Static Headspace Analysis of Residual Solvents in Flexible Packaging and Quantitation with Multiple Headspace Extraction Following EN : 2002

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1 Static eadspace nalysis of Residual Solvents in Flexible ackaging and Quantitation with ultiple eadspace Extraction Following E 8-: Silvia emme and assimo Santoro Thermo Fisher Scientific, ilan, taly pplication ote 9 Key Words Flexible packaging, TRE, Trilus S, hromeleon DS, static headspace, E 8-, E, cling film, plastic wrap ntroduction Flexible packaging is essential in ensuring the safety, quality and shelf-life of packaged consumer products. Such packaging, commonly referred to as cling film or plastic wrap, is often comprised of layers bonded together with adhesives (multilayer) and imprinted with product information. During the process of manufacturing, shipping or storage, the packaging itself might leach solvents from the adhesives and printing inks or finishes into the very product it was meant to protect. When these are food products, those solvents can pose significant health risks and negatively impact the taste, aroma, or appearance of the product. Food manufacturers need to both ensure the quality of their food for commercial success and to comply with government food safety standards. For this and other applications with non-food products, headspace (S) gas chromatography is the recommended method of analysis. The method for the quantitative determination of residual solvents in flexible packaging by static headspace is reported in the European Standard absolute method E 8-:. E 8-: in particular specifies methods for the quantitative determination of residual solvents in flexible packaging by static headspace chromatography where the chemical identities of the residual solvents are known before commencing analysis. Quantification is achieved by the multiple headspace extraction (E) procedure using external or internal standards. E eliminates any effect of the sample matrix by extracting the whole amount of analytes in a few consecutive extraction cycles of the same sample. E 8-: applies to flexible packaging materials that may consist of mono- or multilayer plastic films, paper or board, foil or combinations thereof and does not apply to residual solvents with amounts lower than. mg/m². Using headspace autosamplers like the Thermo Scientific Trilus eadspace utosampler, quantification is achieved by E. The advantage of using E is high precision in the determination of the residual solvents with a relatively light work load, thanks to a fully automated process. o external calibration solutions or standard additions are required. oal The goal of this application note is to demonstrate the applicability of a modern, high-throughput valveand-loop static headspace autosampler to obtain full compliance with E 8-:.

2 aterials and ethods eadspace analysis was conducted using a Trilus eadspace utosampler equipped with the standard m loop and connected to a Thermo Scientific TRE as hromatograph (). The system was further configured with an instant connect Split/Splitless (SS) injector and an instant connect Flame onization Detector (FD) module. The Thermo Scientific Dionex hromeleon 7. hromatography Data System was used to control the system, acquire data and generate all reports. For the headspace analyses, m headspace vials (/ 8-) with magnetic caps and TFE/silicone septa (/ 8-) were used. For the SS injector, the S/SE straight liner (/ ) was used and a capillary column with a phase dedicated for the separation of volatile compounds was chosen. n example of this kind of column is the Thermo Scientific TraceD T- ( m. mm id. um, 8-). Standard mixtures specifically prepared for residual solvents analysis in packaging were purchased: Residual Solvents in ackaging aterial ixture, analytical standard, 7.% (v/v) (Sigma-ldrich cat# 899-U) Residual Solvents in ackaging aterial ixture, analytical standard, 9.9% (v/v) (Sigma-ldrich cat# 899-U) ethod Development To find the proper equilibration time, µ of each standard mixture was placed in five m headspace vials, then capped and crimped. The headspace vial equilibration times were increased, and the peak area of each compound versus the equilibration time was reported. To find the optimum heating time, the ethod Development ptimization (D) function of Trilus eadspace utosampler was used. The D function automatically increments the heating time in consecutive runs by an amount set by the user. ere, the starting heating time was min and increased in min increments, so the five vials were heated respectively for,,, and min. Figure shows the optimal equilibration time was determined to be min, after which a slight decrease of the peak areas was observed for a few analytes. peak area (p/s) 8 ptimal eating Time cetone -ropanol -ropanol -ethyl--propanol -Ethoxyethyl acetate 7 heating time (min) Figure. eating times shown in five increments of min each through D. ext, µ of each standard mixture was placed into a m headspace vial, then capped and crimped to run an E experiment with extraction repetitions on the same vial. For each compound tested, E 8- requires the correlation coefficient of the natural logarithm of the peak area from the consecutive four analyses plotted against the number of E cycles to be at least articular instrument parameters (equilibration time and temperatures) had to be used to run the analysis for the determination of residual solvents in the samples to allow the required correlation coefficient to be obtained. Table shows the system parameters that were used for method development, and for the method used to produce the data in this note. To analyze real samples and determine the residual solvents, the flexible packaging material (plastic films or paper) was trimmed into a piece with a surface of cm, placed into a m headspace vial, capped and crimped. f this analysis is repeated using different headspace vial volumes, it must be considered that E 8- requires the ratio between the specimen area (in cm²) and the vial volume (in m) to be between three and five.

