The Truth About Dioxin Analysis: Using High Resolution GC-TOFMS and GCxGC-TOFMS to. Analytical Approaches

Transcription

1 The Truth About Dioxin Analysis: Using High Resolution GC-TOFMS and GCxGC-TOFMS to Uncover the Pollutants Ignored by Targeted Analytical Approaches Peter Gorst-Allman 1, Jack Cochran 2, Jayne de Vos 3 and Eric Reiner 4 1 LECO Africa (Pty) Ltd., 2 Restek Corporation, 3 NMISA, and 4 Ministry of the Environment, Toronto peter@lecoafrica.co.za

2 Common Abbreviations used in the Presentation TCDD PCDD HeCDD HpCDD OCDD PCDD TCDF PCDF HeCDF HpCDF OCDF PCDF GC-HRMS GCxGC Tetrachloro-dibenzo-p-dioxin Pentachloro-dibenzo-p-dioxin Hexachloro-dibenzo-p-dioxin Heptachloro-dibenzo-p-dioxin Octachloro-dibenzo-p-dioxin Polychloro-dibenzo-p-dioxin Tetrachloro-dibenzofuran Pentachloro-dibenzofuran Hexachloro-dibenzofuran Heptachloro-dibenzofuran Octachloro-dibenzofuran Polychloro-dibenzofuran Gas Chromatography High Resolution Mass Spectrometry Comprehensive Gas Chromatography TOFMS HRT EPA SIM POP RRF EI ev LOD MS/MS ppm Da m/z Time of Flight Mass Spectrometry High Resolution Time of Flight Mass Spectrometry Environmental Protection Agency Selected Ion Monitoring Persistent Organic Pollutant Relative Response Factor Electron Ionisation Electron Voltage Limit of Detection Tandem Mass Spectrometry Parts per million Daltons Mass to charge ratio

3 The Current Situation Globally, chlorinated dioxins and furans are analysed by expensive gas chromatography high resolution mass spectrometry (GC- HRMS) using EPA Methods such as 8290A or 1613B, or local methodology based on these

4 Why does HRMS have the edge? Dioxins usually occur at low levels in the presence of much higher matrix interferences The selectivity and sensitivity of HRMS is needed: selectivity is achieved by working at a resolution of +/ , sensitivity by using SIM (selected ion monitoring) Ion abundance ratios are used to confirm identity (e.g. for TCDD / , theoretically 0.77, allowed )

5 Disadvantages of HRMS To achieve the sensitivity required by regulatory methods, the HRMS approach uses selected ion monitoring (SIM) This is a target molecule technique, and requires a list of the selected analytes before running the analysis to set up the experimental parameters Only the targeted compounds are located all other information about the sample is forfeited Using high res systems to do SIM is also expensive and requires a high degree of operator sophistication

6 Can we fashion a different approach? Time of Flight (TOF) mass spectrometers do not use SIM. All analyses provide full range mass spectra for all the analytes in the sample This is an important advantage, and provided the mandated sensitivities can be obtained using TOF, we should then have a method which can locate and identify all components of the sample, while also being able to quantify targeted PCDDs and PCDFs, all in one run This applies both to the Pegasus 4D (GCxGC-TOFMS) and to the Pegasus HRT (High Resolution TOFMS)

7 The Pillars of the TOFMS approach For the GCxGC-TOFMS, Selectivity would be provided by the increased peak capacity of GCxGC, and Sensitivity by the enhanced S/N due to the focussing (improved peak sharpness) provided by the modulator For the HRT, Selectivity would be provided by the accurate mass capability (< 1 ppm), and Sensitivity by the removal of chemical noise due to the high resolution capability

8 The Goal Determine if GCXGC- TOFMS and GC-HRT has the sensitivity to calibrate 2378-TCDD and 2378-TCDF down to 0.5 pg/µl as required by EPA Method 1613, and to analyse samples at this level Determine if GCXGC- TOFMS and GC-HRT can provide the selectivity necessary to measure 17 dioxins and furans (from Method 1613, assigned due to their toxicity) in a variety of sample matrices Determine if the techniques can identify other POP components present in real world samples, which are not located by the target approach

