Name: a two-step pyrolysis-gas chromatography method with mass spectrometric detection for identification of tattoo ink ingredients and counterfeit products
Uploaded: 2019-05-22T15:00:00
Description: 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

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.

a-two-step-pyrolysis-gas-chromatography-method-with-mass

Research

JoVE Journal

Chemistry

Untargeted Metabolomics from Biological Sources Using Ultraperformance Liquid Chromatography-High Resolution Mass Spectrometry (UPLC-HRMS)

Here we present a workflow to analyze the metabolic profiles for biological samples of interest including; cells, serum, or tissue. The sample is first separated into polar and non-polar fractions by a liquid-liquid phase extraction, and partially purified to facilitate downstream analysis. Both aqueous (polar metabolites) and organic (non-polar metabolites) phases of the initial extraction are processed to survey a broad range of metabolites. Metabolites are separated by different liquid chromatography methods based upon their partition properties. In this method, we present microflow ultra-performance (UP)LC methods, but the protocol is scalable to higher flows and lower pressures. Introduction into the mass spectrometer can be through either general or compound optimized source conditions. Detection of a broad range of ions is carried out in full scan mode in both positive and negative mode over a broad m/z range using high resolution on a recently calibrated instrument. Label-free differential analysis is carried out on bioinformatics platforms. Applications of this approach include metabolic pathway screening, biomarker discovery, and drug development.

Untargeted Metabolomics from Biological Sources Using Ultraperformance Liquid Chromatography-High Resolution Mass Spectrometry UPLC-HRMS

Untargeted metabolomics provides a hypothesis generating snapshot of a metabolic profile. This protocol will demonstrate the extraction and analysis of metabolites from cells, serum, or tissue. A range of metabolites are surveyed using liquid-liquid phase extraction, microflow ultraperformance liquid chromatography/high-resolution mass spectrometry (UPLC-HRMS) coupled to differential analysis software.

Here we present a workflow to analyze the metabolic profiles for biological samples of interest including; cells, serum, or tissue. The sample is first ...

Mass Spectrometric Approaches to Study Protein Structure and Interactions in Lyophilized Powders

Amide hydrogen/deuterium exchange (ssHDX-MS) and side-chain photolytic labeling (ssPL-MS) followed by mass spectrometric analysis can be valuable for characterizing lyophilized formulations of protein therapeutics. Labeling followed by suitable proteolytic digestion allows the protein structure and interactions to be mapped with peptide-level resolution. Since the protein structural elements are stabilized by a network of chemical bonds from the main-chains and side-chains of amino acids, specific labeling of atoms in the amino acid residues provides insight into the structure and conformation of the protein. In contrast to routine methods used to study proteins in lyophilized solids (e.g., FTIR), ssHDX-MS and ssPL-MS provide quantitative and site-specific information. The extent of deuterium incorporation and kinetic parameters can be related to rapidly and slowly exchanging amide pools (Nfast, Nslow) and directly reflects the degree of protein folding and structure in lyophilized formulations. Stable photolytic labeling does not undergo back-exchange, an advantage over ssHDX-MS. Here, we provide detailed protocols for both ssHDX-MS and ssPL-MS, using myoglobin (Mb) as a model protein in lyophilized formulations containing either trehalose or sorbitol.

Here, we present detailed protocols for solid-state amide hydrogen/deuterium exchange mass spectrometry (ssHDX-MS) and solid-state photolytic labeling mass spectrometry (ssPL-MS) for proteins in solid powders. The methods provide high-resolution information on protein conformation and interactions in the amorphous solid-state, which may be useful in formulation design.

Amide hydrogen/deuterium exchange (ssHDX-MS) and side-chain photolytic labeling (ssPL-MS) followed by mass spectrometric analysis can be valuable for ...

A Straightforward Method for Glucosinolate Extraction and Analysis with High-pressure Liquid Chromatography (HPLC)

Glucosinolates are a well-studied and highly diverse class of natural plant compounds. They play important roles in plant resistance, rapeseed oil quality, food flavoring, and human health. The biological activity of glucosinolates is released upon tissue damage, when they are mixed with the enzyme myrosinase. This results in the formation of pungent and toxic breakdown products, such as isothiocyanates and nitriles. Currently, more than 130 structurally different glucosinolates have been identified. The chemical structure of the glucosinolate is an important determinant of the product that is formed, which in turn determines its biological activity. The latter may range from detrimental (e.g., progoitrin) to beneficial (e.g., glucoraphanin). Each glucosinolate-containing plant species has its own specific glucosinolate profile. For this reason, it is important to correctly identify and reliably quantify the different glucosinolates present in brassicaceous leaf, seed, and root crops or, for ecological studies, in their wild relatives. Here, we present a well-validated, targeted, and robust method to analyze glucosinolate profiles in a wide range of plant species and plant organs. Intact glucosinolates are extracted from ground plant materials with a methanol-water mixture at high temperatures to disable myrosinase activity. Thereafter, the resulting extract is brought onto an ion-exchange column for purification. After sulfatase treatment, the desulfoglucosinolates are eluted with water and the eluate is freeze-dried. The residue is taken up in an exact volume of water, which is analyzed by high-pressure liquid chromatography (HPLC) with a photodiode array (PDA) or ultraviolet (UV) detector. Detection and quantification are achieved by conducting comparisons of the retention times and UV spectra of commercial reference standards. The concentrations are calculated based on a sinigrin reference curve and well-established response factors. The advantages and disadvantages of this straightforward method, when compared to faster and more technologically advanced methods, are discussed here.

