This work was supported by the intramural research project (SFP #1323-103) at the German Federal Institute for Risk Assessment (BfR).

1. Tattoo ink preparation and sample mounting
<ol>
	<li>Use a 25 mm hollow glass pyrolysis tube as a sample holder and quartz wool for sample preparation.
	<ol>
		<li>Grab the pyrolysis tube with the specialized tweezers for pyrolysis tubes (bake out for decontamination) and insert the necessary amount of quartz wool with pointed tweezers into the tube.</li>
		<li>Insert two steel sticks (bake out for decontamination) at each side of the pyrolysis tube and compress the wool into a 1&#8211;2 mm thick stopper. The stoppe...

<ol>
	<li>Dirks, M., Serup, J., Kluger, N., B&#228;umler, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Tattooed skin and health. Vol. 48. Current Problems in Dermatology. , 118-127 (2015).</li><li>Engel, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Establishment+of+an+extraction+method+for+the+recovery+of+tattoo+pigments+from+human+skin+using+HPLC+diode+array+detector+technology.">Establishment of an extraction method for the recovery of tattoo pigments from human skin using HPLC diode array detector technology.</a> Analytical Chemistry. 78 (15), 6440-6447 (2006).</li><li>Poon, K. W. C., Dadour, I. R., McKinley, A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+situ+chemical+analysis+of+modern+organic+tattooing+inks+and+pigments+by+micro-Raman+spectroscopy.">In situ chemical analysis of modern organic tattooing inks and pigments by micro-Raman spectroscopy.</a> Journal of Raman Spectroscopy. 39 (9), 1227-1237 (2008).</li><li>Timko, A. L., Miller, C. H., Johnson, F. B., Ross, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vitro+quantitative+chemical+analysis+of+tattoo+pigments.">In vitro quantitative chemical analysis of tattoo pigments.</a> Archives of Dermatology. 137, 143-147 (2004).</li><li>Boon, J. J., Learner, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analytical+mass+spectrometry+of+artists'+acrylic+emulsion+paints+by+direct+temperature+resolved+mass+spectrometry+and+laser+desorption+ionisation+mass+spectrometry.">Analytical mass spectrometry of artists' acrylic emulsion paints by direct temperature resolved mass spectrometry and laser desorption ionisation mass spectrometry.</a> Journal of Analytical and Applied Pyrolysis. 64, 327-344 (2002).</li><li>Hauri, U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inks+for+tattoos+and+permanent+make-up+/+pigments,+preservatives,+aromatic+amines,+polyaromatic+hydrocarbons+and+nitrosamines.">Inks for tattoos and permanent make-up / pigments, preservatives, aromatic amines, polyaromatic hydrocarbons and nitrosamines.</a> Department of Health, Kanton Basel-Stadt. Swiss National Investigation Campaign. , (2014).</li><li>Bocca, B., Sabbioni, E., Mi&#269;eti&#263;, I., Alimonti, A., Petrucci, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Size+and+metal+composition+characterization+of+nano-+and+microparticles+in+tattoo+inks+by+a+combination+of+analytical+techniques.">Size and metal composition characterization of nano- and microparticles in tattoo inks by a combination of analytical techniques.</a> Journal of Analytical Atomic Spectrometry. 32 (3), 616-628 (2017).</li><li>Schreiver, I., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synchrotron-based+nano-XRF+mapping+and+micro-FTIR+microscopy+enable+to+look+into+the+fate+and+effects+of+tattoo+pigments+in+human+skin.">Synchrotron-based nano-XRF mapping and micro-FTIR microscopy enable to look into the fate and effects of tattoo pigments in human skin.