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A dilution series connects a colorimeter reading with known glucose concentrations. Use the measured calibration to estimate an unknown rather than relying on colour descriptions alone.
What you'll be able to do
Prepare a range of known glucose concentrations from a stock solution with measured volumes and a common final volume. Use C1V1=C2V2 when volumes are additive in the stated dilution model. Label standards, a zero-glucose control and the unknown simulated urine samples clearly.
Use the centre’s approved colorimetric chemistry, including specified reagents, heating or timing and cooling where required. Treat standards and unknowns comparably. The blank must match the method’s relevant background; a water-only blank is not automatically correct if reagents and the sample matrix also contribute to the reading.
Read absorbance with an appropriate wavelength and consistent cuvettes. Plot response against known glucose concentration and include suitable repeat measurements. The direction and shape of the response depend on the assay and which components are measured; do not assume every glucose test gives the same linear increase.
Benedict’s-based methods require particular care with reaction conditions, colour and any precipitate affecting light transmission. Follow the validated classroom method rather than treating a turbid sample as an ideal clear solution. Use the standards to determine the usable calibration range, and interpolate rather than automatically forcing a straight line through every point.
Use the unknown’s response to read concentration from the calibration. If it was diluted before measurement, multiply the inferred concentration by the total dilution factor to estimate the original. If the response falls outside the range, use an appropriate further dilution and remeasure rather than extrapolating far beyond the standards.
Biological or simulated sample colour, interfering substances and reagent variation can affect the result. The practical estimates glucose under the assay conditions; one classroom reading is not a complete determination of a medical condition. Evaluate uncertainty through repeated standards and unknowns and report sensible precision.
Try each question before opening the worked response. Use precise biological terms, connect each cause to its effect, and check units and assumptions when interpreting data.
Equation recap
Common mistakes to avoid
Key takeaways
Test yourself
Answer a few questions, then review anything you missed.
Start with the quiz above to check the key ideas. You can also choose another topic from the practice library.