Summary and conclusions

Udvikling og validering af en metode til analyse af kolophonium i kosmetiske produkter

Colophonium (rosin) is a common cause of contact allergy and allergic contact dermatitis. According to the EU legislation on dangerous substances – Annex 1 (Directive 67/548 /EEC) a content of >1% colophonium in a product must be declared and the product must be labelled with risk phrase R 43 (“May cause sensitisation by skin contact”). Colophonium is listed under the following CAS numbers: 8050-09-7, 8052-10-6 and 73138-82-6. According to the Cosmetics Directive (76/768/EØF) the component is listed on the INCI-list (Index on Cosmetic Ingredients) under the name ”Colophonium”, (EF. nr. 232-475-7) and there is no restriction for its application.

However, colophonium is a mixture of many compounds. Quantifying a mixture used as an ingredient of another mixture cannot be achieved by any analytical means. This applies to any natural extracts used as ingredient of a compounded consumer product. To overcome the impossibility of quantifying a complex ingredient in a product, the quantification of tracers (= defined substances) specific of the complex natural sources is feasible. Therefore, quantification must be based on chemical analyses of specific major compounds. The objective of the present study was to develop a suitable method to be used for screening of cosmetics with regard to content of colophonium. We have chosen to base our quantification on its two major recin acids abietic acid (CAS no. 514-10-3) and dehydroabietic acid (CAS no. 1740-19-8) together with a tracer, 7-oxodehydroabietic acid (CAS. 18684-55-4), for air oxidation which readily takes place at storage and handling of colophonium.

Earlier published analytical methods for identification and quantification of the major colophonium components have been thoroughly scrutinized from different aspects e. g. possibility to be used outside very sophisticated analytical laboratories, robustness, and possibility to detect compounds without derivatisation. Based on this, it was concluded that a new method was needed for the purpose of the present study. We have thus developed a reversed phase HPLC method with UV detection using diode-array-detector (DAD). Pure non-oxidized recin acids and a stable major oxidation product as a marker for a possible autoxidation and the formation of allergenic oxidation products are used as reference substances. The analytical separation obtained is good and has never been obtained before using HPLC methods.