Summary
Measures the colour intensity of a solution to estimate concentration.
In depth
Colorimeters measure absorbance at a chosen wavelength using filters. A calibration curve from standards allows concentration from absorbance. Used in enzyme assays, such as the Benedict's or Bradford test.
Zero the instrument with a blank. Choose a complementary colour filter. Standards of known concentration give the calibration curve.
Key idea: more concentrated coloured solutions absorb more light.
A colorimeter measures how much light of a particular colour is absorbed or transmitted by a coloured solution, which relates to concentration. A filter or wavelength complementary to the solution colour is chosen, and the instrument is zeroed with a blank (the solvent).
A calibration curve is built by measuring absorbance of standard solutions of known concentration, then the concentration of an unknown is read from the graph. Colorimetry is used in biology to measure reducing sugars (Benedict's), protein (biuret), enzyme activity and bacterial growth by turbidity.
Example: measuring glucose by the intensity of colour produced in a glucose oxidase test.
Key idea: absorbance rises with concentration only within a limited range, so dilute strong samples.
Frequently asked questions
What is Colorimetry?
Measures the colour intensity of a solution to estimate concentration.
Which area of biology covers Colorimetry, and how advanced is it?
Colorimetry is one of the 51 topics in Lab Methods & Biostatistics. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Spectrophotometry, ELISA, NMR in Biology.
Can you give an example of Colorimetry?
Measuring starch breakdown with iodine.
What should I learn before Colorimetry?
Work through the Beginner topics in Lab Methods & Biostatistics first, such as Scientific Method, Hypothesis, Variables, then return to Colorimetry. Intermediate topics assume the Beginner vocabulary.
What topics are related to Colorimetry?
The closest topics to Colorimetry are Spectrophotometry, ELISA, NMR in Biology, Quadrats and Transects. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Colorimetry?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Colorimetry. To practise the whole of Lab Methods & Biostatistics, use the Lab Methods & Biostatistics quiz.
How is Colorimetry different from Spectrophotometry?
Colorimetry: Measures the colour intensity of a solution to estimate concentration. Spectrophotometry: Determines how much light of a given wavelength a sample absorbs, linked to concentration by the Beer-Lambert law. Read both side by side and note what each one explains.
How should I study Colorimetry step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Spectrophotometry and explain the difference aloud. Finally, take the Lab Methods & Biostatistics quiz and come back to this page for any question you miss.