Direct Monitoring of the Role Played by a Stabilizer in a Solid Sample

Article pubs.acs.org/ac

Direct Monitoring of the Role Played by a Stabilizer in a Solid Sample of Polymer Using Direct Analysis in Real Time Mass Spectrometry: The Case of Irgafos 168 in Polyethylene Kevin Fouyer,† Olivier Lavastre,*,† and David Rondeau*,†,‡ †

Institut d’Electronique et de Télécommunication de Rennes (IETR UMR CNRS 6164), Université de Rennes 1, Campus de Beaulieu, 263 Avenue du General Leclerc, 35042 Rennes Cedex, France ‡ Université de Bretagne Occidentale, Département de Chimie, 6 Avenue le Gorgeu, 29238 Brest Cedex 03, France S Supporting Information *

ABSTRACT: Direct analysis in real time (DART) ionization method is used with a time-of-flight (TOF) mass spectrometer to perform the analysis of industrial polyethylene pellets free of additives or containing Irgafos 168 as stabilizing agent without any sampling step. The developed analytical method uses the [M + H]+ ion of the bis(2-ethylhexyl) phthalate (DEHP) for performing the exact mass measurements of the stabilizer and polymer ions using the mass drift compensation procedure available on the AccuTOF mass spectrometer. DEHP is in fact a plastic contaminant always presents on the mass spectra of the analyzed samples. The mass spectra allow one to characterize either the ions of the polyethylene and that of the Irgafos. The analysis of thermally treated samples show that the polymer does not undergo any degradation when the Irgafos is present in the bulk of the material, and the role played by the Irgafos 168 is that of an oxygen trapping agent. Under UV exposure, the DART-TOF MS analyses performed on the exposed polyethylene pellets shows that the Irgafos 168 behavior toward the UV radiations is different since this one reacts by cleavages of its P−O bonds to prevent the degradation of the polymer. These interpretations are supported by all the elemental formula determination of the detected ions.

T

certain induction time when the stabilizers have fully reacted and are lost from the substrate. In others words, if the polymeric material is exposed several times to oxidative conditions, the stabilizers could be totally consumed and the degradation process could start inducing color modification or loss of mechanical properties. It is then important to detect and characterize the stabilizers remaining in the polymer bulk in order to predict the behavior of the material. A fast evaluation method of the real concentration of stabilizers for polymeric materials is an important issue, particularly to control the quality of material or to check if the long-term storage or a specific process did not consume any stabilizers. However, the classical analytical procedures used to determine the amount and the behavior of these additives in polymers require the association of extraction steps and separation methods such as the chromatographic techniques that can be coupled or not with mass spectrometry characterization.10−13 Such procedures are too laborious and time-consuming to offer a fast and straightforward analysis of remaining stabilizing agents. The introduction of ambient desorption ionization methods associated with high-resolution or MS/MS mass spectrometry,

he degradation of polymers such as polyethylene (PE) can be described through a simplified scheme regrouping the major results reported in many reviews (see Figure 1).1−4 The initial step is the homolytic C−H bond cleavage of the polymer resulting from the heating during the melt processing and from the shear stresses during the extrusion step. The produced carbon-centered radical reacts with atmospheric oxygen to form a peroxyl radical that is converted to a hydroperoxide group by intermolecular hydrogen abstraction. Under heat or UV light, the β-scission of the hydroperoxide alkoxyl radical occurs to produce several types of oxygen-containing compounds. In order to avoid either the free radical propagation into the bulk of polymer and the build-up of radical initiators such as the hydroperoxides, stabilizing reagents are added to polymer materials.5 The hindered-amine stabilizers (HLAS) or the phenolic antioxidants are used for their radical scavenger ability, whereas the organic phosphites are described as protecting the polyethylene from the oxidative degradation by decomposing the hydroperoxides through the formation of the corresponding phosphates (see Figure 1).6−9 Stabilizer packages are used for stabilization of polymers. Several research or industrial groups are looking for new stabilizers, their chemistry, and their relative effect to protect polymers. However, this protective effect is proportional to the amount of remaining unaffected stabilizers. It is generally considered that the degradation of a polymer proceeds after a © 2012 American Chemical Society

