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Determination of Selected Polybrominated Diphenylethers and Polybrominated Biphenyl in Polymers by Ultrasonic-Assisted Extraction and High-Performance Liquid ChromatographyInductively Coupled Plasma Mass Spectrometry Shao Mingwu,* Wei Chao, Jia Yongjuan, Dai Xinhua, and Fang Xiang National Institute of Metrology (NIM), Beijing, China A new method has been developed for the determination of selected polybrominated diphenylethers (PBDEs) and polybrominated biphenyl (PBB) in four polymers: highdensity polyethylene (HDPE), polystyrene (PS), acrylonitrile-butadiene-styrene copolymer (ABS), and polypropylene (PP). PBDEs and PBB in the polymers were extracted with toluene, using ultrasonic-assisted extraction (UAE). The extracts were then determined by highperformance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS), using external calibration (single-point). Extraction parameters of UAE and several ICP-MS parameters were optimized. Extraction efficiencies almost reached 100%. The relative standard deviations (RSDs) were in the range of 0.7%5.4%. The results demonstrate that the method possesses advantages of good precision, as well as high extraction efficiency and accuracy. The method especially overcomes the problem of the thermal degradation of highly brominated PBDEs, such as PBDE-209. Brominated flame retardants (BFRs) have been widely used as additives in polymers of electrical and electronic equipment, to improve their fire retardancy properties.1 Among BFRs, polybrominated diphenylethers (PBDEs), hexabromocyclododecane (HBCD), tetrabromobisphenol A (TBBPA), and polybrominated biphenyls (PBBs) are the most common additives in terms of production and consumption.2 However, there is an increasing concern about the adverse effects of BFRs on human health and the environment, because of their lipophilic and bioaccumulative property. It has been demonstrated that BFRs are present in the environment, but the long-term healthy and environmental impacts still are not well-known.3 Propelled by the environmental concern, the European Parliament enacted the directive 2002/96/EG (waste electrical and electronic equipment, WEEE) and the directive 2002/95/EG (restriction of the use of certain hazardous sub* Author to whom correspondence should be addressed. Tel.: +86-01064279562. Fax: +86-010-64271638. E-mail:
[email protected]. (1) Alaee, M.; Arias, P.; Sjodin, A.; Bergman, A. Environ. Int. 2003, 29, 683– 689. (2) Hyotylainen, T.; Hartonen, K. Trends Anal. Chem. 2002, 21, 13–29. (3) de Wit, C. A. Chemosphere 2002, 46, 583–624.
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stances in electrical and electronic equipment, RoHS).4,5 Similar acts have been launched in China (“ACPEIP”, also “China RoHS”) and South Korea (“Korea RoHS”) in 2007 and 2008. RoHS set limits of 0.1% (w/w) for the presence of PBBs and PBDEs in electrical and electronic equipment. Therefore, the development of analytical methods to enable sensitive BFRs detection in polymer is therefore of paramount importance for environmental protection and human health. The current methods include fast qualitative screening methods and accurate quantitative methods. Most methods focused on rapid analysis and identification of BFRs in polymers;6-13 not many works have been published on accurate method for analysis of BFRs in polymers. The majority of methods for BFRs determination are based on existing technologies originally developed for the detection of persistent organic pollutants (POPs). Most of these methods are more suitable for the detection of BRFs present in environmental, biological, and human matrix.3,14-16 Recently, the analysis of BRFs in polymers have attracted much attention. GC and HPLC, as the major separation and injection tools, coupled with different detectors (MS, ECD, DAD/UV), have been widely used for effective material determination.6-13 However, those methods are not very successful for the determination of BFRs in polymers. For example, some flame retardants with a high boiling point (for (4) Directive 2002/96/EC, Off. J. Eur. Union L037, pp 24-39, February 13, 2003. (5) Directive 2002/95/EC, Off. J. Eur. Union L037, pp 19-23, February 13, 2003. (6) Schlummer, M.; Brandl, F.; Maurer, A.; van Eldik, R. J. Chromatogr. A 2005, 1064, 39–51. (7) Pohlein, M.; Llopis, A. S.; Wolf, M.; van