Determination Of Polybrominated Diphenyl Ethers In Soil From E-waste Site

Talanta xxx (2006) xxx–xxx

Determination of polybrominated diphenyl ethers in soil from e-waste recycling site Zongwei Cai a,∗ , Guibin Jiang b a b

Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Hong Kong SAR, China Research Center for Eco-environmental Sciences, the Chinese Academy of Sciences, Beijing, China Received 27 October 2005; received in revised form 10 January 2006; accepted 13 January 2006

Abstract Soil samples collected from an electronic waste recycling site were prepared by using Soxhlet extraction and multiple-step column chromatographic clean-up. Gas chromatography/ion trap mass spectrometry method was developed to determine polybrominated diphenyl ethers (PBDEs) in the sample extracts. The method performance was evaluated by the recovery of 13 C-labeled internal standards and by analyzing quality assurance and quality control samples. Relative error and relative standard deviation obtained from the analysis of duplicated samples and spiked matrix were better than 10%. PBDEs were detected in the field soil samples collected from an e-wastes disposal site at levels from low parts-per-billions to 600 parts-per-billions. © 2006 Elsevier B.V. All rights reserved. Keywords: PBDEs; e-Waste; Soil; GC–ion trap MS

1. Introduction Polybrominated diphenyl ethers (PBDEs) are anthropogenic chemicals that have been extensively used as flame retardants in furniture, building materials and electronic components. PBDEs can be released into the environment, persistent with a high bioaccumulation potential and thus affect human health. The flame retardant have been detected with significant levels in environmental [1–3] and biological [4,5] samples. Recent toxicological studies suggested that several PBDEs and/or their metabolites might have disrupted the endocrine system [6,7]. Thus, trace analysis of PBDEs is important. Illegal recycling operations of electronic wastes (e-wastes) have been reported to cause severe environmental pollution of PBDEs [8–10]. The hazardous e-wastes smuggled from Western countries into the illegal recycling sites in China included computers, electronic appliances and transformer carcasses. In the e-waste sites, recycling operations consist of toner sweeping, dismantling electronic equipment, selling computer monitor

∗

Corresponding author. Tel.: +852 34117070; fax: +852 34117348. E-mail address: [email protected] (Z. Cai).

yokes to copper recovery corporations, plastic chipping and melting, burning wires to recover copper, melting circuit boards over open fires and using acid chemical strippers to recover gold and other metals. In an e-waste recycling site in Taizhou city, Zhejiang Province in China, for example, most of the wastes get processed in large-scale dismantling yards where thousands of labourers sit all day wielding chisel and hammer, breaking down the electronic equipment, although it has been declared that it is illegal to work on waste computers, monitors and televisions and that all work must be done in permitted facilities. These e-waste activities cause severe damage to the environment and expose the workers and local residents to toxic chemicals through inhalation, dermal exposure and oral intake of contaminated foods. The contamination of PBDEs is one of the most concerned problems because the e-wastes contain significant levels of flame retardants made of various PBDEs products [9,10]. However, little information on the PBDE congener profiles and concentrations in the environment around the e-waste recycling site has been reported. This study aims to apply a capillary gas chromatography/ion trap mass spectrometry method for analyzing PBDEs in soil samples collected from the e-waste disposal site. Various contamination sources of PBDEs were discussed based on the obtained analytical results.

0039-9140/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.talanta.2006.01.016 TAL-8298;

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Z. Cai, G. Jiang / Talanta xxx (2006) xxx–xxx

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Table 1 Concentrations of native and 13 C-labeled PBDEs in calibration standard solutions (pg/␮L) Compounds

CSa -1

CS-2

CS-3

CS-4

CS-5

13 C-labeled

BDE-3 BDE-15 BDE-28 BDE-47 BDE-99 BDE-139 BDE-153 BDE-154 BDE-183

1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0

5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0

20 20 20 20 20 20 20 20 20

100 100 100 100 100 100 100 100 100

400 400 400 400 400 400 400 400 400

100 100 100 100 100 100 100 100 100

a

PBDE

Calibration standard.

