Sampling for semivolatile organic contaminants in environmental compartments

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Sampling for semivolatile organic contaminants in
environmental compartments

• Lisa Rodenburg

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The Universe of Non-polar Chemicals
PBTs
VOCs Volatile organic chemicals SOCs
semivolatile organic chemicals POPs Persistent
Organic Pollutants PBTs Persistent,
Bioaccumulative, Toxic
POPs

VOCs
SOCs
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Many classes of contaminants can be sampled and
measured together
PCBs polychlorinated biphenyls myriad uses,
banned since 1970s PBTs PAHs polycyclic
aromatic hydrocarbons combustion by-products
less P, very BT PBDEs polybrominated diphenyl
ethers current use flame retardants not very
P, very B, not sure how T OCPs organochlorine
pesticides (DDT, etc) some in current use (a-
and ?-HCH, a- and ß-endosulfan ), some banned
(DDT) most are PBTs
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PCBs
PCBs consist of 209 congeners, which may have 1
to 10 chlorines. A group of congeners having the
same number of chlorines is a homolog group
PCBs were previously sold as Aroclors and used
as fluids in electrical equipment, particularly
transformers and capacitors. PCBs are classified
as probable human carcinogens and have been shown
to cause a range of serious non-cancer health
effects in animals. The manufacture,
processing, and distribution in commerce of PCBs
were banned in 1976 due to concerns over their
toxicity and persistence in the
environment. About 1.3 million metric tons of
PCBs were produced world-wide.
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PAHs
PAHs are Polycyclic Aromatic Hydrocarbons They
contain 2 or more fused aromatic rings Products
of combustion of any type as well as evaporative
emissions from fuels. A small amount of PAHs are
produced naturally (volcanoes, forest fires,
etc.) Humans are exposed to PAHs by breathing
contaminated air (including tobacco smoke) and
eating grilled foods. The Department of Health
and Human Services (DHHS) has determined that
some PAHs may reasonably be expected to be
carcinogens.
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PBDEs
Can have 1-10 bromines, numbered in same was as
PCBs
2,2,4,4,5-pentabromodiphenyl ether BDE 99
OCPs
Many different structures and numbers of chlorines
heptachlor
DDT
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Outline

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

Sampling
Extraction
QA/QC
Cleanup
Detection
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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 gt 10-3 atmnot on
  atmospheric particles
• SOCs vapor pressure lt 10-6 atmsignificant
  fraction on atmospheric particles
• Some things fall through the cracks, like
  naphthalene.

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VOCs (TO-15)
SUMA Canister sampling
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SOCs
PCBs PAHs Organochlorine pesticides PBDEs Others?
Sampled using a high-volume air sampler
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The Hi-Vol
Filter
Canister (containing PUF or XAD-2 sorbent)
Vacuum pump
Timer
Measure pressure drop before and after every
sample. Calibration curve converts pressure
drop to flow rate. Timer gives time, hence
volume of air sampled.
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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)

Measure breakthrough by occasionally cutting a
PUF in half and analyzing the top and bottom
separately.
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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!

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Breakthrough of PCBs on PUF
PCBs can have 1 10 chlorines. PCBs are
numbered such that higher numbers have more
chlorines.
Heavier PCBs, less breakthrough. Breakthrough
significant for PCBs with 3 or less chlorines
Blank contamination
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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

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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.

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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

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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)

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Rotovap
Blowdown
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Cleanup

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

Adsorbent Sample Matrix Alumina Cleaner Air Si
lica Sediment Florisil Dirtier Sludge Size
Exclusion Chromatography Biota (to remove
lipids)
Surrogate recovery
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Our Alumina Cleanup

• Bake alumina at 550ºC overnight
• Deactivate with 3 wt water
• Precondition column
• F1 13 mL Hexane PCBs
• F2 15 mL 21 DCM/hexane PAHs
• OCPs, PBDEs split between F1/F2

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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

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GC/ECD
Invented by Lovelock around the late 1950s and
early 1960s. Uses a radioactive Beta emitter
(electrons) to ionize some of the carrier gas and
produce a current between electrodes. When
organic molecules that contain electronegative
functional groups, such as halogens, phosphorous,
and nitro groups pass by the detector, they
capture some of the electrons and reduce the
current measured between the electrodes. The ECD
is as sensitive as the FID but has a limited
dynamic range and finds its greatest application
in analysis of halogenated compounds.
Cost 30,000
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GC/MS
Solute molecules are ionized in the ion source
Resulting fragments are separated on the basis
of their mass/charge ratio then detected by an
analyzer unit Ionization by electrons (EI) or
gas molecules (CI, Negative or Positive). NCI
similar to ECD (little fragmentation, best for
halogenated compounds) Scan mode give entire mass
spectrum good for identification of
unknowns SIM (selective ion monitoring) mode
much more sensitive Cost 100,000
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QA/QC

• Sample contamination
• Reproducibility
• Tracking of mass
• Representativeness of samples?

