SIELC Legacy columns

Significance of the topic

High-performance liquid chromatography (HPLC) methods in pharmaceuticals and quality control often rely on United States Pharmacopeia (USP) defined column chemistries. As legacy columns become obsolete, laboratories face costly method redevelopment or project delays. SIELC’s Legacy column series provides drop-in replacements for a comprehensive range of USP designations, preserving validated workflows and ensuring analytical continuity.

Objectives and study overview

This work presents the design, production, and performance evaluation of SIELC’s Legacy columns, which span multiple USP stationary phase categories. The series aims to replicate retention characteristics across reversed-phase, normal phase, ion-exchange, and mixed-mode chemistries. Representative compounds from steroids, pharmaceuticals, vitamins, organic acids, and ions were tested under USP-guided conditions to assess compatibility and reproducibility.

Methodology and instrumentation

Columns were manufactured to meet USP specifications for designations L1, L3, L7–L14, L16, L18, L20, L26, L28, L44, L78, and L85, using porous silica or coated supports with bonded ligands or ion-exchange groups. Chromatographic evaluations employed standard mobile phases and gradients, with UV absorption (200–280 nm) and evaporative light scattering detection (ELSD) to capture a broad analyte scope. Flow rates ranged from 0.2 to 1.5 mL/min, and column dimensions covered microbore to preparative formats.

Main results and discussion

• L1 (C18 reversed-phase) demonstrated consistent hydrophobic retention for corticosteroids, NSAIDs, antibiotics, vitamins, and flavor compounds with recoveries within USP precision limits.
• L3 (normal phase silica) enabled separation of inorganic acids, lecithins, ascorbic and metabolic acids, and nucleosides via polarity interactions.
• L6 (strong cation exchange) and L9 (strong anion exchange) columns effectively separated charged species such as cations, organic anhydrides, and sulfonic acids.
• L8 aminopropyl (HILIC/cation-exclusion) and L16 dimethyl (highly hydrophobic) phases served specialized applications, including peptide oligomers and complex lipid mixtures.
• Mixed-mode L78 (positive surface) and L85 (negative surface) columns offered tunable selectivity through combined reversed-phase and ion-exchange interactions, resolving diastereomers, catecholamine neurotransmitters, antiviral agents, and multi-ionic mixtures.

Advantages and practical applications of the method

• Seamless method transfer and validation for USP procedures without reoptimization.
• Broad analyte compatibility covering pharmaceuticals, nutrients, metabolites, and ions.
• Flexible column formats and chemistries to match legacy systems.
• Cost-effective replacement to minimize downtime.
• High reproducibility meeting USP accuracy and precision criteria.

Future trends and applications

The growing demand for fast, green chromatography will drive microbore and core-shell legacy replacements, eco-friendly mobile phases, and UHPLC-compatible formats. Integration with mass spectrometry for multi-mode detection and automation will expand mixed-mode utility in biopharmaceutical and environmental analysis. Custom functional phases and on-column derivatization strategies represent emerging opportunities.

Conclusion

SIELC’s Legacy column series delivers a robust solution for sustaining USP-based HPLC methods across diverse chemistries and applications. By matching retention profiles and maintaining performance standards, these columns ensure analytical continuity, reduce method development costs, and support seamless workflow integration.