Dual suppressor ion chromatography system

The new dual suppressor allows Metrohm to perform IC gradients,which so far has not been a feature within the Metrohm range.Rather than copy existing technology, Metrohm has kept to itsoriginal innovative philosophy and generated its own novel ideason how IC should be developed.

To date, all anion chromatographyperformed with gradients is completed almost exclusively withalkali eluents.

The problem with alkali (OH) eluent is that it isa weak eluent.

So quite strong concentrations of alkali arerequired to shift late eluting ions off the column.

This is asmall cost as ion chromatographers are happy to work with alkali.When alkali (OH) is chemically suppressed, it is converted fromhydroxide to water, giving a zero conductivity baseline.

Evenwith a gradient, the baseline is flat.

However, it has somepractical difficulties.

The hydroxide eluent is not very stable.It absorbs CO2 very readily, causing shifting in the retentiontimes.

The chromatography is prone to carbonate and system peaks,affecting the quality of the chromatography and the integrity ofthe results generated.

It has been known for a long time that theuse of a bicarbonate / carbonate eluent would be a technicaladvantage over hydroxide eluent.

They are easy to prepare andvery stable.

No expensive eluent generation modules andconsumables would be required.

More importantly, thechromatography, bicarbonate/carbonate eluents are strongereluents than alkali eluents.

This allows shorted run times andfaster column recovery from a gradient use.

Unfortunately, whencarbonate and bicarbonate eluents are chemically suppressed, theyare converted to the carbonic acid.

Carbonic acid is not fullysuppressed as it is only partially dissociated.

So when used in agradient system, the baseline conductivity is not flat.Chromatographers prefer to operate under flat stable baselines.It has long been the 'Holy Grail' of anionchromatography to develop a suppressor which could removecarbonate.

The unique Metrohm new dual suppressor chemicallysuppresses carbonate and removes the carbonic acid.

It is reallya two-stage process.

Hence the name dual suppressor.

There aremany benefits.

You buy two suppressors in one and yet you getthree (a chemical suppressor, a carbonate suppressor, and anelectronic suppressor).

The main advantages over alkali eluentsare: no water dip using a carbonate eluent; no system peak usingthe carbonate eluent; gradient with carbonate eluent; stableeluent, reproducible baselines; shorter chromatography run timesas bicarbonate and carbonate are stronger eluents; shorterrecovery times after a gradient has completed; no solutions arerequired for the suppressor.

It is an electronic suppressor andso continuous.