Identification of organic pigments in tattoo inks and permanent make-up using laser desorption ionisation mass spectrometry.

Markus Niederer,Lydia Kroll,Christopher Hohl,Urs Hauri

doi:10.12688/f1000research.13035.2

Abstract

Nowadays, about 12% of the European and 20% of the US population are tattooed. Rising concerns regarding consumer safety, led to legal restrictions on tattoo and permanent make-up (PMU) inks. Restrictions also include bans on certain colourants. Both ink types use organic pigments for colour-giving, plus inorganic pigments for white and black and colour tones. Pigments are only sparingly soluble in common solvents and occur as suspended particles in the ink matrix. Their detection and identification therefore pose a major challenge for laboratories involved in monitoring the legal compliance of tattoo inks and PMU. We overcame this challenge by developing a direct laser desorption ionisation time-of-flight mass spectrometry method, which included an easy sample clean up. The method proved to be capable of detecting and identifying organic pigments in almost all of the tested ink samples. Method validation and routine deployment during market surveys showed the method to be fit for purpose. Pigment screening of 396 tattoo inks and 55 PMU taken from the Swiss market between 2009 and 2017 lead to the following conclusions: Pigment variety is much greater in tattoo inks (18) than in PMU (10); four prohibited pigments (Pigment Green 7, Pigment Red 122, Pigment Violet 19 and 23) were found in both ink types; for PMU, these four pigments made up 12% of the pigment findings, compared to 32% for tattoo inks. Therefore, legal compliance of PMU was at a higher level. A comparison of pigments found with those declared on tattoo ink labels clearly showed that banned pigments are rarely declared, but rather masked by listing non present legal pigments and label forging; therefore, highlighting the urgency of widespread market controls.

Highlights

Over the last two decades, tattoos have become increasingly popular among younger people, with estimates stating that 12% of the European and more than 20% of the US population are tattooed[1]
We present a validated LDI-TOF-MS approach for the identification of pigments in tattoo inks and permanent make-up (PMU)
Over the last eight years, more than 150 individual colour pigments and about 450 commercial tattoo ink or PMU samples from market surveys were subjected to LDI- or MALDI-TOF-MS analyses

Summary

Introduction

Over the last two decades, tattoos have become increasingly popular among younger people, with estimates stating that 12% of the European and more than 20% of the US population are tattooed[1] These figures, the widespread on-line sales of tattoo related products, and the invasive techniques used during tattooing - where inks are injected into the skin’s dermis - have led to serious concerns on the safety of tattoo inks and permanent make-up (PMU). Namely pigments, being the ingredients, which give tattoo inks and PMU the desired effect, regulations are summarised as follows: a ban on colourants that can form aromatic amines under reductive cleavage, a negative list for specific colourants and a ban for colourants with restricted use in cosmetics Despite this welcome development, safety awareness in this field is still not adequate compared to cosmetics, which have been subjected to stringent regulations for decades, even though their application forms are solely non-invasive.

Methods

Results

Conclusion