Waste Management xxx (2014) xxx–xxx
Contents lists available at ScienceDirect
Waste Management journal homepage: www.elsevier.com/locate/wasman
Monitoring of WEEE plastics in regards to brominated flame retardants using handheld XRF Alexia Aldrian a,⇑, Alfred Ledersteger b, Roland Pomberger a a b
Chair of Waste Processing Technology and Waste Management, Montanuniversitaet Leoben, Franz-Josef-Straße 18, 8700 Leoben, Austria Saubermacher Dienstleistungs AG, Hans-Roth-Straße 1, 8073 Feldkirchen bei Graz, Austria
a r t i c l e
i n f o
Article history: Received 9 July 2014 Accepted 27 October 2014 Available online xxxx Keywords: Brominated flame retardants Handheld XRF Waste electrical and electronic equipment Waste plastics On-site investigation
a b s t r a c t This contribution is focused on the on-site determination of the bromine content in waste electrical and electronic equipment (WEEE), in particular waste plastics from television sets (TV) and personal computer monitors (PC) using a handheld X-ray fluorescence (XRF) device. The described approach allows the examination of samples in regards to the compliance with legal specifications for polybrominated biphenyls (PBBs) and polybrominated diphenyl ethers (PBDEs) directly after disassembling and facilitates the sorting out of plastics with high contents of brominated flame retardants (BFRs). In all, over 3000 pieces of black (TV) and 1600 pieces of grey (PC) plastic waste were analysed with handheld XRF technique for this study. Especially noticeable was the high percentage of pieces with a bromine content of over 50,000 ppm for TV (7%) and PC (39%) waste plastics. The applied method was validated by comparing the data of handheld XRF with results obtained by GC–MS. The results showed the expected and sufficiently accurate correlation between these two methods. It is shown that handheld XRF technique is an effective tool for fast monitoring of large volumes of WEEE plastics in regards to BFRs for on-site measurements. Ó 2014 Elsevier Ltd. All rights reserved.
1. Introduction In the past decades, the consumption of electrical and electronic equipment (EEE) used in households has grown significantly and this trend is continuing to evolve (Ongondo et al., 2011). With the increasing amounts of EEE being disposed of, the development of efficient recycling processes is necessary to meet economic demands as well as legal requirements. The rather high rates of recycling specified in the EU Directive 2002/96/EC on waste of electric and electronic equipment (European Union, 2003b) cannot be fulfilled by glass and metal recycling only. Hence, the other main component of WEEE, namely plastics with about 30 wt.% (Schlummer et al., 2007), may be processed and recycled as well. WEEE contains a whole range of hazardous substances such as heavy metals and organic compounds in significant quantities. The uncontrolled release of those substances during disposal and recycling may cause environmental problems due to leaching processes (Zhou et al., 2013; Kim et al., 2006) and/or emission during treatment of these materials. Previous work showed that considerable amounts of hazardous substances can be found even after ⇑ Corresponding author. Tel.: +43 (0)3842/402 5116; fax: +43 (0)3842/402 5112. E-mail addresses: [email protected] (A. Aldrian), a.ledersteger@ saubermacher.at (A. Ledersteger), [email protected] (R. Pomberger).