A Straightforward Method for Glucosinolate Extraction and Analysis with High-pressure Liquid Chromatography HPLC

Here, we describe in great detail an established and robust protocol for the extraction of glucosinolates from ground plant materials. After an on-column sulfatase treatment of the extracts, the desulfoglucosinolates are eluted and analyzed by high-pressure liquid chromatography.

Glucosinolates are a well-studied and highly diverse class of natural plant compounds. They play important roles in plant resistance, rapeseed oil ...

A Convenient Method for Extraction and Analysis with High-Pressure Liquid Chromatography of Catecholamine Neurotransmitters and Their Metabolites

The extraction and analysis of catecholamine neurotransmitters in biological fluids is of great importance in assessing nervous system function and related diseases, but their precise measurement is still a challenge. Many protocols have been described for neurotransmitter measurement by a variety of instruments, including high-pressure liquid chromatography (HPLC). However, there are shortcomings, such as complicated operation or hard-to-detect multiple targets, which cannot be avoided, and presently, the dominant analysis technique is still HPLC coupled with sensitive electrochemical or fluorimetric detection, due to its high sensitivity and good selectivity. Here, a detailed protocol is described for the pretreatment and detection of catecholamines with high pressure liquid chromatography with electrochemical detection (HPLC-ECD) in real urine samples of infants, using electrospun composite nanofibers composed of polymeric crown ether with polystyrene as adsorbent, also known as the packed-fiber solid phase extraction (PFSPE) method. We show how urine samples can be easily precleaned by a nanofiber-packed solid phase column, and how the analytes in the sample can be rapidly enriched, desorbed, and detected on an ECD system. PFSPE greatly simplifies the pretreatment procedures for biological samples, allowing for decreased time, expense, and reduction of the loss of targets. 
Overall, this work illustrates a simple and convenient protocol for solid-phase extraction coupled to an HPLC-ECD system for simultaneous determination of three monoamine neurotransmitters (norepinephrine (NE), epinephrine (E), dopamine (DA)) and two of their metabolites (3-methoxy-4-hydroxyphenylglycol (MHPG) and 3,4-dihydroxy-phenylacetic acid (DOPAC)) in infants' urine. The established protocol was applied to assess the differences of urinary catecholamines and their metabolites between high-risk infants with perinatal brain damage and healthy controls. Comparative analysis revealed a significant difference in urinary MHPG between the two groups, indicating that the catecholamine metabolites may be an important candidate marker for early diagnosis of cases at risk for brain damage in infants.

We present a convenient solid-phase extraction coupled to high-pressure liquid chromatography (HPLC) with electrochemical detection (ECD) for simultaneous determination of three monoamine neurotransmitters and two of their metabolites in infants' urine. We also identify the metabolite MHPG as a potential biomarker for the early diagnosis of brain damage for infants.

The extraction and analysis of catecholamine neurotransmitters in biological fluids is of great importance in assessing nervous system function and ...

A Two-Step Protocol for Umpolung Functionalization of Ketones Via Enolonium Species

&#945;-Functionalization of ketones via umpolung of enolates by hypervalent iodine reagents is an important concept in synthetic organic chemistry. Recently, we have developed a two-step strategy for ketone enolate umpolung that has enabled the development of methods for chlorination, azidation, and amination using azoles. In addition, we have developed C-C bond&#8211;forming arylation and allylation reactions. At the heart of these methods is the preparation of the intermediate and highly reactive enolonium species prior to addition of a reactive nucleophile. This strategy is thus reminiscent of the preparation and use of metal enolates in classical synthetic chemistry. This strategy allows the use of nucleophiles that would otherwise be incompatible with the strongly oxidizing hypervalent iodine reagents. In this paper we present a detailed protocol for chlorination, azidation, N-heteroarylation, arylation, and allylation. The products include motifs prevalent in medicinally active products. This article will greatly assist others in using these methods.

A two step one-pot protocol for the umpolung of ketone enolates to enolonium species and addition of a nucleophile to the &#945;-position is described. Nucleophiles include chloride, azide, azoles, allyl-silanes, and aromatic compounds.

