Tattooing has become a popular recreational practice among younger adults over the past decade. Although some of the pigments used in
tattooing have been described, very little is known concerning the toxicology, phototoxicology or photochemistry of these pigments. Seven yellow
tattoo inks were obtained from commercial sources and their pigments extracted, identified and quantitatively analyzed. The monoazo compound
Pigment Yellow 74 (PY74;
CI 11741) was found to be the major pigment in several of the
tattoo inks. Solutions of commercial PY74 in
tetrahydrofuran (THF) were deoxygenated using
argon gas, and the photochemical reaction products were determined after exposure to simulated solar light generated by a filtered 6.5 kW
xenon arc lamp. Spectrophotometric and high-pressure liquid chromatography (HPLC) analyses indicated that PY74 photodecomposed to multiple products that were isolated using a combination of
silica chromatography and reversed-phase HPLC. Three of the major photodecomposition products were identified by nuclear magnetic resonance and mass spectrometry as N-(2-methoxyphenyl)-3-oxobutanamide (o-acetoacetanisidide), 2-(hydroxyimine)-N-(2-methoxyphenyl)-3-oxobutanamide and N,N''-bis(2-methoxyphenyl)urea. These results demonstrate that PY74 is not photostable in THF and that photochemical lysis occurs at several sites in PY74 including the
hydrazone and
amide groups. The data also suggest that the use of PY74 in
tattoo inks could potentially result in the formation of photolysis products, resulting in toxicity at the
tattoo site after irradiation with sunlight or more intense light sources.