User:Nicole Bonan/Notebook/Chem 571 Lab Notebook/2016/02/09

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Objective

Today's objective is to synthesize AuNP fibers doped with acetylsalicylic acid (aspirin). We are no longer using Rhodamine in our samples because:

  • Rhodamine fluoresces at about the same wavelength of light as AuNP, making detection of the Rhodamine in the supernatant of the AuNP fibers difficult
  • The peak shifts in some of the fluorescence measurements of the Rhodamine samples are difficult to analyze without more accurate UV-Vis absorption machinery
  • Our goal for this semester was to determine whether acetylsalicylic acid could be incorporated into AuNP fibers anyway, so we just jumped straight to trying to answer this question
  • Acetylsalicylic acid will fluoresce at a wavelength of 335nm if excited at a wavelength of 280nm

Protocol

  • First, Michael made a 1010µM stock solution of acetylsalicylic acid in DI water:
    • 0.04546g acetylsalicylic acid brought up to 500mL in DI water in a 500mL volumetric flask
    • Molecular weight of acetylsalicylic acid: 180.16g/mol
    • The acetylsalicylic acid+DI water were heated on a hot plate at about 80 degrees celsius in order to help the acetylsalicylic acid to dissolve


  • Michael made a fluorescence calibration curve for acetylsalicylic acid and found that we couldn't use much more than a concentration of 200µM of acetylsalicylic acid in our samples or else the fluorescence of the acid would be too high to accurately determine the concentration of the acid in the supernatant. Thus, we made two other stock solutions of acetylsalicylic acid so that we could synthesize samples with a concentration of either 200, 100, or 50µM acetylsalicylic acid:
    • We made a 505.00µM stock of acetylsalicylic acid:
      • 25mL of the 1010µM stock + 25mL of DI water
    • We also made a 252.50µM stock of acetylsalicylic acid:
      • 25mL of the 505.00µM stock + 25mL of DI water


  • We used the same gold stock as last week


  • We made a new stock solution of lysozyme with a concentration of 79.3178µM


We would need to add 198.02µL of acetylsalicylic acid stock to our samples in order to get the desired concentrations of 200, 100, and 50µM of acetylsalicylic acid in our samples. This volume was too large to be negligible. In order to keep the volume constant, we decided to add either 198.02µL of DI water to the samples that would get acetylsalicylic acid before being put into the oven OR 198.02µL of acetylsalicylic acid stock to the samples that would get the acid after being put in the oven.


Our synthesis were as follows:

  • For the "before" samples:
    • We had 9 total before samples. We had 3 samples with one of each of the following concentrations of acetylsalicylic acid: 200, 100, or 50µM
    • Ingredients:
      • 70.05µL lysozyme stock
      • 75.39µL gold stock
      • 198.02µL acetylsalicylic acid stock (we used either the 1010µM stock (to make a final concentration of 200µM) OR the 505.00µM stock (to make a final concentration of 100µM) OR the 252.50µM stock (to make a final concentration of 50µM))
    • We planned to add 198.02µL of DI water to these samples after taking them out of the oven tomorrow.
  • For the "after" samples:
    • We had 9 total before samples. We had 3 samples that would eventually contain one of each of the following concentrations of acetylsalicylic acid: 200, 100, or 50µM
    • Ingredients:
      • 70.05µL lysozyme stock
      • 75.39µL gold stock
      • 854.56µL DI water
    • We planned to add 198.02µL of acetylsalicylic acid stock (we would use either the 1010µM stock (to make a final concentration of 200µM) OR the 505.00µM stock (to make a final concentration of 100µM) OR the 252.50µM stock (to make a final concentration of 50µM)) to these samples after taking them out of the oven tomorrow.
  • For the blanks:
    • For the acetylsalicylic acid+acid blank (no gold/lysozyme):
      • 10µL of 25mM HCl (the HCl was added to keep the acidity constant with that of the samples that contained chloroauric acid (which is what we've been calling gold)
      • 198.02µL of the 1010µM stock of acetylsalicylic acid
      • 791.98µL of DI water
      • 198.02µL of DI water (to be added after incubation in the oven)
    • For the acetylsalicylic acid+gold blanks (no lysozyme):
      • 75.39µL of gold stock
      • 198.02µL of acetylsalicylic acid (either the 1010µM stock (to make a final concentration of 200µM) OR the 505.00µM stock (to make a final concentration of 100µM) OR the 252.50µM stock (to make a final concentration of 50µM))
      • 726.59µL of DI water
      • 198.02µL of DI water (to be added after incubation in the oven)
    • For the "before" and "after" blanks (no acetlysalicylic acid)
      • 70.05µL lysozyme stock
      • 75.39µL gold stock
      • 854.56µL of DI water
      • 198.02µL of DI water (to be added after incubation in the oven)
    • For the acetylsalicylic acid+lysozyme blank (no gold):
      • 70.05µL lysozyme stock
      • 198.02µL of the 1010µM stock of acetylsalicylic acid
      • 10µL of 25mM HCl (the HCl was added to keep the acidity constant with that of the samples that contained chloroauric acid (which is what we've been calling gold)
      • 721.93µL of DI water
      • 198.02µL of DI water (to be added after incubation in the oven)
  • All samples were put in the oven at 80 degrees Celsius for 4 hours.


We labeled the tubes as follows:

  • B= Before
  • A= After
  • b= blank
  • 1= 200µM acetylsalicylic acid
  • 2= 100µM acetylsalicylic acid
  • 3= 50µM acetylsalicylic acid

Data, Analysis, and Observations

See the entry for February 10, 2016 for analysis of the samples synthesized today.


Figure 1: Calibration Curve for Acetylsalicylic Acid (Aspirin) Concentrations

The above figure is Michael's calibration curve for acetylsalicylic acid. It shows the concentration of acetylsalicylic acid in DI water as a function of the integration of the fluorescence curve. The calibration curve was made with an excitation wavelength of 280nm and a fluorescence wavelength of 335nm.



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