Environmental Mass Spectrometry DR. RALPH N. MEAD

Transcription

1 Environmental Mass Spectrometry DR. RALPH N. MEAD MARINE AND ATMOSPHERIC CHEMISTRY RESEARCH LABORATORY DEPARTMENT OF CHEMISTRY AND BIOCHEMISTRY UNIVERSITY OF NORTH CAROLINA WILMINGTON

2 Why Mass Spectrometry for Environmental Research? When coupled to a chromatographic system, GC or LC, acts as a detector Greater sensitivity and selectivity compared to other detectors Added benefit is mass spectrum, information used for structural elucidation (mainlib) Hexane (mainlib) Ethylbenzene Mead et al., 2014

3 Tools of the Trade: Diagram of Mass Spectrometer The basic principle of mass spectrometer is to generate ions from either inorganic or organic compounds by any suitable method, to separate these ions by their mass to charge ratio (m/z) and to detect them qualitatively and quantitatively by their respective m/z and abundance. Atmospheric high vacuum 10-7 torr pressure Inlet Ion source Mass analyzer Detector

4 Mass Spectrometry: Identify & Quantify Mass spectrometry (MS) is an analytical technique that ionizes chemical species and sorts the ions based on their mass-to-charge ratio AmaZon SL Ion Trap Low resolution Nominal mass Targeted analysis = Quantify MRM / SIS methods Used for quantification MicroTOF-Q II High resolution Accurate mass Non-targeted = Screening Full Scan method Used for identification Environmental matrices are complex, so you need to pair something to the MS to separate the compounds (like gas or high performance liquid chromatography)

5 Sample Preparation

6 Method Summary Sample Processing Subsample 500 ml Store 500 ml Collect water in 1 L HDPE bottles; Pour 500 ml of sample into graduated cylinders for volume measurement add 25 ul of surrogate to 500 ml of sample Filter water samples with pre combusted GF/F glass fiber filter Load onto SPE tube Waters Plus style WAX SPE bed All samples Treated same way Trip Spike Blanks Unknowns Calibration LC/MS-MS analysis Reduce eluate under nitrogen gas, transfer ~1000 ul to LC vial insert for analysis Elute analyte into centrifuge tube

7 Perfluorinated Alkyl Substance (PFAS) Distribution in SE NC

8 Middle Cape Fear River Date of Collection 9/19/17 11/21/17 1/30/18 3/26/18 [Gen X] (ng/g dry Sample Site sediments) Site Site Site site

9 Lower Cape Fear River Date of Collection M 61 9/11/17 10/23/17 2/06/18 [Gen X] (ng/g dry Sample Site sediments) M

10 Significance of Preliminary Sediment Results GenX (CAS # ) detected in all sediments analyzed to date This data along with additional measurements will be used to determine any trends or controlling factors on the distribution of GenX in sediments Sedimentary release of GenX into the overlying water column is a possibility even though point source is contained. Impacts to water utilities, environment, etc.

11 Sedimentary Occurrence of PFAS M61 Extracted Ion Chromatogram from LC/QTOF VII and VIII unknown but mass defect and isotope distribution suggests a carbon chain that is perfluorinated and contains one atom of chlorine

12 Atmospheric Processing of PFAS: Precipitation Research at UNCW

13 Hydrolysis Reaction Experiments performed in our laboratory showed the hydration (adding water) to the corresponding carboxylic acid known as GenX (CAS ) occurs in less than 10 minutes. The latter compound is what is detected in drinking water and other matrices. The take home message from this experiment is that the dimer acid fluoride emitted into the atmosphere can rapidly turn into GenX when it encounters water (i.e. rain) and be transported potentially long distances from where it was emitted

14 How does wind direction impact GenX (CAS # ) concentration? E /21-22/17 GenX <3 ppt (ng/l) 0.26 inches received at UNCW site ph not analyzed E /8-9/17 GenX >500 ppt (ng/l) 1.8 inches received at UNCW site ph4.68

15 Summary Many questions remain as to environmental occurrence, transport and fate of replacement PFAS Structure elucidation and discovery remain key research areas that will rely on high and ultra high resolution MS and when applicable couple to NMR for total structure elucidation As structural confirmation progresses keep other stake holders (e.g. toxicologist, utilities, governmental agencies) involved

16 Analysis

17 Timeline of Important Events in the History of Legacy C8 (PFOA and PFAS)

18 Structural Possibilities These are but a few examples of new PFAS Synthesized to replace legacy C8 compounds but still have the properties required to manufacture consumer goods Designed (hoped) to have shorter environmental lifetime and impacts More research is needed to answer these and other questions

19 PFC s have numerous applications, including stain- and moisture-repellent surface coatings for carpets, paper, upholstery, and textiles; firefighting foams; cosmetics; lubricants; and the synthesis of various polymeric materials

20 Analytical Techniqu es

21 Identifying compounds summary Target: Standards available Ion Trap use calibration standards to identify and quantify known compounds Non-Target: No standards available QTOF Use accurate mass spectroemtry and data software to determine molecular formula of unknown. Semi-quantify compound response with gen- X calibration curve

22 What is Fluorine? Atomic number is 9 Group 7 halogens Atomic weight g/mol 13 th most abundant element in Earth s crust More abundant than other halogens (Cl,Br,I) but in form of insoluble salts (Fluorospar and cryolite) No sources of natural organo-fluorine compounds compared to other halogens. Various reasons why. Molecular Fluorine gas

23 Why Organo-Flourine Compounds? Very stable C-F bond energy 485 kj/mol C-C 346, C-N 305, C-O 358, C-Cl 327 kj/mol Imparts enhancement of therapeutic efficacy and pharmacological properties Surfactant properties Emulsifier Compounds are extremely resistant to degradation, leading to their presence in environmental and biological media worldwide.

24 What Products do we use that contain organo-fluorine bonds? Example Pharmaceuticals Example Refrigerants Example per and poly-fluorinated Products Polytetrafluoroethylene Ciprofloxacin (antibiotic) R-134a Polyvinylidene fluoride R-132a 5-Fluorouracil (anti-tumor) R-152a (Dust off)

25 What Products do we use that contain Organo-flourine bonds? Example Pharmaceuticals Example Refrigerants Example POLY- and Perfluorinated Products Ciprofloxacin (antibiotic) 5-Fluorouracil (anti-tumor) R-134a R-152a (Dust off) Polytetrafluoroethylene Polyvinylidene fluoride

26 m/z Chlorine containing PFAS Wang et al. 2013

27 Solvay s product n=3 m=0 Functionalized perfluoropolyethers (PFPEs) from Solvay for its PTFE and PVDF (Wang et al 2013)

28 Peak VIII MS/MS Intens M61_qtof_msms_30 40_3_P1-C-1_01_594.d: -MS2( ), 40.0eV, 14.7min #877 Precursor u m/z

29 Peak VII MS/MS Intens M61_qtof_msms_30 40_3_P1-C-1_01_594.d: -MS2( ), 30.0eV, min # m/z

30 Tentative Structures Wang et al., 2013 n = 1 n = 2