Lecture 6 Sample Preparation

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

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

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

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

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’

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

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

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

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

Solid Phase Micro Extraction (SPME) N2 in Sorbent Sample

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

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