Quantification of water in lactose with the OMNIS NIRS Analyzer

Importance of the Topic

Lactose is one of the most widely used pharmaceutical excipients, present in 60–70 % of dosage forms. Excess moisture in lactose can lead to stickiness and hard clustering, complicating processing and affecting product quality. According to USP, lactose monohydrate should contain 4.5–5.5 % water. Traditional moisture determination methods are time consuming, creating a need for rapid, non-destructive alternatives such as near-infrared spectroscopy (NIRS).

Goals and Overview of the Study

This study aimed to develop and validate a NIRS-based calibration model for quantifying water content in lactose monohydrate using the OMNIS NIR Analyzer. By analyzing samples with controlled moisture variations, the research sought to demonstrate accuracy, precision, and feasibility for routine pharmaceutical analysis.

Methodology and Instrumentation

Sample Preparation and Measurement

• Lactose monohydrate samples were either oven-dried or spiked with water to cover a range of moisture levels.
• Spectra were collected in reflection mode across 1000–2250 nm using 19 mm glass vials and a flexible holder.
• Single scans per vial ensured rapid data acquisition.

Data Processing

• OMNIS software with the Quant Development module was used for calibration and cross-validation.
• The calibration set was correlated with reference values obtained by Karl Fischer oven titration.

Used Instrumentation

• OMNIS NIR Analyzer Solid (Metrohm)
• Disposable 19 mm reflection vials
• Flexible vial holder for the OMNIS NIR Analyzer
• OMNIS Stand-Alone and Quant Development software licenses

Main Results and Discussion

• The calibration model achieved a coefficient of determination (R²) of 0.977, standard error of calibration (SEC) of 0.12 %, and standard error of cross-validation (SECV) of 0.14 %.
• Analysis of a certified lactose standard (5.10 ± 0.04 % water) yielded a mean predicted water content of 5.1380 % with a relative standard deviation of 0.029 %, confirming model precision.
• NIR spectra exhibited distinct moisture-related absorbance features, supporting reliable quantification.

Benefits and Practical Applications of the Method

• Analysis time reduced to seconds compared to conventional Karl Fischer titration.
• Non-destructive, reagent-free measurement preserves sample integrity.
• High throughput suitability for routine quality control in pharmaceutical manufacturing.
• Potential for integration into automated process analytical technology (PAT) workflows.

Future Trends and Opportunities

• Extension of NIRS calibration models to other excipients and complex formulations.
• Integration with Industry 4.0 platforms and digital quality management systems.
• Development of portable or at-line NIRS instruments for real-time monitoring.
• Advancement of chemometric techniques for enhanced robustness and transferability across instruments.

Conclusion

The OMNIS NIR Analyzer approach provides a fast, accurate, and non-destructive solution for quantifying water content in lactose monohydrate. It meets pharmacopeial requirements and offers significant efficiency gains for pharmaceutical quality control.

Reference

1. Hebbink GA, Dickhoff BHJ. Application of Lactose in the Pharmaceutical Industry. In: Lactose. Academic Press; 2019:175–229. DOI:10.1016/B978-0-12-811720-0.00005-2.
2. Lactose Monohydrate. United States Pharmacopeia National Formulary. DOI:10.31003/USPNF_M44190_04_01.