</a> Scientific Reports. 7, 11395 (2017).</li><li>Taylor, C. R., Anderson, R. R., Gange, R. W., Michaud, N. A., Flotte, T. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Light+and+electron+microscopic+analysis+of+tattoos+treated+by+Q-switched+ruby+laser.">Light and electron microscopic analysis of tattoos treated by Q-switched ruby laser.</a> Journal of Investigative Dermatology. 97, 131-136 (1991).</li><li>Namduri, H., Nasrazadani, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantitative+analysis+of+iron+oxides+using+Fourier+transform+infrared+spectrophotometry.">Quantitative analysis of iron oxides using Fourier transform infrared spectrophotometry.</a> Corrosion Science. 50 (9), 2493-2497 (2008).</li><li>Burgio, L., Clark, R. J., Hark, R. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Raman+microscopy+and+x-ray+fluorescence+analysis+of+pigments+on+medieval+and+Renaissance+Italian+manuscript+cuttings.">Raman microscopy and x-ray fluorescence analysis of pigments on medieval and Renaissance Italian manuscript cuttings.</a> Proceedings of the National Academy of Sciences of the United States of America. 107 (13), 5726-5731 (2010).</li><li>Manso, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assessment+of+toxic+metals+and+hazardous+substances+in+tattoo+inks+using+Sy-XRF,+AAS+and+Raman+spectroscopy.">Assessment of toxic metals and hazardous substances in tattoo inks using Sy-XRF, AAS and Raman spectroscopy.</a> Biological Trace Element Research. 187 (2), 596-601 (2017).</li><li>Yakes, B. J., Michael, T. J., Perez-Gonzalez, M., Harp, B. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Investigation+of+tattoo+pigments+by+Raman+spectroscopy.">Investigation of tattoo pigments by Raman spectroscopy.</a> Journal of Raman Spectroscopy. 48 (5), 736-743 (2017).</li><li>Yang, S. -. H., Shen, J. Y., Chang, M. S., Wu, G. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differentiation+of+vehicle+top+coating+paints+using+pyrolysis-gas+chromatography/mass+spectrometry+and+multivariate+chemometrics+with+statistical+comparisons.">Differentiation of vehicle top coating paints using pyrolysis-gas chromatography/mass spectrometry and multivariate chemometrics with statistical comparisons.</a> Analytical Methods. 7, 1527-1534 (2015).</li><li>Schreiver, I., Hutzler, C., Luch, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Data+from:+Two-step+pyrolysis-gas+chromatography+method+with+mass+spectrometric+detection+for+identification+of+tattoo+ink+ingredients+and+counterfeit+products.">Data from: Two-step pyrolysis-gas chromatography method with mass spectrometric detection for identification of tattoo ink ingredients and counterfeit products.</a> Dryad Digital Repository. , (2019).</li><li>Schreiver, I., Hutzler, C., Andree, S., Laux, P., Luch, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+and+hazard+prediction+of+tattoo+pigments+by+means+of+pyrolysis&#8212;gas+chromatography/mass+spectrometry.">Identification and hazard prediction of tattoo pigments by means of pyrolysis&#8212;gas chromatography/mass spectrometry.</a> Archives of Toxicology. 90 (7), 1639-1650 (2016).</li><li>Ghelardi, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Py-GC/MS+applied+to+the+analysis+of+synthetic+organic+pigments:+characterization+and+identification+in+paint+samples.">Py-GC/MS applied to the analysis of synthetic organic pigments: characterization and identification in paint samples.</a> Analytical and Bioanalytical Chemistry. 407 (5), 1415-1431 (2015).