Ion chromatography for the pharmaceutical industry

USP General Chapters <621> and <>: Core principles and fundamentals for chromatography

USP General Chapter <621> gives an overview of several chromatographic techniques along with definitions of the apparatus and procedure (e.g., mobile phase, column, types of elution, method procedure), common parameters, and requirements for system suitability testing (e.g., system repeatability, system sensitivity, and peak performance) [16]. Chromatographic column classification is also explained with a list of packings (L-numbers), phases (G), and supports (S), functioning as references for chromatographers [18].
 

For more information, please visit our website.

L-numbers for ion chromatographic USP approaches and insights about the column equivalency procedure are explained in the article below.

Blog post: Applying USP validated methods for separation column equivalency

On the other hand, USP General Chapter <> provides a comprehensive overview of IC [16,17] and its importance as an acknowledged test procedure for identifying and quantifying specific analytes (assays and impurities). Ion chromatography is a valid characterization procedure in many circumstances and aligns with all aspects of pharmaceutical production [8,17]. Its application field is broad, including quality control of raw materials, drug substances, or formulated products, as well as for assessing process waters used for manufacturing, culture media, cleaning solutions, or wastewater streams [17]. USP <> comprises basic knowledge of this technique: what ion chromatography is, instrumentation details (Figure 1), common detection mechanisms, procedures, and important notes for appropriate method development.

More extensive explanations of criteria and requirements for method validation are linked to General Chapter <> Validation of Compendial Procedures. This includes system suitability testing to ensure that the IC system functions properly before analysis by evaluating parameters including resolution, retention time, and peak shape, as well as requirements for validation with key parameters like linearity, accuracy, precision, specificity, limit of detection (LOD), and limit of quantitation (LOQ) [19]. In general, when developing an IC method, it is highly important to select appropriate mobile and stationary phases (Figure 1) to ensure efficient separation and appropriate selectivity and sensitivity (requirements as per USP <>) [17,19]. Mobile phases typically consist of diluted acids, bases or salts dissolved in high-purity water, while stationary phases can be either silica-based or polymer-based materials.

Due to their importance, columns and appropriate mobile phases are embedded in the monographs and General Chapters of USP. However, column equivalency gives users some freedom for implementing the method in the analytical workflow. 

Orun Product Page

Learn more about IC columns in our blog post series, starting here.

Blog post: Best practice for separation columns in ion chromatography (IC) &#; Part 1

Ion chromatography principle

Ion exchange chromatography or ion chromatography (IC) allows the identification of different ions using exchange resins. It is a technique widely used in the chemical analysis of various materials.

Its principle is simple, the CI separates the anions or the cations thanks to a column itself charged oppositely (positively to separate the anions or negatively to separate the cations). An eluent is used to drive the sample through the column. The ions of interest are then detected, mainly by conductivity or by UV/Visible absorbance.

Note: The sample matrix does not influence the separation of ions. In addition, the measurement of traces and ultra-traces by chromato-ionic is possible by the presence of a chemical suppressor and a CO2 suppressor allowing very good signal sensitivity. Indeed, the suppression step decreases the background conductivity of the eluent, minimizes the background noise, optimizes the signal-to-noise ratio and increases the sensitivity of the measurement system.

If you want to learn more, please visit our website IC Ion Chromatography.