Water Testing: How we measure what you can

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Water TestingHow we measure what you cant see
1st Elmvale Water Festival August 4, 2007 Ray
Clement Laboratory Services Branch, Ontario
Ministry of the Environment
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Overview

• Steps taken to analyze water
• What is trace?
• How do we know were 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

• 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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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 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  solvent is withdrawn from the top this process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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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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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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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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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 111418 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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