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I did an experiment using fluorescence spectroscopy on quinine in an aqueous solution using concentrations of 0.0001mcg, 0.001mcg, 0.001mcg, 0.01mcg, 0.1mcg, 1.0mcg, 10mcg. The instrument spit out the data with wavelength in nm on the x-axis and intensity on y-axis.

I superimposed all the data onto 1 graph in excel and saw that 0.1mcg had the wavelength max so i was instructed to use this as my 100% relative intensity in comparison to the other spectra. The wavelengthmax height for 10mcg, 1.0mcg and my unknown were way off the graph, while the wavelengthmax of 0.0001mcg, 0.001mcg, 0.001mcg, 0.01mcg were below 100%.

how would i calculate/use excel to find the uncertainty in relative intensity.

would i take the y values from my reference concentration(0.1mcg) and do a standard deviation  calculation? or take the wavelength max of all the spectrums and do a stdev?