Quality Control of Shampoo

Significance of the Topic

Quality control of shampoo formulations is critical to ensure product performance, consumer safety and regulatory compliance. Surfactant concentrations directly affect cleansing ability, foam stability and skin compatibility. Traditional wet-chemical analyses involve time-consuming sample preparation, extensive use of reagents and high running costs. Implementing a rapid, reagent-free technique can streamline routine analyses and reduce operational expenses.

Objectives and Study Overview

This study evaluates the feasibility of using visible and near-infrared (Vis-NIR) spectroscopy for the simultaneous quantification of five key shampoo ingredients: sodium laureth sulfate (SLES), cocamidopropyl betaine (CABP), cocamidopropylamine oxide (CAW), cocamide diethanolamine (DEA) and carbopol. The primary goals were to develop robust calibration models, assess predictive performance versus reference titrations and compare cost and time efficiency against conventional methods.

Methodology and Instrumentation

Shampoo samples were analyzed directly, without any pretreatment, using the DS2500 Solid Analyzer in transflection mode over 400–2500 nm. A DS2500 Slurry Cup facilitated sample placement and cleaning, while a 1 mm gold diffuse reflector ensured constant path length. Spectral acquisition and chemometric model development were performed in Vision Air Complete software. Partial least squares regression models were built for each analyte and validated by cross-validation.

Main Results and Discussion

High correlations between Vis-NIR predictions and reference titration values were achieved:

• SLES: R² = 0.998, SECV = 0.14%
• CABP: R² = 0.996, SECV = 0.05%
• CAW: R² = 0.998, SECV = 0.058%
• DEA: R² = 0.998, SECV = 0.036%
• Carbopol: R² = 0.969, SECV = 0.41%

These figures of merit illustrate excellent predictive accuracy and precision suitable for routine quality control. Vis-NIR spectra captured subtle absorbance features associated with molecular vibrations of surfactant headgroups and polymer backbones, enabling reliable quantification.

Benefits and Practical Applications

The Vis-NIR approach offers several advantages:

• No chemical reagents or sample preparation
• Analysis time under one minute per sample
• Substantial cost savings: annual running costs reduced from ~$18 200 (titration/HPLC) to ~$2 000
• Minimal waste generation and operator exposure
• Ability to deploy in production environments for in-line or at-line monitoring

These benefits position Vis-NIR spectroscopy as a powerful tool for fast, sustainable QC in personal care manufacturing.

Future Trends and Applications

Prospective developments include:

• Integration of inline NIR sensors for real-time process monitoring
• Expansion of calibration libraries to cover a wider range of formulations and additives
• Application of advanced machine-learning algorithms to improve model robustness
• Miniaturized, portable NIR devices for decentralized testing in multiple production sites

Such trends will further enhance speed, flexibility and decision-making in cosmetic quality assurance.

Conclusion

This work demonstrates that Vis-NIR spectroscopy using the DS2500 Solid Analyzer provides a rapid, accurate and cost-efficient alternative to conventional titrations for shampoo quality control. The method requires no sample prep, delivers results in under one minute, and achieves predictive performance comparable to standard wet-chemical analyses while significantly reducing operational costs and environmental impact.