1 / 13

Lecture 5

Lecture 5. Sample Preparation. What is an extraction?. Move compounds of interest ‘selectively’ to another media. Why extract?. Sampling media cannot be analyzed. Clean-up. Concentration. Why simplify extractions?. Possibility of contamination. All steps involve some loss.

fred
Download Presentation

Lecture 5

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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 KOA KAW Octanol (hydrophobic) Water KOW

  6. Small Non-polar (non-interactive) Air KOA KAW Octanol (hydrophobic) Small Polar (interactive) Water KOW Large Non-polar (non-interactive)

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

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

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

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

More Related