Abstract

DirectProbe (DIP)-atmospheric pressure photo ionization (APPI) and atmospheric pressure chemical ionization (APCI) is coupled to a high resolution time-of-flight mass spectrometer (HR-TOF-MS) for the fast screening of flame retardants in plastics from electronic products. A few milligrams of solid is obtained by simply scratching the surface of the products with a glass capillary. Subsequently the capillary is introduced directly into the source. The analysis is performed within a few minutes. The method is applicable to polybrominated diphenylethers (PBDEs), new brominated flame retardants (BFRs) and organophosphorus flame retardants (PFRs). The combination of DIP with HRMS spectra and data processing based on mass accuracy and isotopic patterns allows the identification of these chemicals at low levels below 0.1% in weight of material.

Introduction

Flame retardants are frequently applied in electronics for enhancing fire safety. The use of PBDEs has been restricted to a maximum concentration of 0.1 % by weight in electronic and electrical equipment [1] due to their persistence and toxic properties.[2],[3] Screening methods proposed in literature for screening flame retardants are mainly based on total bromine content, e.g. X-ray fluorescence (XRF)4.

Authors

Ana Ballesteros Gómez, Pim. E.G. Leonards; Institute for Environmental Studies (IVM), VU University Amsterdam, Amsterdam, The Netherlands

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Application Note # ET-39DirectProbe Atmospheric Pressure Photo Ionization /Atmospheric Pressure Chemical Ionization High Resolution Mass Spectrometry for Fast Screening of Flame Retardants and Plasticizers in Plastics of Electronic Products

Keywords Instrumentation and Software

Flame retardants microTOF II

DirectProbe (DIP) DirectProbe (DIP)

probe is mounted instead of a nebulizer sprayer on top of the vaporizer heater of the the APCI/APPI source (Figure 3). The nebulizer gas is directly connected to the DIP and directed against it. DataAnalysis 4.0 software was used for screening using SmartFormula and CompoundCrawler tools. SmartFormula provides identification on the basis of accurate mass and true isotopic pattern. CompoundCrawler connects to online accurate mass databases (e.g. Metlin, Chemspider) for formula identification in untargeted screening.

Samples

Samples of electronic waste (e-waste, n=2) supplied as shredder material (less than ~1 mm particle size) and a variety of hard plastic parts of consumer products (electrical adaptors, powerboards and televisions, n=9) were also analyzed without further sample preparation. The glass capillary were loaded (in the open side of the tube) with

The DIP methods constitute a good alternative by offering the possibility of identifying the individual flame retardants including those without bromine. They also have a great potential for the identification of unknowns, since sample preparation or chromatography that could lead to losses of compounds, is not needed. Both DIP-APCI/APPI methods are suitable for screening flame retardants, the latter providing more sensitivity for the most apolar flame retardants. The optimization and application of these methods have been recently published.[5],[7]

Experimental

Instrumentation

A micrOTOF II mass spectrometer (Bruker) was used as detector and equipped with APCI and APPI sources, both equipped with a DirectProbe (DIP) assembly (Bruker). The DirectProbe is an add-on to the APCI or APPI source. The

Fig. 1: DIP- APPI(-) spectrum of an electronic waste sample showing brominated flame retardants

Fig. 2: DIP-APCI(+) spectra of a powerboard sample showing the unreported novel flame retardant TTBP-TAZ

a tiny amount of sample (few milligrams) by inserting them directly into the shredder material (e-waste) or by scratching the surface of the solid sample (electronic products) with the capillary to release small particles. The size of sample particles for DIP analysis should be in the micrometer range to obtain an efficient desorption/ionization. This can easily be obtained by just scratching the surface of the material. Main particles in the outer surface of the probe were removed with a lint-free cotton cloth to prevent contamination of the source and a drop of ~5 µL of calibration solution (Agilent APCI tune mix) was added at the outer surface of the probe before introducing it into the MS source. After each run (3-4 min), the probe was removed and the vaporization source temperature increased to 450 ºC (~2 min) for cleaning possible residues. Blanks (unloaded probes with calibration solution) were checked between samples to prevent carry-over contamination. The MS parameters for analysis are given in Table 1.