Eldik, R. J. Chromatogr. A 2005, 1066, 111–117. (8) Dirtu, A. C.; Ravindra, K.; Roosens, L.; van Grieken, R.; Neels, H.; Blust, R.; Covaci, A. J. Chromatogr. A 2008, 1186, 295–301. (9) Vilaplana, F.; Karlsson, P.; Ribes-Greus, A.; Ivarsson, P.; Karlsson, S. J. Chromatogr. A 2008, 1196-1197, 139–146. (10) Hosaka, A.; Watanabe, C.; Tsuge, S. Anal. Sci. 2005, 21, 1145–1147. (11) Pohlein, M.; Bertran, R. U.; Wolf, M.; van Eldik, R. J. Chromatogr. A 2008, 1203, 217–228. (12) Ranz, A.; Maiera, E.; Trampitsch, C.; Lankmayr, E. Talanta 2008, 76, 102– 106. (13) Altwaiq, A. M.; Wolf, M.; van Eldik, R. Anal. Chim. Acta 2003, 491, 111– 123. (14) Heather, M. Stapleton. Anal. Bioanal. Chem. 2006, 386, 807–817. (15) Covaci, A.; Voorspoels, S.; Ramos, L.; Neels, H.; Blust, R. J. Chromatogr. A 2007, 1153, 145–171. (16) Covaci, A.; Voorspoels, S.; de Boer, J. Environ. Int. 2003, 29, 735–756. 10.1021/ac1003618 2010 American Chemical Society Published on Web 05/26/2010
example, PBDE-209) are liable to thermal degradation,17 especially when using split/splitless injections (S/SI), which is not compatible with GC separation. The programmable temperature vaporizing (PTV) injector, with higher precision particularly for PBDE209 than S/SI has been reported to solve this problem.18 The PTV injectors are more complicated than the conventional S/SI, because of the need for the tedious parameters optimization.14 For analysis of BRFs using HPLC-MS, the possible accumulation of the coextraction of polymer components in the ion source was observed and lowered absolute response, so HPLC-MS required the substantial cleanup to increase the absolute responses.6 Recent development in GC-ICP-MS and HPLC-ICP-MS techniques offers a great opportunity for the detection of BFRs in polymers. One of the most attractive properties of ICP-MS as detection tool is compound-independent response. This means that ICP-MS does not suffer from interferences of other coeluted, (nonBr)-halogenated compounds. It is not necessary to chromatographically resolve the PBDEs from other (non-Br)-halogenated compounds, such as organic chlorine pesticides. Vonderheide et al.19 successfully applied GC-ICP-MS to determine PBDEs. However, GC-ICP-MS is faced with the same issue as GC-MS or GC-ECD, namely, the thermal degradation of highly brominated compounds (in particular, PBDE-209). HPLC-ICP-MS overcomes the thermal degradation problem, because the injection is conducted at room temperature, which makes HPLC-ICP-MS a promising method for determination of PBDEs. To the best of our knowledge, so far, the HPLC-ICP-MS technique has not been applied to the analysis of PBDEs in polymers. In this work, a new method, HPLC-ICP-MS, in combination with ultrasonic-assisted extraction (UAE), was developed to determine PBDEs and PBBs in polymers. Typical matrix high density polyethylene (HDPE), polystyrene (PS), acrylonitrilebutadiene-styrene copolymer (ABS) and polypropylene (PP) were used as reference samples for testing recoveries and repeatabilities. Because ICP-MS method is based on Br, not selective for BFRs, several typical PBDEs (PBDE-47, PBDE-183, PBDE-206, PBDE-209) and PBB-209 were selected as measurands. The method has been successfully utilized to detect selected PBDEs and PBBs in PP (international comparison sample) and two real samples. EXPERIMENTAL SECTION Instrumentation. HPLC-DAD System. An Agilent Model 1100 HPLC system (Agilent Technologies Co., Ltd., Palo Alto, CA) was used in this work; it included a diode array detector (model G1315B), a Quat pump (model G1311A), a degasser (model G1322A), an auto sampler (model G1313A) equipped with a 50 µL sample loop (injection volume from 1 µL to 50 µL). Two types of reversed-phase columns were used: Agilent model TC-C18 (4.6 mm ID, 250 mm length, and 5 µm particle size) and Waters PAHs (4.6 mm ID, 250 mm length, and 5 µm particle size). A precolumn of the similar property was used to protect the analysis column. The mobile phase consisted of methanol (A), acetonitrile (B), and water (C). The three gradient elutions (recorded as GE1, GE2, (17) de Boer, J. J. Chromatogr. A 1999, 843, 179–198. ¨ stman, C. J. Chro(18) Bjo ¨rklund, J.; Tollba¨ck, P.; Hiarne, C.; Dyremark, E.; O matogr. A 2004, 1041, 201–210. (19) Vonderheide, A. P.; Montes-Bayo´n, M.; Caruso, J. A. J. Anal. Atom. Spectrom. 2002, 17, 1480–1485.
