QTRam® for Content Uniformity Analysis of Low-Dose Pharmaceutical Tablets

Significance of the Topic

Low-dose solid oral dosage forms require stringent assessment of active pharmaceutical ingredient (API) distribution to meet pharmacopeial standards. Traditional assays such as titration or HPLC involve destructive sample preparation, generate solvent waste and demand significant analysis time. Vibrational spectroscopy techniques, particularly transmission Raman spectroscopy (TRS), offer a non-destructive, rapid alternative by probing a large fraction of tablet volume without consumables.

Objectives and Study Overview

This study evaluates the capability of a compact TRS analyzer (QTRam) to quantify low levels of acetaminophen (APAP) in compressed tablets. A target formulation of 0.5 % w/w APAP in a 300 mg tablet is used to demonstrate content uniformity testing in accordance with USP <905> requirements.

Used Instrumentation

• QTRam transmission Raman spectrometer powered by STRaman technology
• BWAnalyst software (21 CFR Part 11 compliant) on an embedded tablet computer

Methodology

Tablet blends containing APAP, mannitol, silicified microcrystalline cellulose, croscarmellose, and magnesium stearate were prepared at nine concentration levels (0–3 % w/w APAP). Each blend was compressed into 10 mm diameter, 3 mm thick tablets (~300 mg). Transmission Raman spectra were acquired over the 200–1700 cm–1 region, averaging 10 scans of 3 seconds each at a 4 mm sampling aperture. Two to three replicates per tablet ensured representative data.

Chemometric modeling employed PLS1 regression in BWIQ software. Preprocessing steps included:

• Savitzky-Golay first derivative
• Region selection: 200–1700 cm–1
• Standard Normal Variate normalization
• Mean centering

Calibration used eight tablets per blend to average out blending variability.

Main Results and Discussion

An initial survey calibration across all nine blends yielded an RMSEC of 0.046 % APAP w/w with four latent variables. Focusing on the 0–1.5 % range improved performance: RMSEC = 0.022 %, RMSECV = 0.027 % using four latent variables explaining 94 % of spectral variance and nearly 100 % of concentration variance. External validation on 0.5 % and blank tablets produced an RMSEP of 0.023 % with bias of 0.008 %. Calculated limits were LOD = 0.074 % and LOQ = 0.23 % APAP w/w. Method precision (six replicates) gave a standard deviation of 0.016 % APAP w/w.

Benefits and Practical Applications

• Non-destructive analysis allows retention of intact dosage units
• Rapid measurement (30 seconds per spectrum) supports at-line testing
• No solvent or consumable requirements reduce waste and cost
• High sensitivity and precision enable compliance with content uniformity guidelines

Future Trends and Opportunities

Advances in TRS hardware and chemometric algorithms may further lower detection limits and enhance robustness across diverse formulations. Integration with automated sampling systems could enable high-throughput screening in manufacturing. Expansion of spectral libraries and machine learning techniques promises broader applicability to complex multicomponent dosage forms.

Conclusion

The QTRam transmission Raman analyzer demonstrates fast, accurate, and non-destructive quantification of low-dose APIs in compressed tablets. Achieving sub-0.03 % error and robust limits of detection positions TRS as a viable alternative to traditional wet chemistry methods for content uniformity testing.

References

• United States Pharmacopeia chapter 905 Uniformity of Dosage Units
• B&W Tek STRaman technology and BWAnalyst software documentation
• Partial least squares regression and chemometric preprocessing methodologies