valve? Perhaps you were just describing the std injection valve, not a column selector? Were you thinking of 2D multidimensional analysis? I would not recommend you go down that route. Much more complicated and based on your post, it sounds like you are just started to do chromatography for the first time, so stick with simple solutions initially. Try to develop a method with the Hi-Plex Ca column first. Review the application notes and inject clean, filtered samples. Also, find out who in your University has a GC/FID system that could help you run these samples on.

Good luck with your project!

I think you already know this, but you are using the wrong "tool" for the job. A GC/FID or GC/MSD system is the more appropriate type of instrument for the application you describe. You are trying to make a system which is not designed to provide you with everything you need (i.e. HPLC), work for this application. OK, so disclaimers aside...

Method Comments: A Hi-Plex Ca column with RID could be used to resolve many of the compounds you mention. Simple mobile phase, VERY temperature sensitive. RID = isocratic only methods. As such, detection will be limited and vary a lot with each compound. Isocratic analysis also means your peaks are going to be broad. The longer the run, the broader the peak. *A gradient would sharpen them up, but you can not use a gradient with an RID (and you do not have a gradient capable HPLC).

Short column = BAD idea. The more surface area (actually, active sites available to the compounds) the column has, the better to resolve things apart.

Not sure where you are going with the 6-port valve? Perhaps you were just describing the std injection valve, not a column selector? Were you thinking of 2D multidimensional analysis? I would not recommend you go down that route. Much more complicated and based on your post, it sounds like you are just started to do chromatography for the first time, so stick with simple solutions initially. Try to develop a method with the Hi-Plex Ca column first. Review the application notes and inject clean, filtered samples. Also, find out who in your University has a GC/FID system that could help you run these samples on.

Good luck with your project!

   The best place to begin to attack a separation problem ( especially for a novice) is in the LIBRARY. There are hundreds of reports of GC separations of  broad alcohol reaction mixtures  This approach works well, and is  pretty simple to employ.

 There are some  some separations reported by HPLC, but the limitations in detectability of the compounds is an issue. Norman Parris reported the use of infrared detection doing non-acqueous reversed phase chromatography gradients for related mixtures using an infrared detector. Some similar ones can be done using  refractive index detection. These separation techniques are somewhat esoteric.

I detect a reliance on a single commercial vendor, and this can be a mistake, since most of the development of HPLC separations technology and support is found elsewhere. Many hplc column and instrument vendors can provide literature describing the separation of related mixtures, but the open literature and texts are more informative. 

Good luck on the project!

. 

Hi Seongho,

I really feel your limitations. GC is the first choice for the mentioned analytes.  I agree with Bill, But I suggest you use a monolithic column .

Please see: http://www.merckmillipore.com/

problems related to resolution & long retention times decrease dramatically.

But, use of dual column in this simple system is impossible and you are just wasting time and energy. Good luck,

Another approach is to use a very small pore size GPC column. Waters used to sell such a column.  These have been used to do a creditable job on some reaction mixtures related to the ones you describe, using a single pump hplc, and a refractive index detector. 

I think you have a couple of options :

1. C18 3um particle 150 x (3 or 4.6) mm (use a polar-embedded or double endcapped column). Mobile phase: 100% 20mM H3PO4

You can add a bit of acetonitrile in your mobile phase if you see that you have enough retention for all compounds to speed up your analysis. Also you can play a bit with pH and ionic strength of your mobile phase if some acid peaks are falling together, but don't expect too much. However since you only have limited choice in mobile phase, it might be difficult if some peaks are coming together

2. Mixed-mode column (I would choose Scherzo SS-C18): here you can play much more with your mobile phase. Organic acids can be retained and eluted by ion exchange, glycols and alcohols will be retained on the C18-phase. So you can play again with ionic strength, pH and organic modifier of your mobile phase but you have much more control and possibilities than with a simple C18-column. The Scherzo SS-C18 gives much more reversed phase retention than some other mixed-mode columns on the market. This will give you more room to play with the amount of acetonitrile that you can add to your mobile phase

3. Coupling of your current Ca-column with a RP-column or mixed-mode column. You will probably only be able to use 100% water as a mobile phase, but you will drastically improve resolution for your compounds compared to your single column. You just couple your columns in series, starting with the Ca-column, by the use of a column coupler or small piece of tubing.

Of course, once you have another column, you can always keep this option 3. in your head just in case, but I think option 2 will give you already the solution.

I don't see the need for an extra valve and pump.

If you only want to stick with your current type of column (and some other ligands), I would choose for a column with smaller particles (5um) than the Agilent column (8um). You will be able to take smaller dimensions (length or ID) and speed-up your analysis. (see some examples in attachement). I will also put a table with retention times on different ligand-columns. You will see some of your compounds are separable on a H-ligand 5um.

Thank you for giving ideas. 

I don't really stick with my Ca column, I was like to use Ca column as soon as possible and Use HPLC only,

also my lab has already GC(FID) system, 

Anyway,

Simple alcohols, glycols and organic acids can possible to separate by using Scherzo SS-C18 in my HPLC system?  

Scherzo SS-C18 is better than Hi-Plex H ?

or Ca with other column that series connection ?

I would say that you can try with a Scherzo-SS-C18. I think this should work if you play around a bit with pH. Normally you should be able to separate the alcohols and glycols just by their polarity if you use 100% buffer (so using the C18 functionality). Then you could check where the organic acids are eluting. If they interfere with some peaks and there is some space before the peak, you increase the buffer strength (keep pH stable) to move the acid peak forward. Don't exaggerate with the increasing the buffer strength at first, just to see how fas elution time is changing. If you see this has no effect, you could play around with pH to move acid peaks forward or backward. The other molecules are neutral and will barely move. In the end you could also try and add some acetonitrile to speed up the analysis if you have enough resolution between your peaks.

If all that doesn't work, you can couple the Ca-column with the Scherzo and use some small amounts of acid or buffer salt to play around with the pH. But this will most certainly push out the Ca-ions from the stationary phase so after some time you will have to regenerate your column.

It does look to me like a GC type of application, however, Scott and Kirsten provided some really great, specialized LC examples (thank you!)... Ideally, you can use more than one technique when there is any doubt.