Mass spectrometric analysis of transition metal complexes formed through contact of artificial sweat with circulating Euro coins

Abstract

It is well-known that some metals/alloys sensitize the skin of susceptible individuals. Trace amounts of metals and chemical compounds containing metal ions can affect human health, i. e., cause allergy or inflammation. However, the details of this metal-induced allergic reaction are not well understood. Complexes of nickel, copper, and zinc are known to be easily formed through contact of metal alloys with ubiquitously available organic compounds such as triacylglycerols, amino acids, urea, and fatty acids found in skin secretions or skin care products. Thus, an analytical technique is required to characterize and identify metal complexes formed on metallic everyday products, ideally offering a chemically specific, laterally resolved view of allergy-causing processes. Here we present a mass-spectrometry-based analytical workflow to characterize metal-containing compounds formed on the surface of 1-euro coins when in contact with artificial sweat. This study identified different metal complexes by using tandem mass spectrometry (MS/MS). Surface imaging of 1-Euro coins employing laser-based mass spectrometry revealed the lateral distribution of Zn, Cu, and Ni complexes with low-micrometer resolution.