Shelby Bleile
UV/VIS & Fluorescence
Introduction:
The technique using the UV/VIS is primarily quantitative. It is used to test within
the range of electromagnetic spectrum from ~200nm to ~800nm. It measures the
absorbance through the bonding electrons of a molecule that is being tested.
Fluorescence can be used to detect very low levels of analyte molecules. Not all
molecules can utilize fluorescing so the instrument is very selective in that way.
Purpose:
The purpose of this lab is to become familiar with the UV/VIS and fluorescence.
To also run standards and samples on both of the instruments
Procedure:
UV-Vis
1. Investigate the absorbance properties of SA by preparing stock solutions of SA
in hexane. Dilute the stock to an appropriate range.
2. Create an unknown to prove the curve
Fluorescence:
1. Create standards
2. Run standards
3. Run unknown samples based on the calibration range
Results:
Table 1. Results from Fluorescence
Conc. of SA
Excitation
Emission
Wavelength
Intensity
10 ppm
327 nm
379 nm
373 nm
355.612
15 ppm
281 nm
376 nm
370 nm
410.410
20 ppm
279 nm
375 nm
371 nm
427.215
25 ppm
277 nm
373 nm
372 nm
458.092
30 ppm
277 nm
371 nm
372 nm
444.247
Fig. 1 Salicylic acid at 10 ppm
Fig. 2 – Salicylic acid at 15 ppm
Fig. 3 – Salicylic acid at 20 ppm
Fig. 4 – Salicylic acid at 25 ppm
Fig. 5 – Aspirin sample
Fig. 6 – Graph showing all absorbance spectra for samples and standards
Discussion:
This lab went pretty well. We became familiar with the UV/VIS and the
fluorescence. We were able to successfully run standards and samples on both of the
instruments. We were able to get absorbance and transmittance values on different
concentrations of salicylic acid in hexane on the UV/VIS instrument. We were also able
to obtain results from the fluorescence on samples. We obtained optimal wavelengths,
intensities, excitation, and emission values for the different samples of salicylic acid.