</li><li>Russell, J., Singer, B. W., Perry, J. J., Bacon, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+identification+of+synthetic+organic+pigments+in+modern+paints+and+modern+paintings+using+pyrolysis-gas+chromatography-mass+spectrometry.">The identification of synthetic organic pigments in modern paints and modern paintings using pyrolysis-gas chromatography-mass spectrometry.</a> Analytical and Bioanalytical Chemistry. 400 (5), 1473-1491 (2011).</li><li>Silva, M. F., Domenech-Carbo, M. T., Fuster-Lopez, L., Mecklenburg, M. F., Martin-Rey, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+of+additives+in+poly(vinylacetate)+artist's+paints+using+PY-GC-MS.">Identification of additives in poly(vinylacetate) artist's paints using PY-GC-MS.</a> Analytical and Bioanalytical Chemistry. 397 (1), 357-367 (2010).</li><li>Peris-Vincente, J., Baumer, U., Stege, H., Lutzenberger, K., Gimeno Adelantado, J. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+commercial+synthetic+resins+by+pyrolysis-gas+chromatography/mass+spectrometry:+application+to+modern+art+and+conservation.">Characterization of commercial synthetic resins by pyrolysis-gas chromatography/mass spectrometry: application to modern art and conservation.</a> Analytical Chemistry. 81, 3180-3187 (2009).</li><li>Kleinert, J. C., Weschler, C. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pyrolysis+gas+chromatographic-mass+spectrometric+identification+of+polydimethylsiloxanes.">Pyrolysis gas chromatographic-mass spectrometric identification of polydimethylsiloxanes.</a> Analytical Chemistry. 52 (8), 1245-1248 (1980).</li><li>Scalarone, D., Chiantore, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Separation+techniques+for+the+analysis+of+artists'+acrylic+emulsion+paints.">Separation techniques for the analysis of artists' acrylic emulsion paints.</a> Journal of Separation Science. 27 (4), 263-274 (2004).</li><li>Sonoda, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+organic+azo-pigments+by+pyrolysis-gas+chromatography.">Characterization of organic azo-pigments by pyrolysis-gas chromatography.</a> Studies in Conservation. 44, 195-208 (1999).</li><li>Chiantore, O., Scalarone, D., Learner, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+artists'+crylic+emulsion+paints.">Characterization of artists' crylic emulsion paints.</a> International Journal of Polymer Analysis and Characterization. 8 (1), 67-82 (2003).</li><li>Schossler, P., Fortes, I., Figueiredo J&#250;nior, J. C. D., Carazza, F., Souza, L. A. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Acrylic+and+Vinyl+Resins+Identification+by+Pyrolysis-Gas+Chromatography/Mass+Spectrometry:+A+Study+of+Cases+in+Modern+Art+Conservation.">Acrylic and Vinyl Resins Identification by Pyrolysis-Gas Chromatography/Mass Spectrometry: A Study of Cases in Modern Art Conservation.</a> Analytical Letters. 46 (12), 1869-1884 (2013).</li><li>Wallisch, K. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pyrolysis+of+random+and+block+copolymers+of+ethyl+acrylate+and+methyl+methacrylate.">Pyrolysis of random and block copolymers of ethyl acrylate and methyl methacrylate.</a> Journal of Applied Polymer Science. 18, 203-222 (1974).</li><li>Hauri, U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inks+for+tattoos+and+PMU+(permanent+make-up)+/+Organic+pigments,+preservatives+and+impurities+such+as+primary+aromatic+amines+and+nitrosamines.">Inks for tattoos and PMU (permanent make-up) / Organic pigments, preservatives and impurities such as primary aromatic amines and nitrosamines.</a> State Laboratory of the Canton Basel City. , (2011).</li></ol>

