Results
1. Determine Maximum Absorption for Bromophenol Blue
Wavelength
425
450
475
500
525
550
575
600
625
Absorbance
a. What is the wavelength of maximum absorbance for bromophenol blue?
b. What color is this?
2. Standard Curve for Bromophenol Blue
Tube Number
1
2
3
4
5
6
7
8
9
Concentration
Absorbance Units
3. Determination of an Unknown
Unknown Letter: _______________
Absorbance Value: ______________
Conclusions
1. Describe the relationship between absorbance and the concentration of a light-absorbing substance in
a solution.
2. Explain how standard curves can be used to determine the concentration of a substance in a solution.
3. You have a solution that appears green. What color light is/are being transmitted? Absorbed?
4. What is the purpose of a blank when using a spectrophotometer?
5. You are making a standard to be used to measure protein concentration. You have added 2 ml of
protein, 3 ml of water, and 4 ml of an indicator dye. How would you prepare the blank for this
experiment?
6. To a test tube you add 3 ml of a stock 0.05 mg/ml dye and 7 ml of water. What is the final
concentration of dye in this tube?
7. What is the concentration of bromephenol blue in your unknown sample?