Chromatography Forum

My experience is that the "carbonate"-peak (we prefer "system peak") definitely gives a guess for carbonate e.g. sum of carbonate and hydrogen carbonate.

Could you elaborate? Why is the carbonate peak actually sum of carbonate and bicarbonate?

Titration is usually the method of choice for carbonate/bicarbonate determinations.

How can titration determine carbonate and bicarbonate ions concentrations separately?

If you want to use IC, I do recommend to use suppressed ion-exclusion.

What is ion-exclusion please?

To your first question: its bloddy experience and I do not have an explanation.

Titration: If you are titration you are using the unchanged sample. Titrating now with an acid titrates first the carbonate and then the bicarbonate resulting in two endpoints corresponing to carbonate and bicarbonate.

Ion exclusion is a method mainly used for the separation of organic acids. Applying an acidic eluent on a high capacity cation exchanger column. The effect is that anions are eluted in the void. Butweaker acid which are partially protonated are retained. This is also the case for bicarbonate. In the inverse suppression step H+ is replaced ba e.g. Li+ converting the bicarbonate into stable LiHCO3.

Thanks Markus.

Hi,

I am not sure if this thread is still being followed, but I do have some experience using an older Waters 432 Conductivity Detector. It works quite well with an Agilent LC stack. The system is unsupressed, so you can really only run an isocratic method. It also needs to have a control box attached to it to send signals from the stack to the detector and back. If you were buying a newer waters detector, I don't know how that would connect to the Agilent system, but their engineers might have a solution for that.

If you are running just ions, Waters IC-Pak columns work really well, but for organic acids you are better off using an RI detector and one of the OA columns from phenomenex.

If you have the money though, the Thermo/Dionex ICs are the way to go. You could probably get one of the smaller models. They take up a smaller footprint, but don't have all the bells and whistles of the ICS-5000+. You can also find these instruments on auction sites like eBay or equipnet.

This message probably comes 6 years too late for the OP, but hopefully it helps anyone who is finding this thread in the future.

Thermofisher offers an affordable compact IC called the aquion for basic ion analysis

https://www.thermofisher.com/order/cata ... 2176-60002

Another add:

Metrohm offers an affordable Compact IC called "Eco IC" for basic ion chromatography

https://www.metrohm.com/en/products/ion ... hy/eco-ic/

Discover Eco IC, an ion chromatography system that focuses on the essentials while not compromising on quality, robustness, and reliability.

Have you considered the use of a Cecil Instruments’ IonQuest ion chromatography system. They are modular, sensitive, easy to use and robust. http://www.cecilinstruments.com/ionquest-1.html

Carbonate may be analysed using a Hamilton PRP-X100, 150 x 4.1 mm column,
with a mobile phase of 4.0 mM p-hydroxybenzoic acid in 2.5/97.5 % v/v methanol/water, pH 8.9 and direct conductivity.