Name Period title: Separation of Plant Pigments Using Chromatography



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Name______________ Period_____

TITLE: Separation of Plant Pigments Using Chromatography

Purpose: To identify plant pigments by separation and isolation of the pigments using thin layer paper chromatography.

Research Question:_____________________________________________

_____________________________________________________________

The distance traveled by a particular compound can be used to identify the compound. The ratio of the distance traveled by a compound to that of the solvent front is known as the Rf value; unknown compounds may be identified by comparing their Rf's to the Rf's of known standards.

Rf equation:



Rf = distance traveled by compound
        distance traveled by solvent

The different pigments in plants take a long time to separate, so you will need to set this up first and let it run while you complete the first part of the write-up.

Hypothesis:___________________________________________________

Variable Table:



Variable

Names;Symbols/units

Description of use in lab

Independent







Dependent







Constants







Controls-if applicable







Procedure:

  1. Cut a strip of coffee filter (or filter paper). Draw a horizontal line with a pencil (not pen) about half an inch from the bottom. Place a spinach leaf on the line and roll a penny over it so that you get a line of green pigment on the filter. Using a different part of the leaf, roll the penny again over the same line. Repeat this process until the line is fairly dark.
    2. Put about an inch of isopropanol (acetone, fingernail polish remover will work) in a beaker. 
    3. Tape the top of the coffee filter strip to a pencil and balance the pencil across the top of the beaker. See the image below for the set-up.
    4. It is very important that the bottom of the filter strip is in the isopropanol, but the green spot is not in the liquid. If the isopropanol touches the spot directly, the pigment will just dissolve away.
    5. Set the cup aside. The isopropanol will move up the filter paper slowly and deposit the pigment components along the way.

Apparatus:



Data Table:

Assign a band number for each pigment band - you should see greens, yellows, oranges..etc. 



Band Color

Plant Pigment

Distance (mm)

Rf (use formula)

Yellow to Yellow-orange

Carotene







Yellow

Xanthophyll







Bright Green to Blue Green

Chlorophyll a







Yellow Green to Olive Green

Chlorophyll b







Analysis: In essay for write the independent, dependent, control and constants. Then explain the data results.

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Graph: Please draw a bar graph on the graphing paper provided using the results of all the class lab samples.

Conclusion: In essay form, not using pronouns and in complete sentences, answering the following question(s)/statement.

Was the hypothesis supported or refuted?

Evidence from the lab supporting the claims.

Reasons that the presented evidence supports/refutes the claims.

What problems could have influenced the accuracy of the results?



Real world application; Explain how a crime lab could use paper chromatography to determine if lipstick found at a crime scene.

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