Ion Chromatography in the Pharmaceutical Industry

Ion chromatography also finds a large number of applications in the field of pharmaceutical analysis. Here, only selected examples will be explained. 

Ion chromatography plays a prominent role in the characterization of pharmaceutically relevant compounds, predominantly in the early stages of research [275]. This includes the trace analysis of impurities and metabolites, the elemental analysis, and the structural elucidation of counter ions. The latter are often inorganic anions such as chloride and bromide or simple organic acids such as acetate. Somewhat rare counter ions include methyl sulfate, methanesulfonate, and trifluoroacetate. 

50 pL sample peaks (1) chloride and (2) methyl sulfate (taken from [276]). 

Methyl sulfate is not only of analytical interest as a counter ion in pharmaceutically relevant compounds. Rychtman [276] describes the trace analysis of this compound in pharmaceutical products that have been produced via alkylation with dimethyl sulfate. Tetraalkylammonium compounds, for example, may be synthesized by quaternation of tertiary amines with dimethyl sulfate  

For the separation of trifluoroacetate, a modem grafted polymer such as lonPac AS14 is the most suitable stationary phase. Trifluoroacetate may be detected, in addition to chloride and sulfate, in very low concentrations in peptides and stems from mobile phases used for the HPLC separation of peptides. With a mixture of carbonate and bicarbonate as an eluant, all these anions can be determined in one nm. The chromatogram shown in Fig. 9-181 was obtained by injecting 10 pL of a peptide sample (40 pg/mL) purified by gel permeation chromatography, in which 6.5 mg/L TFA could be detected. 

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