Analytical Methods Flashcards
Spectrometry
Spectrophotometry, AAS, MS
Luminescence
Fluorescence & Chemiluminescence
Electromagnetic methods
Electrophoresis, Potentiometry & Amperometry
Chromatography
Gas, Liquid, Thin-layer
Photons of energy traveling in waves
Electromagnetic radiation
E = hv
Planck’s formula
Transmitted via electromagnetic waves that are characterized by their frequency & wavelength
Energy
Distance between 2 successive peaks
Wavelength
Number of vibrations of wave motion per second
Frequency
400-700nm
Visible spectrum
<400nm
UV
> 700nm
IR
Most common light source in visible & near-IF
Incandescent tungsten/tungsten-iodide lamp
Light source used for UV
Deuterium & mercury arc
Type of monochromator: A wide band of radiant energy & have decreased transmittance of the selected wavelength
Colored glass filter
Type of monochromator: Principle of constructive interference of waves
Interference filters
Type of monochromator: Narrow beam of light focused on a prism is refracted as it enters the denser glass
Simple glass prism
Type of monochromator: Most commonly used; wavelengths bend as they pass a sharp corner
Diffraction gratings
The presence of an intense static magnetic field will cause the wavelength of the emitted radiation to split into several components
Zeeman effect
It is checked by didymium filter or cobalt chloride or potassium dichromate
Wavelength accuracy
It is checked with quartz mercury arc lamp/transmission standards
UV spectro
It’s checked by running different concentration of the same solution
Photometric linearity
It’s checked with Nickel sulfate at 510nm
Photometric accuracy
It detects baseline drift
Baseline stability
Difference between the maximum wavelengths, excitation & emitted fluorescence
Stokes shift
The total range of wavelengths transmitted
Bandpass
The most commonly used photodetector
Photomultiplier tube (PMT)
Measures light at a multitude of wavelengths - detect less amount of light
Photodiode
Corrects absorbance caused by the color of the reagents
Reagent blank
Measures absorbance of the sample & reagent in the absence of the end product
Sample blank
It measures light emitted by a single atom burned in a flame
Flame Emission Photometry (FEP)
Internal standard used in FEP
Lithium/Cesium
It measures light absorbed by atoms dissociated by heat
Atomic Absorption Spectrophotometry
It is used to convert ions to atoms
Atomizer (Nebulizer/Graphite furnace)
It is added to samples in AAS to form stable complexes with phosphate
Lanthanum or strontium chloride
Most frequently used sources of excitation radiant energy in Fluorometry
Gas discharge lamps (mercury & xenon arc)
Most commonly used in filter fluorometers
Mercury vapor lamps
Large particles scattering light predominantly in the forward direction
Mie scatter
Small particles scattering light in all directions with maximum scatter forward & backward
Rayleigh scatter
It is used to determine the accuracy of reference & indicator electrodes, the stability of standard solution & the potentials of liquid junctions
Hydrogen electrode
E = I x R
Ohm’s law
Opposing force to flow of electrons (in ohms)
Resistance
Electrical charge (in coulombs/second; measured in amperes
Current
The movement of buffer ions & solvent relative to the fixed support
Electroendosmosis/Endosmosis
Measuring electrical potential in voltage; follows the Nernst equation
Potentiometry
Measuring aspects of current, including rate of electron flow; often used in titration of ions; follows Faraday’s law
Coulometry
Measuring current in amperes/current flow produced by an oxidation reaction
Amperometry
Measuring current at an electrode using a specific voltage generated at another electrode
Voltammetry
Measurement of current flowing as electrons are formed in an oxidation-reduction system
Osmometry
Reference electrode commonly used in potentiometry
Calomel
Frequently used electrode in potentiometry but disadvantage is it’s slow to reach a new stable voltage; unstable above 80C
Mercury/Mercurous chloride
Another frequently used electrode in potentiometry; used for increased temperature up to 275C
Ag/AgCl
3 major ISE types
Inter metal, metal electrode & membrane electrode
Dioctylphenyl phosphonate
Calcium ISE
Valinomycin
Potassium ISE
Organic ionophore = monensin (from Streptomyces spp.)
Sodium ISE
Measured as tCO2
HCO3- ISE
Affect the charge of ampholytes
ph & ionic strength
Fundamental concept in Capillary Electrophoresis
Electro-osmotic flow (EOF)
Bulk flow of liquid toward the cathode upon application of an electric field & it is superimposed on electromagnetic migration
Electro-osmotic flow (EOF)
Type of chromatography: based on competition between sample & mobile phase
Adsorption/Liquid-solid chromatography
Type of chromatography: based on relative solubility
Partition/ Liquid-liquid chromatography
Elution strength of mobile phase is constant throughout the separation
Electron ionization
2 types of ionization for LC-MS
Electrospray Ionization (ESI) & Atmospheric Pressure Chemical Ionization (APCI)
Type of ionization: Passing the LC effluent through a capillary to which a voltage has been applied
ESI
Type of ionization: droplets aren’t charged & the source contains a heated vaporizer to allow rapid desolvation of the drops
Atmospheric Pressure Chemical Ionization (APCI)
Allows only ions of a single selected m/z value to pass through the analyzer to the detector
Quadrupole MS
Specific masses can be selected to monitor a few target analytes
Selected Ion Monitoring (SIM)
It can also measure vit. D, testosterone & immunosuppresant drugs; can detect multiple analytes in one run
LC-MS
Separates solutes in the sample based on their solubility in the 2 phases as well as different electrical charges
Ion Exchange Chromatography
The relative distance of migration from the point of application
Retention factor (Rf)
It is based on fragmentation & ionization of molecules using a suitable sources of energy
Mass Spectroscopy
It separates molecules by migration through a pH gradient
Isoelectric focusing
Emission of light is created from a chemical or electrochemical reaction & not from absorption of electromagnetic energy
Chemiluminsecence
A 1 mOsm/kg has a freezing point depression of?
0.00186 C
Blood plasma (285 mOsm/kg) has a freezing point of?
-0.53 C
It is the measurement of differences in current at a constant voltage; follows Ilkovic equation
Polarography
LASER stands for:
Light Amplification by Stimulated Emission Radiation