CH 461 & 461H                                                                                                                         F ‘06

Experiment 2B.

Determination of Riboflavin - MOLECULAR FLUORESCENCE SPECTROSCOPY

II.        SOLUTIONS 

            The following stock solutions are available in the main laboratory: 100, 75, 25, and 10 μg/mL riboflavin in MP water. Prepare in the main laboratory the following (use volumetric pipets and flasks throughout):

a)        100 or 50 mL of 2.5, 1, 0.25, and 0.1 μg/mL riboflavin standard solutions in water from higher concentration stock or standard solutions (listed above) and MP water. Transfer these solutions to prepared amber bottles and store in refrigerator if you do not use them the day they are prepared or if you need the volumetric flasks for other solutions.

b)        One synthetic unknown sample by quantitatively transferring the total contents of the vial to a 100-mL volumetric flask and diluting to volume with water.

c)        Three dilutions, one for each vitamin tablet X solution. Prepare 100 mL of a 1 to 50 dilution for each of the X solutions (the undiluted one from experiment 2A). Label these Z1, Z2, and Z3. Check with instructor for modifications.

Place the blank (MP water) in a labeled wash bottle. Use a fresh blank solution each day as the blank can become contaminated over time.

Experiment 2C.

Determination of Riboflavin - HPLC

Standard Solutions. Two standard solutions each containing both vitamins are available in the lab:

            1.         10 μg/mL vitamin B1 and 10 μg/mL vitamin B2 in the mobile phase

            2.         20 μg/mL vitamin B1 and 20 μg/mL vitamin B2 in the mobile phase

Sample Solution

For your samples, use the three “Y” sample solutions prepared in part 2A (“Y” samples are 1 to 5 dilution of solution X).