Received: June 25, 2012 Accepted: September 18, 2012 Published: September 18, 2012 8642

dx.doi.org/10.1021/ac301759q | Anal. Chem. 2012, 84, 8642−8649

Analytical Chemistry

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helium is used, the atoms at a exited state have an internal energy Eint[He(23S)] = 19.8 eV. These ones induce a Penning ionization of the atmospheric water. In positive ion mode, the mechanism of ion production involves mainly the formation of ionized water clusters followed by a proton transfer reaction between the analyte (M) and the hydrated hydronium-ion clusters ((H2O)n+1) such as H+(H 2O)n + 1 + M → [MH]+ + (H 2O)n + 1

(1)

The gas-phase ionization of the sample described in eq 1 occurs if the proton affinity (PA) of the analyte is greater than that of the water cluster ((H2O)n+1), i.e., PA(M) > PA(H2O)n+1. The molecular ion formation by charge exchange reactions has been also described.36 This one involves either He(23S) or the atmospheric oxygen, the later being ionized during the primary DART process. This charge exchange process leads to the M•+ radical cation formation if the ionization energy (IE) of the analyte (M) is sufficiently low, i.e., IE(M) < Eint[He(23S)] or IE(M) < IE(O2) = 12.7 eV. In many cases such as alkane detection in DART, the molecular ion can lose a hydrogen atom to yield characteristic [M − H]+ species.36 A transient microenvironment mechanism (TMEM) has been also proposed to account for the solvent effects observed in DART-MS.37 For solvents such as methanol, ethanol, and acetonitrile, the odd-electron ion (S•+) produced from the solvent (S) reacts with the solvent aggregates (Sn) to produce protonated clusters [Sn + H]+ that will lead to a [M + H]+ ion formation from analyte molecules M if PA(M) > PA(Sn):

Figure 1. Simplified scheme illustrating the oxidative degradation of polyethylene (PE) and the type of activity of the stabilizing agents (in italic in the figure).

such as desorption electrospray ionization (DESI)14 and direct analysis in real time (DART),15 has allowed for minimizing the sample preparation steps by performing direct, rapid, and highthroughput analyses. In DESI, the analyte is deposited onto a surface and the charged droplets produced by a pneumatically assisted electrospray emitter are directed on this surface where they form an initial liquid layer.16 This layer undergoes the impact of further charged microdroplets for producing secondary ions by interaction with the neutral analyte.14,17 The interest of the DESI method has been demonstrated in many applications fields such as the detection of explosives,18,19 the analysis of agrochemical residues in food, or lipid characterization.20−22 Mass spectrometry of tryptic peptides and relatively high molecular weight proteins can been performed with the DESI source due to the typical electrospray mechanisms leading to the multicharged ion formation.23−26 The analysis of relatively low-molecular weight polymers was also performed in DESI-MS.27−29 However, to our knowledge, the direct detection of organic additives in rubbers by DESI-MS has never been reported in the literature. The different mass spectrometry methods dedicated to the direct analysis of stabilizers in polymer samples have mainly involved ionization sources such as electronic impact (EI), chemical ionization (CI), fast atom bombardment (FAB), field desorption (FD), laser desorption ionization (LDI), matrix-assisted laser desorption ionization (MALDI), and secondary ion mass spectrometry (SIMS).30−35 All these methods require the sample introduction in a chamber under vacuum. As a result, they cannot be used for the rapid detection of polymer stabilizers in a high-throughput analysis. The DART ionization can be then considered with a great interest in such context since it avoids additional solvent preparation steps that must be still taken into account when the DESI method is used. The description of the DART technique and its ionization mechanisms has been previously reported in the literature.15,36,37 DART is based on the interactions of a sample in a water containing ambient atmosphere with a gas in a metastable state heated to a temperature up to 250 °C. When

[Sn + H]+ + M → [M + H]+ + Sn

(2)

+

By contrast, [Sn + H] protonated clusters are not observed when aromatic solvents such as toluene or xylene are used. The solvent odd-electron ion (S•+) produces in fact the M•+ molecular ion from the analyte when IE(S) > IE(M): S•+ + M → M•+ + S

