Quantitative Analysis of Anions at ppb/ppt Levels with Capillary Electrophoresis and Conductivity Detection: Enhancement of System Linearity and Precision Using an Internal Standard

Abstract

Capillary electrophoresis with conductivity detection is evaluated for quantitative analysis of anions at low- to sub-ppb concentration levels in the presence and absence of a conductive sample matrix composed of 2 ppm ammonia and 50 ppb hydrazine. The low-level sensitivity is extended by a transient isotachophoretic stacking procedure. The linear range of the CE system and conductivity detector is graphically evaluated on the basis of absolute and corrected (normalized) chloride and sulfate peak profiles using an ASTM linearity criterion. The influence of random contamination bias from ubiquitous entities of nonsample chloride and sulfate levels introduced by liquid handling, laboratory atmosphere, and bulk chemical residues is quantitatively compared against an internal (contamination) reference ion.