Quantitative Analytical Chemistry Exam 3 Terms

Beer's law

A=ebC. A = absorbance, e = molar absorptivity (L mol-1 cm-1), b = path length (cm-1), C = concentration (L mol-1).

Molar absorptivity

A spectrophotometric constant indicating the amount of light a chemical species absorbs at a particular wavelength.

Pathlength

The distance that light travels through a standard/sample solution in a cuvette.

Transmittance

The fraction of radiant intensity transmitted by a sample.

Absorbance

A logarithmic measure of the amount of light absorbed as light passes through a sample/substrate.

Reagent blank

A solution of the same composition as a sample without a concentration of the analyte under study, used to compensate for any process that stops light from hitting the detector that is not due to color.

Calibration

Use of a set of standard solutions to determine the relationship of the instrument signal to the concentration of the analyte under study.

Dark current

The constant signal generated by a transducer/detector during periods when it is not actively being exposed to light.

Stray light

Light of any wavelength that hits the detector from a source other than the instrument's light source.

Monochromator

An optical device that transmits a mechanically selectable narrow band of wavelengths of light chosen from a wider range.

Light source

An incandescent bulb that emits a spectrum of light in the UV/visible range, producing a stable, high-power output.

Cuvette

A vessel for holding a solution for analysis in a UV/Vis instrument, must be transparent to the radiation used and be chemically inert.

Detector

A solid-state device (transducer) that produces a proportional number of electrons to the flux of photons hitting the detector surface.