Spectroscopic Methods

Methods that are based upon attenuation ( or weakening) of a beam of light when it interacts with an analyte

Methods that are based upon the light given off after an analyte has been excited by thermal, electrical, or radiant energy

UV-VIS, IR, Raman, Microwave, NMR, mass spec

Atomic spec, fluorimetry,

Measures adsorption of ultraviolet and visible light in a species

The fraction of incident radiation transmitted by the sample T = I/Io

Quantity defined by A = £bc, where £ is the molar absorptivity, b is the length of the measuring cell, and c is the concentration

A = -logT = 2 - log(%T) = £bc

Spectroscopic technique that analyzes the vibrations of a molecule due to the adsorption of IR radiation

The band shapes and positions depend on the symmetry of the molecule’s vibrations

Symmetric stretch, asymmetric stretch, twist, wag, bending, rocking, scissoring

The higher the bond order the higher the IR frequency The greater the mass difference of the atoms involved in the vibrating bond the greater the frequency

Are associated with specific groups of atoms producing IR bands that are composite modes of vibration. Several of these groups consist of organic functional groups

Complements IR, measures the difference in the frequencies of the scattered light after it hits a compound resulting in emergent light that contains frequencies that differ from the original one, used for identification purposes

Analyzes the absorption of light in the microwave region which results in changes in the rotational frequency levels of gaseous polar molecules. Used for structural information

Measures the chemical shift of the protons or atoms in order to identify the compound

The energy gap corresponds to the radio-frequency range, and radiation in that range can excite the nuclei, inducing spin flips between the higher and lower energy states

Signals of more shielded protons, to the right

The signals of less shielded protons, to the left

Indicative of the magnetic nonequivalence of protons located on adjacent carbon atoms. N+ 1 peaks are observed in the slitting of a given proton signal of N magnetically equivalent protons are found in the adjacent carbon

Based on the emission of radiati n after the adsorption of energy by a sample, usually used for elemental trace analysis

The sample is volatilizations and decomposed to produce particles, which can either be atoms or ions

Caused by the absorption of radiant energy and reemission of some of this energy in the form of light, light emitted is almost always a high wavelength then the light absorbed

The phenomenon that occurs when an interstate crossing occurs to a state of different multiplicity, the light is emitted with a time delay