Lowering Detection Limits for the Analysis of PBDEs by Large Volume Injection and SIM on a Single Quadrupole
The Application Notebook
Polybrominated diphenyl ethers (PBDEs) are bioaccumulativetoxic compounds that are used as flame retardants. They have high boiling points and low thermal stability which makes analysis by GC–MS challenging. Additional bromines increase the thermal instability. A method was developed to analyze for polybrominated biphenyls using a large volume injection, short analytical column, and high mass tuning algorithm on the Thermo Scientific DSQ II with detection by EI Single Ion Monitoring (SIM).
Jessie Butler and Eric Phillips, Thermo Fisher Scientific
Polybrominated diphenyl ethers (PBDEs) are bioaccumulativetoxic compounds that are used as flame retardants. They have high boiling points and low thermal stability which makes analysis by GC–MS challenging. Additional bromines increase the thermal instability. A method was developed to analyze for polybrominated biphenyls using a large volume injection, short analytical column, and high mass tuning algorithm on the Thermo Scientific DSQ II with detection by EI Single Ion Monitoring (SIM).
Experimental Conditions
The analysis of flame retardants was performed using a Thermo Scientific TRACE GC, Thermo Scientific TriPlus autosampler and DSQ™ II single quadrupole in EI operated in SIM mode. Fourteen PBDE congeners were studied on a baffled deactivated glass liner with an injection speed of 2 μL/s. In the large volume injection mode, the sample is injected into the liner at the boiling point of the solvent with the Split Vent open to eliminate the solvent before the sample enters the column. The SIM scan was optimized at a dwell time of 100 ms with 3 ion quantitation and ion ratio verification at ±20%. The source temperature of the mass spectrometer was set to 275 °C. A TR-5MS capillary column was used at a programmed column flow rate of 1.5 mL/min for 13 min and then ramped to 2.5 mL/min for 4 min. The oven was programmed with an initial temperature of 120 °C increasing to 330 °C.
The full scan spectra for the BDE-209 showed elevated intensities for the m/z 959 bromine cluster with accurate mass assignment.
The calibration curve was run from 0.1 to 10 pg/μL (0.5 to 50 pg/μL for BDE-209) in the vial and replicate injections at 0.1 and 0.5 pg/μl were run to determine of detection limits (the results are in Table I). All compounds showed an average relative % RSD of 9.2%. BDE-209 generated a least squares fit of R2 = 0.9999.
Table I: DL, and Linear Fits. *quadratic fit
Results
The method incorporated the use of a temperature programmable injector which minimizes thermal degradation of PBDEs caused by hot inlets. A short analysis time of 16 min gave better response for the higher congeners due to shorter residence time in the column, decreasing adverse interactions in the stationary phase during separation. Finally the DSQ II was tuned for enhanced sensitivity for high mass PBDEs and demonstrated accurate mass assignment.
Conclusion
Analysis of PBDEs can be completed in less time with little to no degradation and very low sensitivity with large linear range calibration curves. Analysis of the range of low levels for sensitivity and high concentrations for heavy contamination is possible without the need for dilutions or reruns, resulting in a more efficient and less costly process.
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