2. Experimental 2.1. Chemical reagents and standard solutions Chemicals used in this study were analytical or higher grade. The PBDE standard solutions were purchased from Wellington Laboratories (Ontario, Canada). Cleaned sand was purchased from Fluka (Milwaukee, USA) and used for method development. A set of 5 PBDE calibration standard solutions (CS-1–CS5) contained 19 native PBDEs and 10 13 C-labeled PBDEs. The concentrations of mono- to hepta-brominated diphenyl ethers ranged from 1 to 400 pg/␮L while the 13 C-labeled standards were maintained constantly at 100 pg/␮L (Table 1). 2.2. Sample preparation and analysis Cleaned sand was spiked with known levels of PBDE standards prior to the sample preparation for evaluating method accuracy and precision. Environmental soil samples were collected from six sampling points around an approximate 30-m2 disposal site of e-wastes. The samples were thoroughly mixed and ground prior to the sample preparation. One gram of each of the sand and field soil sample was mixed with 10 g anhydrous sodium sulphate and 5 g of acid washed copper powder. After 1 ng of 13 C-labeled PBDE internal standard was added, the sample was Soxhlet extracted with a solvent containing hexane and acetone (1:1, v/v) for 12 h. The sample was cleaned-up with columns of acidic silica gel and activated neutral alumina for the GC/MS/MS analysis. One microliter of the sample extract was injected into a DB-5 column (60 m, 0.25 mm i.d., 0.25 ␮m film thickness) with injector temperature of 280 ◦ C and splitless injection mode on a ThermoQuest Trace GC/PolarisQ ion trap mass spectrometer. The column temperature was programmed from 110 ◦ C (1 min) to 180 ◦ C at rate of 8 ◦ C/min; from 180 ◦ C (1 min) to 280 ◦ C at 2 ◦ C/min and finally hold for 10 min at 280 ◦ C. Ion trap was used for the electron impact ionization (EI) MS/MS analysis. The MS source temperatures, source energy and emission current were set at 250 ◦ C, 70 eV and 250 mA. Collision-induced dissociation (CID) experiments were conducted on selected precursor ions for the PBDE congeners. The ion trap MS parameters included isolation width (1.0 amu), isolation time (8 ms), excitation time (15 ms), resonant excitation voltage (1.00 V), and q-value (0.45).

3. Results and discussion Sample preparation procedure for PBDEs in solid samples was performed by using Soxhlet extraction and column chromatographic clean-up [11]. Quantitative recoveries (more than 65%) were achieved for the sample preparation procedure, except for the mono-BDE congener (BDE-3) which had an average recovery of 40%. BDE-3 has relatively low boiling point, which might result in losses during the concentration procedure. Nevertheless, low recovery should not affect the method accuracy and precision because isotope dilution GC–MS technique is applied. The accuracy and precision of the method were evaluated by analyzing the cleaned sand samples spiked with known amount PBDEs. The obtained relative errors and relative standard deviations were less than 30% (n = 6) when the added PBDE levels were 1 parts-per-billion (ppb). Calibration standards were analyzed under the optimized MS/MS parameters. Linear calibration was obtained within the range of 1–400 pg for the PBDE congeners. For the ion trap MS/MS analysis, the most intensive ion peak of each PBDE congener was selected as the parent ion [9,10]. The selected parent ions were isolated in the ion trap and fragmented by using tandem mass spectrometry. MS/MS spectra of all analytes were recorded, from which a characteristic ion was selected as quantitative ion. The quantitative ions were selected based on the criteria of peak intensity and ion specificity as well as potential interference from other compounds. The [M − COBr]+ fragment ion was observed as the base peak for PBDEs with ortho-substituted bromine, while the fragmentation ion with the loss of Br2 ([M − Br2 ]+ ion) was the base ion for non-ortho substituted congeners. Identification of the PBDEs in soil samples was performed with the criteria of chromatographic retention time, selected characteristic ion and bromine isotope ratio. Method detection limits obtained with the developed sample preparation procedure and with the optimized GC–MS parameters ranged from 0.008 to 0.1 ng/g (dry weight) for the targeted PBDEs when 10 g of soil were analyzed. Limits of quantitation was defined as five times of the method detection limits,

Fig. 1. Total ion chromatogram from the GC–ion trap MS analysis of the sample extract of soil 6. BDE-3 was not detected. Peaks of other PBDEs were observed, but not identified due to the unavailability of standards.

Z. Cai, G. Jiang / Talanta xxx (2006) xxx–xxx

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Table 2 Levels (ppb) of PBDEs detected in the soil samples (dried weight) Congener

Blank

Soil 1

Soil 2

Soil 3

Soil 4

Soil 5

Soil 6

Soil 6-dup

Spiked soila

BDE-3 BDE-15 BDE-28 BDE-47 BDE-99 BDE-139 BDE-153 BDE-154 BDE-183

ndb nd nd nd nd nd nd nd nd

nd 0.60 4.10 206 520 26.1 68.0 42.0 10.4

nd 0.69 5.22 195 502 32.4 70.3 39.2 12.7

nd 0.81 5.37 264 534 41.8 82.4 48.5 14.3

nd 0.76 5.18 220 578 30.7 69.8 54.9 13.0

nd 0.78 4.41 213 599 33.0 76.9 52.3 11.2

nd 0.92 5.78 204 579 46.0 77.2 57.1 12.2

nd 0.89 5.25 199 530 42.5 72.9 54.5 11.4

4.50 5.17 4.85 4.46 5.20 5.09 4.80 4.51 4.76

a b

± ± ± ± ± ± ± ± ±

0.19 0.40 0.31 0.30 0.43 0.21 0.16 0.38 0.11

Spiked levels of PBDEs were 5 ppb in soil blank matrix (n = 3). nd = not detected.

