Simultaneous determination of positive and negative counterions in pharmaceutical preparations using Zic-Hilic column containing an extremely versatile zwitterionic stationary phase
The simultaneous determination of cations and anions can be performed in a single gradient chromatographic analysis via hydrophilic-interaction chromatography using a 4.6x250mm, 5um Zic-Hilic column with evaporative light scattering detection.
The Zic-Hilic column contains an extremely versatile zwitterionic stationary phase that is based on sulfobetaine groups.
The method, which employs an acetonitrile-ammonium acetate buffer gradient, is capable of readily separating the cations and anions from each other, as well as from the parent pharmaceutical molecules.
It was developed by DS Risley and DW Peck of Eli Lilly Research Laboratories (Indianapolis, IN) who reported that they were able to determine the concentration of 33 commonly used pharmaceutically relevant cations and anions (both organic and inorganic ions).
In addition, the method was capable of analyzing ten pharmaceutically relevant preparations, including ions with a single charge (+1 or -1), as well as multiple charges (+2 or -2).
Excellent linearity was observed in most cases (R2 0.999) using a three point calibration curve; most determinations were within 2.5 % of the theoretical salt concentration and had a precision of <2.0%.
This new, rugged analytical method dramatically simplifies the analysis of cations and anions in pharmaceutical preparations.
Previously, quantitation of anions and cations required the use of more than one column and two chromatographic runs.
The analyst now has a universal set of HPLC conditions with a single column, detector and gradient to analyse for a broad range of cationic and anionic compounds of pharmaceutical interest.
