Enhanced conductometric detection of cyanide in suppressed ion chromatography

Weak-acid anions such as berate and cyanide, present problems in chemically suppressed ion chromatography, since the acids are weakly ionised, giving low conductivity and therefore decreased sensitivity. For berate this problem was overcome by converting the weak acid to its sodium salt, by the use of a second anion micromembrane suppressor (AMMS) as an ion exchange reactor (IER), flushed by EDTA reagent, to supply sodium ions for the conversion. This paper will discuss the use of this IER system to determine cyanide, which is also a very weak acid, with a similar pK(a) to berate. The detection limit for cyanide of 50 mu M compare favourably with indirect conductivity detection. (C) 2000 Published by Elsevier Science B.V.