Assessment of dermally bioaccessible elements by sweat-simulated extraction. Analytical approach and application to tattoo inks

The determination of soluble elemental contaminants in tattoo inks is challenged by the lack of standardized extraction procedures, limiting the comparability of analytical results and the assessment of exposure-relevant fractions under the European REACH framework. In this study, artificial sweat extraction was applied as a mild and physiologically relevant approach to evaluate elements potentially released from tattoo inks under sweat-simulated skin-contact conditions. Seventy-eight commercial tattoo inks of different colors were extracted with artificial sweat at 37 °C for 1 h and analyzed by inductively coupled plasma mass spectrometry. Optimization of collision/reaction cell conditions, dilution strategy, and internal standard correction effectively reduced matrix-related interferences caused by the high salt and chloride content of artificial sweat, ensuring reliable quantification. Matrix-matched calibration was required due to significant signal suppression for several analytes. Method accuracy and precision, assessed using NIST 1643f and spiked samples, were generally satisfactory. Elemental release showed marked color-dependent trends, particularly for Cu, Zn, Ba, Al, Ga, Si, Sr, and Zr, reflecting differences in pigment composition and formulation. Soluble Ba, Cu, and Zn remained below EU regulatory limits. While total digestion remains essential for complete characterization, the proposed methodology provides a simple and transferable tool for exposure-oriented assessment of potentially bioaccessible elements in tattoo inks.