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

Significance of the Topic

Near-infrared spectroscopy (Vis-NIR) offers a rapid, non-destructive alternative to conventional chromatographic techniques for quality control in complex cosmetic matrices. By eliminating chemical extraction steps and reducing analysis time, Vis-NIR supports fast decision-making in production and quality assurance of hair care products.

Objectives and Overview of the Study

The primary goal was to develop and validate a qualitative Vis-NIR method capable of detecting out-of-specification levels of an antibacterial active ingredient (AI) in hair creams. A feasibility study was conducted using a small set of formulated samples with varying AI concentrations, complemented by a pure AI reference.

Methodology and Instrumentation

The study employed the following workflow and equipment:

• Sample set: 14 hair cream formulations (AI 0.0–3.1 %) and one pure AI reference
• Instrument: Metrohm NIRS DS2500 Analyzer (400–2500 nm range)
• Sampling accessory: NIRS SlurryCup and gold diffuse reflectors for transflectance measurements
• Data acquisition and processing: Vision Air Complete software
• Chemometric approach: 2nd derivative pretreatment to correct multiplicative scattering effects; maximum distance algorithm focusing on AI-specific bands (1554–1750 nm and 2210–2340 nm)

Key Results and Discussion

Spectral analysis revealed distinct absorption features corresponding to the AI in two wavelength regions. The chemometric model successfully classified samples as within specification when AI content fell between 1.8 % and 2.5 %. Samples below or above these limits were flagged as out-of-specification. The method demonstrated clear separation of compliant and non-compliant batches without any sample preparation beyond direct loading in the SlurryCup.

Benefits and Practical Applications of the Method

The developed Vis-NIR approach provides several practical advantages:

• Elimination of solvent-based extraction and associated waste
• Analysis time reduced from ~30 minutes (LC-MS) to under 1 minute per sample
• Minimal operator training required for routine screening
• Potential for at-line or inline integration in manufacturing environments

Future Trends and Potential Applications

Advancements likely to expand the utility of Vis-NIR in cosmetic quality control include:

• Integration with process analytical technology (PAT) for real-time monitoring
• Application to additional active compounds and complex formulations
• Implementation of advanced machine learning algorithms for enhanced prediction accuracy
• Miniaturization of portable NIR devices for on-site field testing

Conclusion

This feasibility study confirms that Vis-NIR spectroscopy is an effective tool for rapid, reagent-free qualification of antibacterial actives in hair creams. The method offers robust classification of specification compliance, streamlining quality control workflows and reducing environmental impact.

References

• Metrohm Application Note NIR-47, August 2017