treatment of separately collected small WEEE, leading to significant dispersion of pollutants during further processing (Salhofer and Tesar, 2011). In order to limit the impact of hazardous substances of next generations of WEEE, the EU Directive (European Union, 2003a) on the restriction of hazardous substances (RoHS) (2002/95/EC) defines threshold values and also stipulates the substitution for the use of lead, cadmium, mercury, hexavalent chromium, polybrominated biphenyls (PBBs) and polybrominated diphenyl ethers (PBDEs) in new EEE produced for the EU market after 1st July, 2006. The maximum tolerable mass fractions for PBBs and PBDEs are 0.1 wt.% in homogeneous materials. These legal requirements are directly applicable in regards to the recycling of WEEE since recyclable materials also have to fulfil the regulations given the further utilisation. PBBs and PBDEs belong to the group of brominated flame retardants (BFRs). They were used extensively as cheap flame retardants in various products, e.g. computers, televisions, textiles, foam furniture, electronic circuitry, insulating foams and other building materials to reduce the flammability of the materials (Birnbaum and Staskal, 2004). Flame retardants are either incorporated by covalent bonding to the polymer (reactive type) or are dissolved in the polymeric matrix (additive type). Due to the weaker bond to the polymers, the additive type sometimes shows high volatility
http://dx.doi.org/10.1016/j.wasman.2014.10.025 0956-053X/Ó 2014 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Aldrian, A., et al. Monitoring of WEEE plastics in regards to brominated flame retardants using handheld XRF. Waste Management (2014), http://dx.doi.org/10.1016/j.wasman.2014.10.025
2
A. Aldrian et al. / Waste Management xxx (2014) xxx–xxx
and generally a tendency to leave the polymer resin more easily than the reactive type. Therefore, the leaching and the release of additive retardants such as PBBs and PBDEs are more likely to occur (Rahman et al., 2001). Due to several advantages regarding thermal stability and manageability, aromatic bromine compounds have been used extensively as cheap flame retardants all over the world for several decades. Currently, about 75 different BFRs are commercially available (Beard and Angeler, 2010). The most commonly used BFRs are polybrominated diphenyl ethers (PBDEs), polybrominated biphenyls (PBBs), tetrabromobisphenol A (TBBPA), tetrabromophthalic anhydride, dibromoneopentylglycol and brominated styrene (Rahman et al., 2001). PBBs and PBDEs are structurally similar to polychlorinated biphenyls (PCB) and dioxins/furans (PCDD/F) and therefore show comparable chemical and physical characteristics (de Wit, 2002). Depending on the number and positions of the bromine atoms on the two phenyl rings 209 congeners are possible. PBBs and PBDEs are stable substances that are resistant towards heat and light as well as chemical compounds (e.g., acids, bases, reducing and oxidising compounds). Trace levels detected even in remote areas suggest that they can undergo long-range atmospheric transport and are now already a worldwide problem. Due to their lipophilic properties PBBs and PBDEs tend to accumulate and therefore are found in biological samples and sediments all over the world. (Rahman et al., 2001) Former consumer goods such as television sets or computer monitors that were manufactured 10–20 years ago often contain high amounts of PBDE and are disposed of at present. The potential health risk for living organisms and the consequence of the spread of this compounds have not yet been fully understood (McDonald, 2002), but PBDEs are regarded as so-called endocrine disruptors because of their influence on the hormonal regulation in humans and animals. Due to their environmental impact, the use of PBDEs and PBBs is regulated today, especially in Europe. For instance, octaBDE and pentaBDE were used quite extensively in the past but were terminated in Europe in August 2004. Currently, the only commercial PBDE based products in Europe are decaBDE mixtures. (Beard and Angeler, 2010). Although a variety of alternatives to PBDEs and PBBs as flame retardants are being developed by the industry (e.g., compounds based on aluminium, phosphorus, nitrogen) (Beard and Angeler, 2010), the plastic parts of the currently disposed electric and electronic equipment partly contain large amounts of these brominated compounds as being produced mostly before implementation of legal specifications. In the mid-1990s, 150,000 tonnes of BFRs were produced annually, which equals to about 30% of the worldwide production of flame retardants (Hyötyläinen and Hartonen, 2002). By the end of the 1990s, the produced amount had almost doubled Eljarrat and Barceló, 2004). Due to the extensive usage of BFRs, the monitoring of the present waste plastics is imperative to prevent next generations of hazardous waste. For this purpose, reliable analyses methods for the determination of PBDEs and PBBs are