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Water Testing

Water Testing:How we measure what you can’t see

Water Testing:How we measure what you can’t see

1st Elmvale Water FestivalAugust 4, 2007

Ray ClementLaboratory 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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Water Testing

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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Water Testing

Objectives of Water Analysis• 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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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 Testing

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solvent have mixed well, the solvent is withdrawn from the top – this process is repeated 2-3 times to make sure all organic compounds are removed

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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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Water Testing

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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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• 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?

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New Millennium – New Challenges• 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 ofEnvironmental 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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