Quantifying hydrogen peroxide in iron-containing solutions using leuco crystal violet.

Area of Science:

• Environmental Chemistry
• Analytical Chemistry
• Biocatalysis

Background:

• Hydrogen peroxide is prevalent in natural and wastewater.
• Its reactivity with Fe(II) leads to rapid decomposition, forming hydroxyl radicals.
• This short lifetime complicates direct detection in environmental samples.

Purpose of the Study:

• To adapt and validate the leuco crystal violet (LCV) method for hydrogen peroxide quantification.
• To assess the influence of pH and iron concentration on the LCV method.
• To demonstrate the method's utility for analyzing hydrogen peroxide in challenging matrices like pyrite-water slurries.

Main Methods:

• Utilized the leuco crystal violet (LCV) assay with the enzyme peroxidase.
• Investigated the effect of varying pH and Fe(II) concentrations on LCV oxidation.
• Employed ethylenediaminetetraacetic acid (EDTA) to chelate Fe(II) and stabilize hydrogen peroxide.
• Applied the method to quantify hydrogen peroxide in pyrite-water slurries.

Main Results:

• The LCV method enables detection of hydrogen peroxide at low micromolar concentrations using standard equipment.
• Optimal LCV oxidation occurred at pH 4.23, showing strong pH dependence.
• Chelation of Fe(II) with EDTA effectively stabilized hydrogen peroxide for analysis.
• Pyrite-water slurries exhibited surface area-dependent hydrogen peroxide generation when Fe(II) was chelated.

Conclusions:

• The enhanced LCV method provides a stable and reliable approach for hydrogen peroxide quantification.
• The method's stability, particularly the long-term stability of the crystal violet ion (CV+), makes it suitable for field applications.
• This technique offers a valuable tool for environmental monitoring and research involving hydrogen peroxide detection.