Plants Pigment

...

8:2

Distance from origin to component spot for Spinach (cm)

Distance from origin to component spot for Purple Carrot (cm)

0.6

1.4

1.1

5.6

1.4

2.5

3

5.6

Pigment

Colour

Rf value

carotene

yellow-orange

0.93

pheophytin a

grey

0.55

pheophytin b

light grey

0.47-0.54

chlorophyll a

blue-green

0.46

chlorophyll b

green

0.42

xanthophylls

yellow

0.41

xanthophylls

yellow

0.31

xanthophylls

yellow

0.17

A663 = 0.222

A645 = 0.120

The equations given in the prac notes:

A663 = 82.0 Ca + 9.3 Cb (1)

A645 = 16.8 Ca + 45.6 Cb (2)

where Ca and Cb are the concentrations in g/L of chlorophyll a and b, respectively.

Substitute the experimental values for the measured solution into (1) and (2):

0.222 = 82.0 Ca + 9.3 Cb (3)

0.120 = 16.8 Ca + 45.6 Cb (4)

Solve equations (3) and (4) for Cb by making Ca equal. First multiply (4) by 4.88 (82.0 Ca /16.8 Ca) to give:

0.5856 = 82.0 Ca + 222.5 Cb (5)

Then subtract (3) from (5) to give:

0.3636 = 213.2 Cb

Thus Cb = 0.001705 g/L or 1.705 mg/L of the measured solution.

Rearrange (3) to give:

Ca = (0.222 - 9.3 Cb)/82.0 (6)

Substitute the concentration of Cb to give:

Ca = [0.222 – (9.3 x 0.001705)]/82.0

Ca = 0.002513 g/L of the measured solution.

Ca = 2.513 mg/L of the measured solution.

You started with 5 g spinach leaf. Since the measured solution (in this example) was the 1:5 dilution, it represented 1/5 x 5 g = 1 g spinach leaf. Since the total volume of the measured solution was 100 ml, there was 10 g spinach per L measured solution.

Thus the concentration of chlorophyll a was 2.513 mg/10 g spinach leaf or 0.2513 mg per g spinach leaf.

And the concentration of chlorophyll b was 1.705 mg/10 g spinach leaf or 0.1705 mg per g spinach leaf