A colleague with whom we're cooperating on IC analysis, informed us that (according to Dionex-stuff) when one does Anions analysis with IC, using an eluent consisting of carbonate, they should use quadratic fit. Would it be possible that anyone explains why could/should this happen (or paste a link either here or on an email to me of a relative document?) I've been searching the website of DIONEX but haven't found any document that suggests this for this specific application.

Thanks in advance,

Vanglis,

The most detailed reference is: M. Doury-Berthod, et al. Analytical Chemistry, Volume 57 (1985) page 2257. You'll also find information regarding this aspect on pages 277-279 of Paul Haddad's book: Ion Chromatography, Volume 46 of the Journal of Chromatography Library.

Basically, the weakly acidic character of the carbonic acid background induces a minor amount of nonlinearity. You don't really to worry about a quadratic fit unless you are dealing with a very broad calibration range.

many many thanks Chris,