Spectrophotometry

Beer-Lambert (absorbance to concentration): practice problems

Work out the concentration from the absorbance. Every answer here is computed by the same tested calculator the rest of the site uses, so a solution can never drift away from the maths.

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Problem 1 Beer-Lambert (absorbance to concentration)

Work out the concentration from the absorbance.

  • Wavelength (nm): 412
  • Extinction coefficient: 14150
  • Absorbance (A): 0.5
  • Show result in: µM
Show the answer and the working

Your sample is 35.34 µM at 412 nm.

  1. Beer-Lambert: c (mol/L) = A · DF / (ε · l)
  2. Substitute: c = 0.5 · 1 / (14150 · 1) = 0.00003534 M

Open this in the calculator to change the numbers.

Problem 2 Beer-Lambert (absorbance to concentration)

Work out the concentration from the absorbance.

  • Wavelength (nm): 280
  • Extinction coefficient type: E0.1% (0.1% w/v = 1 g/L)
  • Extinction coefficient: 0.667
  • Absorbance (A): 0.75
Show the answer and the working

Your sample is 1.124 mg/mL at 280 nm.

  1. Beer-Lambert: c (mg/mL) = A · DF / (E0.1% · l)
  2. Substitute: c = 0.75 · 1 / (0.667 · 1) = 1.124 mg/mL

Open this in the calculator to change the numbers.

Problem 3 Beer-Lambert (absorbance to concentration)

Work out the concentration from the absorbance.

  • Wavelength (nm): 750
  • Extinction coefficient: 6220
  • Absorbance (A): 0.4
  • Show result in: µM
Show the answer and the working

Your sample is 64.31 µM at 750 nm.

  1. Beer-Lambert: c (mol/L) = A · DF / (ε · l)
  2. Substitute: c = 0.4 · 1 / (6220 · 1) = 0.00006431 M

Open this in the calculator to change the numbers.

Problem 4 Beer-Lambert (absorbance to concentration)

Work out the concentration from the absorbance.

  • Wavelength (nm): 100
  • Extinction coefficient: 14150
  • Absorbance (A): 0.5
  • Show result in: µM
Show the answer and the working

Your sample is 35.34 µM at 100 nm.

  1. Beer-Lambert: c (mol/L) = A · DF / (ε · l)
  2. Substitute: c = 0.5 · 1 / (14150 · 1) = 0.00003534 M

Open this in the calculator to change the numbers.

Problem 5 Beer-Lambert (absorbance to concentration)

Work out the concentration from the absorbance.

  • Wavelength (nm): 400
  • Extinction coefficient type: E0.1% (0.1% w/v = 1 g/L)
  • Extinction coefficient: 0.667
  • Absorbance (A): 0.3
Show the answer and the working

Your sample is 0.4498 mg/mL at 400 nm.

  1. Beer-Lambert: c (mg/mL) = A · DF / (E0.1% · l)
  2. Substitute: c = 0.3 · 1 / (0.667 · 1) = 0.4498 mg/mL

Open this in the calculator to change the numbers.

Problem 6 Beer-Lambert (absorbance to concentration)

Work out the concentration from the absorbance.

  • Wavelength (nm): 300
  • Extinction coefficient: 6220
  • Absorbance (A): 0.75
  • Show result in: µM
Show the answer and the working

Your sample is 120.6 µM at 300 nm.

  1. Beer-Lambert: c (mol/L) = A · DF / (ε · l)
  2. Substitute: c = 0.75 · 1 / (6220 · 1) = 0.0001206 M

Open this in the calculator to change the numbers.

Problem 7 Beer-Lambert (absorbance to concentration)

Work out the concentration from the absorbance.

  • Wavelength (nm): 150
  • Extinction coefficient: 14150
  • Absorbance (A): 0.5
  • Show result in: µM
Show the answer and the working

Your sample is 35.34 µM at 150 nm.

  1. Beer-Lambert: c (mol/L) = A · DF / (ε · l)
  2. Substitute: c = 0.5 · 1 / (14150 · 1) = 0.00003534 M

Open this in the calculator to change the numbers.

Problem 8 Beer-Lambert (absorbance to concentration)

Work out the concentration from the absorbance.

  • Wavelength (nm): 100
  • Extinction coefficient type: E0.1% (0.1% w/v = 1 g/L)
  • Extinction coefficient: 0.667
  • Absorbance (A): 0.15
Show the answer and the working

Your sample is 0.2249 mg/mL at 100 nm.

  1. Beer-Lambert: c (mg/mL) = A · DF / (E0.1% · l)
  2. Substitute: c = 0.15 · 1 / (0.667 · 1) = 0.2249 mg/mL

Open this in the calculator to change the numbers.

Problem 9 Beer-Lambert (absorbance to concentration)

Work out the concentration from the absorbance.

  • Wavelength (nm): 100
  • Extinction coefficient: 6220
  • Absorbance (A): 0.4
  • Show result in: µM
Show the answer and the working

Your sample is 64.31 µM at 100 nm.

  1. Beer-Lambert: c (mol/L) = A · DF / (ε · l)
  2. Substitute: c = 0.4 · 1 / (6220 · 1) = 0.00006431 M

Open this in the calculator to change the numbers.

Problem 10 Beer-Lambert (absorbance to concentration)

Work out the concentration from the absorbance.

  • Wavelength (nm): 300
  • Extinction coefficient: 14150
  • Absorbance (A): 0.4
  • Show result in: µM
Show the answer and the working

Your sample is 28.27 µM at 300 nm.

  1. Beer-Lambert: c (mol/L) = A · DF / (ε · l)
  2. Substitute: c = 0.4 · 1 / (14150 · 1) = 0.00002827 M

Open this in the calculator to change the numbers.

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