Investigating Tattoo Pigments Composition with UV-Vis and FT-IR Spectroscopy supported by Chemometric Modelling

Aims: This study investigates the composition of tattoo pigments to ensure their safe application in tattoo art, evaluating the viability of UV-Vis and FT-IR spectroscopy, coupled with chemometrics, for predicting pigment contents in tattoo inks. Background: Analyzing pigments in tattoo inks poses challenges in maintaining quality. This study addresses the difficulties by proposing the use of UV-Vis and FT-IR spectroscopy, along with chemometrics, as potential solutions for effective monitoring. Objective: The aim of this study was to determine the content of red (PR) 170/254 and pigment blue (PB) 15:3 in tattoo inks from diverse suppliers and examine the distinct chemical structures and existing impurities in the samples using UV-Vis and FT-IR spectroscopy, employing regression models for data analysis. Method: We collected UV-Vis and FT-IR spectra from the tattoo ink samples and utilized regression models for data analysis. We assessed correlations across spectrum areas, emphasizing coefficients of determination for cross-validation. Subsequently, we compared the results obtained from both spectroscopic methods in terms of pigment identity and evaluated the suitability of UV-Vis spectroscopy for analyzing changes in pigment concentration and structural evolution. Finally, we employed chemometric modeling to enhance predictions of FT-IR parameters, particularly in the functional group and fingerprint region of the spectra. Results: Significant correlations were observed across both UV-Vis and FT-IR spectrum areas, with coefficients of determination for cross-validation exceeding 0.7 for most parameters. Both spectroscopic methods yielded nearly identical results regarding pigment identity. UV-Vis spectroscopy proved to be a suitable method for analyzing changes in pigment concentration and structural evolution. Chemometric modeling enhanced predictions of FT-IR parameters, particularly in the functional group and fingerprint region of the spectra. Conclusion: The study underscores the significance of utilizing UV-Vis and FT-IR wavelengths from various suppliers to determine pigment structures in tattoo inks. The consistent and comparable results from both spectroscopic methods highlight their efficacy in characterizing pigments. UV-Vis spectroscopy, in particular, emerged as a valuable tool for assessing changes in pigment concentration and structural evolution. The improved predictions through chemometric modeling further emphasize the utility of these analytical approaches in ensuring the safe use of tattoo inks in the art of tattooing.