Question

1.2 1.0 0.8 0.6 0.4+ 0.2 0+ 300 350 400 450 500 550 600 650 700 Wavelength (nm) The absorption spectrum of a certain red dye is shown above. If a student analyzing the same concentration of this dye neglected to wipe fingerprints off the cuvette before placing it in the spectrophotometer, how would the absorption curve be affected? Absorbance

Answer 1

UV-VIS spectrometer works by measuring the amount of light that gets absorbed by the sample solution when the cuvette containing the sample is placed in the path of the light source.

Now, if the cuvette contains fingerprint from the student, this might result in the smudge created from fingerprint absorbing some of the light. Hence, the light absorbed or reflected due to  fingerprint in cuvette will be wrongly attributed to the sample. Hence, we will get a higher absorbance value for the sample than the actual value. This higher absorbance will lead to a wrongful analysis of the concentration which now will be higher than the actual concentration.

Hence, to summarize, the smudge created by not wiping the fingerprint off the cuvette will result in a high value of absorbance in the absorption curve. Even some of the light might be reflected by the smudge of fingerprint and result in wrong value of absorbance for the same concentration of dye.

Answer 2

The peak of curve would be lower because less light would be absorbed.