Experiment Three Report
Riboflavin Fluorescence Spectra
Name: Holly

Experimental Section: Include all details on preparation of standard solutions. Also include the vitamin tablet brand name; the listed mass of vitamin B2 per tablet; procedure used for extraction of the tablet and dilutions performed.
The experiment began by determining the best wavelength at which to excite the riboflavin molecule, by examining the graph given in the laboratory manual[1]. Because plastic cells that absorb UV light were being used to hold the solutions, the wavelength had to be >320nm. To ensure that we could clearly see the peak of the riboflavin fluorescence in the stock solution, the peak we chose to measure was the one approximated at
Section 2. Examine how the fluorescence intensity varies with the concentration of riboflavin in solution. Include a plot of fluorescence intensity values as a function of riboflavin concentration. Include best fit and error calculations.

Figure 2. Fluorescence Intensity vs Concentration of Riboflavin
The fluorescence intensity vs concentration graph of riboflavin above was created by diluting a stock solution of 50ppb, to 40, 30, 20 and 10ppb and measuring it in the fluorescence instrument. As can be seen in figure 2, as the concentration of riboflavin increases, so does the fluorescence intensity, and the graph is linear, in the form y=mx+c. The error in m=±0.133 and the error in c=±4.413 according to WinCurveFit.
Section 3. Determine the concentration of riboflavin in your vitamin tablet. Include the calculation of the mass of riboflavin per tablet. Include error calculations.
Determining the number of dilutions needed for our vitamin tablet to get it in the range of 050ppb. First the concentration of the vitamin tablet in ppb needed to be determined. First
100mg of riboflavin in the tablet (stated on the bottle) was diluted to 50mL with acetic acid. ppb=μg/L=100mg/50mL=0.1g/0.05L=100,000μg/0.05L= 2,000,000 ppb
Working backwards, a concentration of between 0-50ppb is needed, so 20ppb should be a good value to get a reading, and easy to use in calculations. 5mL extractions were decided to enable ease of calculations and a lower error.