Part C: Testing Plant Extract

Question

Determine the absorption spectrum for the pigments in the coleus leaf following the steps provided.
Materials:
Blank prepared in Part B
Plant extract from Part A
Kimwipes
Procedure:
1. Look at the data table and note the readings range from 400 nm – 700 nm (with increments of 20nm). This is the range for testing.
2. Set the wavelength on the spectrophotometer to 400 nm.
3. Set the mode to “absorbance” by pressing the A/T/C button until an A appears at the right of the digital display.
4. Insert the blank (clean with a Kimwipe) in the cell holder and close the door.
5. Press the 0 ABS/100%T key to set the blank to 0 absorbance.
6. Remove the blank and insert the clean cuvette containing the chlorophyll extract.
7. Record the digital readout for the absorbance in the data table.
8. Continue to increase the wavelength by 20 nm each time and repeat steps 4-7. Remember to use the blank for each new wavelength setting!!
9. Graph the data using the instructions provided for Excel 2007.
10. Dispose of the leaf extract in the waste container in the fume hood.
use the above information and write a good procedure in a practical correctly in a sentence form.

Answer 1

Procedure: Testing Plant Extract Absorption Spectrum

To determine the absorption spectrum of pigments in a coleus leaf, begin by examining the data table which specifies readings ranging from 400 nm to 700 nm in increments of 20 nm. First, set the spectrophotometer to a wavelength of 400 nm and ensure it is in "absorbance" mode by pressing the A/T/C button until an "A" appears on the digital display.

Next, carefully clean the blank cuvette with a Kimwipe to avoid contamination and insert it into the cell holder of the spectrophotometer, then close the door. Press the 0 ABS/100%T key to calibrate the blank to 0 absorbance. After calibration, remove the blank and replace it with a clean cuvette containing the chlorophyll extract, ensuring it is also cleaned with a Kimwipe prior to insertion.

Record the absorbance reading displayed on the spectrophotometer for the chlorophyll extract. Continue this process, systematically increasing the wavelength in 20 nm increments up to 700 nm, and repeat the calibration with the blank and recording of absorbance for each new wavelength setting.

Once all readings have been collected, graph the data using the instructions provided for Excel 2007. Finally, dispose of the leaf extract in the designated waste container located in the fume hood to ensure proper disposal of materials.