Determination of acetylsalicylic acid in aspirin using Total Fluorescence Spectroscopy

Importance of the Topic

Fluorescence spectroscopy offers a rapid and sensitive approach to quantify compounds with intrinsic fluorescence, such as acetylsalicylic acid in aspirin. Ensuring accurate dosage and compliance with pharmacopeial standards is critical for patient safety and product consistency.

Objectives and Study Overview

This application note demonstrates the use of total fluorescence spectroscopy to measure the concentration of acetylsalicylic acid (ASA) in commercial aspirin tablets. The study aims to establish a reliable calibration, evaluate potential analytical interferences, and verify compliance with the British Pharmacopeia.

Methodology and Instrumentation

The method employs a 1% v/v acetic acid solution in spectroscopic-grade chloroform as solvent. Pure ASA standards ranging from 0 to 50 mg/L were prepared for calibration. Aspirin tablets were crushed, dissolved in the same solvent, filtered, and diluted (1:100 and 1:1000) before measurement. Fluorescence readings were taken within 45 minutes to minimize hydrolysis.

• Instrumentation:
• Cary 1/3E UV-Vis Spectrophotometer
• Cary 1/3E Fluorescence Accessory with UG5 Emission Filter
• Quartz Stoppered Fluorescence Cells
• Whatman #1 Filter Paper
• Cary Concentration Application Software
• Printer

Main Results and Discussion

A calibration curve was generated by measuring total emission between 300 and 420 nm upon excitation at 290 nm. Although fluorescence intensity ideally scales linearly with concentration, the observed curve displayed slight curvature attributed to self-absorption when excitation and emission bands overlap. Measured ASA levels in five tablets ranged from 298 to 309 mg per tablet, fitting within the 95–105% content requirement of the British Pharmacopeia.

Benefits and Practical Applications

The described fluorescence method is non-destructive, rapid, and requires minimal sample preparation. It provides a robust quality-control tool for pharmaceutical manufacturers and analytical laboratories to ensure dosage accuracy and regulatory compliance.

Future Trends and Applications

Advances in fluorescence instrumentation, such as time-resolved and multi-dimensional fluorescence techniques, may further improve sensitivity and selectivity. Integration with automated sampling and chemometric data analysis could enable high-throughput screening and real-time monitoring in production environments.

Conclusion

Total fluorescence spectroscopy on a Cary 1/3E platform, combined with appropriate software, delivers accurate ASA quantification in aspirin tablets. The method meets pharmacopeial standards and offers a reliable workflow for routine pharmaceutical quality control.

References

1. Lane RJ. UV-Visible Spectroscopy – Applications of Total Fluorescence. 1973.
2. Schenk GH, Boyer FH, Miles CI, Wirz DR. Analytical Chemistry. 44(9):1593–1598. 1972.
3. Department of Health. British Pharmacopeia. Vol. 2. 1993.