Chemical approach to contact dermatitis caused by household products. III. Analysis of dithiocarbamate-type accelerators in commercial rubber gloves and incidence of positive reactions in patch testing.

Abstract

A method for the determination of dithiocarbamates (DTCs), rubber accelerators, was studied by reversed-phase high performance liquid chromatography (HPLC) with Nucleosil 5C18 column by using methanol-water (95 : 5, 90 : 10, 85 : 15) as mobile phases. After extraction of rubber samples by shaking with a mixture of acetone-chloroform (1 : 1) at room temperature, zinc (II) (Zn complexes) of DTCs were converted into their cobalt (III) (Co complexes) and analyzed by HPLC with a ultraviolet (UV) detector at 320 nm. Accelerators in 37 different brands of commercial rubber gloves mainly for domestic use, which were used as samples for the analysis of antioxidants in previous paper [Eisei Kagaku, 30, 126 (1984)], were analyzed by the proposed method. However, when more than two Zn were present in the rubber sample, mixed complexes with different ligands in a Co complex molecule were formed and HPLC chromatograms obtained were found to be too complicated to determine DTCs directly. The following procedure was chosen to analyze Zn : 1) analyze amines by nitrogen-phosphorus detection gas chromatography, 2) prepare standard mixtures of Zn corresponding to amines detected, 3) convert the mixtures in to Co and analyze by HPLC, 4) choose the standard mixture which gives the most similar HPLC chromatogram to that of the sample, 5) calculate the contents of Zn by the comparison of sum of all peak heights between the chosen standard mixture and sample. Zinc dimethyldithiocarbamate (ZDMC), zinc diethyldithiocarbamate (ZDEC), zinc dibutyldithiocarbamate (ZDBC), zinc ethylphenyldithiocarbamate (ZEPC) and zinc pentamethylenedithiocarbamate (ZPC) were detected. Their frequencies of detection and range of content were as follows : ZDMC, 10/37, 9-156 μg/g ; ZDEC, 18/37, 27-16500 μg/g ; ZDBC, 19/37, 11-755 μg/g ; ZEPC, 6/37, 105-2940 μg/g ; ZPC, 10/37, 19-3290 μg/g. ZEPC was detected only in the gloves manufactured in Japan. Thiuram disulfides (Thiurams), accelerators, were also analyzed by HPLC. But, none of them was detected in the gloves. Patch testing to DTCs and Thiurams was also studied in 40 patients with allergic contact dermatitis from rubber or polyvinyl chloride materials (rubber group or PVC group), who were subjects for patch testing to antioxidants reported in the previous paper. Generally speaking, rubber group reacted to DTCs and Thiurams in higher incidence than PVC group. Thiurams reacted in higher incidence than DTCs. The order of the incidence of positive reactions among DTCs and Thiurams with 5 kinds of N-substituents was as follows : dimethyl » diethyl, ethylphenyl>dibutyl, pentamethylene.