Atmospheric Solid Analysis Probe–Ion Mobility Mass Spectrometry of

Article pubs.acs.org/ac

Atmospheric Solid Analysis Probe−Ion Mobility Mass Spectrometry of Polypropylene Caroline Barrère,†,‡,§ Florian Maire,†,‡,§ Carlos Afonso,*,†,‡,§ and Pierre Giusti⊥ †

Université de Rouen, IRCOF, rue Tesnière, 76130 Mont-Saint-Aignan, France INSA de Rouen, avenue de l’Université, 76801 Saint Etienne du Rouvray, France § CNRS UMR 6014, COBRA, rue Tesnière, 76130 Mont-Saint-Aignan, France ⊥ TOTAL Refining and Chemicals, European Research and Technical Center, 76700 Harfleur, France ‡

S Supporting Information *

ABSTRACT: Polyolefin, including polypropylene (PP), constitutes an important class of materials. In particular, the recent interest in recycling plastic wastes necessitates their characterization as well as their degradation mechanism being understood. PP materials characterization by mass spectrometry, including polymer and additives parts, is not direct and generally involves a pyrolysis step to produce ionizable species. In this study, we extended the use of atmospheric solid analysis probe (ASAP) in combination with traveling wave ion mobility mass spectrometry (TWIM-MS) for the characterization of PP materials, including polymer as well as additives. Different commercial PP samples, from polymer standard to plastic item, were studied. The use of ASAP allow analysis to be done without any sample preparation, while TWIM-MS permitted a clear separation of polymer ions and additive signals. Several series of polymer pyrolysis residues, similar to those produced by classic pyrolysis, were obtained. Moreover, additive characterization has been done and supported by accurate mass measurements and tandem mass spectrometry experiments. Finally, this strategy put in evidence the role of additives in polymer degradation.

P

cleavage of PP chain. Then, a backbiting mechanism allows a more stable tertiary radical to be obtained. To finish, a cascade of radical reaction, including homolytic cleavage and H• abstraction or addition, leads to six distributions of residue, referred to as A to F letters, shown in Scheme 1. These distributions have been classified by Lattimer in three classes. The first class, including distributions with molecular weight of A: Mw = 42.047n, B: Mw = 42.047n + 14.016; C: Mw = 42.047n + 28.031, corresponds to residues with one double bond, i.e., n is the number of propylene units. The second class of distribution having molecular weight of D: Mw = 42.047n + 30.047 corresponds to saturated residues. The last class with distributions with molecular weight of E: Mw = 42.047n + 12.000 and F: Mw = 42.047n + 40.031 presents two double bonds. In other works, Lattimer reported the characterization of different polyolefins including polyethylene and polyisobutylene with the same strategy.5 As an alternative to pyrolysis, different approaches have been proposed for analysis of intact polyolefins.6,7 For instance, Yalcin et al. have developed a metal powder substrate assisted laser desorption ionization time-offlight (TOF) MS strategy for polyethylene characterization.6 Their strategy uses the assistance of cobalt metal powder rather

olyolefins and in particular polypropylene (PP) constitute a very important class of polymer. They are very attractive due to their excellent material properties and interesting cost/ performance ratio leading to a wide range of applications, from food packaging to pipet tip. In recent years, the growing interest in recycling plastic wastes increases the necessity to characterize well PP samples as well as understand their degradation mechanism. Industrial polymer materials contain additives to protect them from degradation during processing or outdoor exposure, resulting from reaction with O2 or UV light. Several classes of additives, such as antioxydant or UV stabilizers, are used together to optimize polymer stability.1,2 Thus, the full analysis of commercial materials includes characterization of both stabilizers and polymer. While additives were generally easily characterized, PP was particularly difficult to analyze by mass spectrometry (MS). Indeed, due to its aliphatic nature, it has no organic function allowing cation attachment and is too large for classical electron ionization. Therefore, the classical way reported to study polyolefins involves a step of pyrolysis before MS analysis.3 For instance, Lattimer reported the characterization of several polypropylenes by pyrolysis followed by gas chromatography and mass spectrometry (Py-GC/MS) analysis, using various ionization sources such as electron ionization, chemical ionization, or field ionization. He described both characterizations of stabilizers and PP pyrolysis residues.4 Radical mechanisms were proposed to explain the formation of the different PP ion series. First, pyrolysis induces a homolytic © 2012 American Chemical Society