Py-GC-MS is a useful screening method for a broad range of substances in tattoo inks that can also be used for the analysis of other products. Compared to other methods, py-GC-MS can be conducted with only minimal sample preparation. GC-MS devices can be found in most analytical laboratories compared to more specialized methods such as MALDI-ToF-MS and EDX.
The data evaluation of pyrograms may be challenging, since the list of possible ingredients is infinite in theory and library searches tha...

Tattoo inks are complex mixtures consisting of pigments, solvents, binders, surfactants, thickening agents, and, sometimes, preservatives1. The increased popularity of tattooing in the last decades has led to the establishment of legislation addressing tattoo ink safety across Europe. In most instances, color-giving pigments and their impurities are restricted and therefore should be monitored by state laboratory market surveys to control their compliance with law.
Using the approach of online pyrolysis-gas chromatography mass spectrometry (py-GC-MS) described here, multiple ingredients can be identified simultaneously. Since volatile, semi-volatile and non-volatile compounds can be separated and analyzed within the same process, the variety of target compounds is high compared to other methods used for tattoo ink analysis. Liquid chromatography methods are mostly carried out with pigments solubilized in organic solvents2. Raman spectroscopy as well as Fourier-transform infrared (FT-IR) spectroscopy have been described as suitable tools for the identification of pigments and polymers but are limited with multi-ingredient mixtures since no separation technique is used in standard laboratory applications3,4. Laser desorption/ionization time-of-flight mass spectrometry (LDI-ToF-MS) has also been used for pigment and polymer identification5,6. Altogether, most methods lack the analysis of volatile compounds. The lack of suitable commercial spectral libraries is a common disadvantage of all of these methods. The identification of inorganic pigments has often been carried out with either inductively coupled plasma mass spectrometry (ICP-MS)7,8 or energy dispersive X-ray spectroscopy (EDX)4,9. Also, FT-IR and Raman spectroscopy have been used for the analysis of inorganic pigments such as titanium dioxide or iron oxides in other research fields10,11,12,13.
The goal of this study was to establish a method applicable in standard analytical laboratories with moderate financial costs to upgrade existing and common devices. Py-GC-MS as described here is a non-quantitative approach for identification of organic ingredients from mixtures. Upon identification of suspicious substances in a py-GC-MS screening, target substances can be quantified with more specialized approaches. It is especially interesting for the analysis of non-volatile and non-soluble substances like pigments and polymers.
The described method can be adapted for inks and varnishes in other fields of application. The data evaluation methods described are applicable to all pyrolysis investigations. Also, counterfeit products, mostly from Asian markets, display a potential source of risk to the consumer and a financial burden to manufacturers (personal communication at the 3rd ECTP in Regensburg, Germany, 2017). The method described here can be used to compare the characteristics of putative counterfeit inks to an original bottle, similar to published forensic approaches for car varnish identification14.