i.e., 0.04–0.5 ng/g. The developed method was applied for the determination of PBDEs in soil sample collected from the ewaste site located in Taizhou, Zhejiang Province in China. Fig. 1 shows the total ion chromatogram obtained from the GC–ion trap MS analysis of the sample extract of the soil 6 collected from the e-waste deposit site. BDE-3 was not detected. Peaks of other PBDEs were observed, but not identified due to the unavailability of standards. Isotope dilution MS technique was applied for the PBDE quantitation. Relative response factors of the native PBDEs to the corresponding 13 C-labeled internal standards were measured and used to quantify the PBDE levels in the samples. Only the PBDEs, whose 13 C-labelled internal standards were available (Table 1), were quantitatively analyzed. The recoveries of the 13 C-labeled internal standards were better 60% with relative standard deviation ranging from 8 to 26%. The developed method was applied to determine PBDEs in six soil samples collected from an e-waste recycling site. Table 2 lists the quantitative results of the detected PBDE congeners. Both individual and averaged concentrations of the PBDEs are presented for the soil samples. Because the soil samples were collected from the sampling points around the same e-wastes disposal site, the detected PBDE levels were similar with a standard deviation of less than 30%. The data indicated that the PBDEs existed in the soil samples with concentrations ranging from sub-ppb to about 600 ppb (dry weight). MonoBDE (BDE-3) was not detected in the collected soil samples. BDE-15 (di-BDE) was detected at concentrations from 0.60 to 0.92 ppb in the soil samples. The average concentration of the tri-BDE (BDE-28) was 5.01 ppb with a standard deviation of 0.62. Other PBDE congeners detected in the soils were BDE-47, BDE-99, BDE-139, BDE-153, BDE-154, and BDE-183, whose averaged levels varied from 12.3 to 552 ppb. Tetra- (BDE-47), penta- (BDE-99) and hexa-BDE (BDE-139, BDE-153, BDE154), were the predominant isomers and its congener pattern was similar to a commercial penta-BDE formulation [12]. Thus, the high levels of the PBDE congeners probably resulted from the commercial penta-BDE product used in the fire retardants because the soil samples were collected in the vicinity of a site for the e-wastes disposal. Uncontrolled disposal and recycling have apparently resulted in the soil contamination with the PBDEs.

The quality assurance and quality control (QA/QC) included the sample analysis of matrix blank, spiked matrix and duplicated samples (Table 2). Recovery of the 13 C-labelled internal standards was again better than 60% for the QA/QC samples. No PBDEs were detected in the matrix blank. The variation between the duplicated samples (soil 6) was less than 10% for all targeted PBDEs. Results from the analysis of three spiked matrix blanks indicated that the method had good accuracy and precision with relative error and relative standard deviation of less than 10% (n = 3). Acknowledgements The authors would like to thank the financial support from Faculty Research Grant (FRG/01-02/II-34) of Hong Kong Baptist University and the Environment and Conservation Fund (ECF-13/2004). We would also like to acknowledge the National Distinguished Young Scholar Award from the National Science Foundation of China (#20329701) and the Support from the CAS International Partnership Project. References [1] B. Strandberg, N.G. Dodder, I. Basu, R.A. Hites, Environ. Sci. Technol. 35 (2001) 1078. [2] S. Lacorte, M. Guillamon, E. Martinez, P. Viana, D. Barcelo, Environ. Sci. Technol. 37 (2003) 892. [3] K. Hartonen, S. Bøwardt, S.B. Hawthorne, M.-L. Riekkola, J. Chromatogr. A 774 (1997) 229. [4] M. Alaee, D.B. Sergeant, M.G. Ikonomou, J.M. Luross, Chemosphere 44 (2001) 1489. [5] J.W. Choi, T.S. Fujimaki, K. Kitamura, S. Hashimoto, H. Ito, N. Suzuki, S. Sakai, M. Morita, Environ. Sci. Technol. 37 (2003) 817. [6] J.R. Fowles, A. Fairbrother, L. Baecher-Steppan, N.I. Kerkvliet, Toxicology 86 (1994) 49. [7] I. Meerts, J.J. van Zanden, E. Luijks, I. van Leewen-Bol, G. Marsh, E. Jakobsson, A.A. Bergman, A. Brouwer, Toxicol. Sci. 56 (2000) 95. [8] G. Soderstrom, S. Marklund, Environ. Sci. Technol. 36 (2002) 1959. [9] D. Wang, Z. Cai, G. Jiang, A. Leung, M.H. Wong, R.W.K. Wong, Chemosphere 60 (2005) 810. [10] D. Wang, Z. Cai, G. Jiang, M.H. Wong, W.K. Wong, Rapid Commun. Mass Spectrom. 19 (2005) 83. [11] T. Hyotylainen, K. Hartonen, Trends Anal. Chem. 21 (2002) 13. [12] C. de Wit, Chemosphere 46 (2002) 583.