(3) +

One will also note that [M + NH4] ions have been observed in DART-MS when ammonia vapors are used as the NH4+ source for the detection of ammonium adducts from compounds of low polarity.38 The DART ionization has been used in drug analysis,38,39 forensic science,14,40 and food quality control.41−45 Different supports were also submitted to DART analysis, such as planar chromatography46 or self-assembled monolayers.47 The detection of polymer additives by DART from plastics, such as polypropylene or poly(vinyl chloride), has also been described.48−50 However, to our knowledge, no study has been reported in literature concerning the degradation of a stabilizing agent and its relation to polymer aging. In this paper, we report the possibility to use DART-TOF MS analysis for the rapid monitoring of a stabilizer, such as Irgafos 168 (see Scheme 1), directly in plastics, such as polyethylene pellets. DART ionization is also used to determine the real impact of the presence or the absence of the stabilizer on the degradation of the polyethylenes submitted to thermal or UV degradation. From the behavior of the stabilizer highlighted by DART-TOF MS, a protection mechanism of the Irgafos 168 during the thermal or UV treatment of the polyethylene is proposed.

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EXPERIMENTAL SECTION Materials. All the polyethylene (PE) pellets were obtained from Total Petrochemicals (Feluy, Belgium) and used without 8643



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a 12 W UV lamp (from Fischer Bioblock Scientific) at a 254 nm wavelength for 24 h. Mass Spectrometry. All analyses were performed using a JEOL JMS-T100CS (AccuTOF CS) orthogonal time-of-flight (TOF) mass spectrometer (Peabody, MA) equipped with an IonSense DART Source (Danvers, MA). Helium was used as the reagent gas at a flow rate of 3 mL min−1 and under a 190 °C temperature. DART was used in positive ion mode. The following DART-needle, discharge electrode, and the grid electrode voltage values used were 3000, 100, and 250 V, respectively. The voltage values of orifice 1, orifice 2, and the ring lens were set at 15, 5, and 10 V, respectively. The orifice 1 temperature was kept at 80 °C. The ion guide potential was kept at 750 V for a mass range comprised between 0 and 800 m/z. The detector voltage was set at 2300 V. The mass spectra were recorded every second and with a resolution of 6000 (fwhm definition). The mass scale was calibrated using the [M + H]+ ion series of a poly(ethylene glycol) (PEG 600) sample diluted in a water/methanol mixture (1:1) and analyzed with DART-MS. The mass drift compensation procedure available on the main program that controls the AccuTOF CS was used for compensating for the m/z drift in the range of m/z 200− 800 and performing the exact mass measurements of the analyzed sample. In this case, the m/z 391.2848 [M + H]+ ion of the bis(2-ethylhexyl) phthalate (DEHP) was selected as an internal standard. DEHP is indeed a plasticizer always observed in the positive ion mode DART-TOF mass spectra due to its presence on the walls of the sampling material. The presence of its [M + H]+ ion is indicated by an asterisk (∗) on all the mass spectra presented in the Results and Discussion section of this paper. A typical DART to orifice 1 distance was of ∼1 cm, and

Scheme 1. Structure of Irgafos 168 Used As Stabilizing Agent in Industrial Polyethylene

any treatment. A series of three pellets containing Irgafos with polyethylene densities ranging from 0.92 to 0.962 g cm−3 and one PE pellet free of stabilizer were used in the present work. Thermal Treatment of the Polyethylene Pellets. A ceramic thin layer chromatography (TLC) plate heater purchased from CAMAG (Muttenz, Switzerland) was used for maintaining a uniform heat over the entire surface. Accurate monitoring of the temperature was provided by an LCD display and a manual regulator. PE pellets of 10 mg were placed in 6 mm deep regular holes of a 10 cm × 12 cm steel leaky plate. Once the temperature reached 200 °C, the steel leaky plate was positioned at ambient air under a fumehood, on the plate heater. After 10 min at a 200 °C constant temperature, the plate heater was cooled down at a rate of 10 °C per minute until room air temperature. UV Treatment of the Polyethylene Pellets. Polymer samples were left in ambient air and at room temperature under

Figure 2. DART-TOF mass spectrum of an Irgafos 168 containing polyethylene pellet (see Table 1 for the attribution of exact mass measurements). *Peak of the di(2-ethylhexyl)phthalate [M + H]+ ion used as a standard for the internal drift compensation function (see the Experimental Section). 8644