<table>
	<tbody>
		<tr>
			<td>99.999% Helium carrier gas</td>
			<td>Air Liquide, D&#252;sseldorf, Germany</td>
			<td>-</td>
			<td></td>
		</tr>
		<tr>
			<td>5975C inert XL MSD with Triple-Axis Detectors</td>
			<td>Agilent Technologies, Waldbronn, Germany</td>
			<td>-</td>
			<td></td>
		</tr>
		<tr>
			<td>7890A gas chromatograph</td>
			<td>Agilent Technologies, Waldbronn, Germany</td>
			<td>-</td>
			<td></td>
		</tr>
		<tr>
			<td>AMDIS software (Version 2.7)</td>
			<td>The National Institute of Standards and Technology, Gaithersburg, MD, USA</td>
			<td>-</td>
			<td>can be used for GC/MS peak integration, e.g. for transfer to pyrogram evaluation software</td>
		</tr>
		<tr>
			<td>Cold Injection System (CIS)</td>
			<td>Gerstel, M&#252;hlheim, Germany</td>
			<td>-</td>
			<td></td>
		</tr>
		<tr>
			<td>electron impact (EI) source</td>
			<td>Agilent Technologies, Waldbronn, Germany</td>
			<td>-</td>
			<td></td>
		</tr>
		<tr>
			<td>Enhanced ChemStation (E02.02.1431)</td>
			<td>Agilent Technologies, Waldbronn, Germany</td>
			<td>-</td>
			<td>used to generate Average Mass Spektra (AMS), can be used for peak integration and standard GC/MS library search</td>
		</tr>
		<tr>
			<td>J&#38;W HP-5MS GC Column, 30 m, 0.25 mm, 0.25 &#181;m, 5975T Column Toroid Assembly</td>
			<td>Agilent Technologies, Waldbronn, Germany</td>
			<td>29091S-433LTM</td>
			<td></td>
		</tr>
		<tr>
			<td>MassHunter Software</td>
			<td>Agilent Technologies, Waldbronn, Germany</td>
			<td>-</td>
			<td>no Version specified, can be used for GC/MS peak integration and standard GC/MS library search</td>
		</tr>
		<tr>
			<td>Microcapillary tube Drummond Microcaps, volume 2 &#181;L</td>
			<td>Sigma-Aldrich, St. Louis, MO, USA</td>
			<td>P1549-1PAK</td>
			<td></td>
		</tr>
		<tr>
			<td>MS ChromSearch (Version 4.0.0.11)</td>
			<td>Axel Semrau GmbH &#38; Co. KG, Sprockh&#246;vel, Germany</td>
			<td>-</td>
			<td>specialized pyrogram evaluation software</td>
		</tr>
		<tr>
			<td>NIST MS Search Program (MS Search version 2.0g)</td>
			<td>The National Institute of Standards and Technology, Gaithersburg, MD, USA</td>
			<td>-</td>
			<td>used for MS and AMS library generation and corresponding substance search with selfmade and commercial libraries</td>
		</tr>
		<tr>
			<td>NIST/EPA/NIH Mass Spectral Library (EI) mainlib &#38; replib (Data version: NIST v11)</td>
			<td>The National Institute of Standards and Technology, Gaithersburg, MD, USA</td>
			<td>-</td>
			<td>used commercial mass spectral library</td>
		</tr>
		<tr>
			<td>Polystyrene (average Mw ~192,000)</td>
			<td>Sigma-Aldrich, St. Louis, MO, USA</td>
			<td>430102-1KG</td>
			<td></td>
		</tr>
		<tr>
			<td>Pyrolysis tubes, tube type - quartz glass - lenght 25 mm; 100 Units</td>
			<td>Gerstel, M&#252;hlheim, Germany</td>
			<td>018131-100-00</td>
			<td></td>
		</tr>
		<tr>
			<td>Pyrolyzer Module for TDU</td>
			<td>Gerstel, M&#252;hlheim, Germany</td>
			<td>-</td>
			<td></td>
		</tr>
		<tr>
			<td>Quartz wool</td>
			<td>Gerstel, M&#252;hlheim, Germany</td>
			<td>009970-076-00</td>
			<td></td>
		</tr>
		<tr>
			<td>Steel sticks</td>
			<td>Gerstel, M&#252;hlheim, Germany</td>
			<td>-</td>
			<td></td>
		</tr>
		<tr>
			<td>Thermal Desorption Unit (TDU 2)</td>
			<td>Gerstel, M&#252;hlheim, Germany</td>
			<td>-</td>
			<td></td>
		</tr>
		<tr>
			<td>Transport adapter</td>
			<td>Gerstel, M&#252;hlheim, Germany</td>
			<td>018276-010-00</td>
			<td></td>
		</tr>
		<tr>
			<td>Tweezers for Pyrolysis tubes</td>
			<td>Gerstel, M&#252;hlheim, Germany</td>
			<td>009970-074-00</td>
			<td></td>
		</tr>
		<tr>
			<td>Zebron Z-Guard Hi-Temp Guard Column, GC Cap. Column 10 m x 0.25 mm, Ea</td>
			<td>Phenomenex Ltd. Deutschland, Aschaffenburg, Germany</td>
			<td>7CG-G000-00-GH0</td>
			<td></td>
		</tr>
	</tbody>
</table>

a two-step pyrolysis-gas chromatography method with mass spectrometric detection for identification of tattoo ink ingredients and counterfeit products

