Chapter 20 - Applications of capillary liquid chromatography

Capillary liquid chromatography (CLC) represents a highly advanced and promising analytical technique for the separation and analysis of complex samples, ranging from small molecules to biological macromolecules. Over the past decade (2014–24), CLC has gained increasing recognition due to its exceptional performance characteristics, including high separation efficiency, resolution, sensitivity, and compatibility with green chemistry principles. The technique operates with capillary columns typically featuring an inner diameter (ID) between 150 μm and 500 μm and flow rates in the range of 1–10 μL/min, as defined by one of the most widely used classifications in miniaturized liquid chromatography (minLC). This chapter examines the principal applications of CLC across various fields, including (i) biological, (ii) food, (iii) environmental, (iv) pharmaceutical, (v) clinical and forensic, and (vi) miscellaneous analyses. A comprehensive literature review was conducted using Scopus, PubMed, and ISI Web of Science databases, identifying key publications that were categorized based on their primary application field. Additionally, a secondary classification was introduced, organizing studies according to the analyte class or specific purpose of application. The growing application of CLC is driven by its numerous advantages, including its ability to achieve high-resolution separations, fast analysis times, minimal sample and mobile phase requirements, and straightforward hyphenation with mass spectrometry (MS). These benefits have led to its widespread adoption in fields such as bioanalytical research, environmental monitoring, food safety, pharmaceutical analysis, and clinical diagnostics. Notably, innovations in stationary phases—such as monolithic columns, porous-layer open tubular columns, and advanced polymer-based materials—have further enhanced the technique’s performance, particularly for biomolecular separations and the analysis of complex sample matrices. Key chromatographic parameters (column type and stationary phase, separation mechanism, mobile phase composition, flow rate) and performance characteristics (e.g., recovery, limit of detection (LOD), limit of quantitation (LOD), peak capacity, and efficiency) have been thoroughly examined and compiled in tables in this chapter, based on reported applications. Additionally, technical advancements are emphasized, as well as sample preparation techniques used in various investigations, providing a thorough summary of cutting-edge CLC-based analytical procedures. This chapter highlights the promise of CLC as a potent instrument for high-performance minLC, enabling enhanced analytical capabilities across a broad range of scientific fields by combining recent technological developments with real-world applications.