Received: July 25, 2012 Accepted: October 8, 2012 Published: October 8, 2012 9349

dx.doi.org/10.1021/ac302109q | Anal. Chem. 2012, 84, 9349−9354

Analytical Chemistry

Article

PP.14 More recently, Trimpin et al. have shown that the ASAP probe could be used for a simultaneous identification of stabilizer and ions resulting from thermal decomposition of polyethylene terephtalates (PET) and polyamide.15 Whitson et al. have used direct probe strategy with atmospheric pressure chemical ionization for the characterization of cross-linked copolymers.16 Lattimer and Polce also used direct probe APCI as well as direct probe chemical ionization for the analysis of different materials as plastic sheet, acrylic latex, or coated paper.17 They observed pyrolysis residue and several stabilizers. Identification of stabilizers in PP samples was also realized using the direct analysis in real time (DART) source which is an atmospheric ionization source presenting some analogies with ASAP.18 Indeed, due to its ability to characterize polymer directly with no sample preparation, the direct insertion probe technique, such as ASAP, was interesting for simultaneous characterization of polymer and stabilizers.19 However, this method yields to the simultaneous ionization of all the species present in the polymer, which can yield to complex mass spectra. Ion mobility (IM) is a postionization separation method based on drift of ions in a gas-filled tube under the influence of an electric field. Interfaced to MS, IM adds an extra dimension, which is a function of charge (z), mass (m), and collision crosssection (Ω) of the ions. Traveling wave ion mobility (TWIM) is a type of IM based on low-voltage waves pushing the ions across a gas-filled ion guide.20 TWIM cell was incorporated recently in commercially available hybrid quadrupole/time-offlight mass spectrometers.20,21 While the combination of TWIM and MS was essentially applied for biomolecules, it was recently successfully used for synthetic polymers analysis by several authors.22−24 In this work, we propose to use the combination of ASAP and TWIM-MS to characterize PP materials including stabilizer and polymer part. AP-Py of PP allowed by ASAP gives volatile and ionized species, which were then separated and analyzed by TWIM-MS.

Scheme 1. Structures Proposed by Lattimer for the Six Distributions of PP Pyrolysis Residue Observed by Py-GC/ MS

than classical matrix and silver nitrate as cationizing agent to produce intact polyethylene ions in the gas phase. Schwarzinger et al. have also used MALDI-TOF-MS for a quantitative analysis of different additives in polymer sample.8 The activity of the different stabilizers as well as their quantification was an important point of material characterization. In particular, the photostabilizing effect of hindered amine light stabilizers (HALS), currently not fully understood, was widely studied. Tagushi et al. used MALDI-TOF-MS to study HALS and their photostabilizing action in PP materials. They developed a solid sampling method to avoid the difficulty of solvent extraction and studied the structural changes of HALS due to UV irradition.9 More recently, they extended this method to quantitative analysis of HALS.10 In their works, Coulier et al. used Py-GC/MS and high performance liquid chromatography (HPLC) in combination with different detectors. Py-GC/MS experiments allowed structural identification of HALS to be performed while quantification was permitted by the use of a combination of detectors during HPLC experiments.11 Lowe et al. have studied the modification of HALS structure due to oxidative conditions in complex polymer matrixes. The structural characterization was performed by tandem mass spectrometry experiments (MS/MS) using electrospray ionization.12 Many strategies have been developed for the characterization of PP materials, including polymer and stabilizer. Most of them included a time-consuming step of solvent extraction, chromatographic separation, and/or an important sample preparation process. In order to simplify and shorten the analytical process, an alternative method such as atmospheric solid analysis probe (ASAP) can be used. ASAP was developed by McEwen in 2006 as an atmospheric ionization source for rapid analysis by mass spectrometry with no sample preparation.13 This probe consists of a glass capillary tube on which a liquid or solid sample was deposited. A heated gas flow is used for thermal desorption of compounds. Plasma was generated by a corona discharge, which allows ionization to occur. McEwen has shown that ASAP could be used for atmospheric pressure pyrolysis (AP-Py) of polymer such as

