Selective determination of gas dialysable components in complex sample solutions using triangle programmed coulometric titration in continuous flow systems

A precisely and sensitively working coulometric flow titration procedure was developed to determine ammonium/ammonia and sulphide/hydrogen sulphide in leachate from a municipal waste landfill site. The selectivity of coulometric titration with electrogenerated hypobromite could be essentially improved by the combination with a continuously and quantitatively working thin layer gas dialysis cell, which was integrated in the flow titration setup in one measuring device. During the flow titrations both ammonium/ammonia and sulphide/hydrogen sulphide were quantitatively separated from the sample solutions. Both the commonly used biamperometric and the chemiluminescence flow detection could be applied to follow the titration course. By triangle-programmed coulometric titration ammonium/ammonia were detected in a linear range from 10−3 to 10−6 M (relative standard deviation (RSD) = 1%, n = 6, confidence level α = 0.05) using biamperometric detection and from 5 × 10−4 to 10−6 M (RSD = 3%, n = 6, α = 0.05) using chemiluminescence detection. Sulphide/hydrogen sulphide could be determined in a linear range from 5 · 10−4 to 2 · 10−6 M (RSD = 4%, n = 6, α = 0.05). Up to 30 flow titrations could be implemented per hour.