ANALYTICAL METHODS AND INSTRUMENTATION part 2 Flashcards
- when atoms return to the ground state, they emit radiation which lies mainly in the visible region of the spectrum
. FLAME PHOTOMETRY
- 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
FLAME PHOTOMETRY
- Rule: light intensity = the ________ of atoms = ________ of analyte
number
concentration
serves as the LIGHT SOURCE and CUVETTE
FLAME
- 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
. ATOMIC ABSORPTION SPECTROPHOTOMETRY
unexcited state of atoms
- ground state
it is used principally for the quantitative determination of metal elements in aqueous and solid samples
ATOMIC ABSORPTION SPECTROPHOTOMETRY
What is the light source of AAS?
Hollow-cathode lamp
measures light scattered
NEPHELOMETRY
detector is at 90’ or 30’ angle from the incident light
NEPHELOMETRY
detection of light scattered or reflected toward a detector that is not in the direct path of transmitted light
NEPHELOMETRY
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
increased forward scatter
excitation and detection wavelengths of a nephelometer will be set to the _______
same value
- 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)
TURBIDIMETRY
used to measure the intensity of light scattering
turbidimeter
Applications
- microbiology
- hematology
. TURBIDIMETRY
- reaction of unknown with an indicator
- examples: Schales and Schales method (Chloride); EDTA Titration method (Calcium)
VOLUMTERY/ TITRIMETRY
- it measures the electrical potential from the activity of free ions
- also measures the difference in voltage at a constant current
POTENTIOMETRY
- it measures the difference in current at a constant voltage
. POLAROGRAPHY
- measures the amount of electricity at a fixed potential
COULOMETRY
it measures the current flow produced during redox reactions
AMPEROMETRY
separation of molecules according to their density once there is an application of an electric current
ELECTROPHORESIS
migration of charged solutes or particles in an electric field
ELECTROPHORESIS
consists of 5 components:
- electrical power
- supporting medium: can be cellulose acetate, agarose gel, starch gel, or polyacrylamide gel
- buffer
- sample
- detecting system
ELECTROPHORESIS
mixtures are separated, identified and determined according to their movement in the stationary phase
- consist of:
- mobile phase
- stationary phase
CHROMATOGRAPHY
Chromatography may be ______________ or ___________.
Planar or columnar
- clinically used for urine drug test screening
Thin Layer
used to separate volatile solutes
Gas-liquid
- uses pressure for fast separation
- used to separate hemoglobin, lipids, and drugs
High Performance Liquid
used for the separation of amino acids, proteins, and nucleic acids
Ion Exchange
used to separate lipoproteins, carbohydrates, and antibodies
Affinity
- the chemical reaction yields an electronically excited compound that emits light as it returns to its ground state, or that transfers its
energy to another compound, which then produces emission.
CHEMILUMINESCENCE
light is emitted from the excited product formed in the oxidation reaction
- does not use a light source
- Does not require a monochromator
- requires a photodetector
CHEMILUMINESCENCE
measures light in chemiluminescence
Luminometer
Limitations of Chemiluminescence:
1. Light ___________
2. Light ___________
3. High background________from assay reagents and reaction vessels
4. Very high ___________
leaks
piping
luminescence
intensity emission