Separation technique, Thin-Layer Chromatography of Plant Pigments PDF

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Separation Technique: Paper Chromatography Organic Chem Laboratory ManualSeparation technique :Thin-Layer Chromatography of Plant PigmentsObjectives: (3 points)• To separate pigments of leaves using Thin Layer Chromatography• To calculate Rf values in the pigments• To identify what compounds are pre...

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Separation Technique: Paper Chromatography

Organic Chem Laboratory Manual

Separation technique : Thin-Layer Chromatography of Plant Pigments

Objectives: (3 points)

• • •

To separate pigments of leaves using Thin Layer Chromatography To calculate Rf values in the pigments To identify what compounds are present and responsible for each pigments

DA DAT TA: Thin-Layer chromatogr chromatography aphy of plant pigments. The distance travelled by the different pigments from hibiscus leaves are listed in the following table. Calculate the Rf values.

1.

Rf values of plant pigments. (2 points each) Pigment

solvent

Distance trav traveled, eled, mm

53

Rf value

N/A 0.98

Bright yellow

52 0.60

Dark green

32 0.43

Light green

23 0.26

Light yellow

14

Separation Technique: Paper Chromatography

Organic Chem Laboratory Manual

Based on the above information, what are the compounds responsible for each pigment.

2.

(2 points each) Color

Bright yellow Dark green Light green Light yellow

Compound β-Carotene Lutein Violaxanthin

Chlorophyll b

QUESTIONS: 1.

a) Which pigment is the most soluble in the developing solvent? (1 pt.) •

Bright Yellow

b) Explain. (2 points) • The pigment “bright yellow” is the most soluble among all pigments because it travel at a greatest distance than others.

What does a small Rf value indicate with respect to its polarity? (2 pts )

2. •

If the pigment travel at a smaller distance among all pigments it means that its Rf value is lower than others, it may conclude that the pigment is more polar because the pigment stick to the adsorbent in the first place.

If the developing solvent is changed, would the Rf be the same? (yes or No) (1pt)

3.

Explain (2 pts) • •

No. The Rf values will not stay the same if the solvent is change because solvent are one of the factors affecting Rf value.

Separation Technique: Paper Chromatography

Organic Chem Laboratory Manual

Is it possible to have an Rf value greater than 1? Why or why not? (3 pts)

4. •

There’s no way the Rf values will be Greater than 1, if so it makes the experiment and the Rf values unreliable. The retention factor values will always stay less than 1.

The experimental results show that leaves contain different pigments, explain why we only

5.

see green color. (3 pts) •

The leaves contain different pigments as the result of the experiment, but because of the cell leaves contain chloroplast it can only hold chlorophyll and can’t able to hold others. That’s why it only reflect green color.

What is the developing solvent used? Indicate the ratio. (1 pt)

6. •

The experiment used 75% petroleum ether and 25% acetone as developing solvent.

7.

Is it polar or nonpolar? Underline (1 pt)

8.

What is the stationary phase? (1 pt) •

Silica Gel

9.

Is it polar or nonpolar? Underline (1pt)

10.

From the chromatographic results, arrange the different pigments according to increasing polarity. (3 pts)

•

Bright yellow < dark green < light green < light yellow...