By means of azide analysis in Irbesartan a simple, fast, precise and accurate ion chromatographic method for the determination of traces of inorganic contaminants in pharmaceuticals is described. Traces of toxic azides in pharmaceutical products can accurately be determined in the sub-ppb range after Metrohm Inline Matrix Elimination using isocratic ion chromatography (IC) with suppressed conductivity detection. While the azide anions are retained on the preconcentration column, the interfering pharmaceutical matrix is washed away by a transfer solution, ideally consisting of 70% methanol and 30% ultrapure water. The analytical setup provides a well-resolved azide peak and thus alleviates the common drawback of excipient interferences, especially from the nitrate anion. Calibration with azide standards is linear over the range of 5…80 ppb, providing a coefficient of determination of 0.9995. The limit of detection (LOD) and the limit of quantification (LOQ) of azide in Irbesartan are 5 and 30 µg/L respectively; the relative standard deviations (RSD) for the peak area, peak height and retention time being smaller than 3.9%. Robustness testing involved variation of column oven temperature and composition of the transfer solution and, in terms of peak area, provided RSDs smaller than 2.8% and 3.1% respectively.