necessary. Several analyses methods have been described and applied in the last years: gas chromatography with electron-capture detection (ECD) (Pöhlein et al., 2008; Król et al., 2012a) or mass spectrometry (Eljarrat and Barceló, 2004; Binici et al., 2013; Kemmlein et al., 2009) as well as liquid chromatography with different detectors (Schlummer et al., 2005, 2007). Scanning electron microscopy with energy dispersive spectrometry is also a frequently used analysis tool (Taurino et al., 2010). Radivojevic et al. (2004) used laser-induced plasma spectroscopy (LIPS) for the detection of bromine in electronic consumer goods. These methods are, however, rather time consuming and require sophisticated equipment as well as fairly complex and extensive sample preparation procedures (Hyötyläinen and Hartonen, 2002; Fulara and Czaplicka, 2012; Vilaplana et al., 2009) and
labour-intensive sampling (Beigbeder et al., 2013). Whilst the use of on-site near-infrared (NIR) devices have already been tested for the automated sorting of different polymers recently (Król et al., 2012b), they may only determine the composition of polymeric materials and are not conducive in regards to PBBs and PBDEs. Companies such as Titec GmbH or Pellenc SA offer automated systems for the removal of highly contaminated black plastic pieces using also XRF or LIBS (Laser induced plasma spectroscopy) technique. The high acquisition costs and low flexibility within the process using such systems are two of the major drawbacks. Tange et al. (2014), however, used a XRF sorter in the course of their study and presented promising results. Field portable X-ray fluorescence (XRF) techniques, however, provide a non-destructive and rapid-screening analytical approach (Kalnicky and Singhvi, 2001). Analyses results are available immediately and therefore allow an efficient utilisation of data. The use of portable XRF technology has already been reported for many different studies on environmental samples (Fulara and Czaplicka, 2012; Kalnicky and Singhvi, 2001; Melquiades and Appoloni, 2004; Higueras et al., 2012) and has gained widespread acceptance. Kilbride et al. (2006) compared results of different heavy metal contents gained by field portable XRF with those of the conventional acid extraction followed by an ICP-OES analysis and reported good accordance. The main aim of this contribution is to prove suitability of a fast characterisation of WEEE plastics in regards to BFRs. This research is focused on the on-site determination of the bromine content in two different types of WEEE, namely the outer housing of television sets (TV) and computer monitors (PC) with a handheld XRF. This approach allows the examination of samples in regards to the compliance with legal specifications for PBDEs and PBBs directly after disassembling and facilitates the sorting out of plastics with high contents of BFRs. The use of handheld XRF allowed for constant and fast monitoring of very large volumes of WEEE plastics and the collection of data on the waste plastics currently being disposed of. 2. Experimental section 2.1. Validation of handheld XRF for monitoring bromine in TV and PC waste plastics Before application of handheld XRF for monitoring purposes of bromine during routine operations, the method was verified and the application of the device optimised (e.g. measurement time). Fig. 1 shows an overview of the methodical validation process for this study. For all measurements, a handheld XRF (Niton XL 2 Goldd) by Thermo Scientific with the manufacturer’s default software program ‘‘Environmental samples’’ was used. The material of the anode used in the XRF is silver and the tube’s maximum voltage is 45 kV, the maximum current 100 lA. The detection of X-rays is achieved by a high resolution Silicon-PIN detector that was especially developed for the detection of lighter element. The company-specific name for this detector is GOLDD (Geometrically Optimized Large Area Drift Detector). The XRF instrument was directly placed on the surface of the already dismantled, plain plastic housing of television and personal computer sets for measurement. The housings did not contain any electronic parts. The measurements were carried out in an designated area. Therefore, the surroundings and the influence of potential chemical interferences were the same for every sample. The accuracy of results obtained with XRF was verified by testing six different individual pieces of waste plastics (TV and PC casings) and comparing the results to a well-established reference method (GC–MS after extraction and clean-up steps). The same pieces were first used for the XRF analyses and afterwards
Please cite this article in press as: Aldrian, A., et al. Monitoring of WEEE plastics in regards to brominated flame retardants using handheld XRF. Waste Management (2014), http://dx.doi.org/10.1016/j.wasman.2014.10.025
3
A. Aldrian et al. / Waste Management xxx (2014) xxx–xxx
Fig. 1. Overview on validation approach for this application.
