UV-Vis quantification of hydroxyl radical concentration and dose using principal component analysis

Area of Science:

• Environmental Chemistry
• Analytical Chemistry
• Water Treatment Technologies

Background:

• Hydroxyl radicals (∙OH) are potent oxidizers crucial in environmental processes and water purification.
• Accurate quantification of ∙OH is challenging due to their short lifespan and high reactivity.
• Existing methods often require sophisticated and costly instrumentation, limiting accessibility.

Purpose of the Study:

• To develop a novel, cost-effective method for measuring steady-state ∙OH concentration and total dose.
• To enhance precision in quantifying ∙OH production during hydrogen peroxide (H2O2) photolysis.
• To enable accurate ∙OH measurements using only benchtop UV-Vis spectroscopy.

Main Methods:

• Monitoring the degradation of salicylic acid (SA) as a probe for ∙OH.
• Applying principal component analysis (PCA) to UV-Vis spectral data for precise SA loss measurement.
• Utilizing benchtop UV-Vis spectroscopy for data acquisition.

Main Results:

• Achieved a >10-fold improvement in measurement uncertainty for steady-state ∙OH concentration compared to previous methods.
• Reduced the variance of measured ∙OH concentrations by a factor of 100.
• Established low limits of detection (5.33 × 10⁻¹³ M) and quantitation (1.23 × 10⁻¹² M) for ∙OH.

Conclusions:

• The developed PCA-enhanced UV-Vis method provides accurate and precise quantification of ∙OH.
• This technique expands ∙OH measurement capabilities for resource-limited laboratories.
• The method can be applied to assess ∙OH in natural waters and evaluate the impact of nanoparticles on ∙OH concentration.