UV-Vis Spectroscopy Flashcards
The electromagnetic Spectrum
HIGH Frequency(v), HIGH Energy
|
V
LOW Frequency(v), LOW Energy
X-RAY
UV
INFRARED
MICROWAVE
RADIO
FREQUENCY
___ has many different applications in ORGANIC and BIOLOGICAL CHEMISTRY
Most basic of these application is the use of the ___ to deptermine the concentration of a ___.
UV-Vis Spectroscopy
Beer-Lambert Law
Chromophore
Part of the molecule where the ABSORPTION occurs and where the main change of the geometry or electron density, etc. appears after the excitation process.
Chromophore
The ___ is the application of the observation that, within CERTAIN RANGES, the ABSORBANCE of a chromophore at a given WAVELENGTH VARIES in a linear fashion with its CONCENTRATION
TLDR; HIGHER CONCENTRATION, GREATER ABSORBANCE
Is what makes SPECTROPHOTOMETRIC DETERMINATION of ORGANIC COMPOUNDS feasible
Beer-Lambert Law
True or False: Inorganic species cannot absorb
FALSE, a number of inorganic species can absorb
many IONS of the TRANSITION METALS are COLORED in solution and can thus be determined by spectrophotometric measurement.
SPECIES that show CHARACTERISTIC ABSORPTION BANDS (6)
NitrITE
NitrATE
Chromate IONS
OXIDES of NITROGEN
Halogens
Ozone
___ can be determined photometrically by causing them to react with ___ to produce products that ABSOR STRONGLY in UV and VISIBLE regions.
non-absorbing analytes
chromophoric reagents
The successful application of these COLOR-FORMING REAGENTS usually requires that their REACTION with the ANALYTE be forced to ___ unless they use methods such as KINETIC methods.
NEAR COMPLETION
Typical INORGANIC REAGENTS for NON ABSORBING:
Thiocyanate ion for (3)
Iron
Cobalt
Molybdenum
Typical INORGANIC REAGENTS for NON ABSORBING:
Hydrogen Peroxide for (3)
Titanium
Vanadium
Chromium
Typical INORGANIC REAGENTS for NON ABSORBING:
Iodide ion for (3)
Bismuth
Palladium
Tellurium
____ that FORM STABLE COLORED COMPLEXES WITH CATIONS are even more important.
Organic chelating reagents
Common examples for ORGANIC CHELATING REAGENTS for NON ABSORBING:
Copper
Lead
Iron
Nickel
Common examples for ORGANIC CHELATING REAGENTS for NON ABSORBING:
Copper - Diethyldithiocarbamate
Lead - Diphenylthiocarbazone
Iron - 1,10 Phenanthroline
Nickel - Dimethylglyoxime
particularly important for quantitative analysis because MOLAR ABSORPTIVITIES are unusually LARGE
(e > 10,000 L mol-1 cm-1 ), which leads to HIGH SENSITIVITY.
Many INORGANIC and ORGANIC complexes exhibit this TYPE OF ABSORPTION and are therefore called ____
consists of an ___ bonded to an ___
charge-transfer complexes
electron-donor group, electron acceptor
When a CHANGE-TRANSFER COMPLEX absorbs radiation, an ____ from the DONOR is transferred to the ____ that is largely associated with the ACCEPTOR.
The EXCITED STATE is this the product of a kind of INTERNAL ___ / ___ process
This behavior DIFFERS FROM ORGANIC CHROMOPHORE in which the excited electron is in a molecular orbital that is shared by ___.
Electron , Orbital
Oxidation / Reduction
two or more atoms
TYPICAL INSTRUMENTS:
use a FILTER FOR WAVELENGTH SELECTION in conjunction with a suitable RADIATION TRANSDUCER (converts a signal or light into a current or voltage).
have the advantages of SIMPLICITY, RUGGEDNESS, and LOW COST; most often used for the ___; good signal-to-noise ratio.
find considerable use as detectors for chromatography, electrophoresis, immunoassays, or continuous flow analysis.
Photometers
VISIBLE REGION
Offer the considerable advantage that the WAVELENGTH USED CAN BE VARIED CONTINUOUSLY, making it possible to record ____
cover the ___ and occasionally the ___region
Spectrophotometers
Absorption Spectra
UV/visible , near-infrared
TO FIND IDENTITY of the absorbing groups by COMPARING the spectrum of an ANALYTE with those of ___ containing various ___.
SIMPLE MOLECULES
chromophoric groups
TRUE or FALSE: ultraviolet spectra have sufficient fine structure to permit an analyte to be identified
FALSE, ultraviolet spectra do not have sufficient fine structure to permit an analyte to be identified unambiguously.
ultraviolet qualitative data must be supplemented
Evidence that supplements UV qualitative data: (6)
Infrared
Nuclear Magnetic Resonance
Mass Spectra
Solubility
Melting
Boiling point
Important characteristics of SPECTROPHOTOMETRIC and PHOTOMETRIC methods
Wide applicability
High Sensitivity
Moderate to High Selectivity
Good Accuracy
Ease and Convenience
WIDE APPLICABILITY:
Nonabsorbing species can also be determined after ____ .
Large majority of determinations performed in clinical laboratories
chemical conversion to absorbing derivatives
HIGH SENSITIVITY:
TYPICAL DETECTION LIMITS for absorption spectroscopy range from ___; can be extended to ___ with procedural modifications.
10^-4 to 10^-5 M
10^-6 or even 10^-7 M
MODERATE TO HIGH SELECTIVITY:
Often a WAVELENGTH can be found at which THE ANALYTE ALONE ABSORBS
HOWEVER, ___ DO OCCUR, corrections based on ADDITIONAL MEASUREMENTS AT OTHER WAVELENGTHS sometimes ELIMINATE THE NEED for a separation step.
When SEPARATIONS are required, spectrophotometry often DETECTS THE SEPARATED SPECIES
Overlapping Absorption bands
