Question

The linear relationship between the variables in Beer’s Law does not hold for absorbance values over 2.0. Briefly explain an experimental strategy you would use if a protein solution of unknown concentration gives you an absorbance reading of >2.0.

Answer 1

The linear relationship between the variables in Beer’s Law does not hold for absorbance values over 2.0. If a protein solution of unknown concentration gives you an absorbance reading of >2.0, then dilute the solution with suitable solvent.

For example, a protein solution of x M concentration gives absorbance over 2.0. To 1 mL of this solution, add 9 mL of suitable solvent (in which protein is soluble). The concentration of protein will decrease from x M to 0.1x M as the solution is diluted to 10 times. The absorbance will decrease from more than 2.0 to around 0.2. Use the linear relationship between the variables in Beer’s Law to determine the concentration of diluted protein solution and multiply it with 10 to determine the concentration of original protein solution.