Beer’s law states A=ebc, which directly relates the concentration of a sample, its molar absorptivity (e) and the absorbance of a sample. Instead of bothering with a standard curve why not make two measurements: first, measure the A of a sample of known concentration in order to compute e. second, measure the absorbance of the solution with unknown concentration and use the e from the first calculation to calculate the concentration. Why would this or would not, be a better method than doing the standard curve with different measurements.