The 8th Mass Spectrometry CVG Annual Symposium - Full Day Event!!!
Presentation No. 2 - Dioxin Analysis by Gas Chromatography-Fourier Transform Mass Spectrometry
Vincent Y. Taguchi1; Ray E. Clement1; Stefan Krolik3; Robert Nieckarz1,2; Robert Williams4
1Ministry of the Environment, Toronto, ON; 2University of Waterloo, Waterloo, Canada; 3Consultant to Varian Inc, Montreal, Canada; 4Varian Inc, Lake Forest, CA
Novel Aspect: GC-FTMS analysis of brominated- and chlorinated-dioxins at ultrahigh resolution
Introduction: The monitoring of chlorinated-dibenzodioxins/furans (CDDs/CDFs) is an important environmental priority. Monitoring of brominated-dibenzodioxins/furans (BDDs/BDFs) and mixed brominated-/chlorinated-dibenzodioxins/furans (BCDDs/BCDFs) is also important because brominated compounds are expected to be generally of comparable or greater toxicity than chlorinated compounds.The standard method of analysis of CDDs/CDFs involves the targeted use of high resolution mass spectrometers operating at 10,000 resolution. Using this method, BCDDs/BCDFs cannot be differentiated from CDDs/CDFs because ultrahigh resolution is required. Fourier transform mass spectrometers (FTMS) can provide ultrahigh resolution and ultrahigh mass accuracy, capabilities that can be used to expand the range of analyzable BCDDs/BCDFs, improve selectivity and, more significantly, potentially provide a rapid screening method for detecting total CDDs/CDFs, BDDs/BDFs, BCDDs, BCDFs in a single method.
Methods: Analyses were performed on a Varian 920-MS equipped with a 9.4T superconducting magnet, a triple quadrupole front end, a CP-3800 GC and a CP-8400 autosampler. The instrument was operated in electron ionization mode at 80,000 to 100,000 resolution with a cycle time of 1.5 seconds over the mass range 200-650 Th. The GC conditions were optimised to give a total run time less than 20 minutes. CDD/CDF standards consisting of CS1 to CS5 were used to assess the method in terms of sensitivity and reproducibility. Samples taken from a fire were used to assess the viability of using this as a screening method and results were compared to those obtained using the standard GC-HRMS method.
Results: The preliminary data obtained from CDD/CDF and BCDD/BCDF standards showed excellent reproducibility and precision compared with the standard GC-HRMS method. Isotope ratios obtained were well within the acceptable range. The sensitivity obtained was approximately 20 times less than that using the standard method. Several factors that could improve the sensitivity were identified and are being addressed. Resolutions in the range of 80,000 to 100,000 were obtained on the capillary GC time scale. The mass accuracy on standards was better than 0.5 ppm using external mass calibration and was better than 2 ppm on samples. Where mass accuracies were out of this range, analyte interferences could be observed. A significant benefit of the method developed was in the domain of screening. Results of total CDDs and CDFs from "real-world" samples showed a good correlation between those obtained using the GC-FTMS and the standard GC-HRMS method. Moreover, due to the acquisition of full mass range, ultrahigh resolution spectra using the FTMS, as opposed to SIM using the GC-HRMS method, it was possible to analyze the data and screen for other possible sample components such as the mixed BCDD/BCDF in the same analysis.
