Last Month's Most Accessed Feature: Peroxide blonde: Detecting hydrogen peroxide with ion-exchange chromatography

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  • Published: Oct 3, 2017
  • Categories: Ion Chromatography
thumbnail image: Last Month's Most Accessed Feature: Peroxide blonde: Detecting hydrogen peroxide with ion-exchange chromatography

Peroxide blonde: Detecting hydrogen peroxide with ion-exchange chromatographyReacting to detection

Hydrogen peroxide has a wide range of uses, from bleaching hair to disinfecting surfaces to propelling rockets. It is also regularly used to break down organic compounds in wastewater treatment, by generating lots of highly-reactive hydroxyl radicals. This wide range of uses means that hydrogen peroxide is increasingly found in bodies of water, and while not particularly harmful scientists would like to know more about its kinetics and behavior in these bodies.

On the face of it, this shouldn’t be a problem, because there are an equally wide range of methods for detecting hydrogen peroxide in water, based on spectroscopy, electrochemistry, colorimetry and fluorescence detection. Despite their obvious differences, however, these methods almost all involve reacting hydrogen peroxide with another compound. Rather than detect hydrogen peroxide directly, they detect the product generated when hydrogen peroxide reacts with this other compound.

The downside to this approach is that the compound can often react with other molecular species in the water, including anions, organic compounds and other oxidants, to produce similar products that interfere with the detection of hydrogen peroxide. So Baiyang Chen and his colleagues at the Harbin Institute of Technology in Shenzhen, China, have now developed a novel ion-exchange chromatography method that can detect hydrogen peroxide directly, without needing it to react with another compound.

Alkaline mobile phase

In developing this method, Chen and his colleagues took advantage of the fact that hydrogen peroxide (H2O2) naturally deprotonates to form the hydroperoxyl ion (HO2-) at alkaline pHs, above around 12. Not only can the hydroperoxyl ion be readily separated from potentially interfering compounds by anion-exchange chromatography, but it also absorbs ultraviolet (UV) light, offering an easy way to detect it.

In order to conduct ion-exchange chromatography at alkaline pHs, Chen and his colleagues used potassium hydroxide (KOH) as the mobile phase, finding that a 10mM KOH solution performed best. They also optimized various other separation parameters, including mobile phase flow rate and UV wavelength, as KOH can absorb UV light strongly at certain wavelengths.

After determining the optimum parameters, which included using a detection wavelength of 210nm, they tested their method on water containing hydrogen peroxide at various different concentrations. They found that the method could reliably detect hydrogen peroxide in the water at concentrations as low as 0.027mg/L and accurately determine concentrations varying from 0.1mg/L to 50mg/L. This makes the method more sensitive than many existing methods, including those based on spectroscopy and colorimetry.

Tap, river and rain

What is more, unlike most of these other methods, this ion-exchange chromatography method was not hampered by interference from anions, organic compounds or other oxidants in the water. When Chen and his colleagues tested the method on water containing hydrogen peroxide with fluoride anions and glycolate, which in other methods are known to cause interference, they could still accurately determine the hydrogen peroxide concentrations. The same thing happened when they tested the method on water containing hydrogen peroxide and the oxidant monochloramine.

They also found that their ion-exchange chromatography method was just as accurate on real-world samples of water, including tap water, river water and rainwater, spiked with hydrogen peroxide, which likely contained various interfering compounds. All of which bodes well for discovering exactly what hydrogen peroxide is doing in such real-world samples.

Analytical Chemistry (Article in Press): "A facile, non-reactive hydrogen peroxide (H2O2) detection method enabled by ion chromatography with UV detector"

Article by Jon Evans

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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