9 The Approach Run the relevant 13 C labelled standard set for 1613B Use these Spike and run Data mine the results to the sample set samples for obtain and calculate other POPs response quantitative which may be factors for the values for the present in the PCDD/Fs PCDD/Fs samples

10 Six soil and sediment samples (provided by Prof Eric Reiner from the Ministry of the Environment, Toronto) Sample Set These samples had been extracted and worked up according to the procedures outlined in:

11 Sample Preparation for POPs Analysis Air-dry samples Addition of labelled standards Soxhlet extraction Column clean-up Acid-base-AgNO 3 Si Alumina Carbon Concentrated to 20µL GC-HRMS EI at lower ev (35eV) 10,000 Resolution SIM LECO Pegasus GC-HRT LECO Pegasus 4D GCxGC-TOFMS

12 Analysis Conditions GC-HRMS Inlet 280 C Constant Flow He at 0.8 ml/min 40m x 0.18mm x 0.18µm DB C (1min), 52 C/min to 200 C, 2.9 C/min to 235 C (3 min), 3 C/min to 267 C (3 min), 7 C/min to 310 C (Hold until OCDD el utes) Transfer Line 280 C HRMS, EI+, SIM, 35 ev

13 Analysis Conditions GC-HRT Inlet 280 C Corrected Constant Flow He at 1 ml/min 40m x 0.18mm x 0.18µm Rtx-Dioxin2 (Arylene backbone-modified siloxane column selective for coplanars) 140 C (1min), 50 C/min to 200 C, 3 C/min to 260 C, 1 C/min to 280 C, 6 C/min to 310 C (5 min) Transfer Line 300 C HRT, EI+, 140 to 520 Da, 3 spectra/sec, 50 ev

14 Analysis Conditions GCxGC-TOFMS 40m x 0.18mm x 0.18µm Rtx-Dioxin2 (Arylene backbone-modified siloxane column selective for coplanars) 120 C (2min), 20 C/min to 200 C, 5 C/min to 320 C ( 3 min) 1.0m x 0.15mm x 0.15µm Rxi-17Sil MS (50% phenyl (silarylene) / 50% methyl type siloxane) + 5 C offset from primary column Corrected Constant Flow He at 1.4 ml/min (Speed optimized flow) Thermal modulation, 2.0 sec (Hot time 0.70 sec, Cool time 0.30 sec) TOFMS, EI+, 45 to 750 Da, 100 spectra/sec

15 Sample 1 INSTRUMENT TCDF TCDD PCDF PCDF PCDD HxCDD GC-HRT ND ND GC-HRMS GCxGC- TOFMS GCxGC- TOFMS (x5) ND ND ND ND ND 11 ND ND ND ND ND INSTRUMENT HxCDD HxCDD HpCDF HpCDD HpCDF OCDF OCDD GC-HRT 3.1 ND ND ND GC-HRMS GCxGC- TOFMS GCxGC- TOFMS (x5) ND ND ND ND ND ND ND ND pg/g

16 Sample 2 INSTRUMENT TCDF TCDD PCDF PCDF PCDD HxCDD GC-HRT GC-HRMS GCxGC- TOFMS ND ND INSTRUMENT HxCDD HxCDD HpCDF HpCDD HpCDF OCDF OCDD GC-HRT GC-HRMS GCxGC- TOFMS ND ND ND pg/g

17 Sample 3 INSTRUMENT TCDF TCDD PCDF PCDF PCDD HxCDD GC-HRT GC-HRMS GCxGC- TOFMS INSTRUMENT HxCDD HxCDD HpCDF HpCDD HpCDF OCDF OCDD GC-HRT GC-HRMS GCxGC- TOFMS pg/g

