Experiment 3 -TLC_updated (1).pdf - FALL 2019 CHEM 3210 Experiment 3 Thin Layer Chromatography University of North Texas Thin Layer Chromatography

Experiment 3 -TLC_updated (1).pdf - FALL 2019 CHEM 3210...

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FALL 2019 CHEM 3210 University of North Texas Experiment 3: Thin Layer Chromatography 1 Thin Layer Chromatography Chapter 8 Objectives: Learning the TLC Technique. Perform the TLC of knowns and unknown - on a same or a different TLC plate(s) Determine the unknown by comparing with known Perform the TLC for some colored compounds (that have clear separation on TLC) Determine Rf (retardation factor) for all the samples (known and unknowns) Comment on polarity of knowns and unknowns based on Rf values Perform or observe the usage of iodine chamber for TLC application Experiment: Identification of an “unkown” analgesic by comparison with known analgesics Procedure: 1) Prepare TLC plate a. Mark a line ~1 cm from the bottom of the plate, lightly with a pencil b. Mark where spots will be on line (divide line into 3 parts) 2) Prepare developing chamber a. In a 250-mL beaker add: I. 3.8 mL ethyl acetate II. 0.2 mL acetic acid III. Filter paper (for saturating the chamber with mobile phase, helps to prevent drying of the TLC plate) IV. Aluminum Foil top or a Watch glass (keep it ready) 3) Spot plates a. Plate 1: Acetaminophen, Unknown, Aspirin b. Plate 2: Caffeine, Unknown, Ibuprofen 4) Make sure spots are on the plate – use UV light, if not try one more time 5) Develop plates in developing chamber (one at a time) 6) Once solvent front reaches ~1 cm from top, remove plate from chamber and: a. Mark solvent front with pencil b. Let the plate dry c. Visualize spots with UV lamp d. Mark spots with pencil e. Calculate R f values f. identify the unknown (results) g. Comment on the polarity of the knowns and unknown (arrange them according to their polarity – observations and results)
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FALL 2019 CHEM 3210 University of North Texas
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