ANALYTICAL METHODS AND INSTRUMENTATION part 2

• when atoms return to the ground state, they emit radiation which lies mainly in the visible region of the spectrum

• each element will emit radiation at a wavelength specific for that element • based on the characteristic emission of light by analytes (low oxidation states) which are easily excited when exposed to sufficient

• Rule: light intensity = the ________ of atoms = ________ of analyte

serves as the LIGHT SOURCE and CUVETTE

• measures light absorbed by atoms at a ground state which is reflective of the concentration of the atom • intended for analytes which are not easily excited by the flame

unexcited state of atoms

it is used principally for the quantitative determination of metal elements in aqueous and solid samples

What is the light source of AAS?

measures light scattered

detector is at 90’ or 30’ angle from the incident light

detection of light scattered or reflected toward a detector that is not in the direct path of transmitted light

some nephelometers are designed to measure scattered light at an angle other than 90’ to take advantage of the __________ -scatter intensity caused by light scattering from large particles

excitation and detection wavelengths of a nephelometer will be set to the _______

• measures light blocked by particles/ reduced by a particle in the solution • amount of light reduced is measured at 180’ • dependent on the size of particle and wavelength • detector in line with the incident light thus, decrease in transmission • the higher the concentration, the lower the transmittance (greater the amount of light blocked)

used to measure the intensity of light scattering

Applications - microbiology - hematology

• reaction of unknown with an indicator • examples: Schales and Schales method (Chloride); EDTA Titration method (Calcium)

• it measures the electrical potential from the activity of free ions • also measures the difference in voltage at a constant current

• it measures the difference in current at a constant voltage

• measures the amount of electricity at a fixed potential

it measures the current flow produced during redox reactions

separation of molecules according to their density once there is an application of an electric current

migration of charged solutes or particles in an electric field

consists of 5 components: - electrical power - supporting medium: can be cellulose acetate, agarose gel, starch gel, or polyacrylamide gel - buffer - sample - detecting system