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The presence of the Irgafos 168 oxidized form was confirmed through the detection of an ammonium adduct [Ox-Irgafos + NH4]+ at m/z 680.4803 (not labeled in Figure 2). The elemental composition of this ion is proposed with a mass error below 0.3 ppm (see Table 1). The presence of such an adduct can be attributed to the presence of ammonia in an atmospheric pressure interface contaminated by previous electrospray analyses. The formation of [M + NH4]+ ions during DARTMS analysis of stabilizer sample has been already observed and described in the literature.49 It must be note that the oxidized form of Irgafos 168 was never mentioned during the DART-MS analysis of pure sample of this stabilizer.49 The accurate mass measurements performed in this work are reported in Table 1. These results confirm the presence of this Irgafos oxidized form through the detection of their [Ox-Irgafos + NH4]+ and [OxIrgafos + H]+ ions in a polyethylene sample when the pellets were directly submitted to DART-TOF MS analysis. From the molecular formula determination results regrouped in Table 1, it appears also that aside from the presence of protonated bis(2ethylhexyl)phthalate, the ions with m/z ratios encompassed in the 300−600 Th range, are [M − H]+ ions of polyethylene. The formation of these ions from such nonpolar compounds is not surprising if one refers to the observations made by Cody during DART-MS analysis of saturated alkanes.36 The production of molecular and [M − H]+ ions has indeed been described as being favored in the absence of non-protonating solvent or residual moisture and for a relatively high helium stream temperature as used in this work (see the Experimental Section).36,37 The presence of oxygen as charge exchange reagent and the position of the solid sample close to the mass spectrometer sampling orifice would also be involved in the

the polypropylene pellets to be analyzed were manually introduced into the DART gas stream by using tweezers.

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RESULTS AND DISCUSSION A typical DART-TOF mass spectrum of polyethylene solid sample containing Irgafos 168 as an additive is shown in Figure 2. The most intense ions depicted in the Figure 2 are the peaks at m/z 279.1603, m/z 647.4566, and m/z 663.451. They correspond to the quasi-molecular ions of the dibutylphtalate [bisbutylphtalate + H]+, the Irgafos 168 [Irgafos + H]+, and its oxidized form [Ox-Irgafos + H]+. All theses attributions were established by accurate mass measurements for the determination of elemental formulas as reported in Table 1. Table 1. Results of Exact Mass Measurements Performed from the Mass Spectrum of the Figure 2 Related to the DART-TOF MS Analysis of a Polyethylene Solid Sample measured mass

proposed formula (observed ion)

calculated mass (error in ppm)

279.16032 309.3551 337.3837 365.4239 393.4488 421.4809 449.5082 477.5406 505.5739 647.4566 663.4511 680.4803

C16H23O4 ([M + H]+) C22H45 ([M − H]+) C24H49 ([M − H]+) C26H53 ([M − H]+) C28H57 ([M − H]+) C30H61 ([M − H]+) C32H65 ([M − H]+) C34H69 ([M − H]+) C36H73 ([M − H]+) C42H64O3P ([M + H]+) C42H64O4P ([M + H]+) C42H67NO4P ([M + NH4]+)

279.1596 309.3512 337.3834 365.4147 393.4460 421.4773 449.5086 477.5399 505.5712 647.4593 663.4542 680.4808

(+ 2.44 ppm) (+ 9.79 ppm) (+ 0.81 ppm) (+ 5.00 ppm) (+ 7.02 ppm) (+ 8.56 ppm) (− 0.87 ppm) (+ 1.36 ppm) (+ 5.27 ppm) (− 4.17 ppm) (− 4.67 ppm) (− 0.29 ppm)

Figure 3. DART-TOF mass spectrum of the Irgafos 168 containing polyethylene pellet analyzed in the case of the Figure 1 and having undergone an additional thermal treatment (see Table S-1 in the Supporting Information for the attribution of exact mass measurements). *Peak of the di(2ethylhexyl)phthalate [M + H]+ ion used as a standard for the internal drift compensation function (see the Experimental Section). 8645



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Figure 4. DART-TOF mass spectrum of a stabilizer free polyethylene pellet submitted to an additional thermal treatment: (a) full scan mass spectrum and (b) expansion of the mass range encompassing the m/z 421 and 449 ions of the polyethylene. *Peak of the di(2-ethylhexyl)phthalate [M + H]+ ion used as a standard for the internal drift compensation function (see the Experimental Section).

