High performance liquid chromatographic determination of naphthol AS and related dyes in cotton flannel nightdresses.

Abstract

By the collaborative study with Nagoya University Branch Hospital, we have found that naphthol AS (2-hydroxy-3-naphthanilide), an azoic coupling component, might be a causative agent of pigmented contact dermatitis from cotton flannel nightdresses (This journal, 32, 359 (1986)). In the course of the study, we developed a simple method for the determination of naphthol AS in cotton flannels. Naphthol AS could be extracted quantitatively from flannels under reflux with methanol, and purified by silica gel column chromatography by using ethyl acetate as an eluate. After methylation with diazomethane, it could be determined by high performance liquid chromatography (HPLC) by use of the following conditions : column, Nucleosil 50-5 (Nagel, 250 mm×4.6 mm i.d.) ; mobile phase, hexane-chloroform (12 : 5) ; flow rate, 1.0 ml/min ; detector, ultraviolet detector ; detection wavelength, 254 nm. Under these conditions, naphthol AS showed its peak at about 10 min, and its detection limit was found to be about 1 μg/g. Azo dyes in the methanol extracts were also determined by HPLC. Naphthol AS was detected in all cotton flannel nightdresses worn by the patients of pigmented contact dermatitis (contents : 850-11700μg/g, average : 5240μg/g). It was also detected in 5 kinds of commercial products, all of which were cotton flannel nightdresses dyed in the same manner as those worn by the patients (contents : 920-10200μg/g, average : 5760μg/g). It could not be found in other types of flannels. These results could support the idea that naphthol AS may be a causative agent of contact dermatitis from cotton flannel nightdresses.