Results and Discussion

Bromine containing compounds were analyzed by APCI or APPI in the negative mode. The main ion was [M−Br+O]-, except for tetrabromobisphenol A (TBBPA) and hexabromocyclododecane HBCD ([M-H]-), 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE) (fragment C6Br3H2O

-) and hexachlorocyclopentenyl-dibromocyclooctane (HCDBCO) ([M-Cl+O]-). PFRs were analyzed in the APCI or APPI positive mode, monitoring the ion [M+H]+, except for 2-ethylhexyldiphenyl phosphate (EHDPHP) [M-C8H17+H2]. In general, the APPI source generated cleaner spectra than

Fig. 3: The DirectProbe assembly (left) is an add-on to the Bruker APCI II ion source. Sample preparation involves simply dipping the disposable glass capillary (green) into the solid or liquid sample and sliding it into the APCI II source where vaporization and ionization takes place.

Bruker APCI II ion source with DirectProbe assembly (DIP)

the APCI source at the same temperature (more selective ionization mechanism) and, as expected, a better sensitivity for highly non-polar compounds. The introduction of a dopant solvent in DIP-APPI was not needed for the efficient desorption/ionization of flame retardantsThe source vaporizer temperature had a strong influence on the desorption/ionization process and the optimal value was dependent on the compound type. Due to these differences and in order to obtain a certain degree of separation between matrix components and target compounds, two vaporizer temperature segments were set in the program of the analysis (see Table 1). Regarding the samples, highly brominated PBDEs and TBBPA were frequently detected in both e-waste and plastic consumer products when operating negative mode [5]. Regarding PFRS, tris(phenyl) phosphate (TPHP) was the most common PFR in e-waste and consumer products (only not found in one television sample), tris(methylphenyl) phosphate (TMPP) was detected in one e-waste sample and one television sample and tris(2-chloroethyl) phosphate (TCEP) was also detected in one television [5]. Two novel PFRs, namely resorcinol bis(biphenylphosphate) (PBDPP or RDP) and bisphenol A bis(bisphenylphosphate) (BPA-BDPP or BDP), for which data is still scarce in the literature [7], were identified in many of the consumer products [5]. An unreported brominated flame retardant, 2,4,6-tris(2,4,6-tribromophenoxy)-1,3,5-triazine (TTBP-TAZ), was also identified in many products [6]. All the results were confirmed by standard GC-MS or LC-MS techniques. Some results are shown in Table 2.

System TOF Parameters

Direct Probe-APCI-HRTOF

Capillary (neg./pos.) -/+1000 VEnd plate offset (neg.) -1000 (pos.) -500Corona (neg.) -8000 nA (pos.) +5000 nADry gas 2 L/min barNebulizer 4 barDry Heater 220 ºCVaporizer temperature at 210 ºC (0-1.5 min) and at 280 ºC (1.5-3 min) in APCI (-) and at 250 ºC (0-1.5 min) and at 300 ºC (1.5-3 min) in APCI (+)

Direct Probe-APPI-HRTOF

Capillary (neg./pos.) -/+700 VEnd plate offset (neg.) -1000 (pos.) -500Dry gas 4 L/min barNebulizer 3 barDry Heater 220 ºCVaporizer temperature at 250 ºC (0-1.5 min) and 300 ºC (1.5-3 min) in APPI(-) and at 250 ºC (0-1.5 min) and 325 ºC (1.5-3.0 min) in APPI (+)

Table 1: MS-HRTOF parameters

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Bruker Daltonik GmbH

Bremen · GermanyPhone +49 (0)421-2205-0Fax +49 (0)421-2205-103sales@bdal.de

Bruker Daltonics Inc.

Billerica, MA · USAPhone +1 (978) 663-3660Fax +1 (978) 667-5993ms-sales@bdal.com

www.bruker.com

For research use only. Not for use in diagnostic procedures.