Tattoo inks are complex mixtures of ingredients. Each of them possesses different chemical properties which have to be addressed upon chemical analysis. In this method for two-step pyrolysis online coupled to gas chromatography mass spectrometry (py-GC-MS) volatile compounds are analyzed during a first desorption run. In the second run, the same dried sample is pyrolyzed for analysis of non-volatile compounds such as pigments and polymers. These can be identified by their specific decomposition patterns. Additionally, this method can be used to differentiate original from counterfeit inks. Easy screening methods for data evaluation using the average mass spectra and self-made pyrolysis libraries are applied to speed up substance identification. Using specialized evaluation software for pyrolysis GS-MS data, a fast and reliable comparison of the full chromatogram can be achieved. Since GC-MS is used as separation technique, the method is limited to volatile substances upon desorption and after pyrolysis of the sample. The method can be applied for quick substance screening in market control surveys since it requires no sample preparation steps.

The method includes a two-step chromatographic approach for each sample (Figure 1). In the first run, the sample is dried inside the injector system at 90 &#176;C before volatile compounds are transferred onto the column. Since the drying process is incomplete in most cases, residual solvents and volatile compounds are transferred and analyzed. In the second run, the previously dried sample is subsequently pyrolyzed to facilitate the analysis of non-volatile ...

Watch this Scientific Journal Video about A Two-Step Pyrolysis-Gas Chromatography Method with Mass Spectrometric Detection for Identification of Tattoo Ink Ingredients and Counterfeit Products at JoVE

A Two-Step Pyrolysis-Gas Chromatography Method with Mass Spectrometric Detection for Identification of Tattoo Ink Ingredients and Counterfeit Products

This method for two-step pyrolysis online coupled to gas chromatography with mass spectrometric detection and data evaluation protocol can be used for multi-component analysis of tattoo inks and discrimination of counterfeit products.

Tattoo inks are complex mixtures of ingredients. Each of them possesses different chemical properties which have to be addressed upon chemical analysis. ...

