Quality control of an active ingredient in hair spray using near-infrared spectroscopy

Quality Control of Hair Spray Active Ingredients Using Near-Infrared Spectroscopy

Significance of the Topic
Cosmetic formulations such as hair sprays may include functional actives for anti-dandruff or anti-lice purposes. Ensuring the correct dosage of these ingredients is critical for product performance and consumer safety. Conventional techniques like LC-MS/MS are accurate but involve lengthy analysis times and generate chemical waste. Near-infrared spectroscopy (NIRS) offers a rapid, non-destructive alternative for in-line quality control.

Objectives and Study Overview
The aim of the study was to establish a NIRS-based calibration model capable of quantifying an active ingredient in hair spray samples and rapidly flagging out-of-specification batches. Fifteen samples from five production batches, covering active concentrations from 0.0% to 8.4%, were evaluated.

Used Instrumentation

• NIRS DS2500 Analyzer (400–2500 nm, transflection mode)
• LiquidKit for NIRS DS2500 with gold reflector
• Vision Air Complete software for data acquisition and chemometric modeling

Methodology

• Approximately 3 g of each hair spray was placed in a transflection vessel and measured with a gold reflector.
• Spectra were recorded over 400–2500 nm and pretreated using a second derivative to enhance spectral features.
• Partial Least Squares (PLS) regression was performed on spectral windows at 1590–1720 nm and 2090–2220 nm.

Main Results and Discussion

• A PLS model with three latent factors yielded a Standard Error of Calibration (SEC) and Cross-Validation (SECV) of 0.034% for active concentration.
• Second-derivative spectra between 1608–1628 nm displayed clear variation correlating with active levels from 0.0% to 8.4%.
• Excellent correlation was observed between NIRS predictions and LC-MS reference values, validating the model’s accuracy.

Benefits and Practical Applications
NIRS enables high-throughput screening of hair spray batches without sample preparation, producing results within seconds and eliminating chemical waste. The non-destructive approach allows samples to be retained for further testing and efficiently differentiates conforming and non-conforming lots for QC workflows.

Future Trends and Potential Applications
Further enhancements may involve using transmission-based NIRS analyzers with disposable vials (e.g., XDS RapidLiquid) to simplify sample handling. Expanding the methodology to other cosmetic matrices and active agents can increase its utility across industrial QA/QC laboratories.

Conclusion
The developed NIRS method offers a fast, reliable, and eco-friendly approach to quantify active ingredients in hair sprays, providing an effective alternative to traditional LC-MS assays for routine quality control.

References

• NIR Application Note NIR-48, Metrohm, Version 1, August 2017