production of M+• ion. As shown through the published DART mass spectra of the n-hexadecane, this molecular ion can lose a hydrogen atom to form a [M − H]+ ion.36 In our case, these ions are observed when a low-density polymer pellet was analyzed by DART-TOF MS (see Figure 2). The nature of these ions produced from the polyethylene oligomers was confirmed by accurate mass measurements (see Table 1). One will note that for these species, half of the mass measurements lies in an error range less than 5 ppm by comparison with the theoretical mass calculated from the elemental formulas (see Table 1). The polyethylene pellet of the mass spectrum reported in Figure 2 has been submitted to a thermal treatment (see the Experimental Section). A typical DART-TOF mass spectrum of this heated solid sample is shown in Figure 3. The protonated form of bis(2-ethylhexyl)phthalate is present on the DART mass spectrum of Figure 3 as mentioned for Figure 2. However, in Figure 3, the m/z 391.2848 is the base peak. Its relative intensity is greater than that observed in Figure 2 and is due to the additional sampling step used for transferring the heated polymer after thermal treatment. This step involves the use of vials whose walls contain bis(2ethylhexyl)phthalate as plastizer. A warm-up of theses vials led indeed to a diffusion of the phthalates into the treated polymer sample and the observation of their ions in DART-MS. The mass spectrum of Figure 3 highlights the fact that during thermal treatment the polyethylene sample has not undergone any structural modification. The ions characteristics of the polyethylene oligomers are indeed still present on the mass spectrum of Figure 3. This is confirmed by the elemental formula determination obtained from the exact mass measurements reported in Table S-1 available in the Supporting

Information. In this case, the calculated mass errors are even lower than those reported in Table 1, namely, for the m/z 337 and m/z 421 ions. From these measurements, it appears that polymer ions up to m/z 309 and until m/z 561 are present on the DART-TOF mass spectrum of the thermally treated polyethylene pellet (see Figure 3). The presence of theses oligomers of relatively higher mass illustrates the protection role of the Irgafos 168 toward the polyethylene degradation during the thermal treatment. When comparing the mass spectrum of the starting sample (see Figure 2) and the mass spectrum of the same pellet after thermal treatment (see Figure 3), it appears that the ratios between the intensities of the Irgafos 168 ion (m/z 647.4600) ([Irgafos + H]+) and that of its oxidized forms represented by the ions at m/z 663.4545 ([OxIrgafos + H]+) and m/z 680.4801 ([Ox-Irgafos + NH4]+) are quite different. The ratio (I647/(I663 + I680)) is 2.3 for the nontreated sample (see Figure 2) and 0.9 in the case of the MS analysis of the heated polyethylene (see Figure 3). This trend has also been noted for the DART mass spectra of five additional samples analyzed before and after thermal treatment. Considering then a set of six samples, the average ratio (I647/ (I663 + I680)) is 1.9 (with a 0.58 standard deviation) for the starting pellets. This average ratio is of 0.8 (with a standard deviation of 0.18) in the case of DART-TOF MS analyses of the samples after thermal treatment. By focusing on the behavior of the stabilizer, we can correlate the relative increase of the Irgafos 168 oxidized form, through the monitoring of the m/z 663 and m/z 680 ions, with the polyethylene protection toward the thermal degradation. This also confirms that the Irgafos 168 fully plays its role of oxidation inhibitor during the thermal degradation of the solid polyethylene by trapping the molecular oxygen or decomposing a generated hydroperoxide 8646



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Figure 5. DART-TOF mass spectrum of the Irgafos 168 containing polyethylene pellet analyzed in the case of the Figure 1 and having undergone an additional UV treatment. *m/z ratio of the di(2-ethylhexyl)phthalate [M + H]+ ion used as a standard for internal drift compensation function (see the Experimental Section).

