Ion chromatography system

[Edde]

I am considering to purchase an ion chromatography coupled to ion suppressor and conductivity detector system for inorganic anion and cation and organic anions.

Anyone knows which brand is better? Dionex, Metrohm, or Waters (see conductivity detector in Waters website, but I don't know if it still sells Alltech suppressor) or others.

Appreciate any advice and comments.

Thanks.

[Edde]

Anyone used Agilent 1200 LC coupled to Waters conductivity detector? Is this a feasible combination for inorganic anions and cations and organic anions?

How does it compare with Dionex or Metrohm IC - conductivity detector- ion suppressor system ?

Thanks.

[CE Instruments]

All depends on the levels. You can get away with a conductivity detector on a standard LC but only if your analysis levels are high. Non supressed system have a high background and suffer much more with baseline problems and seeing your peaks. Dionex have just been bought by Thermo
My 2c is go supressed from a specialist if you can afford it.
(based on 4 years with Dionex in the 80s)

[Edde]

Thanks for your recommendation.

Buying an IC with suppressor and conductivity detector may be 2-3 times more expensive than a Waters conductivity detector without suppressor (Waters no longer sells Alltech suppressor) connected to my existing Agilent HPLC 1200.

But I wonder if controlling the Waters conductivity detector with Agilent Chemstation will be feasible. The salesperson said no problem.

Anyone has experience with this? Please share.

[H2Oh]

I would vote Dionex with electrolytic suppression as well. If money is tight, I wonder if you could add a chemical suppression cartridge (from Metrohm) to a less expensive system? I haven't ever used them as almost all of my systems are Dionex, but I recall Metrohm claimed they were highly effective and long lasting.

What types of eluents will you be using?
Carb/Bicarb? NaOH? MSA?

[Edde]

Unfortunately, Metrohm does not sell modules separately.

I recall Metrohm claimed they were highly effective and long lasting

Yes, the saleslady said that the suppressor is durable and has extended warranty. She claimed that its systems rarely break down.

I haven't decided which eluent to use. Does it matter?

Thanks.

[H2Oh]

The eluent is usually dictated by column choice. The eluent then dictates which suppressor (cation or anion) to use. Interesting that you can't just buy a chemical suppressor from them. Dionex may have an older one.

Which column(s) are you using?

[Edde]

Dionex doesn't sell separate modules, either.

I haven't decided on which column to use yet. All depends on the approach, i.e. IC or LC connected to conductivity detector I finally use.

I have a Waters anion exchange column in stock but never used it.

My targets are inorganic anions and cations and organic anions. Therefore, eventually I will need a cation exchange, anion exchange and a dedicated organic acid columns.

[gcguy]

I use a simple Metrohm system with a suppressor. The suppressor is only required during anion determination and the system typically gives us detection levels at 0.1-100ppm levels for many common ions. In cation mode the level of sensitvity is about the same. The suppressor has worked for many years without issue, yes there is the addition task of making up regeneration solution but this is not a real problem.

GCguy

[Edde]

Thanks GCguy.

It seems that Dionex IC has ion suppressors for both anion and cation. I thought it was better to have suppressor for cation as well. But I am not sure.

In addition, Dionex IC seems to be more widely used.

From your experience, Metrohm is also a reliable machine. It's really difficult to decide.

[Markus Laeubli, Metrohm]

I am definitely biased, I know.

But Metrohm is selling IC since more than 20 years without the need of cation suppression.

Anion suppression removes the background and increases the response for the anions.

Cation suppression only removes the background conductivity but the response for non-suprressed cations is usually higher and there is no problem with heavy metals in the sample.
But for sure suppressed cation chromatography also works.

[Edde]

Thanks.

If I have to analyze carbonate as well, the Dionex salesperson said that I have to use a self-regenerating eluent system so that carbonate will not be formed from atmospheric CO2 in self-prepared eluents and I may have to use NaOH eluents.

I'm not sure if Metrohm can analyze carbonate with comparable sensitivity and accuracy.

[H2Oh]

There are carbonate removal columns you can add to clean up your eluent prior to the inject valve. That may give you more options.

RFIC hydroxide is great, but I've run manually prepared NaOH without issue. Just be sure to use it promptly and degas the water well.

[Edde]

I can't express how deeply I appreciate all your comments and suggestions. You folks are so helpful.

I will suggest to my boss to consider an IC with suppressed conductivity detection. This approach will cover most of my target ions. But this system is an expensive one (~US$62800).

In the Agilent LC-Waters conductivity detector with Alltech disposable ion suppressor system, the LC system does not guarantee not be leach metal ions in corrosive eluents. Therefore, it is uncertain whether it suits my purpose.

[Markus Laeubli, Metrohm]

again biased!

I never have seen a really accurate determination of carbonate with anion chromatography. Whether using manually made or electrolytically prepared eluents.

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. But the total ion concentration also influences the system peak.

Titration is usually the method of choice for carbonate/bicarbonate determinations. If you want to use IC, I do recommend to use suppressed ion-exclusion.