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Lecture 6 Sample Preparation

Lecture 6 Sample Preparation. Solid Phase Extraction (Exhaustive Extraction). Analyte either ad sorps or ab sorbs to a solid support. Advantages. Large concentrations possible Limited use of solvents Very effective clean-up technique. Disadvantages. Time consuming

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Lecture 6 Sample Preparation

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  1. Lecture 6 Sample Preparation

  2. Solid Phase Extraction (Exhaustive Extraction) Analyte either adsorps or absorbs to a solid support Advantages • Large concentrations possible • Limited use of solvents • Very effective clean-up technique Disadvantages • Time consuming • Precision can be difficult • Expensive

  3. N2 in Sorbent Lab Sample Solid Phase Extraction - Air (Exhaustive Extraction) Vacuum pump Ambient air Environment Sorbent

  4. Solid Phase Extraction - Air (Exhaustive Extraction) Sorbents • XAD • High surface area (290-750 m2/g) • PUF • Polyurethane foam • TENAX • Moderate surface area (19-30 m2/g) • Thermally stable, appropriate for thermal desorption

  5. Environment Sorbent Pump Water Solid Phase Extraction - Water (Exhaustive Extraction) Water sample Sorbent Lab Vacuum manifold

  6. Solid Phase Extraction - Water (Exhaustive Extraction) Sorbents • Silica-based stationary phase • Similar to LC phase - C18 most common • Limited pH stability • ‘Finicky’ to handle • Polymeric • Stable from pH 1-14 • Not ‘finicky’

  7. C18 tails Si Silica-based SPE cartridges Procedure: 1. Condition cartridge 2. Load sample 3. Wash co-extractables 4. Elute analytes of interest Tails ‘solvate’ during step 1 (conditioning), will collapse if the cartridge goes dry. Extraction is ruined

  8. Polymeric SPE cartridges Procedure: 1. Condition cartridge 2. Load sample 3. Wash co-extractables 4. Elute analytes of interest No tails to ‘solvate’, and so extraction can continue even if cartridge goes dry

  9. Polymeric SPE cartridges Because of the wide pH stability are able to use pH to control extraction. Very selective and effective extraction technique.

  10. Solid Phase Micro Extraction (SPME) Only equilibrium extraction method described here. Often used to observed volatile materials in a laboratory setting. N2 in Sorbent Sample

  11. Solid Phase Micro Extraction (SPME) N2 in Sorbent Sample

  12. SPME fibre Solid Phase Micro Extraction (SPME) SPME holder Sample

  13. k k Solid Phase Micro Extraction (SPME) SPME fiber Sample

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