■

EXPERIMENTAL SECTION Samples. Three samples of PP were used in this study. PP1 (Mn ∼ 3700 g mol−1; Mw ∼ 14 000 g mol−1; melting point: 158 °C) and PP3 (Mn ∼ 5000 g mol−1; Mw ∼ 12 000 g mol−1; melting point: 154 °C) were purchased from Sigma Aldrich (St. Louis, MO). PP2 was a pipet tip of 10 μL (melting point: 166 °C) used as purchased. Mass Spectrometry. Data acquisitions were performed using a SYNAPT G2 HDMS fitted with an ASAP source (Waters Corp., Manchester, UK). This instrument is a hybrid quadrupole/time-of-flight mass spectrometer, which incorporates a traveling wave (T-Wave)-based mobility separation device. The instrument and the T-Wave device have been described in detail elsewhere.20,21 For simplicity, the three samples were heated to their melting point in a glass bottle. ASAP capillary tube was dipped in the melt polymer before cooling at room temperature. Indeed, because PP materials were thermoplastics, they could be melted without degradation. ASAP was conditioned to experimental temperature during 1 h before experiments. Finally, the capillary tube was fixed to the ASAP probe holder and introduced in the ionization source. For all experiments, ASAP mass spectra were acquired in positive ion mode during 10 min over the m/z 50−2000 range. Note that a blank was recorded during 1 min before sample introduction. A nitrogen flow of 1200 L h−1 heated at 650 °C 9350

dx.doi.org/10.1021/ac302109q | Anal. Chem. 2012, 84, 9349−9354

Analytical Chemistry

Article

was used for thermal desorption. The corona discharge voltage was 4 kV, and sampling cone voltage was 40 V. Trap and transfer collision gas flow were set at 2.0 mL min−1 (0.02 mbar for Ar cell pressure). Helium cell gas flow was set at 180 mL min−1, and IMS gas flow (N2) was set at 70 mL min−1 of 3.0 mbar for IMS cell pressure. TWIM traveling wave height and velocity were set, respectively, at 40 V and 600 m s−1. Argon was used as target gas for MS/MS experiments. Data acquisition and mass spectra treatment were provided by MassLynx (version 4.1). DriftScope (version 2.1) software was used for the treatment of m/z vs drift-time maps. Note that the peak at m/z 277.0777 observed on mass spectrum is a background ion of the ASAP source; it corresponds to a fragment ion (loss of H•) of triphenylphosphine oxide (C18H14OP), present in flame retardant. This background ion is used as internal standard for accurate mass measurement.

■

RESULTS AND DISCUSSION First, it is important to be precise with the mechanisms involved in the ASAP positive ionization mode (Scheme 2).25,26 Scheme 2. Mechanisms Involved in the Positive ASAP Process for an Analyte A, with n = 1−4