shredded and prepared for analyses with GC–MS. The analyses using GC–MS were done by an accredited German laboratory. accredited according to the international standard ISO 17025. The laboratory performed an accelerated solvent extraction (ASE) with toluene. The extracts were doped with internal 13C12-marked standard solutions containing BDE-28, BDE-47, BDE-99, BDE-153, BDE-183, BDE-197, BDE-207, BDE-209. After a clean-up step of the extract using column chromatography, analysis was done with capillary column gas chromatography coupled with mass spectrometry (GC–MS; Agilent GC 6890 and MSD 5973). The qualitative identification of compounds was done using molecule and fragment ions. The internal standards doped with 13C were used for the quantification of all congeners. The detection limit for the applied method was 5 lg/kg. The uncertainty of this analyses method was 25%. The six analysed waste plastics were chosen in view of their different bromine contents and thus covering the whole working range for this application. In addition, the plastic parts had completely different surface texture (e.g. rough, smooth). Total testing time for each sample was at least five seconds (s), giving a reasonable standard deviation for results. The precision of handheld XRF was determined by repeat measurements of four samples featuring different levels of PBDEs and PBBs. The samples were analysed at the very beginning of a series of measurements, after every fiftieth sample and after site activities were completed. This way, the samples were measured ten times each, allowing for the calculation of mean, standard deviation and relative standard deviation in percent. The influence of the placement of the device on the samples was also assessed by measurements having either a gap between the sample and the device or applying maximum surface to surface contact. Furthermore, the optimum testing time was ascertained, which had a direct influence on the standard deviation generated by the XRF device. Therefore, six samples were analysed for a relatively short period of 5 s as well as a prolonged measurement time of 30 s. 2.2. Appointing a limit value for handheld XRF for routine measurement With XRF, the determination of the bromine content in a sample is possible, but this analysis method cannot give any information on the chemical form of an element. For this purpose several hundred TV and PC monitors were sampled by cutting out 10 mm 10 mm pieces of each monitor. These pieces were then assembled to six separate collective samples. The samples were analysed by an accredited German laboratory in regards to PBBs and PBDEs using the same approach described in Section 2.1. The results showed that mainly high brominated diphenylethers (hexa-brominated diphenylether, hepta-BDE, octa-BDE, nona-BDE, deca-BDE) are found in these
Table 1 Content of PBDE congeners in collective samples of TV waste plastics. PBDE congener
Hexa-BDE Hepta-BDE Octa-BDE Nona-BDE Deca-BDE Weighted empirical factor (–) Average empirical factor (–)
Collective samples (ppm) I
II
III
IV
V
VI
Contents lists available at ScienceDirect
Waste Management journal homepage: www.elsevier.com/locate/wasman
Monitoring of WEEE plastics in regards to brominated flame retardants using handheld XRF Alexia Aldrian a,⇑, Alfred Ledersteger b, Roland Pomberger a a b
Chair of Waste Processing Technology and Waste Management, Montanuniversitaet Leoben, Franz-Josef-Straße 18, 8700 Leoben, Austria Saubermacher Dienstleistungs AG, Hans-Roth-Straße 1, 8073 Feldkirchen bei Graz, Austria
a r t i c l e
i n f o
Article history: Received 9 July 2014 Accepted 27 October 2014 Available online xxxx Keywords: Brominated flame retardants Handheld XRF Waste electrical and electronic equipment Waste plastics On-site investigation
a b s t r a c t This contribution is focused on the on-site determination of the bromine content in waste electrical and electronic equipment (WEEE), in particular waste plastics from television sets (TV) and personal computer monitors (PC) using a handheld X-ray fluorescence (XRF) device. The described approach allows the examination of samples in regards to the compliance with legal specifications for polybrominated biphenyls (PBBs) and polybrominated diphenyl ethers (PBDEs) directly after disassembling and facilitates the sorting out of plastics with high contents of brominated flame retardants (BFRs). In all, over 3000 pieces of black (TV) and 1600 pieces of grey (PC) plastic waste were analysed with handheld XRF technique for this study. Especially noticeable was the high percentage of pieces with a bromine content of over 50,000 ppm for TV (7%) and PC (39%) waste plastics. The applied method was validated by comparing the data of handheld XRF with results obtained by GC–MS. The results showed the expected and sufficiently accurate correlation between these two methods. It is shown that handheld XRF technique is an effective tool for fast monitoring of large volumes of WEEE plastics in regards to BFRs for on-site measurements. Ó 2014 Elsevier Ltd. All rights reserved.