and GE3) were used at a flow rate of 0.8, 1.0, 1.0 mL/min, respectively. GE1 started from an initial composition of 70:20:10 (A/B/C), and was ramped to 85:9:6 (A/B/C) in 10 min, 90:7:3 (A/B/C) in 18 min, and then 90:10 (A/B) in 19.2 min and was subsequently held for 6 min. GE2 started from an initial composition of 85: 0:15 (A/B/C), and was ramped to 80:10:10 (A/B/C) in 10 min, 88:7:5 (A/B/C) in 15 min and was subsequently held for 13 min. GE3 started from an initial composition of 70:20:10 (A/B/C), and was ramped to 85:15 (A/B) in 10 min, 90:10 (A/B) in 15 min and was subsequently held for 5 min. GE1 with the TC-C18 column and GE2 with the PAHs column were used for the mixture solution of PBDEs and PBB209, while GE3 with the TC-C18 column was used for technical PBDE-209. The column had to be allowed to equilibrate for 5 min between runs. The injection volume was 5 µL at room temperature (25 °C). The UV-vis absorbance was recorded at 226 nm. ICP-MS System. An Agilent Model 7500ce inductively coupled plasma-mass spectrometry system (Agilent Technologies, Tokyo, Japan) was employed for detection. The carrier gas was argon (Ar, 99.999%). The optional gas composition was 20% O2 and 80% argon. The instrument operating parameters were as follows: RF power, 1550 W; RF matching, 1.6 V; sample depth, 11 mm; Torch-H, 0 mm; Torch-V, -1.5 mm; carrier gas flow rate, 0.4 L/min; optional gas, 20%; extract 1, 3.5 V; and extract 2, -140 V. Isotopes 79Br and 81Br were monitored. Materials. Reagents and Standard Solution. All solvents were HPLC grade; toluene was purchased from J.T. Baker/Mallinckrodt Baker, Inc. (Phillipsburg, NJ). Methanol and acetonitrile were purchased from Merck (Darmstadt, Germany). Iso-octane was purchased from Tedia (Fairfield, OH). High-purity water was prepared using a Milli-Q system (Millipore, Bedford, MA). Table S-1 in the Supporting Information lists detailed information of the investigated BFRs in the work. The technical PENTA, OCTA, and DECA compounds (97% purity) and the high-purity PBDE-209 compound (99.5% purity) were obtained from Great Lakes Chemical Corporation (Indianapolis, IN). PBB-209 (99% purity) was purchased from Chem Service, Inc. (PO Box 599 West Chester, PA). TBBPA and HBCD were obtained from SigmaAldrich (Steinheim, Germany). Individual standard stock solutions of PBDEs (50 µg/mL in nonane): PBDE-47, PBDE-99, PBDE-100, PBDE-153, PBDE-154, PBDE-183, PBDE-196, PBDE-197, PBDE203, PBDE-206, and PBDE-207 were purchased from Cambridge Isotope Laboratory (Andover, MA). Each stock solution (500 µg/mL) of PBDE-209 (high-purity), PBB-209, HBCD, PENTA, OCTA, and DECA was prepared in toluene. The stock solution (500 µg/mL) of TBBPA was prepared in methanol. Working standard solutions were diluted with toluene by weight to certain concentrations. Mixed solution (recorded as solution A) of PBB-209, PENTA, OCTA, and DECA was prepared by diluting their stock solutions with toluene and used to achieve feasible chromatographic separation conditions. Mixed solutions (recorded as solution B) of TBBPA, HBCD, and PBDE-209 were prepared by diluting their stock solutions with toluene and used for interference testing. Individual working solutions of each PBDE, PBB-209, TBBPA, and HBCD were prepared by diluting their stock solutions with toluene to certain concentrations. They were injected individually under the same conditions as solution A, to identify each major component. Individual standard working Analytical Chemistry, Vol. 82, No. 12, June 15, 2010
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solutions of PBDE-47, PBDE-183, PBDE-206, PBDE-209, and PBB209 were prepared by diluting their stock solutions with toluene to concentrations near to those of the analytes in the extract and used for quantification by external calibration. The mixed working solutions (recorded as solution C) of PBDE-47, PBDE-183, PBDE-209, and PBDE-PBB-209 was prepared by diluting their stock solutions to a certain concentration and used to test the limit of detection (LOD) and the limit of quantification (LOQ). The LOD and LOQ values were defined as the analyte amount with signal-to-noise ratios (S/N) of 3 and 10, respectively. They were obtained by injecting 5 µL of solution C under the optimized conditions. A serial of working standard solutions of PBDE-209 was prepared by diluting the stock solution to detect elemental bromine to obtain the calibration curve. Reference Materials. Four reference materials investigated in this study were HDPE, ABS, PS, and PP. PP was an international comparison (CCQM-P114) sample that was supplied by IRMM (Institute for Reference Materials and Measurements, Geel, Belgium). It included two bottles coded as CCQM-P114, Nos. 1805 and 0916. For more information on PP and CCQM-P114, refer to the literature.20,21 The spiked HDPE, PS, and ABS samples were prepared by Guangzhou Kingfa Science and Technology Co. Ltd. (Guangzhou, PRC) by spiking DECA into the original HDPE, PS, and ABS. The purity (97%) of spiked technical DECA was determined using HPLC-DAD. The amounts of DECA spiked were 370 mg/kg (HDPE, low level), 1150 mg/kg (HDPE, high level), 50000 mg/kg (PS), and 1000 mg/kg (ABS). The preparation method, which is similar to the industrial production process, consists of mixing (technical PBDE and original plastic)-melting, extrusion-pelletizing-mixing-melting, extrusion-pelletizinghomogeneity testing (XRF)-packing. Grinding of Matrix Samples. HDPE samples, which were embrittled with liquid nitrogen, were ground to a particle size of