As proposed in Scheme 2, ionization can occur (i) by proton transfer from residual H3O+ ions if the analyte is more basic than water or (ii) by charge transfer from N2+• ion if the ionization energy (IE) of the analyte is lower than that of N2 (IE(N2) = 15.6 eV). We can assume that Penning ionization may also take place in the ionization source as metastable N2* species are expected to be produced within the plasma, but this should be a minor process as its excitation energy is fairly low (8.52 eV).27 Nonpolar compounds such as PP or stabilizers are preferentially ionized by charge transfer mechanism. Moreover, it is important to note that this ionization process can be highly exothermic and produces fragmentation that can be similar to low energy EI.14 It should be noted that the main difference between the ASAP ionization and the atmospheric pressure chemical ionization (APCI) is the absence of any solvent, which attenuates the role of proton transfer reactions.28,29 The results of ASAP-TWIM-MS experiments for PP1 and PP2 were similar and, respectively, shown in Figures 1a and 2a. These 2D plots present m/z ratio on the x-axis and drift time of the detected ions (tD in ms) on the y-axis. In both cases, the m/z-drift time plots present two diagonals, which can be individually used. Stabilizers Characterization. In the case of PP1, the diagonal with lower slope corresponds to ions having lowest drift-times (i.e., ions with low collision cross sections). The extracted mass spectrum (Figure 1b) shows a peak distribution separated by 56 u. The highest m/z value at 1176.8 could correspond to the molecular ion (M+•) of an antioxidant, Irganox 1010 (C73H108O12). We assume that this ion is subjected to in-source fragmentation, which leads to successive

Figure 1. ASAP-TWIM-MS results of PP1 sample. (a) m/z-drift time and the extracted mass spectrum obtained, respectively, for (b) stabilizers and (c) pyrolysis products.

losses of terbutyl group (56 u). The diagonal, corresponding to ions that present the highest drift-times (i.e., ions with large collision cross-section), shows a superposition of ion distributions (see Figure 1c). The most intense peaks at m/z 530.5 and m/z 682.6 could be attributed to the molecular ions of other antioxidants, Irganox 1076 (C35H62O3) and Irganox PS 802 (C42H82O4S). Note that all identification of stabilizers was supported by accurate mass measurements (see Supporting Information). The ion at m/z 530.5 was selected and collisionally activated. These results (see Supporting Information Figure S3) show fragment ions at m/z 219.2, 263.2, 459.4, 474.4, and 515.6. The same series of ions was already observed in the ASAP mass spectrum and could be attributed to Irganox 1076 molecular ion in-source fragments. We can note that for PP1, only one stabilizer, Irganox 1010 was clearly separated from PP pyrolysis residues. This could be explained regarding 9351

dx.doi.org/10.1021/ac302109q | Anal. Chem. 2012, 84, 9349−9354

Analytical Chemistry

Article

only few organic functions, not sufficient to induce significant differences in term of collision cross section needed to obtain a separation on the m/z-drift time plot. On the contrary, Irganox 1010 have a star-like 3-dimensional structure with a carbon atom as core yielding a more compact structure, sufficiently different from PP pyrolysis residue to obtain a separation by TWIM. In the case of PP2, the spectrum corresponding to the diagonal with lower slope is given in Figure 2b. As previously mentioned, the extracted mass spectrum shows several distributions of peak separated by 56 u that could be attributed to Irganox 1010 in source fragment ions. The diagonal with higher slope shows intense signals whose spectrum is given Figure 2c. This spectrum highlights a peak at m/z 646.5 corresponding to the molecular ion of the antioxidant Irgafos 168 (C42H63O3P). We can note an overlapping of spectrum shown in Figure 2c,d for Irgafos 168 ion at m/z 646.5. As proposed by Trimpin et al., the peak at m/z 662.5 could be assign to oxidized Irgafos 168 ion.15 Moreover, tandem mass spectrometry experiment with m/z 646.5 as precursor ion allows the ion at m/z 441.3 to be identified as a fragment of molecular ion of Irgafos 168 (see Supporting Information Figure S4). In the same way of that for PP1, Irganox 1010 was clearly separated from PP pyrolysis residues on the m/z-mobility plot. Moreover, Irgafos 168, as well as oxidized Irgafos 168, presents star-like 3-dimensional structures with a phosphorus atom as core, leading to significant differences in term of collision cross section, compared to PP pyrolysis residues or Irganox 1010, allowing their separation by TWIM. Polymer Characterization. Concerning PP1, the spectrum in Figure 1c shows several distributions of peaks, separated by 42 u from m/z 500 to m/z 1100. As proposed by McEwen, these ion distributions could be attributed to AP-pyrolysis products of PP.14 An expanded view given Figure 3a allowed five ion distributions to be detected A: Mw= 42.047n, B: Mw = 42.047n + 14.016, C: Mw = 42.047n + 28.031, E: Mw = 42.047n + 12.000, and F: Mw = 42.047n + 40.031, which is consistent with Lattimer results.4 The distribution A was detected as the most intense with a relative intensity of 95%. The distributions C and F have similar intensity (65%), while distributions E and B were slightly lower with, respectively, relative intensity of 40% and 30%. An additional intense distribution, with a relative intensity of 50% and corresponding to Mw = 42.047n + 26.015, hereafter referred as X, was also observed. We assume that this new distribution could come from a degradation process similar to that observed for F, including an abstraction/loss of CH3• instead of H• and probably leading to a species with two double bonds at the chain ends. As expected with an energetic ionization source such as ASAP, several additional distributions were detected to a lesser extent and could be explained by insource fragmentation from the main distributions. Moreover, compared to the Lattimer results, we can note the absence of distribution D. Indeed, this distribution necessitates an H• addition during the pyrolysis process, while a distribution C presenting a similar mechanism with an H• abstraction is observed. This could be explained by additional radical reaction occurring in the gas phase at atmospheric pressure due to the presence of N2+•. Under such conditions, ion−molecule reactions can take place, promoting radical abstraction rather than radical addition. Concerning PP2, the extracted mass spectrum of pyrolysis was shown in Figure 2d. The expanded pyrolysis residue spectra of the different samples were

