Studies on purity and stability of photopatch test substances

Abstract

Nineteen photo substances [Bithionol, Chlorpromazine hydrochloride, Diphenhydramine chloride, Fentichlor, Hexachlorophene, 6-methylcoumarine, Musk ambrette, Para-aminobenzoic acid, Promethazine hydrochloride, Tetrachlorosalicylanilide, Thiourea, Tribromosalicylanilide, Trichlorocarbanilide, Triclosan, Benzocaine, Buclosamide, Chlorhexidine acetate, Chlorhexidine gluconate, Dichlorophene] were studied by TLC as fresh solutions, and during storage under various conditions. Chlorhexidine was excluded as it is sparingly soluble and only used in commercial products as a derivative. Trichlorocarbanilide was the only substance shown to be impure from the start. Only benzocaine, buclosamide, chlorhexidine acetate and chlorhexidine gluconate remained unchanged to the naked eye, and in TLC. The other substances were changed in color and/or in their TLC-pattern. An extraction method is described which makes it possible to use TLC for the examination of substances in petrolatum preparations. UV-absorption spectra were also examined for all the substances.