Dear Phuc Nguyen,

Carbonate eluents:

The carbonate eluent has the advantage that the total ionic strength as well as the proportions of the mono valent (HCO3-) and the divalent (CO32-) can be varied to optimize the retention time and the selectivity between monovalent and multivalent sample ions.

The Hydroxide eleunts:

The advantage of using the hydroxide eluent is that it is transformed into pure water in the suppressor reaction, and consequently give a very low back-ground conductivity.

Since the hydroxide eluent has a pH of 12, separation columns of some brands can be susceptible to damage by strongly alkaline eluents. In addition, strong bases dissolve silica from glassware, and the silicates contribute to a higher background and can also cause other problems. Therefore it is recommended to use plastic bottle for the eluent.

For more on the pros and cons of the two eluents, please use the following link:

http://www.nestgrp.com/pdf/Zp1/Sp1/ION_Manual.pdf

Hoping this will be helpful,

Rafik

Both answers above are correct. I would like to add a litle more.

Carbonate/bicarbonate and hydroxide eluents can vary in pH from slightly alkanine to strong alkaline. with the combinations of carbonate, bicarbonate, and hydroxide it is possible to cover this whole range.

Suppression is no problem for all these eluents, also gradients are available for all eluents.

Thereforeit's not the question which eluting ion is better. But which eluent fits best to my column and separation requirements.

Markus

The carbonate eluent is the better option for routine isocratic major inorganic anions analysis. However, if you need to analyze very low concentrations of inorganic anions and/or low-molecular weight organic acids, then you have to work with hydroxide gradient.

we do very low concentrations and short chain organic acids with carbonte eluents as well.