Figure 2. ASAP-TWIM-MS results of PP2 sample. (a) m/z-drift time plot and the extracted mass spectrum obtained, respectively, for (b) Irganox 1010, (c) Irgafos 168, and (d) PP pyrolysis products.

the 3-dimensional structure/collision cross-section of the different ions. Indeed, pyrolysis residues of PP were linear carbon chains, which yield a relatively high drift-time. Irganox 1076 as well as Irganox PS 802 present similar structures with 9352

dx.doi.org/10.1021/ac302109q | Anal. Chem. 2012, 84, 9349−9354

Analytical Chemistry

Article

Figure 3. Expansion of pyrolysis residue spectra obtained for the different samples (a) PP1, (b) PP2, and (c) PP3.

spectrum of PP3 and could be, respectively, explained by H• or CH3• losses. Other fragment ions, also observed on MS spectra, were detected at m/z 501.6 and m/z 543.6. These results seem to indicate that PP3 is more advanced on the pyrolysis cascade of radical reaction than PP1 or PP2. These polymers were quite similar in terms of molecular weight or melting point, not allowing this difference of distribution to be explained. We assume that the presence of stabilizer prevents degradation of PP1 and PP2 samples.

compared in Figure 3. We can see that the same distributions were observed for PP1 and PP2 with similar relative intensity. Indeed, for PP2, the distribution A was also detected as the most intense at a relative intensity of 85%. The distributions C, X, E, and F have similar relative intensity compared to PP1, respectively, 80%, 50%, 45%, and 45%. Only distribution B presents a higher relative intensity at 80%. Finally, the main distributions observed using ASAP-TWIMMS technique were similar to those obtained by the classical pyrolysis approach. However, this ionization technique involving AP-pyrolysis allows additional residues from a longer degradation process, to be obtained compared to classical pyrolysis. Influence of Stabilizers on PP Degradation. The previous results show that the ASAP-TWIM-MS approach gives similar spectra to the classical pyrolysis approach, for comparable commercial PP samples, i.e., samples containing stabilizers (PP1 and PP2). An additional commercial sample PP3 was then analyzed in the same conditions as those previously mentioned. We can see on the m/z-drift time plot presented in Figure 4a that no stabilizers could be detected for this sample. The extracted mass spectrum of the polymer pyrolysis products presented in Figure 4b is significantly different than those obtained for the previous samples. We can see on the expanded spectrum presented in Figure 3c that the distributions E and F, coming from a longer degradation process, were clearly more intense than for PP1 or PP2. Indeed, they were, respectively, detected at 90% of relative intensity in PP3 vs 45−65% for PP1 and PP2. In the contrary, distributions A, B, and C have almost disappeared. Indeed, they were detected with relative intensity lower than 20% while they were the most intense, with relative intensity globally higher than 50% for PP1 and PP2. Only the distribution X presents a similar relative intensity for the three samples. Moreover, additional intense ion distributions were observed. To identify these new distributions, the ion at m/z 642.7 from distribution E was selected for tandem mass spectrometry experiments. The obtained spectrum, presented in Figure 4c, shows fragment ions at m/z 641.7 and m/z 627.7. Both were observed in the mass

