Dosage of residual peroxides

Peroxides are oxidizing agents that can be used as initiators in polymerization processes or form naturally through oxidative degradation. Residual peroxides in cosmetic polymers, resins, oils, or emulsions can alter the stability of finished products, cause unwanted side reactions, or affect the functional properties of materials.

The measurement of residual peroxides is therefore essential for assessing the oxidative stability of formulations, checking the end of the reaction in industrial processes or controlling the conformity of products according to safety and quality standards.

Analytical methods
The analysis of residual peroxides is based on different validated approaches:

• Iodometric titration : a classic and widely used method measuring the oxidizing capacity of peroxides by reduction of iodine.
• Peroxide value method : used in food or cosmetic oils and fats, it allows the degree of oxidation to be monitored and rancidity to be assessed.
• UV-Vis spectrophotometry : applied to certain formulations, it offers increased sensitivity for liquid or complex matrices.

These methods can be adapted according to the nature of the product analyzed and the applicable standards.

Matrices concerned
The dosage of residual peroxides applies to a wide range of products and materials:

• Synthetic polymers and resins resulting from polymerization processes
• Cosmetic emulsions, creams and lotions
• Vegetable or mineral oils used in food or cosmetics
• Inks, varnishes or adhesives containing oxidizing agents

Industrial applications

• Polymeric packaging and materials : check the stability of polymers and detect residues that could interfere with migration to foodstuffs.
• Cosmetics : control the stability of emulsions and lipid-rich formulations, limit the risks of oxidation and guarantee consumer safety.
• Food industry : monitor the freshness and quality of vegetable oils, fats and butters by monitoring their peroxide index.
• Industrial processes : validate the end of the reaction during the manufacture of polymers or resins.

Additional analyses
The dosage of peroxides can be integrated into a broader analytical strategy:

• Acid number assay to assess free fatty acid content and monitor hydrolysis.
• Dosage of the peroxide index specific to oils and greases.
• Monomer determination to identify residues of starting substances in polymers.
• Global migration tests to assess the safety of packaging in contact with food.

Regulations and quality issues
In the food industry, the measurement of residual peroxides is part of the quality controls required for oils and fats to prevent oxidation and ensure compliance with international standards. In the field of packaging and polymers, this analysis helps demonstrate the stability of materials, anticipate degradation risks and meet the requirements of Regulation (EU) No. 10/2011 for materials in contact with food.

In cosmetics, monitoring peroxides is a key indicator to ensure the sustainability of formulations and limit the occurrence of oxidative reactions likely to alter the performance or safety of the product.

YesWeLab Expertise
YesWeLab collaborates with a network of ISO 17025-accredited laboratories, selected for their expertise in the analysis of polymers, oils, and cosmetic formulations. Based on your needs, we identify the most suitable method and the most competent laboratory to ensure reliable, compliant, and rapid results.

Our digital platform facilitates analysis management by centralizing your quote requests, sample tracking, and final report review. Since 2020, many manufacturers and distributors have entrusted us with the management of their analytical controls.