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Instrumental Quiz 3

Instrumental Analysis Quiz 3 Material

TermDefinition
Atomic Absorption Absorption of radiation by atoms. Radiation is supplied by external source. Atomic analog of molecular absorption spectroscopy.
Atomic Fluorescence Re-emission of radiation by atoms from excited state. Emitted radiation is of longer wavelength than that of the initial absorption.
Atomic Emission Energy from some external process raises atoms into a spectroscopically excited state
Hollow Cathode lamp Typical narrow line source used in atomic absorption spec. Consists of anode and cathode sealed in a glass tube at low pressure (<30 torr). Cathode made of element of interest.
Boltzmann Distribution Law Relationship that describes statistical distribution of a population of atoms/molecules in a set of energy levels (m and n) at thermal equilibrium. (Nm/No)=(gm/gn)*exp[(delta E)/KT]
Degree of Degeneracy Statistical likelihood (gm and gn) of particular energy states (m and n)
Flame Atomization Process of reducing a molecular sample into a population of its constituent atoms by burning that sample into a flame
Nebulization Process of converting a liquid sample into a fine mist of tiny droplets
Pneumatic Nebulization Uses flow of gas past orifice of capillary tube to pull liquid in tube into gas phase due to reduced pressure (Venturi effect), surface tension of liquid causes leftover liquid to break apart into droplets.
Desolvation Process that evaporates solvent, leaving a solid/gas aerosol
Volatilization Process that vaporizes the aerosol gas leaving behind gaseous molecules
Atomization Process that breaks down gaseous molecules into its constituent atoms
Sauter Equation Expression relates mean diameter of a nebulized droplet to: 1) viscosity of analyte solution, 2) density of analyte solution, 3) surface tension of solvent, 4) flow rate of nebulized gas, 5) flow rate of aspirated solution, 6) velocity of nebulized gas
Ultrasonic Nebulizer Alternative to a pneumatic nebulizer that uses an ultrasonically driven crystal to vibrate the sample into droplets, tends to produce small, monodisperse droplet size distribution
Electrothermal/Graphite Furnace Alternative to flame atomization, cylindrical graphite tube equipped with optical windows. Sample is added to the tube and dried/ashed/atomized by electrical heating of the graphite tube to a final T of ~3000 K
Continuous Source Background Correction Atomic spec background correction method using a continuous source (D2 lamp) in conjunction with hollow cathode lamp line source; radiation from HCL and D2 lamp passes through beam splitter or rotating chopper, each signal is detected separately.
Zeeman Background Correction Atomic spec background correction method that uses a magnetic field to split atomic energy levels; split components absorb polarized radiation from atomic transitions
Analyte-shifted Zeeman Background Correction Magnetic field surrounds sample and splits sample atomic vapor into parallel and perpendicular polarizations.
Source-shifted Zeeman Background Correction Magnetic field surrounds source and splits emission spectrum of HCL into parallel and perpendicular polarization.
Smith-Hieftje/Source Self-Reversal Background Correction Uses properties of Self-Reversal/Absorption behavior of HCL at high currents; high currents with short modulation produce nonexcited state atoms, quenching excited state species (background); low current produces total absorbance (background + absorbance)
Compound Formation Interferences Most common type of chemical interference; anions form compounds of low volatility and reduce rate at which analyte is atomized; typical for refractory oxide formation M+O=MO; reduced using fuel rich flame to increase reducing species and free M atoms
Ionization Interferences Type of chem interference common at high temps, usually with O2 or N2O as oxidant; M+ has different electronic config than neutral M atom and interferes with desired atomic absorption and emission; reduced by adding ionization buffer to sample
Condensed Phase Chemical Interferences Type of chem interference due to formation of strong complexes in solution that don't readily dissociate at flame temps; reduced by forming competing complexes with analyte M that will more easily dissociate in flame (La3+, EDTA, H+)
Spectral Interferences Type of interference due to unwanted absorption or emission from molecular species or from overlapping spectral lines of two analytes; solved by changing fuel gas, increasing T, using appropriate background correction, decreasing slit width
Light Scattering Type of interference due to scattering, rather than absorption, of particles in the flame that are roughly same size as wavelength of light; solved by increasing T, using appropriate background correction, and decreasing slit width.
Matrix Effects Interference where observed spectrum is negatively affected by sample parts; worse for solid samples and graphite furnace AA, DC arc, or AC spark sources; caused by variation of rate of sample volatilization; solved by using similar standards at higher T
Plasma Electrically conducting gaseous mixture containing a large conc of cations and electrons with net charge of 0; Ar is usual gas but O2 is possible
Inductively Coupled Plasma (ICP) Name given when power supply used to energize plasma is a radiofrequency induction coil
Direct Current Plasma (DCP) Name given when power supply used to energize plasma is a direct current source
Microwave-Induced Plasma (MIP) Name given when power supply used to energize plasma is a microwave generator
Direct Current (DC) Arc Source for atomic emission spectrochemical analysis formed from graphite/metal electrodes a few mm apart; current passed between cause high temp arcing and sample atomization
Alternating Current (AC) Spark Source for atomic emission spectrochemical analysis formed from graphite/metal a few mm apart; typical operating conditions result in spark gap temps of 40,000 K
Created by: Erobison
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