1. Introduction In the past decades, the consumption of electrical and electronic equipment (EEE) used in households has grown significantly and this trend is continuing to evolve (Ongondo et al., 2011). With the increasing amounts of EEE being disposed of, the development of efficient recycling processes is necessary to meet economic demands as well as legal requirements. The rather high rates of recycling specified in the EU Directive 2002/96/EC on waste of electric and electronic equipment (European Union, 2003b) cannot be fulfilled by glass and metal recycling only. Hence, the other main component of WEEE, namely plastics with about 30 wt.% (Schlummer et al., 2007), may be processed and recycled as well. WEEE contains a whole range of hazardous substances such as heavy metals and organic compounds in significant quantities. The uncontrolled release of those substances during disposal and recycling may cause environmental problems due to leaching processes (Zhou et al., 2013; Kim et al., 2006) and/or emission during treatment of these materials. Previous work showed that considerable amounts of hazardous substances can be found even after ⇑ Corresponding author. Tel.: +43 (0)3842/402 5116; fax: +43 (0)3842/402 5112. E-mail addresses: [email protected] (A. Aldrian), a.ledersteger@ saubermacher.at (A. Ledersteger), [email protected] (R. Pomberger).
treatment of separately collected small WEEE, leading to significant dispersion of pollutants during further processing (Salhofer and Tesar, 2011). In order to limit the impact of hazardous substances of next generations of WEEE, the EU Directive (European Union, 2003a) on the restriction of hazardous substances (RoHS) (2002/95/EC) defines threshold values and also stipulates the substitution for the use of lead, cadmium, mercury, hexavalent chromium, polybrominated biphenyls (PBBs) and polybrominated diphenyl ethers (PBDEs) in new EEE produced for the EU market after 1st July, 2006. The maximum tolerable mass fractions for PBBs and PBDEs are 0.1 wt.% in homogeneous materials. These legal requirements are directly applicable in regards to the recycling of WEEE since recyclable materials also have to fulfil the regulations given the further utilisation. PBBs and PBDEs belong to the group of brominated flame retardants (BFRs). They were used extensively as cheap flame retardants in various products, e.g. computers, televisions, textiles, foam furniture, electronic circuitry, insulating foams and other building materials to reduce the flammability of the materials (Birnbaum and Staskal, 2004). Flame retardants are either incorporated by covalent bonding to the polymer (reactive type) or are dissolved in the polymeric matrix (additive type). Due to the weaker bond to the polymers, the additive type sometimes shows high volatility
http://dx.doi.org/10.1016/j.wasman.2014.10.025 0956-053X/Ó 2014 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Aldrian, A., et al. Monitoring of WEEE plastics in regards to brominated flame retardants using handheld XRF. Waste Management (2014), http://dx.doi.org/10.1016/j.wasman.2014.10.025
2
A. Aldrian et al. / Waste Management xxx (2014) xxx–xxx
and generally a tendency to leave the polymer resin more easily than the reactive type. Therefore, the leaching and the release of additive retardants such as PBBs and PBDEs are more likely to occur (Rahman et al., 2001). Due to several advantages regarding thermal stability and manageability, aromatic bromine compounds have been used extensively as cheap flame retardants all over the world for several decades. Currently, about 75 different BFRs are commercially available (Beard and Angeler, 2010). The most commonly used BFRs are polybrominated diphenyl ethers (PBDEs), polybrominated biphenyls (PBBs), tetrabromobisphenol A (TBBPA), tetrabromophthalic anhydride, dibromoneopentylglycol and brominated styrene (Rahman et al., 2001). PBBs and PBDEs are structurally similar to polychlorinated biphenyls (PCB) and dioxins/furans (PCDD/F) and therefore show comparable chemical and physical characteristics (de Wit, 2002). Depending on the number and positions of the bromine atoms on the two phenyl rings 209 congeners are possible. PBBs and PBDEs are stable substances that are resistant towards heat and light as well as chemical compounds (e.g., acids, bases, reducing and oxidising compounds). Trace levels detected even in remote areas suggest that they can undergo long-range atmospheric transport and are now already a worldwide problem. Due to their lipophilic properties PBBs and PBDEs tend to accumulate and therefore are found in biological samples and sediments all over the world. (Rahman et al., 2001) Former consumer goods such as television sets or computer monitors that were manufactured 10–20 years ago often contain high amounts of PBDE