Tattoo ink controls
The popularity of tattoos appears to be growing, whether they be delicate motifs or full-blown body art across the torso and limbs. A recent EU report published in 2016 estimated that about 12% of the European population was decorated with at least one tattoo, corresponding to about 60 million people. However, acquiring a tattoo might not be completely safe and their wider use has raised concerns regarding the potential risks from infections and non-regulated ingredients.
Tattoos and permanent make up are not regulated by the EU. They do not qualify as cosmetics, which are controlled, since they are applied by intradermal injection. Instead, supervision of tattoo inks is governed by individual national regulations, these being based on EU recommendations. They cover the expected ingredients such as dyes, solvents, stabilisers and pH regulators but scientists in Italy have identified a further health risk.
Maria Cristina Gaudiano and colleagues from the National Center for the Control and Evaluation of Medicines in Rome were concerned by reports that tattoo inks containing anaesthetics are available over the Internet. While their addition to the inks might be for legitimate reasons, to nullify the pain experienced during the tattoo process, their unregulated presence could cause adverse effects such as allergic reaction, skin inflammation or even seizures.
These concerns led the research group to devise a method for detecting and measuring eight anaesthetics of the "caine" type in tattoo inks, which could be added to the inventory of safety tests.
The new method was based on LC/MS and was established and validated using standard solutions of the drugs in aqueous acidic acetonitrile. A mixture of articaine, bupivacaine, lidocaine, mepivacaine, prilocaine, procaine, tetracaine and benzocaine was separated on a C18 column comprising a unique patented bidentate silane with double endcapping.
Gradient elution with increasing concentrations of acetonitrile in dilute aqueous formic acid ensured separation of six of the anaesthetics from each other within 6.5 minutes. The remaining two, benzocaine and tetracaine, partly coeluted around 6.8 minutes. The eluates were directed towards a quadrupole-time-of-flight mass spectrometer for analysis, using electrospray ionisation in positive mode.
The distinct anaesthetics were identified from protonated molecule peaks in the mass spectra as well as the characteristic peaks observed in their tandem mass spectra. A further identification factor for the majority was the retention time. The overlapping elution of benzocaine and tetracaine did not present identification problems due to the distinct masses observed from each compound with the extracted ion chromatogram.
The limits of detection and quantification fell in the ranges 0.01-0.03 and 0.03-0.08 µg/mL, respectively, and the calibration curves were linear using an internal standard. The other analytical criteria also proved acceptable, so the method was applied to three tattoo inks thought to contain anaesthetics that were seized by police in two different regions of Italy.
Unsafe tattoo inks
The inks were extracted with methanol and analysed by the new LC/MS method. All of the samples contained lidocaine at levels of 4.5-4.9% and tetracaine at 1.7-2.3%, so the total anaesthetic concentrations were nearly 7%.
In general clinical practice, both lidocaine and tetracaine are used solely for topical applications or for percutaneous infiltration anaesethesia. With these adulterated tattoo inks, the maximum permitted levels of lidocaine would be reached for a tattoo of 17 cm2. Tetracaine is more potent and toxic, so could also present problems for tattoo subjects.
Given that there have been no published safety studies on the interactions of anaesthetics with the other ink components, and that the sources and purities of the anaesthetics are unknown, these products present a serious health risk. This is compounded by the aforementioned side effects that the anaesthetics might have on individual subjects. The researchers recommended that Official Medicines Control Laboratories should incorporate tattoo ink screening procedures, since the inks contain anaesthetics and are effectively a "challenging kind of medicine in disguise".
Manna, L., Gaudiano, M.C., Bartolomei, M., et al. (2019). A special case of medicine in disguise: Tattoo inks containing anaesthetics. Talanta 198: 337-343.
The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.
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