User:Allison K. Alix/Notebook/CHEM-581/2013/03/08

Measuring Dye Absorbance

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Objectives -Suspend hydrogels back into solution -Attach dye to hydrogels once they are in solution -Measure the amount of dye absorbed Procedures Part 1 1) Add 0.1 g of hydrogel (1 sample with lecithin and one without) in 5mL phosphate buffer 2) Sonicate for ~25 minutes or until hydrogels have separated 3) Add 5 μL of dye. 4) Allow hydrogels to absorb dye 5) Measure the absorbance of each solution in 15 minute intervals (1mL aliquots) 6) Add 1 mL distilled water for every 1mL taken out of solution Part 2 1) Place 2mg of PVOH (w/ R6G, w/o lecithin) in 1.5mL of the following solutions: a) distilled water b) phosphate buffer c) 1M NaOH d) 1M HCl e) glutaraldehyde fixant solution (NaCl) 2) Allow hydrogels to stay in solution for 1 hour 3) Centrifuge for 5 minutes 4) Take absorbance measurements Data The above image shows the UV-Vis Spectra of the two samples from part 1. The timing aspect of the procedure was abandoned and instead we measured the absorbance of the solution (after centrifugation) all together. It can be observed that the sample containing no lecithin showed a higher absorbance value than that containing lecithin. From this, we can conclude that the inclusion of lecithin has a significant impact on how dye is absorbed, more specifically it hinders the dyes ability to get into the polymeric matrix. The above image shows the UV-Vis spectra of 2mg hydrogel in various solvents. From this graph, it is evident that not much dye leakage occured. This may mean that the amount of dye added to the hydrogel (for this specific hydrogel the dye was added during formation, NOT afterwards) is the appropriate amount.