Journal of Chromatography A 2003-05-02

Modification and validation of the pyromellitic acid electrolyte for the capillary electrophoretic determination of anions.

Thomas Ehmann, Laszlo Fabry, Herbert Rüfer, Ludwig Kotz, Siegfried Pahlke, Claus Mantler

Index: J. Chromatogr. A. 995(1-2) , 217-26, (2003)

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Abstract

For the determination of inorganic and organic anions, the pyromellitic acid (PMA) electrolyte is widely used. The pH adjustment of the self-prepared electrolyte was very challenging to satisfy the pH of specification of pH 7.8 +/- 0.1. A modification was proposed to provide a more simple electrolyte by buffering the PMA electrolyte with triethanolamine (TEA) only instead of adjusting the pH by NaOH and TEA. Thus, the proposed electrolyte consisted of 2.25 mmol l(-1) PMA, 0.75 mmol 1(-1) hexamethonium hydroxide and 12 mmol 1(-1) TEA. The performance of the PMA electrolyte buffered by TEA only was compared to a commercial available PMA and statistically validated in accordance with the methodology of Taguchi. No statistically significant difference could be found for both electrolytes assessing the performance and detection limits of hydrodynamic, stacking and electrokinetic injection with transient isotachophoretic preconcentration as well as repeatability of migration times, peak resolutions and peak symmetries.