Trace determination of skin-irritating metals in tea tree oil by GFAAS

Tea tree oil, originating from Australia, is nowadays used worldwide as all-round home remedy. It is applied diluted or undiluted for the treatment of skin and nail infections, against lice, scabies, athlete's foot, and ringworms. Furthermore it is used topically as a local antiseptic for cuts and abrasions, for burns and insect bites. Tea tree oil is considered safe when put on the skin, but it may cause also skin irritation and swelling. In rare cases skin dryness, itching, stinging, burning, and redness have been observed. Skin irritation is mainly associated with the organic compounds, but may also be caused by allergenic metals, such as nickel, cobalt or chromium. Thus, the presented study focuses on the determination of selected skin-irritating metals in tea tree oil samples available on the European market. The measurements are performed by graphite furnace atomic absorption spectrometry (GFAAS). Although only a single-element method, it offers substantial advantages for the given analytical task. The oil sample can be applied directly without any sample pre-treatment, reducing time and labour as well as the risk of contamination by the reagents used for digestion. The method is optimised for each analyte regarding drying, pyrolysis and atomisation step, and the application of modifiers. The obtained characteristic masses for the elements analysed are close to the comparative values. Thus, the proposed method can be used for the analyses of tea tree oil. It is supposed that this method is also appropriate for investigating other oils used for instance in aromatherapy or for massages. (C) 2016 Elsevier B.V. All rights reserved.