PCBs In Water And Oil

Analytical Services Unit School of Environmental Studies Queen’s University Kingston, Ontario, Canada Matthew P. Ponsford

Purpose
Background – PCBs
Background – Laboratory Methods
Analytical Procedure
Results
Environmental Regulations
Discussion
Sources of Error
Recommendations
Conclusions

To determine the concentration of polychlorinated biphenyls (PCBs) in unknown water and oil samples

PCBs are organic compounds consisting of two aromatic rings substituted with chlorine atoms
209 different congeners ( 130 commonly used commercially
Odourless, tasteless, low vapour pressure

Widely used until production banned in the 1970s
Dielectric fluids in transformers and capacitors
Coolants
Pesticides
Flame retardants
Adhesives, sealants, and paints
Production banned due to toxicity and tendency to bioaccumulate
Not easily biodegradable - persistent organic pollutant

Between 1930 and 1977, estimated 1.5 million tons produced
600,000 tons produced in the US
450,000 tons produced in Europe
40,000 tons imported to Canada
Detected in the atmosphere around the world
Great Lakes, Hudson River, Kenora, Resolution Island

PCBs extracted from unknown water and oil samples
Analyte solutions cleaned and solvated in hexanes
PCBs analyzed by gas chromatograph (GC) with electron capture detector (ECD)

PCBs sparingly soluble in aqueous phase
Easily separable by LLE using dichloromethane
Clean-up with Florisil columns
Solvent replacement – DCM replaced with hexanes so as not to overload ECD
1000 ppm Aroclor 1260 standard solution used for calibration
Surrogate used to determine efficiency

Chemically equivalent to analytes but with different retention time
Solutions spiked with 100 µL of surrogate (DCBP)
Assumed to have same extraction efficiency as analytes
Corrects for losses incurred during recovery

PCBs already in organic phase
Analytes extracted and samples cleaned using Florisil columns
Samples solvated in hexanes
5 ppm and 50.01 ppm Aroclor 1260 standard solutions used for calibration

Gas chromatograph:
PCBs stable and volatile at high temperatures
Viscous liquids analyzed (HPLC non-ideal)
Electron capture detector:
Good sensitivity when detecting electronegative compounds
Analytes contain multiple chlorine atoms
Analytes only combust at extreme high temperatures (FID non-ideal)

Used to separate and analyze compounds
Inert gas mobile phase (ie, nitrogen)
Microscopic polymer layer stationary phase
Vapourizes analytes and elutes them according to increasing volatility

Beta-particles emitted by radioactive decay of metal foil
Electrons captured by electronegative atoms
Proportion of electrons absorbed gives accurate estimate of analyte concentration

Efficiency of extraction of PCBs from water checked using surrogate (decachlorobiphenyl, DCBP)
Extraction efficiency for PCBs from oil assumed 100%
Accuracy of results tested with spiked quality control solutions (1000 ppm Aroclor 1260)
Solvent effects checked with reagent blanks

Trace quantities found in both water samples
Table 1: Summary of analysis of PCBs in water samples by LLE and GC-ECD Sample Extraction Efficiency (%) PCB Concentration (ppb) Water Sample 1 79.1 8.7 Water Sample 2 77.0 3.8 Water Quality Control 77.4 32.2

PCB concentrations in Resolution Island oil samples below method detection limit
Concentration in Sample 1 much higher than in water samples
Table 2: Summary of analysis of PCBs in oil samples by GC-ECD Sample PCB Concentration (ppm) Oil Sample 1 16.74 ASU # 8429 < MDL ASU # 8342 < MDL Oil Quality Control 38.75

Transport of PCBs regulated (TDGA, 1985 )
Storage regulations ( 1988 )
PCB Waste Export Regulations ( 1990 )
Levels of PCBs of 50 ppm or higher must be reported and removed (CEPA, 2000 )

Table 3: Maximum allowable PCB concentrations in Ontario
PCB concentrations in samples greater than allowable limits
PCB concentrations below levels requiring reporting and removal
Location of PCBs in Environment Maximum Allowable Concentration (ppb) Drinking water 3.0 Fresh water 1.0 Soil (Residential, Agricultural) 0.005 Soil (Industrial, Commercial) 0.025 Waste 0.05

Water sample levels above 3.0 ppb regulation for drinking water
Sample 1 concentration: 8.7 ppb
Sample 2 concentration: 3.8 ppb

PCBs in Resolution Island oil samples below method detection limits
High concentration in Sample 1
Sample 1 concentration: 16.74 ppm
PCBs in 1 barrel ( 159 L) of Sample 1 oil enough to contaminate:
More than 532,000 tonnes of residential surface soil ( 0.005 ppb)
More than 887,000 L of drinking water ( 3.0 ppb)

Reasonably effective analysis method
Quality control samples close to theoretical values
60% error amounts to approximately 10 ppb ( 0.01 ppm)
Table 4: Evaluating method by quality control percent error Sample Matrix [PCB] theor (ppm) [PCB] exp (ppm) % Error (%) Water 0.02 0.03 59.5 Oil 50.0 38.8 -22.5

Reproducibility unknown
Potentially faulty assumptions (extraction for oil samples)
Analytes lost during rotary evaporation
DCBP significantly less volatile than analytes

Additional extraction steps
Could improve extraction efficiency
Use surrogate for oil extraction
Verify 100% extraction efficiency
Use of replicate samples to check reproducibility
Use distillation column instead of rotary evaporator – multiple distillations

Water samples contained significant PCB concentrations
1 of 3 oil samples contained PCBs
Extraction efficiencies around 80%
Significant sources of error
Analysis method appropriate to experiment

PCBs In Water And Oil

by Matthew Ponsford on Dec 04, 2009

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