The concentration of acetylsalicylic acid, C9H8O4, in aspirin tablets is determined by hydrolyzing it to the salicylate ion, C7H5O3-, and de¬termining its concentration spectrofluorometrically. A stock standard solution is prepared by weighing 0.0774 g of salicylic acid, C7H6O3, into a 1-L volumetric flask and diluting to volume. A set of calibration standards is prepared by pipeting 0, 2.00, 4.00, 6.00, 8.00, and 10.00 mL of the stock solution into separate 100-mL volumetric flasks that contain 2.00 mL of 4 M NaOH and diluting to volume. Fluorescence is measured at an emission wavelength of 400 nm using an excitation wavelength of 310 nm with results shown in the following table.
3. The concentration of acetylsalicylic acid, C9H8O4, in aspirin tablets is determined by hydrolyzing it to the salicylate ion, C7H5O3-, and de¬termining its concentration spectrofluorometrically. A stock standard solution is prepared by weighing 0.0774 g of salicylic acid, C7H6O3, into a 1-L volumetric flask and diluting to volume. A set of calibration standards is prepared by pipeting 0, 2.00, 4.00, 6.00, 8.00, and 10.00 mL of the stock solution into separate 100-mL volumetric flasks that contain 2.00 mL of 4 M NaOH and diluting to volume. Fluorescence is measured at an emission wavelength of 400 nm using an excitation wavelength of 310 nm with results shown in the following table.
(a) Why is the excitation wavelength (310 nm) shorter than the emission wavelength (400 nm)?
(b) How is the emission wavelength isolated from the excitation wavelength in a fluorescence instrument?
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