[electriclizard69]

I wish to plot the wavelength of the maximum absorbance of a dye against another quantity that I will be measuring in an experiment. However, certain dyes, such as N719, N3, etc. have multiple peaks in their absorption spectra. Which wavelength should I consider in that case?

For example this absorption spectra for N719: https://www.researchgate.net/figure/Absorbance-spectrum-of-N719-and-BD-dye-solution-in-ethanol-10-10-5-M_fig1_302449760, which wavelength should I consider?

[Borek]

There is no simple rule, a lot depends on the circumstances. Given several wavelength to choose from I would select one that sits in the middle of the instrument range and/or one that has as low as possible interference from other substances possibly present in the samples.