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Collection of Samples for Chemical Analysis

Collection of Samples for Chemical Analysis. Outline. Reasons for Sampling Sampling Protocols Controlling Variability Quantifying Variability Discussion. Reasons for Sampling. Regulatory Compliance HACCP requirement Risk Assessment Product Quality Monitoring Response to Complaint.

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Collection of Samples for Chemical Analysis

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  1. Collection of Samples for Chemical Analysis

  2. Outline • Reasons for Sampling • Sampling Protocols • Controlling Variability • Quantifying Variability • Discussion

  3. Reasons for Sampling • Regulatory Compliance • HACCP requirement • Risk Assessment • Product Quality Monitoring • Response to Complaint

  4. Sampling Protocols • Will vary based on the reasons for sampling • Consult with your analytical lab BEFORE sampling • Follow regulatory requirements to a tee

  5. Types of Samples • Grab Samples • Composite Samples • Random Samples • Targeted Samples • Market Basket Samples • Partial vs. Whole sample

  6. Sampling Considerations • Containers • Sample sensitivity to ambient conditions (light, heat, air) • Preservatives • Holding Times

  7. Water Sample Containers

  8. Containers • Flexible • Rigid • Plastic • Glass • Native Packaging (unopened if possible)

  9. Preservatives • Chemical Preservatives used primarily with water sampling • Stabilize the target analyte by decreasing chemical or biological degradation • May render sample unsuitable for other analytes • Refrigeration vs Freezing • Cooling vs. keeping cool

  10. Example preservatives • Sodium thiosulphate • Dechlorinator • Nitric acid • Stabilizer for metals in water • Sulphuric Acid • Stabilizer for ammonia, oil and grease

  11. Example Preservatives

  12. Holding Time • Clock starts at sampling • Holding time is under specified conditions • Usually taken to be the time when the variability due to degradation becomes significant compared to the expected variability of analysis

  13. Example Preservatives and HOLD Times • Volatiles in water • 3 X 40 ml septum vial (no headspace) • Sodium bisulphate • 14 days • BOD in wastewater • 1 litre • 48 hours • Keep at 4 deg C.

  14. Controlling Variability • Sampling • Methodology • Preferred Lab ? • Others factors

  15. Sampling Data to be Recorded • Who, When and Where • Record on CoC or traceable notes • Environmental Conditions during sampling • Any information that may influence results or interpretation of results

  16. Quantifying Variability • If we can’t control it, we must try to measure it • Often as simple as noting changes in case they impact data • Field duplicates • Understanding “Measurement Uncertainty” in assessing your data

  17. Questions? • Contact Information • Walter Brandl • Silliker JR Labs • walter.brandl@silliker.com • 604-432-9311

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