AN-NIR-095
2021-11
Quality Control of Hand Sanitizers
Multiparameter determination within one minute
Summary
The most effective hand sanitizers contain between 62–95% alcohol. Alcohols are effective against most vegetative forms of bacteria, fungi, and enveloped viruses, but are ineffective against bacterial spores. The addition of hydrogen peroxide (3%) to the product may solve this, but due to its corrosive nature it must be handled with caution during production. Additionally, water and small amounts of emollient (e.g. glycerol) are added to protect the skin. Depending on the exact percentage of these constituents, hand sanitizer is either found in a liquid or gel form. Determination of the concentrations of these reagents is typically performed with gas chromatography (for glycerol and ethanol), Karl Fischer titration (for water), and redox titration (for H2O2). The disadvantage is that two different methods are needed which are time-consuming and require chemical reagents. Near-infrared spectroscopy (NIRS) on the other hand allows for the rapid and reliable simultaneous quantification of ethanol, glycerol, hydrogen peroxide, and water content in hand sanitizer formulations.
Results
All measured Vis-NIR spectra (Figure 2) were used to create a prediction model for quantification of the key quality parameters of gel and liquid sanitizer formulations. The quality of the prediction model was evaluated using correlation diagrams, which display a very high correlation between the Vis-NIR prediction and the reference values. The respective figures of merit (FOM) display the expected precision of a prediction during routine analysis.
Ethanol content in gel
Figures of Merit | Value |
---|---|
R2 | 0.9832 |
Standard Error of Calibration | 0.33 w/w% |
Standard Error of Cross-Validation | 0.37 w/w% |
Glycerol content in gel
Figures of Merit | Value |
---|---|
R2 | 0.9632 |
Standard Error of Calibration | 0.08 w/w% |
Standard Error of Cross-Validation | 0.11 w/w% |
Water content in gel
Figures of Merit | Value |
---|---|
R2 | 0.941 |
Standard Error of Calibration | 0.07 w/w% |
Standard Error of Cross-Validation | 0.09 w/w% |
Ethanol content in liquid
Figures of Merit | Value |
---|---|
R2 | 0.9964 |
Standard Error of Calibration | 0.36 w/w% |
Standard Error of Cross-Validation | 0.36 w/w% |
Water content in liquid
Figures of Merit | Value |
---|---|
R2 | 0.9999 |
Standard Error of Calibration | 0.12 w/w% |
Standard Error of Cross-Validation | 0.18 w/w% |
Hydrogen peroxide content in liquid
Figures of Merit | Value |
---|---|
R2 | 0.9986 |
Standard Error of Calibration | 0.05 w/w% |
Standard Error of Cross-Validation | 0.06 w/w% |
Conclusion
This application note demonstrates the feasibility to determine multiple key parameters of the quality control of liquid and gel-type hand sanitizer products with NIR spectroscopy. Vis-NIR spectroscopy enables a fast alternative to primary methods with high accuracy, and therefore represents a suitable alternative to the standard determination methods.
Parameter | Metod | Time to result |
---|---|---|
Ethanol | GC | ∼5 minutes (preparation) + ∼5 minutes (GC) |
Glycerol | GC | ∼5 minutes (preparation) + ∼5 minutes (GC) |
Water | Karl Fischer titration | ∼ 5 minutes |
Hydrogen peroxide | Permanganate titration | ∼5 minutes |