and are disposed of at present. The potential health risk for living organisms and the consequence of the spread of this compounds have not yet been fully understood (McDonald, 2002), but PBDEs are regarded as so-called endocrine disruptors because of their influence on the hormonal regulation in humans and animals. Due to their environmental impact, the use of PBDEs and PBBs is regulated today, especially in Europe. For instance, octaBDE and pentaBDE were used quite extensively in the past but were terminated in Europe in August 2004. Currently, the only commercial PBDE based products in Europe are decaBDE mixtures. (Beard and Angeler, 2010). Although a variety of alternatives to PBDEs and PBBs as flame retardants are being developed by the industry (e.g., compounds based on aluminium, phosphorus, nitrogen) (Beard and Angeler, 2010), the plastic parts of the currently disposed electric and electronic equipment partly contain large amounts of these brominated compounds as being produced mostly before implementation of legal specifications. In the mid-1990s, 150,000 tonnes of BFRs were produced annually, which equals to about 30% of the worldwide production of flame retardants (Hyötyläinen and Hartonen, 2002). By the end of the 1990s, the produced amount had almost doubled Eljarrat and Barceló, 2004). Due to the extensive usage of BFRs, the monitoring of the present waste plastics is imperative to prevent next generations of hazardous waste. For this purpose, reliable analyses methods for the determination of PBDEs and PBBs are necessary. Several analyses methods have been described and applied in the last years: gas chromatography with electron-capture detection (ECD) (Pöhlein et al., 2008; Król et al., 2012a) or mass spectrometry (Eljarrat and Barceló, 2004; Binici et al., 2013; Kemmlein et al., 2009) as well as liquid chromatography with different detectors (Schlummer et al., 2005, 2007). Scanning electron microscopy with energy dispersive spectrometry is also a frequently used analysis tool (Taurino et al., 2010). Radivojevic et al. (2004) used laser-induced plasma spectroscopy (LIPS) for the detection of bromine in electronic consumer goods. These methods are, however, rather time consuming and require sophisticated equipment as well as fairly complex and extensive sample preparation procedures (Hyötyläinen and Hartonen, 2002; Fulara and Czaplicka, 2012; Vilaplana et al., 2009) and
labour-intensive sampling (Beigbeder et al., 2013). Whilst the use of on-site near-infrared (NIR) devices have already been tested for the automated sorting of different polymers recently (Król et al., 2012b), they may only determine the composition of polymeric materials and are not conducive in regards to PBBs and PBDEs. Companies such as Titec GmbH or Pellenc SA offer automated systems for the removal of highly contaminated black plastic pieces using also XRF or LIBS (Laser induced plasma spectroscopy) technique. The high acquisition costs and low flexibility within the process using such systems are two of the major drawbacks. Tange et al. (2014), however, used a XRF sorter in the course of their study and presented promising results. Field portable X-ray fluorescence (XRF) techniques, however, provide a non-destructive and rapid-screening analytical approach (Kalnicky and Singhvi, 2001). Analyses results are available immediately and therefore allow an efficient utilisation of data. The use of portable XRF technology has already been reported for many different studies on environmental samples (Fulara and Czaplicka, 2012; Kalnicky and Singhvi, 2001; Melquiades and Appoloni, 2004; Higueras et al., 2012) and has gained widespread acceptance. Kilbride et al. (2006) compared results of different heavy metal contents gained by field portable XRF with those of the conventional acid extraction followed by an ICP-OES analysis and reported good accordance. The main aim of this contribution is to prove suitability of a fast characterisation of WEEE plastics in regards to BFRs. This research is focused on the on-site determination of the bromine content in two different types of WEEE, namely the outer housing of television sets (TV) and computer monitors (PC) with a handheld XRF. This approach allows the examination of samples in regards to the compliance with legal specifications for PBDEs and PBBs directly after disassembling and facilitates the sorting out of plastics with high contents of BFRs. The use of handheld XRF allowed for constant and fast monitoring of very large volumes of WEEE plastics and the collection of data on the waste plastics currently being disposed of. 2. Experimental section 2.1. Validation of handheld XRF for monitoring bromine in TV and PC waste plastics Before application of handheld XRF for monitoring purposes of bromine during routine