Analytical Chemistry Absorption
Terms in this set (44)
A reverse bias is applied to a pn junction, which acts as a capacitor. Light strikes the surface and holes and electrons are created which moves towards the opposite charge.
Accelerated electrons are emitted from a photosensitive surface & strike a second suface, knocking more than one electron from that surface and towards the other surface. Process is repeated until there are 10^6 electrons collected per photon
Charge Coupled Device
A two-dimensional array of pn junctions that stores electrons until they are read sequentially with very high quantum efficiency
Interference from the overlap of analyte signal with signals from other atoms or molecules, the flame or furnace
Interference from any component of the same sample that reduces automization of the analyte
Interference by ions with a similar mass-to-charge ratio
Interference of analyte atoms which decreases the concentration of neutral atoms
The determination of elemental composition b using electromagnetic spectrum, respectively to optical or mass spectroscopy
S to S.
T. to S
The linear relationship between Absorbance and Concentration
Presence of flourescense & phosphorescence
Changes in refractive index at high analyte concentration
Scattering of light due to particles in the sample
Shift in chemical equilibria as a function of concentration
Atomic Absorption Spectrometry
Is an X,Y plot of absorbance Vs wavelength of light
Wavelength of maximal absorption
Fraction of light of a specific wavelength which passes through a solution
Measure of how much a light is absorbed by the solution at a specific wavelength
The ratio of the number of molecules fluorescing to the number of excited molecules
A process in which molecules in an excited state relax to the ground state through the release of a photon
Non-radiative relaxation of a molecule from low energy vibration level of excited state to high energy vibration level of lower electronic state
The difference between the wavelength of radiation used to excite an atom and the wavelength of radiation emitted by the atom during relaxation
Observed when excited atoms emit radiation that is the same as wavelength as the radiation used to excite them.
Occurs when an unexcited analyte atom absorbs the radiation emitted from an excited analyte atom
Occurs as excited atoms collide with surrounding molecules such as the solvent & lost energy without the emission of a photon
Changes in absorption or emission of electromagnetic radiation to detect the endpoint
Containing only one color
Refers to an atom, ion or molecule with an electron in a higher than normal energy level than its ground state.
A straight-sided, optically clear container for holding liquid samples in a spectrophotometer or other instrument.
A source of air, noise, water contamination or electromagnetic radiation that emanates from a linear (one-dimensional) geometry
A measurement of how strongly a chemical species absorbs light at a given wavelength.
the overall length of the path followed by a light ray or sound wave.
Certain arrangements of atoms within molecules that give rise to absorption bands
An instrument used to measure Ultraviolet-Visible absorption/transmittance
A low-pressure gas-discharge light source often used in spectroscopy when a continuous spectrum in the ultraviolet region is needed.
Convert a light intensity into a measurable electrical signal
• A rapid gas flow breaks the liquid into droplets
• This method of nebulization results in a wide range of droplet sizes
• Larger droplets are removed from the stream
• Typically less than 10% of sample reaches the atomizer
• Vibrate a plate at ultrasonic frequencies which produces an aerosol of sample
• Use of these nebulizers can increase mass transport to the tomizer and decrease detection limits
• Detection limits for techniques that employ a ultasonic nebulizer are often 100 times better than those that use pneumatic nebulization
Most common and lest expensive method
Requires fuel and oxidant gases
LIGHT BEAM DIRECTED ACROSS LENGTH OF FLAME
Furnace is placed in light path
Heated electrically to atomize sample in 3-step process
-Drying to remove water
-Ashing to remove organic matter
Ionized gas at high temperature which functions as a highly efficient atomizer
Inductively Coupled Plasma (ICP
A torch used to produce plasma in lab
Aren't used in AA analysis, but are used in AE
Consists of concentric quartz tubes