Presentation on theme: "Paper Chromatography Chromatography is a method of separating and identifying various components in a mixture, which are present in small trace quantities."— Presentation transcript:
1Paper ChromatographyChromatography is a method of separating and identifying various components in a mixture, which are present in small trace quantities. There are several types of chromatography, one of which is paper chromatography. This uses a stationary phase (paper) and a mobile phase (solvent). As the solvent wicks up the paper by capillary action, an equilibrium is established for each chemical in the mixture. Part of the time the particular pigment is moving in the solvent, while at other times it is adsorbed into the paper. The pigments separate in the sample due to polarity; the paper is more polar than the solvent so nonpolar substances will spend more time in the nonpolar mobile phase and will travel further up the paper
2Spinach Chromatography Lab ObjectiveSeparate pigments from spinach using paper chromatographyCalculate Rf values of separated pigments*Rf = distance substance travelsdistance solvent front travelsMaterialsChromatography paper stripsPetroleum Ether: Acetone Solution1 vial spinach leaf extractCapillary pipetParafilm squaresMSDSTransparent TapeMetric rulersGraduated Cylinder (100mL)Graphite pencil
3Pre-lab Questions What is chromatography? Calculate the Rf of a substance that traveled 5.2 cm on chromatography paper. The solvent front traveled 8.1 cm.Does each spot on the developed chromatography paper represent one substance?
5ProceduresPrepare a piece of chromatography paper by measuring 2cm from bottom of paper and drawing a line with pencilAt the other end, attach a piece of tape long enough to drop the paper to the bottom of the graduated cylinder and attach the top of the tape to the cylinder mouthAt center station, touch the capillary pipet with pigment to center of line; allow the spot to dryPour 5mL petroleum ether: acetone solution into 100mL graduated cylinderCover the top of cylinder with Parafilm square6. Place chromatography paper inside cylinder so that the paper extends into the solvent 7. Wait 10 minutes, then remove the paper from the cylinder, and mark the location of the solvent front with pencil. Trace pigment outlines with pencil after solvent evaporates 8. In your notes, draw a life-size picture of the developed chromatography paper, labeling the locations and colors of the spots. 9. Measure the distance each spot and the solvent front traveled from the pencil line; calculate the Rf values for each pigment.
6Follow-up Questions Find the distance traveled by: Solvent front _______cmCarotene ________cmXanthophyll _______cmChlorophyll a ______cmChlorophyll b_______cmCalculate Rf for each pigment:Carotene ________Xanthophyll _________Chlorophyll a ________Chlorophyll b ________Which pigment is most polar? Which is least?