Spectrophotometry Case

Aim:

The aim of this laboratory is to determine the quantity of Iron using UV- Visible spectrophotometry to determine the quantity of quinine in tonic water using spectrofluorimetry and the quenching of quinine fluorescence by chloride, bromide and iodide ions.

Introduction:

Spectroscopy is any measurement of a quantity as a function of either wavelength or frequency. Spectrometry is often used for the identification of a substance by the spectrum emitted or absorbed by them.

UV Visible Spectrometry is an analytical method used to determine the concentrations of

Substances that absorb wavelengths within the UV - Visible region of the electromagnetic spectrum. When light of a characteristic wavelength is absorbed by an atom, electrons within the atom will either move up an orbital or remain dormant. Dependendent on the wavelength and energy differences between the energy levels in an atom an electron moves orbitals. If the wavelength is similar to the energy difference, the electron will absorb this energy and

will be in an excited state. A UV Visible spectrometer will measure this absorbance and make a graph.

Spectrofluorimetry is similar to UV Visible spectrometry as they both rely on the molecules

to absorb electromagnetic radiation. In spectrofluorimetry the absorbed radiation can

be transferred to the surrounding molecules by collision and as it does so it loses this absorbed energy. As the excited molecule decreases in energy it descends to a lower vibrational level and its excess energy is emitted as radiation. This is then measured by the spectrofluorimeter.

.Materials and Methods:

Reagents

For Part A the reagents used were hydroxylamine hydrochloride, 0.85M sodium citrate, phenanthroline monohydrate, ethanol, FeSO4(NH4)2SO4.6H2O, 1M H2SO4, Bromophenol Blue

Instruments

For part A the instruments used were pH meter, Sonicater and UV spectrophotometer.

Procedures

The experiment was carried out in accordance with laboratory manual CS351 chapter 3