Electrokinetic Detection in Reversed Phase High Performance Liquid Chromatography Part II. Quaternary Ammonium Ion-Pairs of Some Volatile Fatty Acids

Abstract

The conditions of electrokinetic detection were elaborated for tetraethylammonium, TEA⁺, ion-pairs of volatile fatty acids(acetic, propionic, isobutyric and valeric) in reversed phase high performane liquid chromatography, HPLC. To eliminate the dependence of the retention volume V _R, on the concentration of acids found in the first part of this work, TEA⁺ was added to the non-buffered mobile phase. In the presence of pairing TEA⁺ ions, V _R appeared to be invariant with the concentration of acids in the sample in a definite concentration range. The detectability of the detector, with a polytetrafluoroethylene, PTFE, capillary as its working unit, was of the order of 10⁻¹⁰ mole and the reproducibility was 5% (relative standard deviation, R. S. D., for ten consecutive injections). The linear dynamic range extended over two orders of magnitude of the acid concentrations.