What are the drawbacks in non-suppressed conductivity ?

[lgchrom]

some columns are optimized for non-suppressed conductivity.

what does this mean and what is the catch?

i am interested in an inorganic anions application.

[tom jupille]

No catch, really.

The basic issue is that conductivity detection measures the difference in conductivity between the analyte ions and the ions in the buffer. If both have similar equivalent conductance (i.e., similar conductivity on a molar basis), then the sensitivity will be poor.

"Suppressed" conductivity detection (the most common approach) selectively converts the buffer ions to a less conductive form before actually measuring conductivity. "Non suppressed" conductivity detection relies on choosing buffer ions with a large difference in equivalent conductance from the analytes in the first place.

Non-suppressed is simpler from an equipment standpoint. Suppressed is arguably more sensitive (for most ions). Choice of detection technique will determine the choice of buffer, and the choice of buffer will determine the choice of a compatible column.

[H.Thomas]

We use a column intended for suppressed conductivity detection (Dionex AS14) for analysis of inorganic anions with unsuppressed conductivity detection - without problems.

[Markus Laeubli, Metrohm]

mariosapm

You are asking questions to my original field of work.

As Tom already mentioned, non-suppressed measures the difference of the conductivity of the analyte ion and the eluent ion.

Suppressed measures the sum of the analyte ion and the counter ion introduced by the suppression reaction (H+ in anion IC). For strong and medium stron acid anions you get better response with suppressed IC. But weak acid anions like cyanide silicate and so on you will suppress their signal as well. Here non-suppressed might be a good solution.

In my experience it is possible to solve around 90 % of the applications non-suppressed as well. But suppressed IC is in many cases just more straight forward.