18 Sample 4 INSTRUMENT TCDF TCDD PCDF PCDF PCDD HxCDD GC-HRT GC-HRMS GCxGC- TOFMS INSTRUMENT HxCDD HxCDD HpCDF HpCDD HpCDF OCDF OCDD GC-HRT GC-HRMS GCxGC- TOFMS pg/g

19 Sample 5 INSTRUMENT TCDF TCDD PCDF PCDF PCDD HxCDD GC-HRT 40 ND ND ND GC-HRMS GCxGC- TOFMS 43 ND ND ND INSTRUMENT HxCDD HxCDD HpCDF HpCDD HpCDF OCDF OCDD GC-HRT ND GC-HRMS GCxGC- TOFMS pg/g

20 Sample 6 INSTRUMENT TCDF TCDD PCDF PCDF PCDD HxCDD GC-HRT GC-HRMS GCxGC- TOFMS ND INSTRUMENT HxCDD HxCDD HpCDF HpCDD HpCDF OCDF OCDD GC-HRT GC-HRMS GCxGC- TOFMS 10 ND pg/g

21 Comparison of HRT and HRMS Data Regression Comparison HRMS (pg/g) HRT (pg/g)

22 Regression Comparison Reduced Concentration Range HRMS (pg/g) HRT (pg/g) Removed points above 400 for weighting

23 Comparative Results for TCDF 2378-TCDF y = 1.058x R² = HRMS (pg g/g) HRT (pg/g)

24 Overview of Quantitative Results Values from the three instruments correlate well, considering the low levels analysed At the lowest level the Pegasus 4D (GCxGC-TOFMS) system is not capable of detecting analytes This can be partially offset using concurrent solvent recondensation The ease of use and low cost of the Pegasus 4D suggest a role as a screening tool, where access to high resolution systems is limited The results from the two high resolution systems are in excellent agreement showing that the HRT can achieve the requirements of EPA 1613B

25 Limits of Detection: GC-HRT The results for the standard set can be used as an indication of the LOD possible, bearing in mind that, in dioxin work, the achievable LOD depends critically on matrix interference The low level standard which contains TCDD and TCDF at 0.5 pg/µl was used to confirm that the GC-HRT could achieve the levels required by 1613B

26 Standard Results for CS1 HRT Extracted Ion Chromatograms at 500 fg/µl TCDF TCDD

27 Limits of Detection: GCxGC-TOFMS Two sterilized soil samples were spiked with native dioxins at different concentration levels After adding labeled material, extraction by accelerated solvent extraction, clean-up with Gel Permeation Chromatography and concentration, we could calculate LODs for PCDD/Fs in the soil samples Using a S/N ratio of 3:1, LODs for 2378-TCDD were: Sample 1: 353 fg and Sample 2: 322 fg This is consistent and indicates that the method can attain the low levels for 2378-TCDD required by EPA 1613 (500 fg)

28 Comprehensive Sample Evaluation As mentioned previously, with SIM (and also MS/MS) analyses only the targeted compounds are located all other information about the sample is forfeited TOF mass spectrometers do not use SIM. All analyses provide full range mass spectra for all the analytes in the sample We should then be able to locate and identify all components of the sample, while also being able to quantify targeted PCDDs and PCDFs, all in one run Lets look at the samples above and see if additional POPs can be located, whi ch have not been seen in the GC- HRMS method

29 GCxGC-TOFMS Chromatogram (Sample 2) Extracted ion plot showing m/z 360

30 Identification of m/z 360 Peak

31 GC-HRT Results for the Same Peak Measured Mass = Da Calculated Mass = Da (for C 16 H 8 Br 2 ) Mass Accuracy = ppm

32 GC-HRT Chromatogram (Sample 6) Extracted Ion plot showing m/z

33 Identification of m/z Peak (significant ions) Measured Mass = Da Calculated Mass = Da (for C 12 H 6 Br 4 O) Mass Accuracy = ppm

