Pre-Assignment

1. How does fluorescence intensity depend on the excitation power? Can the fluorescence sensitivity be increased by working with high excitation powers?
2. What should be the fluorescence intensity for sample blank (analyte concentration is 0)?
3. Excitation with a laser will yield a better fluorescence intensity than if a lamp were used for excitation . Why?
4. The product φF I0 determines the sensitivity of fluorimetry for the analyte. Justify your answer.
5. Consider a case where a fluorophore molecule gets excited more than once. How will this effect (called the photon-burst effect) affect your result?
6. Why is it advised that add acid to water while diluting concentrated H2SO4?
7. Explain how a mass of 0.120 g of quinine sulfate is needed to prepare a quinine stock solution of 100 g/mL concentration. (Given (C20H24N2O2)2.H2SO4.2H2O), MW= 782.97)

Post-Assignment

1. In real experimental measurements, one should start with the lowest concentration solution first and proceed to next higher concentration and so on and should rinse the cuvette every time by taking a small portion of the experimental solution prior to filling up the cuvette with the solution. Why?
2. Is there evidence of non-linearity in the relationship between the fluorescence intensity and the analyte concentration at high concentrations? What is the most likely source of the non-linearity?
3. Will the linearity relationship hold well if photodecomposition of the molecule takes place on excitation?
4. How can one verify whether concentration quenching is present or not?
5. Why is the fluorescence intensity usually plotted in arbitrary units unlike absorbance in absorption spectrum? What is the unit of absorbance?
6. How many ppb (parts per billion) is 0.0250 ppm (parts per million)?
7. Express 0.01 ppm quinine concentration in mol/L unit.