I've got a water sample in witch I like to analyse ions (all ionised molcules) with (ofcourse) HPLC... What kind of detection, column, eluent, etc is the best to use?

Thanks,

Jorim

That all depends on the nature of your analytes. Are you interested in analyzing anions, cations or both? Do the ions contain UV chromaphores? Are the ions inorganic, organic or both? Are the ions monovalent, multivalent or both?

Dear Jorim,
You can download our brochure "Primesep with ELSD: New Alternative to Ion Chromatography". It allows you to analyze organic and inorganic compounds in one matrix.

http://www.allsep.com/Brochures_Home.php

This technology is suitable for concentration of ions above 20 ppm. We are working on another approach which will allow us to analyze ions at 1 ppm level. You can use regular HPLC system equipped with ELS detector.
Contact us mail@allsep.com for more information.

Enough Allsep commercials!! You don't even know what the ions are. How can you be recommending your products in the absense of such information?!!!

Dear Chris,
Your completely right, this is not enough information to give a good advice (AllsepTech :P). I'd like to determine all kinds of chlorides (example: after electrolyses of a NaCl solution)...

Jorim,

If you're really only interested in chloride and you would like to do this on a standard HPLC using a reversed phase column, then I would suggest using a tetrabutylammonium phosphate eluent system with a UV detector. Chloride doesn't absorb very strongly in the UV unless you work at low wavelengths so you should try using either 210 or 215 nm depending upon your sensitivity requirements. It's been a while since I did this separation on an HPLC but if I remember right, 5 mM tetrabutylammonium phosphate with about 15% acetonitrile should give you reasonable retention of chloride.

Note to Allsep: See, it's actually possible to give advice without selling your company's products!

Is it possible to use ionexchange columns?? there are anions. If so, how ??

Thanks!

Jorim,

You can definitely use ion exchange columns for separating chloride but if you're planning on using UV detection, it would be advisable to use a relatively low capacity column. With anion exchange it's preferable to use polymeric stationary phases since this provides you with the flexibility of operating under alkaline conditions which allows separation anionic of species under conditions where most analytes exhibit reasonable retention. However, since chloride is a strong electrolyte it is amenable to separation even at very low pH. Also, it's generally preferable to utilize fairly hydrophilic polymeric materials in order to provide optimal selectivity for polarizable anions. You can obtain a selection of such from a number of vendors including Dionex, Showdex, Tosoh, Alltech, Hamilton and Metrohm. If you are going to use UV detection, a good eluent system is sulfate which does not absorb in the UV but phosphate can also be useful for this purpose. The recommended ionic strength in this case depends on both the choice of anion and the choice of column.