34 GC-HRT Chromatogram (Sample 2) Extracted Ion plot showing m/z

35 Identification of m/z Peak (significant ions) Measured Mass = Da Calculated Mass = Da (for C 12 H 6 Cl 4 ) Mass Accuracy = ppm

36 Some Other Components in the Samples Sample Compound Similarity Mass Accuracy (ppm) 1 2,4,4,6- Tetrachlorobiphenyl H-Benz[de]anthracen-7-one Perylene ,6,8-Trichloropyrene ,5,4 -Trichloroterphenyl Benz[a]anthracene ,10-Dichloroanthracene ,3,4,4 -Tetrachlorobiphenyl Benzo[e]pyrene Coronene ,2,4,4 -Tetrachlorobiphenyl ,3,3,4,4 -Pentachlorobiphenyl ,3,4,4,6-Pentachlorobiphenyl ,3,3,4,4,5-Hexachlorobiphenyl Benzyl butyl phthalate Tetrabromodiphenylether

37 Some Other Components in Sample 1 2,4,4,6- Tetrachlorobiphenyl Mass Accuracy = 2.20 ppm 7H-Benz[de]anthracen-7-one Mass Accuracy = ppm

38 Some Other Components in Sample 2 2,5,4 -Trichloroterphenyl Mass Accuracy = ppm Perylene Mass Accuracy = ppm 1,6,8-Trichloropyrene Mass Accuracy = 0.29 ppm Benz[a]anthracene Mass Accuracy = ppm 9,10-Dichloroanthracene Mass Accuracy = ppm

39 Some Other Components in Sample 3 & 4 Sample 3 3,3,4,4 -Tetrachlorobiphenyl Mass Accuracy = ppm Sample 4 Benzo[e]pyrene Mass Accuracy = 0.23 ppm

40 Some Other Components in Sample 5 Coronene Mass Accuracy = ppm 2,2,4,4 -Tetrachlorobiphenyl Mass Accuracy = 1.57 ppm 2,3,3,4,4 -Pentachlorobiphenyl Mass Accuracy = 0.51 ppm

41 Some Other Components in Sample 6 2,3,4,4,6-Pentachlorobiphenyl Mass Accuracy = 0.84 ppm 2,3,3,4,4,5-Hexachlorobiphenyl Mass Accuracy = 1.82 ppm 2,2,4,4 -Tetrabromodiphenylether Mass Accuracy = 0.62 ppm Benzyl butyl phthalate Mass Accuracy = ppm

42 Relative Isotope Abundance For compounds with pronounced molecular ion clusters (arising from the presence of Cl or Br in the molecule) measurement of relative isotopic abundance is an important confirmation of molecular formula In general differences of up to 30% are considered acceptable when working with POPs at low levels

43 Relative Isotope Abundance MEASURED CALCULATED RELATIVE RELATIVE DIFFERENCE ION (Da) HEIGHT ABUNDANCE ABUNDANCE (%)

44 Relative Isotope Abundance MEASURED CALCULATED RELATIVE RELATIVE DIFFERENCE ION (Da) HEIGHT ABUNDANCE ABUNDANCE (%)

45 Conclusions 1 GC-HRMS or GC- MS/MS analysis of PCDD/Fs requires a targeted approach Not able to locate other POPs in the samples TOF technology, using either GCxGC or High Resolution, provides an alternative approach capable of: Quantifying at levels mandated for analysis by regulatory authorities Locating and identifying other priority pollutants present in the sample in the same analytical run

46 Conclusions 2 GCxGC-TOFMS system, (make the correct choice of column combination) Permits good separation of PCDD/Fs from matrix interference (and other POPs) Mass accuracy for PCDD/Fs and other POPs present in the samples is excellent Isotope ratio measurement for the molecular ion cluster is an additional confirmation of formula assignment HRT results are usually < 1ppm. That allows confident formula assignment The results obtained with the HRT are in good agreement with the theoretical values

47 Acknowledgements Jack Cochran, Restek, USA Jayne de Vos, NMISA Eric Reiner, Ministry of the Environment, T oronto