■

CONCLUSION

These results show that ASAP is a convenient ionization source for the study of PP materials, including stabilizers and polymer part. Several antioxidants as well as UV light stabilizers were readily detected in PP1 and PP2 samples without any sample preparation. The use of TWIM-MS analysis in combination with ASAP overcomes the overlapping of stabilizers and PP pyrolysis residue signals. Moreover, we have shown that AP-Py gives similar results to those obtained by classical pyrolysis for comparable compounds (i.e., containing stabilizers). For PP3 sample, for which no stabilizers were detected, a different pattern of pyrolysis residues was observed. MS/MS experiments allow smaller pyrolysis residues, due to a longer degradation process, to be characterized. These differences on pyrolysis pattern were attributed to the absence of stabilizers in PP3 sample. These results were of particular interest for the study of stabilizer activity. Until now, many studies were interested in the action of the different class of polymer additives, but because PP was particularly difficult to characterize, they focused mainly on additive structural modifications after UV light exposure, for example. The combination of ASAP and TWIM-MS is a novel and powerful approach for the study of stabilizer activity, allowing stabilizers and polymer characterization at the same time. This coupling offers the ability to ionize hydrocarbon species by charge exchange reactions and to separate polymer pyrolysis products from additives by the postionization ion mobility separation. Finally, the MS/MS experiment could provide additional structural information for mechanistic study of the stabilizing activity. 9353

dx.doi.org/10.1021/ac302109q | Anal. Chem. 2012, 84, 9349−9354

Analytical Chemistry

■

Article

ACKNOWLEDGMENTS We thank the Region Haute-Normandie, ERDF funding (UE) and Total Refining and Chemicals for financial support. We thank also Mr. Majed Rejaibi for polymer melting point measurements.

