Water Testing
Water Testing:
How we measure what you can’t see
1st Elmvale Water Festival
August 4, 2007
Ray Clement
Laboratory Services Branch, Ontario Ministry of the Environment
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Water Testing
Overview
• Steps taken to analyze water
• What is trace?
• How do we know we’re right?
• New environmental issues and challenges
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Steps in Water Analysis
• Determine objectives
• Take a sample for testing
• Prepare sample for analysis
• Analyze sample
• Interpret results with quality control
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Objectives of Water Analysis
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Ensure safety of drinking water
Emergency Response (e.g., industrial spills)
Litigation
Research
The specific methods used depend on the
study objectives, type of water tested
(drinking, surface, other), and other factors
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Sampling Considerations
• Sample taken must be representative
of the water body being tested
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Sampling Artifact?
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Sampling Considerations
• Sample taken must be representative
of the water body being tested
• Sampling containers must be
appropriate and specially cleaned
before use (e.g., plastic for metals, glass
for organics)
• Shipping and storage considerations
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Water Testing
Prepare Sample for Analysis
• Extraction step
• Interference removal step
• Concentration step
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Water Testing
Extraction Step
• Methods used depend on substance we
are testing for
• For organic chemicals like PCBs or
pesticides, use organic solvent not
miscible with water
• Sometimes, water filtered and
particulates extracted separately
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Water Extraction Setup
• In this example, hexane was
added to a 1.0 Liter drinking
water sample
• When the water and solvent
are mixed vigorously,
organic molecules move
from water into the solvent
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Water Extraction Setup
• After the water and
solvent have mixed
well, the solvent is
withdrawn from the
top – this process is
repeated 2-3 times to
make sure all
organic compounds
are removed
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Water Testing
Solids Extraction Setup
• If particulates are in water, they
are filtered and the filter
extracted by Soxhlet
• Solvent in the flask at the bottom
is continually recycled, bringing
organic chemicals to the bottom
• Process similar to brewing coffee
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Water Testing
Interference Removal Step
• The compounds you are looking for are
not the only ones in the sample
• Other compounds – Interferences – can
result in incorrect results
• Interferences are removed by various
chemical operations known as Cleanup
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Interference removal
example for dioxin
analysis
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Concentration Step
• The sample must be reduced in size
before analysis because it is too dilute
to achieve really low detection limits
• ppb = parts-per-billion [1 part in 109]
• ppt = parts-per-trillion [1 part in 1012]
• ppq = parts-per-quadrillion [1 part in 1015]
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Water Testing
Typical Concentration Factors
• Typical water
sample size for trace
analysis is about 1.0
Litres
• Final sample 10-100
microlitres (10-6 L)
• Concentration factor
is about 104 to 105
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Water Testing
Other environmental sample types
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Sample Analysis Considerations
• Many different types of chemical
instrumentation are available for the
final analysis step
• For metals, one of most effective is
called an Inductively-Coupled Plasma
Mass Spectrometer (ICP-MS)
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Water Testing
ICP-MS Metals Analysis
• ICP-MS uses a hot plasma
(flame) to atomize metals
in sample
• Metals identified by
atomic mass
• Number of atoms detected
related to concentration in
sample
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Water Testing
GC-MS Organics Analysis
• For organics, instrumentation used is
called a gas chromatograph-mass
spectrometer (GC-MS)
• Dozens of types of GC-MS systems exist,
costing from $100K to $1.5 million
• Capabilities of systems different, but
basic principles the same
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Inject Sample Into GC-MS
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Complexity of Soil Samples
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Basic Operation of GC-MS
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Each Molecule has Fingerprint
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High Resolution Mass Spectrometer
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Characteristics of Methods
• Detection Limit
• Accuracy
– How close to the real concentration?
• Precision
– Related to measurement uncertainty
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Detection Limits
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Detection Limits
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Precision and Accuracy
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Data Interpretation: Public Understanding
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Analysis of dioxin in lake water
3 samples on consecutive days
Detection limits 0.1 – 0.3 ppt
Actual results:
Day 1 – 0.2 ppt
Day 2 – 0.4 ppt
Day 3 – not detected
What was the newspaper headline?
Water Testing
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New Millennium – New Challenges
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Pharmaceuticals & Personal Care Products
Perfluorinated compounds
Water Disinfection Byproducts
Brominated Flame Retardants (BFRs)
Algal Toxins: microcystins, anatoxins
Organometallic Compounds: tin, lead
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The Future of
Environmental Trace Analysis
More of less, faster
and cheaper
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How Many Chemicals?
Date:
08/1/2007 11:14:18 EST
Count: 32,261,560 organic/inorganic substances
15,057,189 commercially available chemicals
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New Challenges: New Tools
• Fourier
Transform (Ion
Cyclotron
Resonance) Mass
Spectrometer
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