Method Development for the Analysis of USP Acetaminophen and Caffeine Tablets

Importance of the Topic

The simultaneous measurement of acetaminophen and caffeine in tablet formulations is a cornerstone of pharmaceutical quality control. A robust assay ensures product safety, regulatory compliance, and consistent therapeutic efficacy.

Objectives and Study Overview

This study compares USP-compliant HPLC methods using traditional totally porous C18 columns (5 μm and 3.5 μm) and a modern superficially porous (Poroshell 120, 4 μm) column. The goal is to assess chromatographic performance, system suitability, and ease of method transfer within USP Chapter 621 guidelines.

Methodology and Instrumentation

The analyses were conducted on an Agilent 1200 Series Rapid Resolution LC system equipped with:

• G1312B Binary Pump SL
• G1376C Automatic Liquid Sampler SL
• G1316B Thermostatted Column Compartment SL
• G1316C Diode Array Detector SL (275 nm)

Columns evaluated:

• Agilent ZORBAX Eclipse Plus C18, 4.6×100 mm, 5 μm
• Agilent ZORBAX Eclipse Plus C18, 4.6×100 mm, 3.5 μm
• Agilent Poroshell 120 EC-C18, 4.6×100 mm, 4 μm

Mobile phase: water/methanol/glacial acetic acid (69:28:3), flow rate 2.0 mL/min, column temperature 45 °C, injection volume 2 μL.

Main Results and Discussion

All column formats met USP system suitability criteria: tailing factors ≤1.2, resolutions ≥1.4, and RSDs ≤2%. Key observations:

• Poroshell 4 μm yielded plate counts (N) of ~9 000–9 300, outperforming the 5 μm column (N ~5 000–5 300) and matching the 3.5 μm column (N ~7 800).
• Resolution between acetaminophen and caffeine improved on the 4 μm column (Rs ~7.9 vs. 7.2 for 5 μm) and maintained >9 for the 3.5 μm.
• Peak symmetry was optimal on the superficially porous column, with tailing factors near unity.

Benefits and Practical Applications

The superficially porous Poroshell column can substitute the traditional 5 μm column without major method changes, offering:

• Higher chromatographic efficiency and sharper peaks
• Comparable run times and system suitability compliance
• Simplified method transfer and validation

Future Trends and Possibilities

Emerging strategies include broader adoption of superficially porous particles in pharmaceutical QC, integration with UHPLC for further throughput gains, and extension to multi-component dosage forms. Automation and green solvent initiatives may also refine these assays.

Conclusion

All tested columns satisfy USP criteria for acetaminophen and caffeine tablet assays. The Agilent Poroshell 120 EC-C18 4 μm column delivers enhanced performance and seamless method transfer, making it a practical alternative in regulated environments.

Reference

USP Monograph: Acetaminophen and Caffeine Tablets, USP-35: 2036-2037. U.S. Pharmacopeial Convention, Rockville, MD, USA.