Using Redox Titration for the Determination of Hydrogen Peroxide in Sanitizers

Hydrogen peroxide (H₂O₂) is a chemical compound with strong oxidizing capabilities, which acts against a variety of microorganisms, including bacteria, viruses, fungi, yeasts and spores^1,2. It has been utilized in several formulations of bleaching agents, disinfectants and sanitizers.

The concentration of H₂O₂ differs according to the objective of the formulation¹. While a concentration of 3% H₂O₂ is a potent disinfectant, up to 0.5% concentration of H₂O₂ is thought to be effective against surface viruses².

The low concentration of H₂O₂ is included in formulations to help terminate bacterial spores that contaminate a solution³. For this application, H₂O₂ content is established with redox titration methods utilizing cerium (IV) sulfate as a titrant and DMi140-SC electrode.

Sample preparation and procedures

1. Titrant: Cerium sulfate, Ce(SO₄)₂, 0.1 mol/L

• Precisely weigh out 40.43g Ce(SO₄)₂.4H₂O into a 1000 mL glass beaker and introduce 500 mL deionized water.
• Add 10 mL 98% H₂SO₄, stir the solution while heating it to ~50 °C. Wait until cerium sulfate is dissolved completely.
• Decant the solution into a 1000 mL volumetric flask and fill to the mark with deionized water.
• For titer determination, use application note M297 for reference.

2. 5% H₂SO₄ solution:

• Gradually add around 25.50 mL of 98% H₂SO₄ into a 500 mL volumetric flask that contains approximately 150 mL of deionized water.
• Using deionized water, cool and dilute the solution to the mark.

3. Standard / Sample titration:

• Add 40 mL of 5% H₂SO₄ in the thermostatable titration beaker.
• Using a thermostat,  the temperature of the solution in the beaker should be maintained between 5-10 ^oC.
• Introduce 0.2 mL of disinfectant sample solution to the titration beaker using Rainin pipette (5 mL for sanitizer sample).
• Using standardized Ce(SO₄)₂, 0.1 mol/L solution, titrate the solution.

Chemistry

H₂O₂ + 2Ce(SO₄)₂ → Ce₂(SO₄)₃ + H₂SO₄ + O₂

Solutions

• Chemicals: 98% Sulfuric acid, H₂SO₄ Deionized water
• Standard/sample: Standard: 1.5% Hydrogen peroxide (H₂O₂), M = 34.02 g/mol, z=2 Sample: Disinfectant and sanitizer with 3% and 0.125% H₂O₂ content respectively.
• Titrant: Cerium sulfate, Ce(SO₄)₂.4H₂O, M=404.3 g/mol, z=1 c (Ce(SO₄)₂)= 0.1 mol/L

Instruments and accessories

• Burette DV1020 20 mL (51107502)
• DMi140-SC, platinum ring electrode (51109520)
• DT1000 temperature sensor
• LabX^TM software
• Manual Titration Kit with titration stand, compact stirrer and accessories (51109220)
• Rainin Pipette and Tips 1 mL, 5 mL and 10 mL
• Spatula
• The method can be adapted on G10S (30267117) / G20S (30252669) titrators.
• Thermostatable titration beaker, glass 100 mL (23517)
• Thermostat (Lauda)
• Titration Excellence T5 (30252672) T7 (30252675) or T9 (30252676)
• XPR205 Analytical Balance (30355411)

Results

1.  Titer determination of Cerium sulfate
     c(Ce(SO₄)₂) = 0.1 mol/L
     Titer value obtained = 1.00505
     s = 0.00172
     srel = 0.171%
     n = 6

2. Sample results

(a) Standard 1.5% H₂O₂ solution:

Table 1. Source: Mettler Toledo - Titration

(b) Sample

Table 2. Source: Mettler Toledo - Titration

The H₂O₂ content in disinfectant and sanitizer samples is established and values acquired by redox titration with cerium sulfate are in sound agreement with the content of H₂O₂ anticipated in both samples. The repeatability achieved for standard as well as sample is excellent in terms of comparable standard deviation, i.e., srel.

Remarks

• This application note has been prepared for the sample mentioned. Optimizing the method parameters as per sample may be necessary for the best results.
• The temperature of the titrating solution should be kept below 10 ^oC.
• It is essential to first optimize the sample size to ensure the titrant volume consumption is between 20 to 80% of the burette volume.
• When exposed to other peroxygens, this method of titration using Ce(SO₄)₂ is selective towards the determination of hydrogen peroxide (H₂O₂). In the determination of H₂O₂ utilizing potassium permanganate (KMnO₄), KMnO₄ reacts with other peroxygens or substances that limit KMnO₄ in acidic conditions and initiates higher results.
• The method can be adapted on G10S / G20S titrators

Waste disposal and safety measures

Precipitate cerium with NaOH, filter, and handle as special waste.

References and Further Reading

1. The Use of Hydrogen Peroxide for Disinfection and Sterilization Applications, Gerald McDonnell, Peroxides (2014)
2. Chemical Disinfectants, Guideline for Disinfection and Sterilization in Healthcare Facilities (2008). 
3. WHO-recommended handrub formulations. https://www.who.int/gpsc/information_centre/handrub-formulations/en/

Further information

http://www.mt.com/ch/en/home/products/Laborat ory_Analytics_Browse/Product_Family_Browse_titr ators_main/Titration_Excellence.html?cmp=als_Tit ration-Excellence

Measured values

Table 3. Source: Mettler Toledo - Titration

Table 4. Source: Mettler Toledo - Titration

About Mettler Toledo - Titration

METTLER TOLEDO instruments are used in research, scientific and quality control labs, amongst many others in the pharmaceutical, chemical, food and cosmetics industries. They are a global market leader with the three instrument groups most frequently used in the laboratory, like balances, pipettes, and pH meters, and we are a pioneer in the field of Automated Chemistry.

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