Simultaneous determination of xanthan gum, optical density, and glucose in aqueous solutions by Vis-NIRS

Significance of the Topic

Xanthan gum is a versatile natural polysaccharide widely used as a thickener and stabilizer in cosmetic, food and pharmaceutical formulations. Quality control of its solutions requires rapid, reliable analysis of viscosity-related parameters such as optical density as well as residual sugars like glucose. Vis-NIR spectroscopy offers a non-destructive, high-throughput alternative to traditional wet-chemical assays, enabling simultaneous multi-component monitoring.

Objectives and Study Overview

This application note describes the development of quantitative Vis-NIR spectroscopy models for the simultaneous determination of glucose concentration, xanthan gum content and optical density in aqueous xanthan solutions. Over 100 industrial samples from 20 fermenters were collected and split into calibration (75%) and validation (25%) sets to establish and evaluate the predictive performance of the models.

Methodology and Instrumentation

Transmission Vis-NIR spectra were acquired over 400–2500 nm at 40 °C using a Metrohm NIRS XDS RapidLiquid Analyzer and 4 mm disposable glass vials. Spectral pretreatment included second derivative transformation to enhance resolution of overlapping bands. Partial Least Squares (PLS) regression was applied for glucose and xanthan gum, while Multiple Linear Regression (MLR) was used for optical density. Wavelength intervals were selected based on absorption features relevant to each analyte. Data acquisition and chemometric modeling were performed with Vision Air 2.0 Complete.

• Equipment: Metrohm NIRS XDS RapidLiquid Analyzer
• Sample containers: 4 mm disposable glass vials
• Software: Vision Air 2.0 Complete

Main Results and Discussion

The calibration and validation results demonstrate strong correlation between Vis-NIR predictions and reference analyses:

• Glucose (0–4.5 %): PLS model using 626–694 and 1662–1744 nm, R²=0.9623, SEP=0.34 %
• Xanthan gum (0–5 %): PLS model using 1662–1744 nm, R²=0.9431, SEP=0.35 %
• Optical density (0–12 AU): MLR model at 893 and 967 nm, R²=0.9052, SEP=0.90 AU

The high coefficients of determination and low standard errors of prediction confirm that Vis-NIR spectroscopy can quantify all three parameters in under one minute without sample preparation.

Benefits and Practical Applications

This approach provides a rapid, cost-effective solution for routine quality control of aqueous xanthan solutions. The non-destructive measurement and simultaneous multi-analyte capability reduce analysis time and consumable usage. The intuitive Vision Air software enables even inexperienced operators to perform analyses, supporting streamlined workflows in quality assurance laboratories.

Future Trends and Potential Applications

Future developments may include integration of inline or at-line Vis-NIR sensors for real-time process monitoring during fermentation or final formulation. Expanding chemometric libraries to other biopolymers and formulation matrices can broaden the scope of this method. Advances in machine learning algorithms and miniaturized spectrometers may further enhance accuracy and accessibility.

Conclusion

Vis-NIR spectroscopy combined with multivariate calibration models offers a robust, high-throughput method for simultaneous determination of glucose, xanthan gum content and optical density in aqueous solutions. The validated models deliver reliable results in under one minute, making this approach well suited for routine quality control and process monitoring in industrial environments.