1. Analysis of Food Dyes in Beverages
Spectometry and Beer’s Law

2. In lab notebooks, fill out:
Title
Source
Partners
Date
Purpose
Safety considerations
Materials
Then, answer the “Pre-Lab Questions” (be sure to glue in the questions that you received in class! )
Copy down “Introductory Activity” Procedures

3. Intro Activity
You would have run the stock solution and dilutions with known concentrations through the spectrophotometer to measure the %T in order to create a calibration curve so that we have something to compare an “unknown” to.

4. Glue following data table in your notebooks (I attached on my website- just print and glue.) after the Intro Activity Procedure. The %T are values that you would have acquired (or close to), if you had actually run the stock blue dye and diluted standards through the spec.
Solution
Dilution ratio
Concentration
% T T A
mL stock/mL water
micromolar
A (stock)
 10/0
 12.2 B
 8/2
 18.7 C
 6/4
 26.0 D
 4/6
 39.3 E
 3/7
 48.6 F
 2/8
 61.0 G
 1/9
 74.2 H
 0/10
 99.0

5. After copying the data table… (1) Complete #7 and 8 from “Introductory Activity” (show work!). Fill out the data table with your answers. (2) Complete #9 from “Introductory Activity”, but you only need to create 1 graph, not 5. Absorbance vs. Concentration of Dye is the only one required! Glue it in your notebook after your work for #7 and 8. BE SURE YOUR GRAPH HAS THE AXES LABELED AND A PROPER TITLE! You can use a computer program to do this, and just print and glue it in.

6. Calculation Hints:
First convert %T to T (move decimal)
Convert to Absorbance (A = -logT)
Use Beer’s Law to calculate concentration (in micromolar) of each using the absorbance measured (like prelab question #3, only solving for C instead of A). Use the same value for ε that was given in prelab question #3.