Question

(a). Why is the wavelength of maximum absorption usually selected for colorimetric determination?(b). Beer’s law is useful for determining the conc. of solute only when the relationship between absorbance and conc. is in a linear relationship. When the conc. of the solute is too high this linear relationship doesn’t exist, why? (c). If a sample is very precious and a technician made a mistake by dissolving all of the sample into a solvent and get a very high absorbance. How to rescue the data under such condition?

Answer 1

a) because at this wavelength the solution to be measured has the greatest sensitivity
the linear relationship explained by the Beer-Lambert law is best observed in the maximum absorption wavelength

b) Beer-Lambery LAW doesn't apply solutions with concentrations too high because that do not allow light to pass through them.
Also purity of the sample can affect it as well.

c) A=xbC
A=Absorbance x=absorbance b=length of solution (constant)
C=Concentration units
Blank is used to clear solute from reading
Absorbance=-log(Light total/Light through sample)

at the very high absorbance concentration will tends to zero