Concentration of Hydrogen Peroxide

For oxidizable or reducible analytes, redox titrations can be used. This approach can be used for a variety of things, from determining the amount of SO2 in wine to determining the amount of hydrogen peroxide in disinfectant solutions. The high oxidising effect of potassium permanganate is employed to oxidise the analyte in manganometric redox titrations. Because of its brightness, no indicator is required to visually detect the equivalence point.

The potassium permanganate method is widely used to detect hydrogen peroxide concentrations. The first permanent pink colour develops when a weighted sample is acidified and titrated with a standard potassium permanganate solution for at least a few minutes.

5 H2O2 + 3 H2SO4 + 2 KMnO4 -> K2SO4 + 2 MnSO4 + 8 H2O + 5 O2

When organic or inorganic stuff that reduces potassium permanganate is present, this procedure cannot be employed. Avoid using hydrochloric acid or other chloride ions since the permanganate may also oxidise chloride ions to chlorine, causing titration errors. Fluoride ions impair permanganate titration, and high concentrations of calcium salts or titanic acid result in poor results.

If you are looking to see how to determine the concentration of hydrogen peroxide, let’s discuss it in detail.

Equipment

• Burette (50 mL)
• Analytical balance with 0.1 mg resolution
• A dropper for the eyes
• Erlenmeyer flasks, 250 mL
• Vial size: 28 mm OD x 57 mm height

Reagents

 Water that has been demineralized or distilled

• Potassium permanganate (0.10N KMnO4) can be compared to sodium oxalate as a primary standard.
• Sulphuric acid, 1:4 vol/vol (pre-mixed and cooled)
• HNO3 (1:1)

Procedure

  Glassware preparation

• Only use fresh eye droppers and weighing vials.
•  New flasks should be treated with 1:1 HNO3 at room temperature overnight, then rinsed 6 to 8 times with water.
• Any glassware used for the concentration of hydrogen peroxide testing should not be cleaned with a chromic acid cleaning solution. For degrading peroxide, trace chromium ions are good catalytic agents, but they are extremely difficult to remove from glassware.

Preparation of Hydrogen Peroxide Samples

• In a 250 mL Erlenmeyer flask, pour roughly 100 mL of water.
• 10 mL sulphuric acid (1:4 vol/vol)
•  Fill a regular eye dropper with about 1 mL of hydrogen peroxide. In a specimen vial, place the dropper.
• Weigh the vial, dropper, and hydrogen peroxide sample to (0.0002) g and note the weight.
• Replace the dropper in the vial, re-weigh, and note the new weight as soon as possible.
• The ultimate weight of the vial, eyedropper, and sample will be subtracted from the initial weight.

Titration

Titrate with 0.10N KMnO4 while constantly stirring. Add less KMnO4 as the endpoint approaches, until the titration continues in fractional drop increments. The first barely visible pink colour that lasts for 30 seconds is the end-point.

To 0.01 mL, estimate and record the volume of the KMnO4 solution used. Apply a volume adjustment factor of 0.1 percent for every 5°C temperature difference from 20°C.

Calculate the concentration of hydrogen peroxide using the following formula:

(mL x N x 0.01701 x 100) / (% H2O2) (sample weight)

Principle

The cobalt ion combines with H2O2 to form a colourful peroxo-cobalt complex. The sample’s 260 nm light absorbance is compared to a standard H2O2 solution-generated reference curve.

Application’s Scope

The accurate measurement of residual H2O2 to 0.1 mg/L is required for new H2O2 applications in the food processing and drinking water industries. This approach works well in these and similar situations where the water matrix is clear and turbid. Samples containing more than 0.2 mg/L can be diluted to a concentration acceptable for this procedure with distilled water.

Interferences

Reducing chemicals like bisulfite (which may take a long time to react with free H2O2) may react fast with the Co- H2O2 complex, resulting in misleading negative readings. Furthermore, any contaminant that absorbs ultraviolet light at 260 nm may affect the method’s accuracy and sensitivity.

Precautions for Safety

Cobalt salts are long-lasting pollutants that should never be released into the environment. Spent solutions should be collected and disposed of according to regulations.

The sulfuric acid concentrate is a caustic and hazardous chemical that should be handled and disposed of according to the MSDS. Working beneath a vacuum hood as well as wearing neoprene gloves and mono goggles is suggested.

H2O2 sample bottles should not be sealed; instead, they should be vented or covered loosely with aluminium foil or paraffin film.

Conclusion

So, that’s a wrap on how to determine the concentration of hydrogen peroxide.

Hydrogen peroxide is utilised in a wide range of applications and industries since it produces just oxygen and water, which is good for the environment. However, because H2O2 is a relatively unstable molecule, the correct concentration must be maintained.

Titration is one of many procedures that can be used to determine the concentration of hydrogen peroxide. However, the majority of them entail handling of volatile chemicals as well as generation of additional chemical waste.