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UV-Visible Spectroscopy

A technique that involves the absorption of ultraviolet or visible light by molecules to analyze their properties.

Chromophore

A group of atoms and electrons within a molecule that is responsible for its color and ability to absorb light, particularly in the UV-visible spectrum.

Transmittance (T)

The ratio of the intensity of transmitted light to the intensity of incident light, defined as T = I/I0, often expressed as a percentage.

Molar Absorption Coefficient (ε)

A measure of how strongly a substance absorbs light at a given wavelength, expressed in units of L mol-1 cm-1.

Specific Absorbance (A(1%, 1 cm))

Represents the absorbance of a 1% m/v solution in a cell of path length 1 cm, widely used in analytical work.

Beer-Lambert Law

A linear relationship describing how the absorbance of a sample is directly proportional to the concentration of the absorbing species and the path length of the sample.

Quantum Efficiency (φ)

The ratio of the number of molecules that fluoresce to the number of molecules that absorb energy; a measure of a fluorophore's efficiency.

Fluorimetry

A method of measuring the concentration of fluorescent compounds by measuring the intensity of emitted light upon excitation.

Partition Coefficient (P)

A measure of the differential solubility of a compound in two immiscible solvents, often used to describe lipophilicity.

Retention Time

The time taken for a compound to travel through the chromatography system from injection to detection.

Synchronous Fluorimetry

A method of fluorescence spectroscopy in which both excitation and emission wavelengths are scanned simultaneously while maintaining a constant wavelength difference.

Calibration Curve

A graphical method used to determine the concentration of an unknown sample by comparing its absorbance or fluorescence to that of standard solutions.

Ion-Exchange Chromatography

A separation method based on the ionic interactions between charged stationary phases and solutes with opposite charges.

High Performance Liquid Chromatography (HPLC)

An advanced form of liquid chromatography that uses high pressure to push the solvent containing the sample through a column of stationary phase.

Gas Chromatography (GC)

A technique for separating volatile compounds in a gas mixture, where the sample is carried by a gas mobile phase through a column.

Peak Area (AUC)

The area under the peak in a chromatogram, used to quantify the concentration of a substance in HPLC.

Fluorescence Quenching

The process by which the fluorescence intensity is decreased due to interactions between molecules, usually at high concentrations.

Electronic Transition

The change of an electron from one energy level to another, often responsible for the absorption of light in spectroscopy.

Absorbance (A)

A measure of the amount of light absorbed by a sample, calculated as A = log(I0/I), where I0 is the intensity of incident light and I is the intensity of transmitted light.

Detector

An instrument component that measures the amount of light absorbed or emitted during spectrophotometric analysis.

Light Source

The device used to emit light for spectroscopic analysis, such as tungsten, deuterium, or xenon lamps.

Monochromator

An optical device that isolates specific wavelengths of light from a broader spectrum to study absorption or emission.