Talanta 80 (2009) 400–402
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Short communication
Solid-phase microcolumn extraction and gas chromatography–mass spectrometry identification of volatile organic compounds emitted by paper ˇ a,1 , Peter Tölgyessy b,∗ , Sona ˇ Figedyová c , Svetozár Katuˇscˇ ák c Ján Hrivnák a
Expertise and Analytical Services, Astrová 46, 821 01 Bratislava, Slovak Republic Water Research Institute, Nábreˇzie L. Svobodu 5, 812 49 Bratislava, Slovak Republic c Faculty of Chemical and Food Technology, Slovak University of Technology, Radlinského 9, 812 37 Bratislava, Slovak Republic b
a r t i c l e
i n f o
Article history: Received 19 March 2009 Received in revised form 10 June 2009 Accepted 15 June 2009 Available online 21 June 2009 Keywords: Gas chromatography Solid-phase microcolumn extraction Paper Volatile organic compounds Adsorption Tenax
a b s t r a c t A rapid non-destructive sampling technique for the analysis of volatile organic compounds (VOCs) emitted by paper sheets is described. A capillary, which is connected to a microcolumn packed with Tenax TA, is inserted between two sheets at the centre of a paper stack encapsulated inside a PET/Al/PE composite foil. The other end of the microcolumn is connected to a gas-tight syringe and an appropriate volume of gaseous phase is aspirated. The microcolumn is then thermally desorbed in a modified GC inlet (modification is presented) and analysed by gas chromatography–mass spectrometry (GC–MS). In the chromatogram from the analysis of artificially aged paper sample 21 compounds were identified. Advantages of the method including the short sampling time (1 min), simplicity and economic aspect are discussed. © 2009 Elsevier B.V. All rights reserved.
1. Introduction Paper emits a complex mixture of volatile organic compounds (VOCs) as it ages. Its composition depends on the nature of the paper, the degree of its degradation, and the pathway by which it degrades [1]. Identification, determination and evaluation of the ratios of different degradation products can be used for the evaluation of condition of aged paper material and it can be suitable for the comparison of the used and newly developed paper modification processes. Analytical methods applied for the evaluation of paper material condition and degree of its degradation can be divided into destructive (size-exclusion chromatography, viscosity measurements, etc.) and non-destructive ones (e.g. headspace methods) [2]. However, the non-destructive ones are the most suitable for examination of valuable artefacts. Recently, a non-destructive solidphase microextraction (SPME) method has been applied to the trapping and analysis of VOCs emitted during ageing of books [3,4]. The contact SPME coupled to GC–MS allowed the characterisation of more than 50 individual organic constituents and enabled
∗ Corresponding author. Tel.: +421 2 59343466; fax: +421 2 54418047. ˇ E-mail addresses:
[email protected] (J. Hrivnák),
[email protected] (P. Tölgyessy), sona.fi
[email protected] (S. Figedyová),
[email protected] (S. Katuˇscˇ ák). 1 Tel.: +421 903707897. 0039-9140/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.talanta.2009.06.035
to monitor relative abundances of the main degradation products. The aim of this work was the application of another recently introduced non-destructive sampling technique, the headspace solid-phase microcolumn extraction (HS-SPMCE), for the analysis of VOCs emitted by paper [5–7]. In the presented method, the loaded microcolumn was thermally desorbed in a modified GC inlet and VOCs were separated and detected by GC–MS.
2. Experimental 2.1. Sample and sampling procedure A sample of a newsprint paper (Jihoˇceské papírny, Vˇetˇrní, Czech Republic) was conditioned for 24 h according to ISO 187 at 23 ± 1 ◦ C, and at relative air humidity of 50 ± 1% [8]. Seventy-five sheets of paper (A5 format) were then encapsulated inside a polyethylene terephthalate/aluminium/polyethylene (PET/Al/PE) composite foil (Tenofan Al/116S) using Polystar 30D impulse tong sealer (Rische + Herfurth, Hamburg, Germany). The sample was submitted to accelerated temperature ageing at 98 ± 2 ◦ C during 15 days according to the ASTM D 6819-02 standard test method [9] in which sealed glass tubes were replaced by the PET/Al/PE foil. The PET/Al/PE foil was pierced and a deactivated fused silica capillary column (12 cm long, 0.25 mm I.D.) equipped with a glass press-fit connector (to protect the paper surface) was inserted
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Fig. 1. Sampling procedure: (1) PET/Al/PE foil, (2) sheets of paper, (3) press-fit connector, (4) fused silica capillary, (5) sorbent-packed microcolumn, (6) short flexible tubing, (7) glass tube, (8) wire for microcolumn manipulation and (9) gas-tight syringe.
