Validation and measurement uncertainty evaluation of a GC/MS method for the quantification of nine phthalates in tattoo and PMU inks

A gas chromatography/mass spectrometry (GC/MS) method for the quantification of nine phthalates in tattoo and permanent make-up (PMU) ink samples was developed and validated in accordance with the criteria of ISO/IEC 17025 and international guidelines. Limit of detection (LOD) and quantification (LOQ) values were 0.02 µg g−1 –0.14 µg g−1 and 0.08 µg g−1 –0.48 µg g−1, respectively. The intermediate precision, in terms of relative standard deviations (RSD), was less than 15 % over the working range selected for all the investigated phthalates. The inter-day recoveries ranged between 76 % and 116 %. The validation study demonstrated that the method is accurate and sensitive although the development of an analytical method for this matrix is quite challenging. The relative expanded uncertainty estimated with a coverage factor (k) of 2 at a confidence interval of 95 % ranged from 7 % to 54 %. The method was applied to the analysis of 44 selected tattoo and PMU ink samples purchased on the Italian market. Phthalate content results were reported taking into account the measurement uncertainty. The uncertainty information is necessary to assess compliance of results with respect to the mass fraction limits established in the upcoming Annex XVII of Regulation (CE) N.1907/2006 (REACH).