1. Lecture 5 Sample Preparation

2. What is an extraction? Move compounds of interest ‘selectively’ to another media.

3. Why extract? Sampling media cannot be analyzed Clean-up Concentration

4. Why simplify extractions? Possibility of contamination All steps involve some loss Random errors possible at all steps

5. Extractions exploit the physical properties of the compounds of interest Air Water Octanol (hydrophobic) K AW K OA K OW

6. Air Water Octanol (hydrophobic) K AW K OA K OW Small Non-polar (non-interactive) Small Polar (interactive) Large Non-polar (non-interactive)

7. pH can control polarity Acidic compounds Basic compounds Low pH (acidic) High pH (basic) nonpolar Polar (charged)

8. Equilibrium vs. Exhaustive Extraction Water Hexane All extractions involve an equilibrium Exhaustive extractions usually involve repeating the process until all of the analyte is essentially in only one phase

9. Liquid-Liquid Extraction (Exhaustive Extraction) 100% 0% ext 1 10% 90% initial ext 2 1% 99% K OW = 10

13. Super Critical Fluid Extraction (Exhaustive Extraction) Very effective Non-toxic Easy to remove solvent Advantages Expensive Disadvantages