Qualitative analysis of cetomacrogol creams by thin-layer chromatography–flame ionization detection (TLC–FID)

Buffered cetomacrogol cream has been described as the cause of iatrogenic allergic contact dermatitis, while patch testing with all ingredients was, in most cases, unable to identify the sensitizing culprit. Several hypotheses had been put forward, among which the formation of a new allergen by interaction of some of the ingredients, so-called ‘compound allergy’. In order to investigate this hypothesis, a method for the qualitative analysis of cetomacrogol creams, using thin-layer chromatography with flame ionization detection (TLC–FID), is presented. All cetomacrogol cream components, i.e., a preservative and excipients were completely separated. A two-step elution system was used to separate the analytes on the Chromarods: in the first step we separated and focussed the paraffins and cetostearyl alcohol with the use of hexane-methanol–methyl tert -butyl ether (100:3:6, v/v). After drying, the same rod was then redeveloped using methanol to resolve sorbic acid from cetomacrogol 1000, whereupon detection of the cream components could be performed by direct flame ionization detection on the Chromarods. The developed method was then applied for the analysis of commercial non-buffered and buffered cetomacrogol cream samples. No newly formed allergen could be detected, thus excluding ‘compound allergy’. This method proved to be simple, cheap, and fast, enabling the separation of the auxiliary substances present in cetomacrogol cream.