■

(1) Gachter, R. Plastics additives Handbook; Hanser/Gardner: Cincinnati, OH, 1996. (2) Chen, S. W.; Her, G. R. Appl. Spectrosc. 1993, 47, 844−851. (3) Blazso, M. J. Anal. Appl. Pyrolysis 1997, 39, 1−25. (4) Lattimer, R. P. J. Anal. Appl. Pyrolysis 1993, 26, 65−92. (5) Lattimer, R. P. J. Anal. Appl. Pyrolysis 1995, 31, 203−225. (6) Yalcin, T.; Wallace, W. E.; Guttman, C. M.; Li, L. Anal. Chem. 2002, 74, 4750−4756. (7) Campbell, J. L.; Fiddler, M. N.; Crawford, K. E.; Gqamana, P. P.; Kenttaemaa, H. I. Anal. Chem. 2005, 77, 4020−4026. (8) Schwarzinger, C.; Gabriel, S.; Beibmann, S.; Buchberger, W. J. Am. Soc. Mass Spectrom. 2012, 23, 1120−1125. (9) Taguchi, Y.; Ishida, Y.; Ohtani, H.; Matsubara, H. Anal. Chem. 2004, 76, 697−703. (10) Taguchi, Y.; Ishida, Y.; Matsubara, H.; Ohtani, H. Rapid Commun. Mass Spectrom. 2006, 20, 1345−1350. (11) Coulier, L.; Kaal, E. R.; Tienstra, M.; Hankemeier, T. J. Chromatogr., A 2005, 1062, 227−238. (12) Lowe, T. A.; Paine, M. R. L.; Marshall, D. L.; Hick, L. A.; Boge, J. A.; Barker, P. J.; Blanksby, S. J. J. Mass Spectrom. 2010, 45, 486−495. (13) McEwen, C. N.; McKay, R. G.; Larsen, B. S. Anal. Chem. 2005, 77, 7826−7831. (14) McEwen, C. N. In Encyclopedia of Analytical Chemistry; John Wiley & Sons, Ltd: Chichester, UK, 2006. (15) Trimpin, S.; Wijerathne, K.; McEwen, C. N. Anal. Chim. Acta 2009, 654, 20−25. (16) Whitson, S. E.; Erdodi, G.; Kennedy, J. P.; Lattimer, R. P.; Wesdemiotis, C. Anal. Chem. 2008, 80, 7778−7785. (17) Lattimer, R. P.; Polce, M. J. J. Anal. Appl. Pyrolysis 2011, 92, 355−360. (18) Haunschmidt, M.; Klampfl, C. W.; Buchberger, W.; Hertsens, R. Analyst 2010, 135, 80−85. (19) Hacaloglu, J.; Hakkarainen, M. Springer: Berlin/Heidelberg, 2012; Vol. 248, pp 69−103. (20) Giles, K.; Pringle, S. D.; Worthington, K. R.; Little, D.; Wildgoose, J. L.; Bateman, R. H. Rapid Commun. Mass Spectrom. 2004, 18, 2401−2414. (21) Giles, K.; Williams, J. P.; Campuzano, I. Rapid Commun. Mass Spectrom. 2011, 25, 1559−1566. (22) Hoskins, J. N.; Trimpin, S.; Grayson, S. M. Macromolecules 2011, 44, 6915−6918. (23) Trimpin, S.; Clemmer, D. E. Anal. Chem. 2008, 80, 9073−9083. (24) Song, J.; Grün, C. H.; Heeren, R. M. A.; Janssen, H.-G.; van den Brink, O. F. Angew. Chem., Int. Ed. 2010, 49, 10168−10171. (25) Horning, E. C.; Horning, M. G.; Carroll, D. I.; Dzidic, I.; Stillwel, Rn Anal. Chem. 1973, 45, 936−943. (26) Good, A.; Durden, D. A.; Kebarle, P. J. Chem. Phys. 1970, 52, 212−221. (27) Boutin, M.; Lesage, J.; Ostiguy, C.; Bertrand, M. J. J. Anal. Appl. Pyrolysis 2003, 70, 505−517. (28) Gao, J.; Owen, B. C.; Borton, D. J., 2nd; Jin, Z.; Kenttamaa, H. I. J. Am. Soc. Mass Spectrom. 2012, 23, 816−822. (29) Yang, Z.; Attygalle, A. B. J. Am. Soc. Mass Spectrom. 2011, 22, 1395−1402.

Figure 4. ASAP-TWIM-MS results of PP3 sample including (a) the m/z-mobility plot and (b) the extracted mass spectrum. (c) MS/MS spectrum of m/z 642.7 ion (pyrolysis product from distribution E) obtained with a ramp of energy in center-of-mass frame from 1.2 to 1.3 eV.

■

ASSOCIATED CONTENT

S Supporting Information *

Additional information as noted in text. This material is available free of charge via the Internet at http://pubs.acs.org.

■

REFERENCES

AUTHOR INFORMATION

Corresponding Author

*Tel.:+33.2.35.52.29.24. Fax:+33.2.35.52.24.41. E-mail: carlos. [email protected]. Notes

The authors declare no competing financial interest. 9354

dx.doi.org/10.1021/ac302109q | Anal. Chem. 2012, 84, 9349−9354