The counter ion is also called counterbalance ion or equilibrium ion. An ion in the electric double layer that has a charge sign opposite to that of the colloidal particle. When the surface of the colloidal particles is negatively charged, the counter ions are cations; when positively charged, the counter ions are anions. The counter-charge mainly plays a role in balancing the surface charge of the colloidal particles, so that the double-layer system on the surface of the colloid is in an electrically neutral state.
More than 50% of the drugs on the market use counterions and their analysis includes basic parts such as drug development, quality control, and batch release processes to ensure patient safety and efficacy. Salt formation is an important step in the development of pharmaceutical and biopharmaceutical drugs because it allows selective drug directed positioning of physicochemical properties such as solubility, drug stability and dissolution rate to ensure good bioavailability. With the continuous development of high performance liquid chromatography, the continuous improvement of counter ion chromatography has been widely used in pharmaceutical analysis in recent years. The reversed phase ion pair chromatography is used for the determination of ionic compounds.
For inorganic counter ion analysis, ion chromatography is usually used. Its sensitivity is high and its selectivity is strong. The use of IC for the determination of cations and anions typically uses inhibitory conductance to reduce interference from the mobile phase while increasing analyte response. From standard pore chromatographic column to capillary-grade columns, you can quickly separate and obtain quantitative information, as well as reduce system startup and equilibration time without reagents. When it comes to organic counterion analysis, the IC provides the ultimate sensitivity through its high selectivity. Due to poor UV sensitivity, many organic acids are difficult to analyze. Conversely, high UV absorption causes excessive interference.
UHPLC offers a high degree of flexibility and a wide range of eluents, columns and detection options to provide universal separation. Although not traditionally used for counter-ion detection, UHPLC incorporates charged aerosol detection (CAD) compared to ICs, providing a more powerful separation method and providing more information in less time. Therefore, it is increasingly used for counter ion detection. As listed drugs become more complex, UHPLC can analyze and detect cation and anion species within the same assay and perform many other types of analysis.
BOC Sciences uses IC and UHPLC to perform drug salt or counterion detection. The choice of these two technologies depends on the type of analysis, the information required, and the sample throughput. We are able to detect counter-ion ions as a complete solution and simplify the laboratory process for detecting counter-ions. In addition, BOC Sciences can combine UHPLC and IC with mass spectrometers (MS) to increase the level of safety of component identification and even provide lower detection limits.
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