Plot absorbance versus concentration in μmol/L of the Tartrazine solution at the wavelength of the maximum absorbance of Allura Red, 480 nm, on a spreadsheet or a programmable calculator, and carefully determine the slope of the best straight line fit through the data. Using this Beer's Law plot, you will determine the value of ε*TZ480. The slope must be accurately determined because it will enable you to solve for the unknown concentrations of your mixture components. CLICK HERE if you would like assistance using an Excel spreadsheet for determining the slope of a best fit line. Enter the value of your slope to 3 significant figures and in units of L/μmol.