Comparative chemical analysis of some traditional Omani-made kohl

Abstract

Fourteen different types of Omani-made kohl were collected from different locations in Oman. The kohl samples were analyzed using different analytical techniques including X-ray powder diffraction, scanning electron microscopy, energy-dispersive X-ray microanalysis, and inductively coupled plasma mass spectroscopy after sample digestion. The results show that six kohls (kohls 1–6) are mineral-based, four of which, namely lasif, cold ethmid, hot ethmid, and original ethmid, contain very high levels of Pb (basically galena). The other two kohls (red ethmid and black ethmid) contain mostly iron (hematite, magnetite, and goethite). The other kohl samples (kohls 7–14) are basically amorphous carbons, one of which is made by charring date stones while the rest are basically soot collected from burning different materials. Compared to the results obtained by inductively coupled plasma mass spectroscopy, energy-dispersive X-ray microanalysis yielded higher concentrations of major elements while some minor elements were not detected; this is probably related to some limitations in the latter technique. Based on this study, carbon-based kohls possess much lower levels of toxic elements than mineral-based kohls; consequently, the former can be considered as the less hazardous kohls. However, concerns about the use of soot in cosmetics are rising because of the presence of some carcinogenic compounds such as polyaromatic hydrocarbons in soot.

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