Eluant preparation: general comments

 

Eluant is the mobile phase that transports the sample ions through the ion chromatograph plumbing, including the columns. The pH, ion concentration, and ion types in the eluant determine the partitioning of the analyzed ions between the stationary phase (ion exchange resin in the columns) and the eluant.

 

Both of our current instruments make their own eluant from deionized water and eluant generator cartridges. The eluant is prepared by electrolysis and ion exchange in the cartridge module. The anion system produces KOH eluant, typically 10 to 50 mM, and the cation system produces methylsulfonic acid (HSO4CH3), typically 10 to 50 mM.

 

We therefore do not have to make any eluant for routine analyses. We still have to make special eluants for cleaning contaminated columns. Instructions are around for these. Basically, once the proper eluants are produced they have to be degassed by putting the solution under vacuum (sink asperator, magnetic stirrer), and then by pressurizing the eluant with helium.