References

[1] Directive 2002/95/EC of the European Parliament and

of the Council on the restriction of the use of certain

hazardous substances in electrical and electronic equipment,

Off. J. European Union, 2003, L37, 19-23

[2] P.O. Darnerud Env.Int. 29 (2003) 841-853.

[3] A.P. Vonderheide , K.E. Mueller, J. Meija , G.L. Welsh,

Sci. Total Environ. 400 (2008) 425-436

[4] C. Gallen, A. Banks, S. Brandsma, C. Baduel, P. Thai,

G. Eaglesham, A. Heffernan, P. Leonards, P. Bainton,

J.F. Mueller, Sci. Total Environ.(2014)

doi: 10.1016/j. scitotenv.2014.01.074

[5] A. Ballesteros-Gómez, S.H. Brandsma, J. De Boer,

P.E.G. Leonards, Anal. Bioanal. Chem. 406 (2014) 2503-2512.

[6] A. Ballesteros-Gómez, J. De Boer, P.E.G. Leonards,

Environ. Sci. Technol. 48 (2014) 4468-4474.

[7] S.H. Brandsma,U. Sellström, C.A. de Wit, J. de Boer, P.E.G.

Leonards, Environ. Sci. Technol. 47 (2013) 14434-14441.

Conclusion

DIP-APPI (and DIP-APCI) coupled to HR-TOF-MS can be successfully applied for the fast screening of flame retardants with detection limits of about 0.025-0.1 % by weight. PBDEs, new BFRs and PFRs, including the novel PBDPP and BPA-BDPP and TTBP-TAZ were detected in many samples of electronic and electrical equipment. The DIP-APPI/APCI-HR-TOF-MS methods are fast (few minutes), easy, inexpensive and provide with a broad scope screening for the identification of flame retardants for compliance with the European WEEE directive and for the identification of unknowns.

Acknowledgements

The first author acknowledges the funding of her postdoctoral fellowship funded by the European Commission Marie Curie ITN INFLAME project (no. 264600).

HeptaBDEcongeners

OctaBDEcongeners

DecaBDETBBPA TCEP TPHP TMPP

Other flame retar-dants identified by DIP analysis

Electronic waste

+(0.1%)

+(0.7%)

+(0.2%)

+(1.6%)

-(n.d.)

+(0.4%)

+(0.2%)

Electrical adaptor

+(0.02%)

+(0.02%)

+(0.8%)

+(6%)

-(n.d.)

+(0.02%)

-(n.d.)

PBDPP, BPA-BDPP, TTBP-TAZ

Electrical powerboard

-(n.d.)

-(n.d.)

+(0.03%)

+(7%)

-(n.d.)

-(n.d.)

-(n.d.)

PBDPP, BPA-BDPP, TTBP-TAZ

Television 1+

(0.01%)+

(0.01%)+

(5%)+

(0.2%)-

(n.d.)+

(1%)-

(n.d.)PBDPP, BPA-

BDPP

Television 2+

(0.04%)+

(0.04%)+

(9%)+

(0.3%)+

(0.1%)+

(0.4%)-

(n.d.)PBDPP, BPA-

BDPP, TTBP-TAZ

Television 3-

(n.d.)-

(n.d.)-

(n.d.)-

(n.d.)-

(n.d.)-

(n.d.)-

(n.d.)TTBP-TAZ

Table 2: Presence of flame retardants in e-waste and consumer products analyzed by DIP-APCI/APPI(-)HRTOF-MS and concentrations determined by a confirmatory technique in parenthesis.

Confirmatory technique (LC-MS or GC-MS). Abbreviations: n.d., not detected; BDE, brominated diphenyl ether; TBBPA, tetrabromo-bisphenol A; TCEP, Tris(2-chloroethyl) phosphate; TPHP, tris(phenyl) phosphate; TMPP, Tris(methylphenyl) phosphate, PBDPP, resorcinol bis(biphenylphosphate); BPA-BDPP, bisphenol A bis(bisphenylphosphate); TTBP-TAZ, 2,4,6-tris(2,4,6-tribromophenoxy)-1,3,5-triazine