Applications of ion-exchange minicolumns in a flow-injection system for the spectrophotometric determination of anions

Displacement of thiocyanate from a strongly basic ion-exchange resin by other anions is used to determine common anions at the 10^?5–10^?4 M level by spectrophotometric detection of the iron(III)/thiocyanate complex. Chloride and sulphate can be removed by incorporating a pre-column containing a cation-exchange resin in the silver form followed by a zinc reductor, thus allowing the determination of nitrate in their presence. Binary mixtures (e.g., chloride and nitrate) can be determined simultaneously by splitting the sample in the flow system so that part goes through the chloride suppressor (giving a nitrate response only) and part by-passes it giving a response to both chloride and nitrate.