Improving USP Monograph Analysis Time Through Scaling by N on an HPLC System Using CORTECS™ Premier Columns

Importance of the Topic

HPLC monograph methods typically employ 5 µm particle size columns and long column lengths to meet efficiency requirements under USP General Chapter <621>. These configurations result in prolonged run times and high solvent consumption. Modernizing such methods through scaling by plate count (N) offers a way to boost throughput, reduce solvent usage and maintain compliance without requiring new LC hardware.

Objectives and Study Overview

• Scale the USP monograph assay and impurities method for zidovudine from a 4.6 × 250 mm, 5 µm column to a 4.6 × 150 mm, 5 µm column using solid-core CORTECS Premier particles.
• Maintain plate count (N) within the ±25–50 % limits defined in USP <621>.
• Quantify improvements in analysis time and solvent consumption.

Methodology and Instrumentation

Samples and standards were prepared according to the USP zidovudine monograph. The assay standard contained 0.2 mg/mL zidovudine; impurity standards at 1 µg/mL and 2 µg/mL related compound B. Chromatography was performed with gradients scaled to preserve retention characteristics on shorter columns. Initial testing employed an XBridge BEH C18, 4.6 × 250 mm, 5 µm column at 1.5 mL/min (45 min run). Scaled methods used CORTECS Premier C18, 4.6 × 150 mm, 5 µm columns at 1.5 mL/min (27 min run) and at 2.25 mL/min (19 min run).

Used Instrumentation

• Arc™ HPLC System with PDA detector (UV 265 nm)
• CORTECS Premier C18 Columns: 4.6 × 150 mm and 4.6 × 250 mm, 5 µm
• XBridge™ BEH™ C18, 4.6 × 250 mm, 5 µm
• Empower™ 3 Chromatography Data System

Main Results and Discussion

On the original 250 mm column, plate count for zidovudine was ~80,000, requiring 16 injections (45 min each) and 1.08 L solvent to meet USP suitability—totaling 12 h run time. Scaling by N to a 150 mm CORTECS Premier column yielded:

• Plate count within the USP-allowed range (59,700–119,400).
• 40 % reduction in run time (27 min) and solvent usage (648 mL), cutting system suitability testing to 7.2 h.

Further increasing flow to 2.25 mL/min (19 min run) achieved a 60 % run-time reduction (5.1 h total) while maintaining acceptable plate count.

Benefits and Practical Applications

• Significant reduction in analysis time improves laboratory throughput and sample turnaround.
• Lower solvent consumption supports greener workflows and cost savings.
• Maintains compliance with USP <621> guidelines without upgrading to UPLC systems.

Future Trends and Opportunities

Integration of advanced column calculators and software will streamline method scaling workflows. Continued adoption of solid-core particle technology can enable further miniaturization and higher flow rates while preserving efficiency. These advances support sustainability goals in pharmaceutical QA/QC and meet growing demand for high-throughput analytics. Emerging AI-driven optimization may further refine gradient and flow adjustments for validated methods.

Conclusion

Scaling the zidovudine assay and impurities monograph by N using CORTECS Premier 5 µm columns effectively reduced run times by up to 60 % and solvent usage by 40 %, all within USP <621> limits. This approach delivers enhanced throughput and operational efficiency on existing HPLC systems.

References

1. USP General Chapter <621> Scaling of LC Methods. USP, 2021.
2. Dubbelman AC et al. Systematic Evaluation of Commercially Available UHPLC Columns. J Chromatogr A, 2014;122–133.
3. Gritt F et al. Kinetic Performance of 1.6 µm Superficially Porous Particles. J Sep Sci, 2014;3418–3425.
4. Ludvigsson JW et al. Core-Shell Column Characterization with APIs. J Sep Sci, 2016;4520–4532.
5. Proposed Changes to Zidovudine Monograph. USP, accessed June 2024.
6. Berthelette K et al. Faster, Simpler Method Scaling Across Particle Sizes Using the Waters Column Calculator. Waters App Note, July 2023.