operations, the method was verified and the application of the device optimised (e.g. measurement time). Fig. 1 shows an overview of the methodical validation process for this study. For all measurements, a handheld XRF (Niton XL 2 Goldd) by Thermo Scientific with the manufacturer’s default software program ‘‘Environmental samples’’ was used. The material of the anode used in the XRF is silver and the tube’s maximum voltage is 45 kV, the maximum current 100 lA. The detection of X-rays is achieved by a high resolution Silicon-PIN detector that was especially developed for the detection of lighter element. The company-specific name for this detector is GOLDD (Geometrically Optimized Large Area Drift Detector). The XRF instrument was directly placed on the surface of the already dismantled, plain plastic housing of television and personal computer sets for measurement. The housings did not contain any electronic parts. The measurements were carried out in an designated area. Therefore, the surroundings and the influence of potential chemical interferences were the same for every sample. The accuracy of results obtained with XRF was verified by testing six different individual pieces of waste plastics (TV and PC casings) and comparing the results to a well-established reference method (GC–MS after extraction and clean-up steps). The same pieces were first used for the XRF analyses and afterwards
Please cite this article in press as: Aldrian, A., et al. Monitoring of WEEE plastics in regards to brominated flame retardants using handheld XRF. Waste Management (2014), http://dx.doi.org/10.1016/j.wasman.2014.10.025
3
A. Aldrian et al. / Waste Management xxx (2014) xxx–xxx
Fig. 1. Overview on validation approach for this application.
shredded and prepared for analyses with GC–MS. The analyses using GC–MS were done by an accredited German laboratory. accredited according to the international standard ISO 17025. The laboratory performed an accelerated solvent extraction (ASE) with toluene. The extracts were doped with internal 13C12-marked standard solutions containing BDE-28, BDE-47, BDE-99, BDE-153, BDE-183, BDE-197, BDE-207, BDE-209. After a clean-up step of the extract using column chromatography, analysis was done with capillary column gas chromatography coupled with mass spectrometry (GC–MS; Agilent GC 6890 and MSD 5973). The qualitative identification of compounds was done using molecule and fragment ions. The internal standards doped with 13C were used for the quantification of all congeners. The detection limit for the applied method was 5 lg/kg. The uncertainty of this analyses method was 25%. The six analysed waste plastics were chosen in view of their different bromine contents and thus covering the whole working range for this application. In addition, the plastic parts had completely different surface texture (e.g. rough, smooth). Total testing time for each sample was at least five seconds (s), giving a reasonable standard deviation for results. The precision of handheld XRF was determined by repeat measurements of four samples featuring different levels of PBDEs and PBBs. The samples were analysed at the very beginning of a series of measurements, after every fiftieth sample and after site activities were completed. This way, the samples were measured ten times each, allowing for the calculation of mean, standard deviation and relative standard deviation in percent. The influence of the placement of the device on the samples was also assessed by measurements having either a gap between the sample and the device or applying maximum surface to surface contact. Furthermore, the optimum testing time was ascertained, which had a direct influence on the standard deviation generated by the XRF device. Therefore, six samples were analysed for a relatively short period of 5 s as well as a prolonged measurement time of 30 s. 2.2. Appointing a limit value for handheld XRF for routine measurement With XRF, the determination of the bromine content in a sample is possible, but this analysis method cannot give any information on the chemical form of an element. For this purpose several hundred TV and PC monitors were sampled by cutting out 10 mm 10 mm pieces of each monitor. These pieces were then assembled to six separate collective samples. The samples were analysed by an accredited German laboratory in regards to PBBs and PBDEs using the same approach described in Section 2.1. The results showed that mainly high brominated diphenylethers (hexa-brominated diphenylether, hepta-BDE, octa-BDE, nona-BDE, deca-BDE) are found in these
Table 1 Content of PBDE congeners in collective samples of TV waste plastics. PBDE congener
Hexa-BDE Hepta-BDE Octa-BDE Nona-BDE Deca-BDE Weighted empirical factor (–) Average empirical factor (–)
Collective samples (ppm) I
II
III
IV
V
VI