Scheme 2. Proposed Structures from the Exact Mass Measurements Reported in Table S-3 in the Supporting Information and Obtained from the DART-TOF MS of the Irgafos 168 Containing Polyethylene Pellets Submitted to an UV Exposure

as illustrated in Figure 1. In such a rapid control method, the goal of the accurate mass measurement is to ensure the specificity of the direct monitoring of the stabilizer behavior by DART-TOF MS. The stability of the measurement toward the accuracy required for the elemental formula determination is illustrated in Figure S-2 (see the Supporting Information). This

one shows that out of 36 measurements performed in DARTTOF MS, 30 exact mass determinations are encompassed into an error range of ±2.5 ppm (from 1 ppm to −4 ppm). This precision of data is to consider if the goal is to introduce a single ion monitoring by DART-TOF MS in a control quality 8647



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CONCLUSIONS The DART ion source associated with time-of-flight mass spectrometry can highlight the role played by a stabilizer such as the Irgafos 168 during the thermal or UV treatment of an industrial polyethylene. The accurate mass measurement results obtained from the analyzed pellets show that under thermal treatment the Irgafos 168 reacts either by decomposing the generated hydroperoxyde or by limiting the formation of peroxide radicals by trapping the oxygen present into the bulk of the polymer. In the absence of Irgafos, the polymer degradation scheme involving homolytic bond cleavage of the polyethylene and a β-scission of its corresponding hydroperoxyde is confirmed by DART-TOF MS analysis. Under UV exposure, the reactivity of the stabilizer toward the treatment appears to be different. This one seems to react not only toward the oxidation mechanism as described above but also toward the UV radiation by an intermolecular breaking that could prevent the in situ formation of the radicals. The description of such behaviors was made possible thanks to the possibility to characterize either the ions of the stabilizer and those of the polymer by DART ionization and exact mass measurement. Also, because of the ability of the DART-TOF MS method used in this study to perform rapid screening of the behavior of polyethylene solid samples, it is reasonable to consider its use to disclose the history of aging of a polymer in a highthroughput analysis context for industrial control.

method that avoids resorting to sample treatment methods involving, for instance, chromatographic separations. In order to better target the role played by the Igafos 168 as a polymer stabilizer during thermal treatment of polyethylene, a free of stabilizer solid sample was thermally treated using the same experimental conditions as above and analyzed in DARTTOF MS. The mass spectrum then obtained is depicted in Figure 4. From the mass differences (Δm/z) measured for two polyethylene ions, it appears that in absence of the Irgafos 168, the polymer is degraded as expected by the mechanism described in Figure 1. The homolytic bond cleavage corresponds to the mass differences Δm/z = 14.0331 and Δm/z = 14.0239 shown in the insert of Figure 4. The β-scission of a hydroperoxyde generated in situ appears to be illustrated by the mass difference between two ions at m/z 421.4593 and 449.5082, i.e., Δm/z = 15.9929, corresponding to an oxygen addition. The role plays by the Irgafos 168 as stabilizing additive during the polyethylene thermal treatment is then confirmed as an oxygen trap and protecting agent toward the bond cleavage. The behavior of the Irgafos 168 toward the photolytically induced polyethylene degradation (see the Experimental Section) is different than that previously observed above during the thermal degradation of the polymer (see Figures 2 and 3). This difference is illustrated in Figure 5 which shows the DART mass spectrum of an Irgafos containing polyethylene pellet submitted to UV exposure. The ions of the low molecular weight fraction of the polyethylene are still present in the mass spectrum of Figure 5, but the m/z 647 [Irgafos + H]+ ion is of very low intensity, whereas its oxidized forms, i.e., the m/z 663 [Ox-Irgafos + H]+ ion and the m/z 680 [Ox-Irgafos + NH4]+ ions, are now the stabilizer predominant ions. The comparison of the mass spectra of Figures 3 and 5 leads to observation that for the later, supplementary mass spectrometry signals appear in the case of the photolytically induced polyethylene degradation. The results of the accurate mass measurements performed from theses ions are regrouped in Table S-3 in Supporting Information. They are compared with the theoretical mass calculated from candidate compositions encompassing: C0−100H 0−200O0−100P0−1. The selection of the formulas presenting the lowest mass errors and the better compatibility with the elemental composition of Iragofos 168 and its oxidized form allows one to propose the chemical structures described in Scheme 2 for the additional ions detected from the UV treatment of the polyethylene pellet. The structures depicted in Scheme 2 allow one to propose that this is the oxidized form of the Irgafos 168 represented by its ion at m/z 663, which would undergo the photolytically induced degradation. This one would start by a cleavage of a P−O bond leading to the formation of the bistert-butyl phenol and a diaryl phosphite residue detected through their protonated forms at m/z 207 and m/z 459, respectively. Under the UV exposure, the produced diaryl phosphite would react in turn as a trapping oxygen agent for producing another oxidized form detected through the m/z 475 [M + H]+ ion. This one would undergo the cleavage of its P−O bond with reaction products detected through their protonated form at m/z 271 and m/z 207. The later can be then considered as a diagnostic ion of the two P−O bond cleavage reactions mentioned above.

