A practical guide to structural analysis of carbohydrates

Colourimetric determination of total protein content

To determine the content of protein in biological matter one can preferably use the either the Lowry or the Bradford test (BioRad protein assay).


  • Sodium deoxycholate, Na-DOC, 2% solution (2g/100mL)
  • Sodium hydroxide, 4M
  • Reagent D:
    • Copper sulphate, 2% solution (2.5g/250mL)
    • Sodium potassium tartrate, 4% solution (5g/250mL)
    • Sodium carbonate, 2% solution (20g/L)
  • Folin-Ciocalteaus reagent, ready-made
  • Standard:
    • 0.02% albumin solution, (20mg/100mL)
    • Blank: 0.5mL water


  1. Take x mL protein solution and dilute to 0.5 mL. Add 0.15mL each of the Na -DOC and the NaOH solution.
  2. Take 0.10, 0.15 and 0.20mL of the standard albumin solution. Dilute to 0.5mL and add 0.15mL each of the NaDOC and the NaOH solution.
  3. Leave the samples, the standards and blank for 10 minutes.
  4. Make reagent D by mixing 0.5mL of CuSO4 solution, 0.5mL of Tartrate solution and 49mL of the Na2CO3 solution. Add 3.0mL of reagent D and leave for 10 minutes (maximum 3 hours)
  5. Folin-Ciocalteaus reagent (0.3 mL) is added immediately shaken and allowed to stand for exactly 30 min.
  6. Read at 750nm against blank.