&#945;-Functionalization of ketones via umpolung of enolates by hypervalent iodine reagents is an important concept in synthetic organic chemistry. ...

Versatile CO2 Transformations into Complex Products: A One-pot Two-step Strategy

CO2 transformations using a one-pot two-step method are presented herein. The purpose of the method is to give access to a variety of value-added products and notably to generate chiral carbon centers. The crucial first step consists in the selective double hydroboration of CO2 catalyzed by an iron hydride complex. The product obtained with this 4 e- reduction is a rare bis(boryl)acetal, compound 1, which is subjected in situ to three different reactions in a second step. The first reaction concerns a condensation reaction with (diisopropyl)phenylamine affording the corresponding imine 2. In the second and third reaction, intermediate 1 reacts with triazol-5-ylidene (Enders&#39; carbene) to afford compounds 3 or 4, depending on the reaction conditions. In both compounds, C-C bonds are formed, and chiral centers are generated from CO2 as the only source of carbon. Compound 4 exhibits two chiral centers obtained in a diastereoselective manner in a formose-type mechanism. We proved that the remaining boryl fragment plays a key role in this unprecedented stereocontrol. The interest of the method stands on the reactive and versatile nature of 1, giving rise to various complex molecules from a single intermediate. The complexity of a two-step method is compensated by the overall short reaction time (2 h for the larger reaction time), and mild reaction conditions (25 &#176;C to 80 &#176;C and 1 to 3 atm of CO2).

Versatile CO2 Transformations into Complex Products: A One-pot Two-step Strategy

CO2 transformations are conducted in a one-pot two-step procedure for the synthesis of complex molecules. The selective 4 e- reduction of CO2 with a hydroborane reductant affords a reactive and versatile bis(boryl)acetal intermediate which is subsequently involved in condensation reaction or carbene-mediated C-C coupling generation.

CO2 transformations using a one-pot two-step method are presented herein. The purpose of the method is to give access to a variety of value-added products ...

Mass Spectrometry-Guided Genome Mining as a Tool to Uncover Novel Natural Products

The chemical space covered by natural products is immense and widely unrecognized. Therefore, convenient methodologies to perform wide-ranging evaluation of their functions in nature and potential human benefits (e.g., for drug discovery applications) are desired. This protocol describes the combination of genome mining (GM) and molecular networking (MN), two contemporary approaches that match gene cluster-encoded annotations in whole genome sequencing with chemical structure signatures from crude metabolic extracts. This is the first step towards the discovery of new natural entities. These concepts, when applied together, are defined here as MS-guided genome mining. In this method, the main components are previously designated (using MN), and structurally related new candidates are associated with genome sequence annotations (using GM). Combining GM and MN is a profitable strategy to target new molecule backbones or harvest metabolic profiles in order to identify analogues from already known compounds.

A mass spectrometry-guided genome mining protocol is established and described here. It is based on genome sequence information and LC-MS/MS analysis and aims to facilitate identification of molecules from complex microbial and plant extracts.

The chemical space covered by natural products is immense and widely unrecognized. Therefore, convenient methodologies to perform wide-ranging evaluation ...

Gas Chromatography-Mass Spectrometry Paired with Total Vaporization Solid-Phase Microextraction as a Forensic Tool

Gas Chromatography &#8211; Mass Spectrometry (GC-MS) is a frequently used technique for the analysis of numerous analytes of forensic interest, including controlled substances, ignitable liquids, and explosives. GC-MS can be coupled with Solid-Phase Microextraction (SPME), in which a fiber with a sorptive coating is placed into the headspace above a sample or immersed in a liquid sample. Analytes are sorbed onto the fiber which is then placed inside the heated GC inlet for desorption. Total Vaporization Solid-Phase Microextraction (TV-SPME) utilizes the same technique as immersion SPME but immerses the fiber into a completely vaporized sample extract. This complete vaporization results in a partition between only the vapor phase and the SPME fiber without interference from a liquid phase or any insoluble materials. Depending upon the boiling point of the solvent used, TV-SPME allows for large sample volumes (e.g., up to hundreds of microliters). On-fiber derivatization may also be performed using TV-SPME. TV-SPME has been used to analyze drugs and their metabolites in hair, urine, and saliva. This simple technique has also been applied to street drugs, lipids, fuel samples, post-blast explosive residues, and pollutants in water. This paper highlights the use of TV-SPME to identify illegal adulterants in very small samples (microliter quantities) of alcoholic beverages. Both gamma-hydroxybutyrate (GHB) and gamma-butyrolactone (GBL) were identified at levels that would be found in spiked drinks. Derivatization by a trimethylsilyl agent allowed for conversion of the aqueous matrix and GHB into their TMS derivatives. Overall, TV-SPME is quick, easy, and requires no sample preparation aside from placing the sample into a headspace vial.