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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.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected] (O.L.) ; david. [email protected] (D.R.). Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors gratefully acknowledge the CNRS, MENRT, and Total (France and Belgium) fort their financial support. The Analytical Platform ONIS (granted by the European Community FEDER, Rennes Metropole, Departement Ille et Vilaine and the Région Bretagne) is also acknowledged.

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REFERENCES

(1) Emanuel, N. M.; Denosov, E. T.; Maizus, Z. K. In Liquid Phase Oxidation of Hydrocarbons; Plenum Press: New York, 1967. (2) Bilingham, N. C.; Calvert, P. D. Degradation and Stabilisation of Polyolefins. In Polymer Stabilisation Mechanisms and Applications; Allen, N. S., Ed.; Applied Science Publishers: London, 1983; pp 1−28. (3) Murphy, J. In Additives for Plastics Handbook, 2nd ed.; Elsevier Advanced Technology: Oxford, U.K., 2001. (4) Scott, G. In Atmospheric Oxidation and Antioxidants; Elsevier: London, 1993. (5) Knigth, J. B.; Calvert, P. D.; Billingham, N. C. Polymer 1985, 26, 1713−1718. (6) Murphy, J.; Smith, A.; Holmes, M. Plast., Addit. Compd. 2000, 2, 34−36. (7) Markarian, J. Plast., Addit. Compd. 2007, 9, 32−35. (8) Pospsil, J.; Horak, Z.; Krulis, Z.; Nespurek, S. Macromol. Symp. 1998, 135, 247−263. 8648



Article

(43) Cajka, T.; Vaclavik, L.; Riddellova, K.; Hajslova, J. LC−GC Eur. 2008, 21 (5), 250−256. (44) Vaclavik, L.; Zachariasova, M.; Hrbek, V.; Hajslova, J. Talanta 2010, 82, 1950−1957. (45) Vaclavik, L.; Rosmus, J.; Popping, B.; Hajslova, J. J. Chromatogr., A 2010, 4204−4211. (46) Morlock, G.; Ueda, Y. J. Chromatogr., A 2007, 1143, 243−251. (47) Kpegba, K.; Spadaro, T.; Cody, R. B.; Nesnas, N.; Olson, J. A. Anal. Chem. 2007, 79, 5479−5483. (48) Rothenbacher, T.; Schwack, W. Rapid Commun. Mass Spectrom. 2009, 23, 2829−2835. (49) Haunschmidt, M.; Klampfl, C. W.; Buchberger, W.; Hertsens, R. Analyst 2010, 135, 80−85. (50) Rothenbacher, T.; Schwack, W. Rapid Commun. Mass Spectrom. 2010, 24, 21−29.

