Experiment: SPECTROPHOTOMETRIC DETERMINATION OF A FOOD DYE
The purpose of this experiment is to measure the concentration of a food dye, Allura Red, in a popular soft drink, Kool-Aid. This experiment will introduce spectrophotornetry as a method for quantitative analysis.
Calculations
Prepare a plot of absorbance versus wavelength (from 400 to 600 nm) for solution number 10. This plot is called a spectrum. Unlike a calibration plot, please connect the data points on your spectrum. This can be done in Microsoft Excel by choosing an XY (scatter) plot with the chart sub-type: "Scatter with data points connected by smoothed lines".
Prepare a plot of absorbance versus concentration for your four standard solutions. Fit a line to this plot, and determine the equation of the best-fit line.
Using the equation of the best-fit line and the absorbance of the unknown soft drink, determine the concentration (in mg/L.) of Red Dye No. 40 in the unknown. Don't forget to take the 10-fold dilution into account!
Show all sample calculations in your lab notebook or properly annotated Excel spreadsheet.