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

Water Testing: How we measure what you can’t see. 1 st Elmvale Water Festival August 4, 2007 Ray Clement Laboratory Services Branch, Ontario Ministry of the Environment. Overview. Steps taken to analyze water What is trace? How do we know we’re right?

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

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  1. 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

  2. Overview • Steps taken to analyze water • What is trace? • How do we know we’re right? • New environmental issues and challenges

  3. Steps in Water Analysis • Determine objectives • Take a sample for testing • Prepare sample for analysis • Analyze sample • Interpret results with quality control

  4. 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

  5. Sampling Considerations • Sample taken must be representative of the water body being tested

  6. Sampling Artifact?

  7. 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

  8. Prepare Sample for Analysis • Extraction step • Interference removal step • Concentration step

  9. 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

  10. 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

  11. Water Extraction Setup • After the water and solvent have mixed well, the solvent is withdrawn from the top – this process is repeated 2-3 times to make sure all organic compounds are removed

  12. 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

  13. 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

  14. Interference removal example for dioxin analysis

  15. 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]

  16. 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

  17. Other environmental sample types

  18. 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)

  19. 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

  20. 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

  21. Inject Sample Into GC-MS

  22. Complexity of Soil Samples

  23. Basic Operation of GC-MS

  24. Each Molecule has Fingerprint

  25. High Resolution Mass Spectrometer

  26. Characteristics of Methods • Detection Limit • Accuracy • How close to the real concentration? • Precision • Related to measurement uncertainty

  27. Detection Limits

  28. Detection Limits

  29. Precision and Accuracy

  30. 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?

  31. 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

  32. The Future ofEnvironmental Trace Analysis More of less, faster and cheaper

  33. How Many Chemicals? Date: 08/1/2007 11:14:18 EST Count:  32,261,560 organic/inorganic substances15,057,189 commercially available chemicals

  34. New Challenges: New Tools • Fourier Transform (Ion Cyclotron Resonance) Mass Spectrometer

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