Total Vaporization Solid Phase Microextraction (TV-SPME) completely vaporizes a liquid sample whilst analytes are sorbed onto a SPME fiber. This allows for partitioning of the analyte between only the solvent vapor and the SPME fiber coating.

Gas Chromatography &#8211; Mass Spectrometry (GC-MS) is a frequently used technique for the analysis of numerous analytes of forensic interest, including ...

Radiosynthesis of 1-(2-[18F]Fluoroethyl)-L-Tryptophan using a One-pot, Two-step Protocol

The kynurenine pathway (KP) is a primary route for tryptophan metabolism. Evidence strongly suggests that metabolites of the KP play a vital role in tumor proliferation, epilepsy, neurodegenerative diseases, and psychiatric illnesses due to their immune-modulatory, neuro-modulatory, and neurotoxic effects. The most extensively used positron emission tomography (PET) agent for mapping tryptophan metabolism, &#945;-[11C]methyl-L-tryptophan ([11C]AMT), has a short half-life of 20 min with laborious radiosynthesis procedures. An onsite cyclotron is required to radiosynthesize [11C]AMT. Only a limited number of centers produce [11C]AMT for preclinical studies and clinical investigations. Hence, the development of an alternative imaging agent that has a longer half-life, favorable in vivo kinetics, and is easy to automate is urgently needed. The utility and value of 1-(2-[18F]fluoroethyl)-L-tryptophan, a fluorine-18-labeled tryptophan analog, has been reported in preclinical applications in cell line-derived xenografts, patient-derived xenografts, and transgenic tumor models.
This paper presents a protocol for the radiosynthesis of 1-(2-[18F]fluoroethyl)-L-tryptophan using a one-pot, two-step strategy. Using this protocol, the radiotracer can be produced in a 20 &#177; 5% (decay corrected at the end of synthesis, n &#62; 20) radiochemical yield, with both radiochemical purity and enantiomeric excess of over 95%. The protocol features a small precursor amount with no more than 0.5 mL of reaction solvent in each step, low loading of potentially toxic 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane (K222), and an environmentally benign and injectable mobile phase for purification. The protocol can be easily configured to produce 1-(2-[18F]fluoroethyl)-L-tryptophan for clinical investigation in a commercially available module.

Radiosynthesis of 1-2-[18F]Fluoroethyl-L-Tryptophan using a One-pot, Two-step Protocol

Here, we describe the radiosynthesis of 1-(2-[18F]Fluoroethyl)-L-tryptophan, a positron emission tomography imaging agent for studying tryptophan metabolism, using a one-pot, two-step strategy in a radiochemistry synthesis system with good radiochemical yields, high enantiomeric excess, and high reliability.

The kynurenine pathway (KP) is a primary route for tryptophan metabolism. Evidence strongly suggests that metabolites of the KP play a vital role in tumor ...

Multi-Faceted Mass Spectrometric Investigation of Neuropeptides in Callinectes sapidus

Neuropeptides are signaling molecules that regulate almost all physiological and behavioral processes, such as development, reproduction, food intake, and response to external stressors. Yet, the biochemical mechanisms and full complement of neuropeptides and their functional roles remain poorly understood. Characterization of these endogenous peptides is hindered by the immense diversity within this class of signaling molecules. Additionally, neuropeptides are bioactive at concentrations 100x - 1000x lower than that of neurotransmitters and are prone to enzymatic degradation after synaptic release. Mass spectrometry (MS) is a highly sensitive analytical tool that can identify, quantify, and localize analytes without comprehensive a priori knowledge. It is well-suited for globally profiling neuropeptides and aiding in the discovery of novel peptides. Due to the low abundance and high chemical diversity of this class of peptides, several sample preparation methods, MS acquisition parameters, and data analysis strategies have been adapted from proteomics techniques to allow optimal neuropeptide characterization. Here, methods are described for isolating neuropeptides from complex biological tissues for sequence characterization, quantitation, and localization using liquid chromatography (LC)-MS and matrix-assisted laser desorption/ionization (MALDI)-MS. A protocol for preparing a neuropeptide database from the blue crab, Callinectes sapidus, an organism without comprehensive genomic information, is included. These workflows can be adapted to study other classes of endogenous peptides in different species using a variety of instruments.

Multi-Faceted Mass Spectrometric Investigation of Neuropeptides in Callinectes sapidus

Mass spectrometric characterization of neuropeptides provides sequence, quantitation, and localization information. This optimized workflow is not only useful for neuropeptide studies, but also other endogenous peptides. The protocols provided here describe sample preparation, MS acquisition, MS analysis, and database generation of neuropeptides using LC-ESI-MS, MALDI-MS spotting, and MALDI-MS imaging.

Neuropeptides are signaling molecules that regulate almost all physiological and behavioral processes, such as development, reproduction, food intake, and ...