Determination of active ingredi- ents in solid (pharmaceutical) dosage forms utilizing solid- state standard additions

Importance of the Topic

Near-infrared spectroscopy (NIRS) offers rapid, nondestructive analysis of pharmaceutical solids, making it an attractive solution for content uniformity testing. By probing overtone and combination bands between 700 and 2500 nm, NIRS enables direct diffuse reflectance measurements without extensive sample preparation. Accurate dosage uniformity is critical for regulatory compliance, patient safety and manufacturing cost control.

Aims and Study Overview

• Evaluate the applicability of solid-state standard additions for quantitative NIRS of aspirin and acetaminophen tablets
• Compare branded and generic products for content uniformity within pharmaceutical specifications (90–110% label claim)
• Assess spectral pretreatment (second derivative) to reduce particle size and packing effects

Methodology and Instrumentation Used

The study employed a FOSS NIRSystems Model 6500 spectrophotometer with a remote reflectance fiber optic probe (recommended successor: NIRS XDS RapidContent Analyzer). Tablets were ground and spiked with known increments of active ingredient (25–200% of nominal dose). Three sample holders were tested: a large closed cup, a single tablet holder and a 1 mm×10 mm Teflon mini-cup. Second derivative spectra minimized variation from particle size and packing. Calibration models were built by multiple linear regression on second derivative spectra and applied to predict active content in individual tablets.

Main Results and Discussion

Analysis demonstrated that repeat scans of the same tablet exhibited smaller variation than scans between different tablets. The mini-cup configuration provided the most consistent sample geometry. Content uniformity results for generic and branded 325 mg aspirin averaged 100.95% and 100.15%, respectively. For 500 mg acetaminophen tablets, averages were 100.23% (generic) and 100.46% (branded). Precision rivaled that of solution HPLC, where duplicate injection reproducibility is typically within 2%.

Benefits and Practical Applications

• Rapid, noninvasive testing directly on solid dosage forms
• Minimal sample preparation and solvent consumption
• High throughput suited for in-process control and release testing
• Comparable precision to conventional HPLC without requiring dissolution

Future Trends and Possibilities for Use

• Integration of advanced chemometric algorithms for multicomponent formulations
• Automation of sample handling and real-time quality monitoring in production lines
• Extension to other dosage forms such as capsules, powders and tablets with coatings
• Coupling with PAT frameworks for continuous manufacturing

Conclusion

This study confirms that NIRS with solid-state standard additions and second derivative treatment is a robust approach for content uniformity analysis of pharmaceutical tablets. The technique delivers accuracy and precision comparable to HPLC while offering faster, greener and nondestructive testing. Its ease of use and adaptability support broader implementation in pharmaceutical quality control environments.