10 cm deep between two sheets at the centre of a paper stack (Fig. 1). The exit end of the capillary was gas-tightly connected to the entrance end of the microcolumn. The other end of the microcolumn was attached to a 20-mL all-glass gas-tight syringe (Poulten & Graf, Wertheim, Germany) and 10 mL of gaseous phase was aspirated through it. 2.2. Apparatus Analyses were conducted using a Hewlett–Packard 6890GC–5972 MS system (Palo Alto, CA, USA) combination equipped with a modified split/splitless (S/SL) inlet. The inlet modification is shown in Fig. 2A (see also in [7]) and the Tenax TA (30 mg) packed glass microcolumn (specified in [5]) and the parts employed are shown in Fig. 2B. The inside of the entrance end of the microcolumn is conically broadened (as in glass press-fit connectors) to make a gas-tight connection when it is put on the end of a capillary column inserted into the bottom part of a glass tube chamber. To place a loaded microcolumn into the glass tube chamber, the modified upper part of the S/SL insert weldment with tubing has previously to be taken out and then replaced. For the separation of analytes a 60 m × 0.32 mm I.D. fused silica HPVOC/MS capillary column with a film thickness of 1.8 m was used. The GC column was temperature programmed from 50 ◦ C (2 min) to 120 ◦ C at 7 ◦ C/min and then to 270 ◦ C (10 min) at 14 ◦ C/min. Desorption of the loaded microcolumn was accomplished at the inlet temperature of 250 ◦ C and a carrier gas (helium) pressure of 5 kPa during 1 min. After desorption, the carrier gas pressure was increased to 50 kPa at 100 kPa/min and maintained at this value for the rest of the analysis. The split ratio in the modified inlet was adjusted to 100:1. Gas chromatographically separated compounds were detected by MS operating in the scan mode scanning from 10 to 300 at 2.59 scans/s. Temperatures of the MS ion source and of the GC–MS interface were 170 ◦ C and 280 ◦ C, respectively. Identification of mass spectra of the detected compounds was carried out by computer matching against an Agilent Wiley7n mass spectra library (Agilent Technologies, USA).
Fig. 2. (A) The split/splitless inlet modification for thermal desorption of a microcolumn: (1) upper part of S/SL insert weldment with tubing, (2) lower nut, (3) inserted microcolumn. (B) The sorbent-packed glass microcolumn and parts employed: (1) upper nut, (2) lower nut, (3) glass tube chamber, (4) microcolumn and (5) wire for microcolumn manipulation.
3. Results and discussion As an example of the method application, a chromatogram from the analysis of the headspace of the artificially aged paper sample is shown in Fig. 3A. In 10 mL of the gaseous phase that had been in contact with the paper stack, 21 organic compounds were identified. The chromatogram (Fig. 3B) of the blank SPMCE–GC–MS analysis of 10 mL of air taken from the empty composite foil bag was clean. The obtained qualitative data together with information on relative abundances of degradation products can be used for the characterisation of the paper condition [2–4]. So far, no method is available in the literature which would allow the determination of the VOCs content in paper material quantitatively on the basis of their concentration in the gaseous phase. For the quantitative VOCs analysis in paper destructive methods can be used, too. However, those are not appropriate for the testing of valuable historic documents. The advantage of using microcolumn adsorption lies in short sampling times (in our case 1 min) in comparison with the SPME
Fig. 3. Chromatograms from the SPMCE–GC–MS analysis (A) of the headspace of the artificially aged paper sample and (B) of the blank run. Peaks: (1) acetone; (2) methyl acetate; (3) 2,3-butanedione; (4) acetic acid; (5) methyl propanoate; (6) 2,3pentanedione; (7) pentanal; (8) toluene; (9) octane; (10) hexanal; (11) furfural; (12) decane; (13) 2-pentylfuran; (14) alpha-terpinene; (15) 1,2,3,4-tetramethylbenzene; (16) limonene; (17) undecane; (18) benzoic acid; (19) dodecane; (20) tridecane; (21) 1-methylethyl tetradecanoate.
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method, in which sampling takes tens of minutes. In the studies [3,4] describing the use of contact SPME for the analysis of VOCs emitted by naturally aged book, the applied sampling times varied from hours to several days, which is not convenient for practical purposes. Another advantage of a method operating up to the adsorbent packing breakthrough capacity, is that the amount ratios of analytes trapped in the microcolumn are comparable with the ratios in the aspirated gaseous phase. In the case of SPME the ratios of the fibre-sorbed analytes depend on the sampling time and the equilibrium is shifted towards the higher boiling components with increasing time. As a result, the use of the microcolumn method is more advantageous for trapping of more volatile compounds. The simple modification of the GC inlet presents an inexpensive alternative to the commercially available thermal desorption systems. The modified inlet can be reversed to its initial S/SL status in a few minutes. During the analysis run, the microcolumn remains inside the GC inlet and is flushed by the carrier gas, so there is no need of subsequent conditioning of the adsorbent. In the case of analysis of higher concentrations of less volatile compounds, the
carryover can be eliminated by repeating the thermal desorption of the microcolumn. The microcolumn makes it possible to analyse hundreds of samples without significant distortion. References [1] T. Doering, P. Fischer, G. Banik, U. Binder, J. Liers, Adv. Print. Sci. Technol. 27 (2001) 27–39. [2] A. Lattuati-Derieux, S. Bonnassies-Termes, B. Lavédrine, J. Cult. Herit. 7 (2006) 123–133. [3] A. Lattuati-Derieux, S. Bonnassies-Termes, B. Lavédrine, J. Chromatogr. A 1026 (2004) 9–18. ´ J. Kolar, G. de Bruin, B. Pihlar, Sensors 7 (2007) 3136–3145. [4] M. Strliˇc, I.K. Cigic, ˇ [5] P. Tölgyessy, J. Hrivnák, J. Chromatogr. A 1127 (2006) 295–297. ˇ [6] P. Tölgyessy, B. Vrana, J. Hrivnák, Chromatographia 66 (2007) 815–817. ˇ ´ J. Occup. Health 51 (2009) [7] J. Hrivnák, E. Král’oviˇcová, P. Tölgyessy, J. Ilavsky, 173–176. [8] ISO 187:1990, Paper, Board and Pulps. Standard Atmosphere for Conditioning and Testing and Procedure for Monitoring the Atmosphere and Conditioning of Samples, International Organization for Standardization, Geneva, Switzerland. [9] ASTM D6819-02:2002, Standard Test Method for Accelerated Temperature Ageing of Printing and Writing Paper by Dry Oven Exposure Apparatus, American Society for Testing and Materials, West Conshohocken, PA, USA.