How do you determine exactly at which extinction the wavelength is maximum for the analysis of dyes?

Answer

Bye Steve

I assume that you have a photometer with which you can scan, ie measure a spectrum.
You must have a solution where your absorbance (or absorbance, but preferably you use the word absorbance) is not too high or too low.
If the concentrations are too low (and the associated color and absorbance), you will not see much.
If the concentration is too high, the device can no longer measure properly and the curve flattens out, so you can no longer see where it is maximum.
It is best to have absorbances between 0.5 and 1 (-1.5).
You record the spectrum over a large wavelength range (if you don’t know where to expect a peak) or over a smaller range (if you know where the maximum should be).
Since you work with dyes, you know their color and you can reason at what wavelength they absorb light.
You see if the absorbance around that maximum (where the values ​​are greatest) is between the limits above.
If necessary, dilute the solution or take a higher concentration.
The question you asked is actually wrong: you have to determine at which wavelength the absorbance is maximum!
Depending on the device, you can simply request this after recording the spectrum or you have to determine it yourself from the graph.
Hopefully you can continue like this.
Success with it!

Kind regards