If a spectrophotometer reports an absorbance value that is too high, which of the following actions should be taken to obtain a more accurate measurement?

• A. Increase the path length of the cuvette.
• B. Dilute the sample and remeasure the absorbance.
• C. Use a higher concentration of the sample.
• D. Decrease the wavelength of the light source.

Answer: (B)

Verified step by step guidance

1. Understand that absorbance (A) is related to concentration (c), path length (l), and molar absorptivity (ε) by the Beer-Lambert Law: \(A = \varepsilon \times l \times c\).
2. Recognize that if the absorbance value is too high, it may exceed the linear range of the spectrophotometer, leading to inaccurate measurements.
3. Consider that increasing the path length or concentration will increase absorbance further, which is not helpful when the absorbance is already too high.
4. Realize that decreasing the wavelength might change the molar absorptivity but does not directly solve the problem of high absorbance due to concentration or path length.
5. Therefore, the best approach is to dilute the sample, reducing its concentration, and then remeasure the absorbance to bring it within the instrument's accurate measurement range.