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Sampling for semivolatile organic contaminants in environmental compartments

The Universe of Non-polar Chemicals. PBTs. . VOCs. POPs. VOCs = Volatile organic chemicalsSOCs = semivolatile organic chemicalsPOPs = Persistent Organic PollutantsPBTs = Persistent, Bioaccumulative,

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Sampling for semivolatile organic contaminants in environmental compartments

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    1. Sampling for semivolatile organic contaminants in environmental compartments Lisa Rodenburg

    2. The Universe of Non-polar Chemicals

    3. Many classes of contaminants can be sampled and measured together:

    4. PCBs

    5. PAHs

    6. PBDEs

    7. Outline Sampling Air Water Other Cleanup The easy way The hard way Detection GC/ECD GC/MS Cautionary Tales

    8. What are semivolatile contaminants? On the basis of vapor pressure, we can divide the nonpolar or slightly polar compounds into VOCs and SOCs. VOCs = vapor pressure > 10-3 atm not on atmospheric particles SOCs = vapor pressure < 10-6 atm significant fraction on atmospheric particles Some things fall through the cracks, like naphthalene.

    9. VOCs (TO-15)

    10. SOCs

    11. The Hi-Vol

    12. Pitfalls Breakthrough of more volatile contaminants (minimize flow rate) Gas/particle partitioning (minimize flow rate) Detection limits (maximize flow rate) Motor instability (pre- and post-calibration) Contamination from motor, O-rings, etc. (keep everything clean, vent motor)

    13. Sorbent choice PUF allows greater breakthrough of polar and volatile compounds. XAD-2 has a huge PAH background, especially low MW PAHs. PUF can be very clean. Run lots of blanks!

    14. Breakthrough of PCBs on PUF

    15. Water Sampling Whole water or grab samples Detection limits require very large samples Blank contamination a big problem Volatilization Dissolved vs. Particulate Filter for particles, sorbent for dissolved Choice of sorbent is tough XAD-2 PAH contamination Tenax, C18 cleanup problems Choice of platforms: Infiltrex – expensive, unreliable TOPS (Trace Organics Platform Sampler) – a better way? Pepsi cans – low tech

    16. Colloids Typically a 0.7 mm filter is used, which allows small particles to pass through to be quantified with the apparent dissolved phase. This leads to the “solids concentration effect”. The apparent distribution between dissolved and particle phases changes as the total amount of solids increases.

    17. Other sampling When sampling for sediment, biota, etc, homogenization and collection of a representative sample are paramount. Volatilization still a problem – refrigerate or freeze immediately

    18. Extraction Techniques: Soxhlet Extraction Accelerated Solvent Extraction (ASE) (high T and pressure minimize amount of solvent needed) Solvents: Dichloromethane (toxicity?) Pet Ether Hexane (leave behind lipids or more polar compounds)

    19. Rotovap

    20. Cleanup Use column chromatography to remove interfering compounds from your sample Type of analytical method determines the rigor of the cleanup

    21. Our Alumina Cleanup Bake alumina at 550ºC overnight Deactivate with 3% wt water Precondition column F1 = 13 mL Hexane = PCBs F2 = 15 mL 2:1 DCM/hexane = PAHs OCPs, PBDEs split between F1/F2

    22. Detection Detection method is determined by concentration of compound in environmental matrixes. PCBs = Electron Capture Detection or High-Resolution GCMS PAHs = GCMS EI PBDEs = GCMS NCI Cl Pesticides = GCMS NCI PCDD/Fs = High-Resolution GCMS

    23. GC/ECD

    24. GC/MS

    25. QA/QC Sample contamination Reproducibility Tracking of mass Representativeness of samples?

    26. Avoiding Contamination Cleanliness Bake glassware at 450°C overnight New aluminum foil High grade solvents New building! Cleaning sampling equipment sometimes difficult Blanks, blanks, blanks

    27. Reproducibility Side-by-side samples Duplicates Matrix spikes Surrogates

    28. Mass Tracking Surrogates Added to track recovery through the various sample processing steps Must have same or similar physical-chemical properties as analytes Deuterated or 13C labeled Non-native congeners (PCBs 14, 23, 65, 166) Internal standards Added to allow quantification of mass even though volume is not known Deuterated or 13C labeled Non-native congeners (PCBs 30, 204; BDE 75)

    29. Representativeness of samples? Homogenize sediments (Bass-o-matic) Take lots of samples 12th day sampling

    30. Special considerations for PBDEs Flame retardants – designed to break down at high temperatures! BDE 209 has 10 bromines extremely labile MW = 960 g/mol! Use cold on-column injection Very short GC column Avoid light

    31. The Pitfalls of Measuring PCBs by ECD

    32. EPA Method 1668A

    33. Trade-Offs

    34. PCB 11

    35. Co-elution a problem even for method 1668A

    36. Cost

    37. The pitfalls of measuring OCPs by ECD

    38. Comparison of ECD and NCI data

    39. Conclusions Dirty matrices Complex mixtures Cost/benefit analyses Cleanliness Blanks, blanks, blanks Trust but verify

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