Tattoo inks and other inks are complex mixtures of ingredients. Our method provides a quick and easy way to analyze multiple components at the same time. Pyrolysis and then coupled to gas chromatography with mass spectrometric detection allows the analysis of nonvolatile and volatile compounds in two consecutive runs.In addition to pure analysis of ink ingredients, this method can also be used to differentiate original and counterfeit products. In general, this method can be used for all kind of liquid samples. The data evaluation approach may also be used for any other kind of pyrolysis data.As with most analytical techniques, data interpretation of pyrograms is the Achilles Heel of this method. Therefore we provide libraries of pyrograms and single-analyzed spectra to ease interpretation of the data. First hold a 25-millimeter hollow glass pyrolysis tube with specialized tweezers and insert the necessary amount of quartz wool into the tube with pointed tweezers.Insert two steel sticks at each side of the pyrolysis tube and compress the wool into a one-to two-millimeter-thick stopper. The stopper must be positioned at the lower third of the pyrolysis tube to achieve adequate heating during the pyrolysis process. Ignite a gas burner and bake the pyrolysis tube and filling for two to three seconds from each side to remove contaminants.Next, manually shake the tattoo ink bottles vigorously for one minute to ensure homogeneity. Dip a two-microliter microcapillary tip in the ink and aspirate about one microliter of ink by filling half the capillary. Insert the capillary into the pyrolysis tube and stain the quartz wool stopper with the ink.A clear color staining must be visible without adding too much ink to the sample. Using the specialized tweezers, attach the prepared pyrolysis tube to a steel transport adaptor for the automated injection unit, and check that the pyrolysis tube is perfectly vertical and does not fall off during shaking. Place the transport adaptor in the tray of the automated injection unit at the desired position for pyrolysis GCMS analysis.For data evaluation of volatile compounds, start the GCMS analysis MS library searching software, and open the chromatogram of the desorption run. Select commercial libraries by clicking on Spectrum"and select Library. Then load the library of interest.Select Integration Parameters, and perform a library search by clicking on Spectrum"and Library Search Report. For pyrolysis data evaluation, open the chromatogram of the pyrolysis run. Mark the whole chromatogram in the GCMS evaluation software.With the right mouse button, press down to obtain an average mass spectra, or AMS. In order to establish a self-made library, click on Spectrum"and Edit Library. Select the library of interest, followed by Add New Entry, and fill in all information of interest.Generate an AMS of the investigated ink pyrogram and use the library search for comparison to the self-made AMS library. Exclude masses from column bleed or other column noises. To identify nonvolatile compounds with specialized pyrogram evaluation software, build a folder with all pyrogram entries that should serve as a library, such as a pigment pyrogram library for pigment identification, or pyrograms of an original ink, to compare it to putative counterfeit products.Load the unknown pyrogram in the tab library search by clicking on Browse. Next, load the library folder and select only MS matching"and RT matching"in the search options, since the overall abundance will vary compared to pyrogram of reference pigments. Click on Advanced"in the search options.Select an RT window width of interest, an area threshold of 0.1%and allow multiple matching. In the Mass Spec"options, select the parameter use only peaks with specified MS spectra, and use a fit threshold of 850. Load the file pigment_search_spectra.spf, or click on Add"to save specified MS spectra from each pyrogram of reference pigments or polymers from the library in the advanced search options. Press OK"to return to the main window. Then click on Search"to start the comparison.If needed, go to the chromatogram match tab and select a compound under the chromatogram match tab. Right-click and select Search spectrum in NIST"to forward the spectra to the MS library software and identify the compound. For manual data evaluation for nonvolatile compounds, start the GCMS analysis MS library searching software and open the chromatogram of the pyrolysis run.Select commercial and pyrolysis libraries by clicking on Spectrum"and Select Library. Load all libraries of interest. Integrate the pyrogram in the GCMS evaluation software and consider all peaks with an area not less than 0.2%of the total area.Next, start the library search by clicking on Spectrum"and Library Search Report. Manually compare all library matches to specific pigment and polymer decomposition products in the text protocol, or fragments stated in literature. Well-produced inks with highly pure ingredients and a limited number of components resulted in chromatograms easy to interpret with standard libraries, since most peaks can be identified.But even in the high-quality inks, non-declared ingredients such as propylene glycol are often found in addition to the declared glycerol. Inks containing multiple ingredients and impurities will result in a pyrogram that is difficult to interpret. Most peaks occurring in the second run may not be baseline separated from each other, making identification difficult.Some substances might also result in peaks below the threshold set during data evaluation. A solution to interpreting complex data might be a step-wise approach using 400, 600, and 800 degrees Celsius in consecutive pyrolysis steps for the same sample. Some pigment decomposition products may descend from multiple pigments.A positive result for counterfeit product identification is demonstrated for three lemon inks purchased from different vendors. Using a forward match factor above 0.9, the chromatogram from the first desorption run and the pyrogram from the second run of the original ink were compared against three independent acquisitions of the original ink, and the two counterfeit products using pyrogram evaluation software. Pyrolysis is useful to identify multiple compounds with just one analytical method.Qualification of specific compounds can be performed afterwards with more specialized methods.

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Research

JoVE Journal

Chemistry

10.9K vistas.  German Federal Institute for Risk Assessment (BfR). Las tintas de tatuaje y otras tintas son mezclas complejas de ingredientes. Nuestro método proporciona una manera rápida y fácil de analizar múltiples componentes al mismo tiempo. La pirólisis y luego acoplada a la cromatografía de gases con detección espectrométrica de masas permite el análisis de compuestos no volátiles y volátiles en dos corridas consecutivas.Además del análisis puro de los ingredientes de la tinta, este método también se puede utilizar para diferenci...

Video: A Two-Step Pyrolysis-Gas Chromatography Method with Mass Spectrometric Detection for Identification of Tattoo Ink Ingredients and Counterfeit Products