Quantification of Sensitizing Metals in Tattooing Pigments by SF-ICP-MS Technique

Allergic reactions to metals and metal salts used in pigments for tattoos are surprisingly frequent. The objective of this study was to quantify the metal content of tattoo inks using the sector field inductively coupled plasma mass spectrometry analysis (SF-ICP-MS). The inks were subjected to a robust microwave digestion in a mixture of nitric and fluoridric acids, and hydrogen-peroxide. A total of 13 tattoo inks including various colors, as black, blue, brown, green, red, violet, white and yellow, were examined for the content of Cd, Co, Cr, Hg and Ni. The limits of detection and quantification were as follows (ng/ml): Cd, 0.02 and 0.07; Co, 0.06 and 0.20; Cr, 0.80 and 2.64; Hg, 0.50 and 1.65; and Ni, 0.40 and 1.32. The method was accurate reporting the following mean recoveries (%): Cd, 92; Co, 94; Cr, 96; Hg, 105; and Ni, 103. The precision of the method was calculated as intra-day (%) and inter-day repeatability (%) and results were: Cd, 2.09 and 5.20; Co, 1.58 and 2.67; Cr, 2.07 and 2.99; Hg, 3.88 and 4.55; and Ni, 4.05 and 5.11. All the tested metals were present in the tattoo pigments, but the relative contribution of elements to the tattoo ink compositions was highly variable between samples and even among like-colored pigments. The highest element was Cr in all the pigments (315-4720 ng/g) followed by Ni (37.5-2318 ng/g) and Cd (6.67-1150 ng/g); the lower elements were Co (2.78-125 ng/g) and Hg (<limit of quantification-179 ng/g). Since no rules regulate tattoo inks, this research can be a starting point for chemical safety assessment of commercial inks and for proposal of regulating legislation.