Friday, March 28, 2008
Migration of charged particles or solutes in an electric field. The net charge of the molecule, their size and shape, the strength of the electric field and the support medium used, influence the rate and speed of distribution of the unknown particles.
Image from: http://en.wikipedia.org/?title=Gel_electrophoresis
• This method measures the concentration of an unknown solution by measuring the emitted flame from these solutions. Metal salts (Li,K,Na) are usually measured making use Of this method.
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'Emission Flame Photometry! link';
Image from http://www.resonancepub.com/images/section701.gif
Image from: http://www.lib.mcg.edu/.../ch4/ch4img/nephelom.jpg
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The light that is scattered by particles in the unknown solution is measured and made as a basis of determining its concentration.
Factors affecting the amount of light scattered are:
a.the wavelength used – dispersion of light is inversely proportional to the
b.the size of the particles
c.the amount of particles in solution
d.the cross sectional area of the particles
e.the source of light - monochromatic lights give more reliable readings because they
minimize sample heating and have more stable readings.
This method measures the fluorescence of substances in solution and make this as a basis of determining the unknown concentration. This is done by measuring the electromagnetic radiation absorption of excited atoms when they return to a higher energy level than their original levels. The wavelength used will be longer to the excitation wavelength.
Parts of a basic filter fluorometer:
1. Energy Source
2. Primary filter
3. cell or Sample holder
5. Secondary filter
6. Detector (Photomultiplier)