What should be done if a sample's analyte concentration exceeds the spectrophotometer's calibration range?

• A. Disregard the result and report as is.
• B. Dilute the sample and re-analyze.
• C. Increase the concentration by adding more analyte.
• D. Use a different instrument.

Answer: (B)

The key idea is staying within the spectrophotometer’s reliable linear range, where absorbance is proportional to concentration. If the analyte is too concentrated, the absorbance can fall outside this range and the Beer-Lambert relationship becomes inaccurate. Diluting the sample brings the concentration into the calibrated range, allowing an accurate measurement. After obtaining the absorbance of the diluted sample, multiply the calculated concentration by the dilution factor to recover the original concentration, and keep careful track of the dilution, cuvette pathlength, and solvents used. If the diluted signal still isn’t within range or if dilution isn’t feasible, reconsider the assay design or instrument, but dilution is the standard, straightforward fix for exceeding calibration range.