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Avoiding Contamination

• Cleanliness
• Bake glassware at 450C overnight
• New aluminum foil
• High grade solvents
• New building!
• Cleaning sampling equipment sometimes difficult
• Blanks, blanks, blanks

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Reproducibility

• Side-by-side samples
• Duplicates
• Matrix spikes
• Surrogates

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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)

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Representativeness of samples?

• Homogenize sediments (Bass-o-matic)
• Take lots of samples
• 12th day sampling

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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

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The Pitfalls of Measuring PCBs by ECD
Some PCBs co-elute, and there aint nothin you
can do about it. Example PCB s 11077
This is a GOOD chromatogram!
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EPA Method 1668A
Uses High-resolution GC/MS (about 1
million) 13C labeled compounds 3 field stds 28
surrogates 3 cleanup stds 5 recovery stds 39
stds
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Trade-Offs
Would you rather have 28 surrogates with 60
recovery, or three surrogates with 95
recovery? 209 congener method can reveal
surprises Contract labs are far from
infallible Contract labs only love your money,
not your samples
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PCB 11
3,3-dichlorobiphenyl is not found in
Aroclors NYSDEC found it accidentally in
effluent from PVSC It is produced inadvertently
during pigment manufacture (see Litten et al.,
2002) Most data sets do not look for it.
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Co-elution a problem even for method 1668A
1668A can differentiate between (for example)
PCBs 110 and 77, even though they co-elute,
because 110 has 5 chlorines and 77 has 4. BUT
PCBs within a homolog group that co-elute are
still quantified together Contract labs report
all co-eluting congeners under the congener with
the lowest IUPAC number.  Example what is
reported as PCB 93 is really 939598100102
(and is primarily PCB 95).
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Cost
Price per sample 1,000
METHOD 1668 CALIBRATION SOLUTIONS from Cambridge
Isotope Laboratories.
METHOD 1668 CALIBRATION SOLUTIONS SET5X0.2ML
2,400.00 METHOD 1668 DAILY CALIBRATION CHECK
STANDARD 0.2 ML 495.00 METHOD 1668A
CALIBRATION SOLUTION CS0.2 0.2 ML 625.00
METHOD 1668A CALIBRATION SOLUTION CS1 0.2 ML
625.00 METHOD 1668A CALIBRATION SOLUTION CS2
0.2 ML 625.00 METHOD 1668A CALIBRATION
SOLUTION CS3 0.2 ML 575.00 METHOD 1668A
CALIBRATION SOLUTION CS4 0.2 ML 625.00
METHOD 1668A CALIBRATION SOLUTION CS5 0.2 ML
625.00 METHOD 1668A CALIBRATION SOLUTIONS
CS1-CS5 SET5X0.2ML 2,450.00 METHOD 1668A
CLEAN-UP STANDARD SOLUTION 1.2 ML 575.00
METHOD 1668A INJECTION INTERNAL STANDARD
SOLUTION 1.2 ML 1,650.00 METHOD 1668A NATIVE
TOXICS/LOC SOLUTION 1.2 ML 795.00 METHOD
1668A TOXICS/LOC/WINDOW DEFINING SOLUTION 1.2 ML
2,450.00
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The pitfalls of measuring OCPs by ECD
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Comparison of ECD and NCI data
4,4-DDE
Jersey City Gas- phase
N 28 P lt 0.0001
2,4-DDT
Because OCPs are abundant enough to be detected
by a regular GC/MS instrument, the mass spec
method is cost-effective.
N 28 P 0.03
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Conclusions

• Dirty matrices
• Complex mixtures
• Cost/benefit analyses
• Cleanliness
• Blanks, blanks, blanks
• Trust but verify