Beer's law states that absorbance is directly proportional to concentration, allowing this lab to use a spectrophotometer to calculate protein levels in milk samples. The students prepared 1:50 dilutions of evaporated and fresh milk with dye, incubated for 40 minutes, and measured absorbance at 595 wavelengths to generate a standard curve and determine that sample A, evaporated milk, had a higher protein concentration than the fresh milk.

1. Lab # 11 Got Protein?
Dr. Ricardo Chiesa
Beer’s law correlates the amount of solute with the absorbance. The absorbance
of a solute at a particular wavelength is directly proportional to the concentration of the
solute in solution. This law will help us calculate proteins present in milk using a
spectrophotometer. Our samples were evaporated milk and fresh milk. Following the
given protocol, we prepared a 1:50 dilution of the milk samples and added a dye reagent.
After incubation for 40 minutes, we compared the color of our unknown samples against
the standard known. At this point, we measured the absorbance of the standard samples
with a wavelength of 595. With this data we were able to make a standard curve to
determine the final concentration of protein in our unknown samples, fresh milk and
evaporated milk. Sample A, evaporated milk, has more protein concentration than fresh
milk.