salicylicacidfluorescence_2005 - CH 426 Fluorescence...

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CH 426 Fluorescence Spectroscopy Determination of Salicylic Acid in Aspirin The active ingredient in aspirin is acetylsalicylic acid. Over time, acetylsalicylic acid hydrolyzes to salicylic and acetic acids. CH 3 O OH + OH O OH H 2 O + O CH 3 O O OH Acetylsalicylic Acid Salicylic Acid Acetic Acid The odor of vinegar in an aspirin bottle indicates that some hydrolysis has occurred. Fluorescence spectroscopy is a sensitive analytical technique that can determine the extent of hydrolysis in aspirin. Both acetylsalicylic acid and salicylic acid fluoresce to some extent, but the difference in the excitation and emission spectra between the two compounds enables the determination of salicylic acid without interference from acetylsalicylic acid. The filter fluorometer in this experiment uses a longwave ultraviolet (UV) lamp with a primary bandpass filter, centered at 360 nm, located between the UV source and the sample. Salicylic acid is excited by this longwave UV radiation whereas acetylsalicylic acid is not excited by wavelengths longer than 300 nm. When acetylsalicylic acid is excited at shorter wavelengths, its fluorescence occurs in the 300 – 400 nm region, but salicylic acid fluorescence has a maximum near 450 nm. A secondary cut-off filter, located between the sample and the detector, only allows wavelengths longer than 460 nm to pass. Even if some of the acetylsalicylic acid fluoresces, the secondary filter would prevent any acetylsalicylic acid fluorescence from reaching the detector. Apparatus
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This note was uploaded on 03/19/2008 for the course CH 426 taught by Professor Staff during the Spring '08 term at UGA.

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salicylicacidfluorescence_2005 - CH 426 Fluorescence...

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