Question

In a spectrophotometry experiment, a wavelength near lambda maximum is chosen. What was the advantage of using a wavelength near max lambda as opposed to using a wavelength where the absorbance is low?

Answer 1

Reasons -

1) At the peak of maximum absorption, the effect of any error in wavelength on the abosrbance measurements is very little as opposed to any other wavelengths.

2) According to Beer-Lambert law: , where A is the absorbance of the sample, c is its concentration, is the molar absorptivity, and l is the path length.

Let us say dA is the error in measurement of A, then -

So, the error in concentration of sample will be less when is high, and because the is high at the maximum absorption, this will reduce the error in measurements. Hence is chosen for all measurements.