3 Table. and headspace parameters used in this method. Trilus eadspace nalyzer parameters for D* heating time optimization for standard mixtures/ sample analysis oven temp manifold temp transfer line temp equilibration time from min to min, increments of min min shaking medium medium pressure mode pressure pressure aux pressure bar bar pressure eq. time. min. min loop fill mode pressure pressure other parameters loop pressure:. bar; loop eq.time:. min loop pressure:. bar; loop eq.time:. min injection time. min. min injection mode standard standard vial venting on on purge time. min. min purge flow m/min m/min others TRE as hromatograph SS mode split SS temperature split flow m/min splitless time min constant purge on carrier mode helium, constant flow carrier flow m/min FD temperature oven program ( min), /min to ( min) for ultiple eadspace Extraction: E multiple, repetitions Quantification of the residual solvent(s) found in a sample was done on the first and second extraction cycles of the E analysis using the equations below, which are reported in E 8-: where: en = (e) (e - e) en is the total peak area of one solvent of the standard mix e is the peak area of the same solvent in the first e is the peak area of the same solvent in the second where: an = (a) (a - a) an is the total peak area of one residual solvent of the sample a is the peak area of the same solvent in the first a is the peak area of the same solvent in the second Q = (an p)/(en S) where: Q is the quantity of one residual solvent (in mg/m ) of packaging material p is the mass of solvent in the standard mix expressed in milligrams (mg) S is the area of specimen expressed in square meters (m )

4 Results and Discussion The elution order of the compounds of the two standard mixtures (Figure ) and their retention times (Table ) were determined using a Thermo Scientific SQ T Single Quadrupole -S running in full scan mode (mass range - m/z). 9 p F inutes Figure. The elution order of the compounds in the two standard mixtures. Table. ompound retention times in the two standard mixtures. eak RTs (min) ompound 8. ethanol.7 Ethanol.7 cetone. -ropanol. ethyl acetate.78 -ropanol 7.9 Ethyl acetate & -utanone F 7.7 -utanol 8.7 Tetrahydrofuran 8.9 yclohexane 9.7 -ethyl--propanol 9.8 sopropyl acetate. -utanol ethoxy--propanol & -ethoxyethanol 9.78 ropyl acetate.8 -Ethoxyethanol.97 -ethyl--pentanone.7 Toluene.8 sobutyl acetate 7.9 utyl acetate 9.9 -ethoxyethyl acetate.78 -Ethoxyethyl acetate. yclohexanone p-. Figure shows the chromatograms and Figure shows the E results of the two standard mixtures. 9 p inutes Figure. E chromatograms for the two standard mixtures with extraction cycles. n eak reas 8 7 Figure. E results for the two standard mixtures (overlay). F Extraction Repetition # F E ultiple eaks R eaks R F p-.

5 lthough not specifically required by E 8-, a linearity check was run by preparing calibration levels with different volumes of Residual Solvents ixture (. µ for evel,. µ for evel,. µ for evel, and µ for evel ) placed in different m headspace empty vials. Figure shows a graph of the excellent correlation coefficients obtained in the linearity check, proving the system can be used for the determination of residual solvents over a wide range of concentrations. rea (p/s) evel The correlation coefficients obtained by plotting the natural logarithms of the peak areas of the residual solvents found in the film sample against the number of E cycles are shown in Figure 7. ln area ln area R² =.997 repetition # F eaks R eaks R evel µ of ix Figure. orrelation coefficients from the linearity check on Residual Solvents ixture. ext, samples of transparent plastic film used to wrap commercial magazines with a surface of 9 cm each, were placed in a m headspace vial, capped and crimped. Then they were analyzed in E mode (Figure ) with extraction repetitions. Figure 7. orrelation coefficients of E extractions on the identified solvents from real samples of transparent plastic film. 9 p F p R² =.998 repetition # ln area R² = 9 repetition # 8. inutes Figure. hromatograms of E extractions from real samples of transparent plastic film.

6 Each residual solvent present in the sample was quantified using hromeleon DS (Table ). Table. mount of residual solvents present in the real samples of transparent plastic film. Residual Solvent Found mount mg/m onclusion The data obtained in this application demonstrate that the technique of headspace gas chromatography using E in an automated fashion easily meets the requirements of the E 8-: standard and provides excellent quantitation results without any sample preparation. ll the quality criteria requested by the method were verified, including the linearity of E curves for all solvents tested. The system configuration of the TRE, Trilus eadspace utosampler, and hromeleon DS proved to be a solid, fully integrated, easy-to-use and reliable platform to perform this analysis with a great degree of automation, from sample analysis to data reporting. With its -vial sample tray and the large 8-vial incubation oven overlap capacity, the Trilus eadspace valve-and-loop autosampler guarantees excellent throughput allowing the analysis of multiple samples at once and ensuring true weekend-long operations. pplication ote 9 Reference. E 8- ctober ackaging. Flexible packaging material Determination of residual solvents by static headspace gas chromatography. art : bsolute methods.. Kolb,., Ettre,.S., Static eadspace hromatography, Theory and ractice. Wiley-V, pp.. Thermo Fisher Scientific nc. ll rights reserved. S is a trademark of the nternational Standards rganization. Sigma ldrich is a trademark of Sigma ldrich o. ll other trademarks are the property of Thermo Fisher Scientific and its subsidiaries. This information is presented as an example of the capabilities of Thermo Fisher Scientific products. t is not intended to encourage use of these products in any manners that might infringe the intellectual property rights of others. Specifications, terms and pricing are subject to change. ot all products are available in all countries. lease consult your local sales representative for details. Thermo Fisher Scientific, ustin, TX US is S 9:8 ertified. frica + ustralia ustria elgium + 7 anada hina (free call domestic) 8 Denmark + 7 Europe-ther + Finland France ermany +9 8 ndia taly Japan +8 9 atin merica iddle East + etherlands ew Zealand orway Russia/S + Singapore Spain Sweden Switzerland UK + US E 8S