ANALYTICAL METHODS AND INSTRMENTATION - PART 2 Flashcards
It measures the light emitted by a single atom burned in a flame
Flame Emission Photometry (FEP)
what is the principle behind the flame emission photometry
Excitation of electrons from lower to higher energy
what is the light source for the flame emission photometry
Flame (also serves as the cuvette)
what is the method used in flame emission photometry
Indirect internal Standard Method
internal standard used for flame emission photometry
Lithium/Cesium
what is the purpose of Lithium/Cesium in flame emission photometry
corrects variations in flame and
atomizer characteristics
It is used for the measurement of excited ions (sodium and
potassium)
Flame Emission Photometry (FEP)
in FEP, “ Flickering light indicates __.
changes in the fuel reading of the
instrument
Purpose of Flame in FES
Breaks the chemical bond to produce atoms
Source of energy absorbed by the atoms to enter an
excited state
in FEP, it’s used to breaks up the solution into
finer droplets so that the atom will absorb heat energy
from the flame and get excited
ATOMIZER OR BURNER
interference filters as monochromator used in FLAME EMISSION PHOTOMETRY
NA, K , LITHIUM
what color do NA produced as an interference filter in FEP
transmit yellow light (589 nm)
what color do K produced as an interference filter in FEP
transmit violet light (767 nm)
what color do LITHIUM produced as an interference filter in FEP
transmit red light (761nm)
QUALITY CONTROL IN FES
referred internal standard; also acts as a radiation buffer
lithium
Reasons why lithium is preferred:
→ Its emission characteristics are similar to those of Na+ and K+
+ → Normally present as a trace element in human tissues and does
not present interferences in the determination
purpose of quality control in FEp
to achieve stability where there is fluctuations caused by
changes in fuel of air pressure which affects flame temperature and
rate of sample aspiration
It measures the light absorbed by atoms dissociated by heat.
Atomic Absorption Spectrophotometry
(AAS)
WHAT IS THE PRINCIPLE OF AAS
Element is NOT EXCITED by merely dissociated from its chemical bond and
place in an unionized, unexcited, ground state.
what is the light source of atomic absorption spectophotometry
Hollow-cathode lamp
what are the interferences for atomic absorption spectophotometry
chemical, matrix (differences in viscosity) and ionization
It is used for measurement of unexcited trace metals (calcium and magnesium)
atomic absorption spectophotometry
It is more sensitive than FEP; it is accurate, precise and very specific
Atomic Absorption Spectrophotometry
(AAS)
what is the internal standard used for atomic absorption spectophotometry
Internal standard is not needed - changes in aspiration have little effect on the
number of ground state atom
what is the atomizer used for the atomic absorption spectophotometry
nebulizer/graphite furnace is used to convert ions to atoms
what is used in atomic absorption spectrophotometry to modulate the light source
chopper
in AAS;
is added to samples to form stable complexes with phosphate
lanthanum
what is the principle behind the volumetric or titrimetric
The unknown sample is made to react with a
known solution in the presence of an indicator
examples of volumetric or titimetric
❑Schales and Schales method: chloride test
❑EDTA Titration Method: Calcium Test
For measuring abundant large particles (proteins) and bacterial
suspension
turbidimetry
what is the principle behind the turbidimetry
It determines the amount of LIGHT BLOCKED (reduction of
light) by a particulate matter in a TURBID SOLUTION
2 things that can affect the turbidimetry
specimen concentration
particle size
The measurement of reduction of light is due to particle formation.
TURBIDIMETRY
Solutions requiring quantitation by turbidimetry are measured
using____
visible photometers or visible spectrophotometers.
what are the uses of turbidimetry
- protein measurements (CSF and urine)
- to detect bacterial growth in broth cultures
- antimicrobial test (broth method)
- to detect clot formation
For measuring the amount of antigen-antibody complexes (proteins).
NEPHELOMETRY
what is the principle for NEPHELOMETRY
It determines the amount of scattered light by a particulate
matter suspended in a turbid solution
2 things that can affect nephelometry
Light scattering depends on WAVELENGTH and PARTICLE SIZE
IN NPHELOMETRY,
Light scattered by particles is measured at an angle, typically ___
degrees to the beam incident on the cuvet.
15-90
Is the migration of charged particles in an electric field. it
separates proteins on the basis of their electric charge and
densities.
ELECTROPHORESIS
has a net charge that can be either
positive or negative depending on pH conditions
Amphoteric
is the movement of
buffer ions and solvent relative to the fixed support
Electroendosmosis/Endosmosis
is the migration of small charged
iontophoresis
is the migration of charged
macromolecules
Zone electrophoresis
Factors Affecting Rate of Migration:
- Net electric charge of the molecule
- Size and charge of the molecules
- Electric field strength
- Nature of the supporting medium
- Temperature of operation
what are the supportng media
Cellulose acetate
Agarose gel
Polyacrylamide Gel
a supporting media that separates by molecular size
cellulose acetate
a supporting media that separates by electrical charge; it does
not bind protein
Agarose gel
a supporting media that separates on the basis of
charge and molecular size; separates proteins into 20
fractions;
polyacrylamide gel
supporting media that is used to study isoenzymes
Polyacrylamide Gel
Stains for Visualization of Fractions
(Bands):
fats fats fats
O S F
OIL RED O
SUDAN BLACK
FAT RED 7B
Stains for Visualization of Fractions
(Bands):
protein
protein
AB
PS
Amido black
Ponceau s
Stains for Visualization of Fractions
(Bands):
CSF PROTEIN
Coomassie Blue
Stains for Visualization of Fractions
(Bands):
very sensitive even to nanogram
quantities of proteins
Gold/Silver stain
It measures the absorbance of stain - concentration of
the dye and protein fraction.
densitometry
It scans and quantitates electrophoretic pattern
Densitometry
It separates molecules by migration through a pH gradient.
Isoelectric Focusing
It is ideal for separating proteins of identical sizes but with
different net charges.
Isoelectric Focusing
In isoelectric focusing,
pH gradient is created by adding acid to the ___ of
the electrolyte cell and adding base to the ___
anodic area; cathode area
in isoelectric focusing, Proteins move in the electric field until they reach a pH equal to their ___.
isoelectric point
what are thr supporting media for isoelectric focusing
agarose gel, polyacrylamide gel and
cellulose acetate
what are the advantages of isoelectric focusing
+ 1. The ability to resolve mixture of proteins.
+ 2. To detect isoenzymes of ACP, CK and ALP in serum.
+ 3. To identify genetic variants of proteins such as alpha-1 antityrpsin.
+ 4. To detect CSF oligoclonal bandin
In this method, sample molecules are separated by electro-osmotic
flow (EOF)
Capillary Electrophoresis
It utilizes nanoliter quantities of specimens.
Capillary Electrophoresis