(9) Allcock, H. R.; Lampe, F. W. In Contemporary Polymer Chemistry, 2nd ed.; Prentice Hall: Englewood Cliffs, NJ, 1990; pp196−231. (10) Schabron, J. F.; Fenska, L. E. Anal. Chem. 1980, 52, 1411−1415. (11) Vandenburg, H. J.; Clifford, A. A.; Bartle, K. D.; Caroll, J.; Newton, I. D.; Garden, L. M.; Dean, J. R.; Costley, C. T. Analyst 1997, 122, 101R−115R. (12) Jenke, D. J. Liq. Chromatogr. Relat. Technol. 2003, 26, 2417− 2447. (13) Mansouri, H.; Yagobi, N.; Ferrier, D. Chromatographia 1998, 48, 491−496. (14) Takáts, Z.; Wiseman, J. M.; Gologan, B.; Cooks, R. G. Science 2004, 306, 471−473. (15) Cody, R. B.; Laramée, J. A.; Durst, H. D. Anal. Chem. 2005, 77, 2297−2302. (16) Takáts, Z.; Wiseman, J. M.; Cooks, R. G. J. Mass Spectrom. 2005, 40, 1261−1275. (17) Takáts, Z.; Cotte-Rodriguez, I.; Talaty, N.; Chen, H. W.; Cooks, R. G. Chem. Commun. 2005, 1950−1952. (18) Cotte-Rodriguez, I.; Zoltán, T.; Talaty, N.; Chen, H.; Cooks, R. G. Anal. Chem. 2005, 77, 6755−6764. (19) Sanders, N. L.; Kothari, S.; Huang, G.; Salazar, G.; Cooks, R. G. Anal. Chem. 2010, 82, 5313−5316. (20) Mäkinen, M.; Nousiainen, M.; Sillanpäa,̈ M. Mass Spectrom. Rev. 2011, 30, 940−973. (21) Paglia, G.; Ifa, D. R.; Wu, C.; Corso, G.; Cooks, R. G. Anal. Chem. 2010, 82, 1744−1750. (22) Suni, N. M.; Aalto, H.; Kauppila, T. J.; Kotiahoa, T.; Kostiainen, R. J. Mass Spectrom. 2012, 47, 611−619. (23) Shin, Y.-S.; Drolet, B.; Mayer, R.; Dolence, K.; Basile, F. Anal. Chem. 2007, 79, 3514−3518. (24) Kaur-Atwal1y, G.; Weston, D. J.; Green, P. S.; Crosland, S.; Bonner, P. L. R.; Creaser, C. S. Rapid Commun. Mass Spectrom. 2007, 21, 1131−1138. (25) Stokes, A. A.; Clarke, D. J.; Weidt, S.; Langridge-Smith, P.; Mackay, C. L. Int. J. Mass Spectrom. 2010, 289, 54−57. (26) Yao, Z.-P. Mass Spectrom. Rev. 2011, 31, 437−447. (27) Cooks, R. G.; Nefliu, M.; Venter, A. Chem. Commun. 2006, 888−890. (28) Jackson, A. T.; Williams, J. P.; Scrivens, J. H. Rapid Commun. Mass Spectrom. 2006, 20, 2717−2727. (29) Harris, G. A.; Nyadong, L.; Fernandez, F. M. Analyst 2008, 133, 1297−1301. (30) Lattimer, R. P.; Harris, R. E.; Rhee, C. K.; Schulten, H. R. Anal. Chem. 1986, 58, 3188−3195. (31) Johlman, C. L.; Wilkins, C. L.; Hogan, J. D.; Donovan, T. L.; Laude, D. A.; Youssefi, M.-J. Anal. Chem. 1990, 62, 1167−1172. (32) Taguchi, Y.; Ishida, Y.; Ohtani, H.; Matsubara, H. Anal. Chem. 2004, 76, 697−703. (33) Wright, S. J.; Dale, M. J.; Langridge-Smith, P. R. R.; Zhan, Q.; Zenobi, R. Anal. Chem. 1996, 68, 3585−3594. (34) Mawn, M. P.; Linton, R. W.; Bryan, S. R.; Hagenhoff, B.; Jürgens, U.; Benninghoven, A. J. Vac. Sci. Technol. 1991, A9, 1307− 1311. (35) Poleunis, C.; Médard, N.; Bertrand, P. Appl. Surf. Sci. 2004, 231−232, 269−273. (36) Cody, R. B. Anal. Chem. 2009, 81, 1101−1107. (37) Song, L.; Gibson, S. C.; Bhandari, D.; Cook, K. D.; Bartmess, J. E. Anal. Chem. 2009, 81, 10080−10088. (38) Cody, R. B.; Fernandez, F. M.; Green, M. D.; Hampton, C. Y.; Mc Gready, R.; Sengaloundeth, S.; White, N. J.; Newton, P. N. ChemMedChem 2006, 1, 702−705. (39) Williams, J. P.; Patel, V. J.; Holland, R.; Scrivens, J. S. Rapid Commun. Mass Spectrom. 2006, 20, 1447−1456. (40) Jones, R. W.; Cody, R. B.; Mc Clelland, J. F. J. Forensic Sci. 2006, 51 (4), 915−918. (41) Hajslova, J.; Cajka, T.; Vaclavik, L. Trends Anal. Chem. 2011, 30, 204−218. (42) Haefliger, O. P.; Jeckelmann, N. Rapid Commun. Mass Spectrom. 2007, 21, 1361−1366. 8649


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