Analysis of Riboflavin in a Vitamin Pill by Fluorescence Spectroscopy Objectives

Question

Analysis of Riboflavin in a Vitamin Pill by Fluorescence Spectroscopy Objectives In this lab, you will use fluorescence spectroscopy to determine the mass of riboflavin in a vitamin pill. Riboflavin fluorescence is extremely sensitive to its environment. It is sensitive to pH, presence of oxidizing species, and exposure to light. These "matrix effects" can be difficult to correct for in quantitative analyses by direct measurement of their influences on fluorescence intensity. A method of sample preparation known as the standard addition method will be used in this analysis. This method cotrects for matrix effects Background ?? OH NH riboflavin At room temperature, Riboflavin (Vitamin B2) can be promoted to various excited vibrational levels within the first electronic excited state by absorption of UV and blue light. The absorption process occurs in-105 seconds (femtoseconds) Absorption is followed by vibrational relaxation, whereby a thermal population distribution of excited molecules is re- established such that they accumulate in the lowest vibrational levels of the electronic excited state. Vibrational relaxation is nearly complete within-1011 sec (-10 picoseconds) following absorption. The electronically excited molecules "relax" to the various vibrational levels of the ground state through a spontaneous emission process in-10-10 sec (-1-100 nanoseconds), resulting in a green fluorescence. in biomedical analyses because it has several e spectroscopy is widely used biomedical advantages over absorption spectrometry. Some of these advantages include: It is more selective since only a small subset of absorbing molecules fluoresce, and it has two spectral variables; the excitation and emission wavelength, (1)

Explanation / Answer

Fluorescence spectroscopy is the process of determine the mass of riboflavin in vitamin pill. It is sensitive to ph,presence of oxidising species and exposure to light.

Fluorescence spectroscopy is widely used in biomedical analysis because it has a several advantages over absorption spectrometry .Here are some advantages :

1.It is more selective since only a small subset of absorbing molecules fluorescent and has two spectral variables ;the excitation and emission wavelength.

2. It is more sensitive since the detector has only to sense the fluorescence radiation ,whereas in absorption measurement the detector must sense the small absorption difference between blank and sample.

Procedure

1. First prepare 50ml of 1 ppm riboflavin solutions in 0.02m acetic acid from the 100 ppm stock solution. Next prepare 100ml of 0.10 ppm standard solution for use in the quantitative analysis of a vitamin pill.

2.weigh several vitamin pills to determine the average mass of a pill.select one pill for analysis and weigh it.

3. Crush the vitamin pill using mortar and pestle and weigh about 0.100g. Record the mass of powder sample and deliver it quantitatively to 100ml volumetric flask and dissolve the powder.

4. Dilute 1.0ml of this sample to 100 ml with 0.02m acetic acid.

5. A 1.0ml aliquot of the solution prepared is pipette into 100ml volumetric flask and the solution is diluted with 0.02m acetic acid.

6. Adjust the measurements at the excitation wavelength 450nm and the emission wavelength at 540nm,then measures the fluorescence signals of solution prepared.

7. Pot fluorescence intensity vs volume Standards in each solution.

8. Use quation to determine riboflavin concentration of sample solution using dilution factors. Calculate the total mass of riboflavin in vitamin pill.

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