Without the proper methods and care-giving", many problems can arise when running a TLC plate. Below are some student lab scenarios involving incorrect TLC techniques and the resulting observations. For each scenario, () highlight the technical error(s) and (ii) recommend a procedural correction. For reference, part (a) is completed for you. (a) Alex runs her plate in an un-capped Coplin jar. Under the UV lamp, Alex observes that the spots on her TLC plate are blurred, elongated, and streaked. Seal Coplin jar with a cap during development
(b) Lance pipettes 0.5 mL of solvent into his Coplin, jar, and then adds in his TLC plate. While watching his plate develop, he notices the solvent front has been stationary in the middle of his plate for 20 minutes. He waits 5 more minutes and still, no solvent movement. He decides to take the plate out, and move on to TLC visualization under the UV light. He notices that all spots on the plate are blended and close together, not idealistically separated. Lance pipettes solvent into his Coplin jar to a depth of about 0.5cm
(c) Josh drops his TLC plate into the Coplin, jar with his hands. This results in an uneven landing where one side of the plate is touching the glass chamber. After development. Josh visualizes his TLC plate under UV light, and notes that the lanes are crooked, and spots are traveling in a diagonal fashion I I
(d) Michael spots compounds A, B, and C on a 0.5 cm origin line, and places the plate into a Coplin jar filled with 4 mL of 95:5 petroleum ether-ethyl acetate. After elution, he takes the TLC plate out and checks for that presence of spots under a UV lamp. To his dismay, Michael does not observe any spots on his TLC plate.
(e) Odell transfers 30:70 petroleum ether-ethyl acetate to his Coplinjar and carefully places his TLC plate inside. After analyzing his plate under UV light he notices that all of the spots are settling along the solvent front.