Ultraviolet Spectroscopy in Analytical Chemistry

Ground State

Lowest energy state of a compound at room temperature.

Electromagnetic Radiation (EMR)

Radiation causing electronic, vibrational, and rotational transitions.

Excited State

Higher energy state of electrons after absorption.

Fluorescence

Emission of light when electrons return to ground state.

Absorbance Spectroscopy

Technique measuring absorbance in UV range (200-400 nm).

Sensitivity

Ability to detect low concentrations (10^-6 M).

Beer's Law

Relationship between absorbance and concentration of a solution.

Deuterium Lamp

UV light source for 200-400 nm range.

Tungsten Lamp

Light source for visible and near-infrared spectroscopy.

Monochromator

Device separating wavelengths of polychromatic light.

Diffraction Grating

Holographic component used in monochromators.

Cuvette

Sample container typically made of quartz.

Diode Array

Detector capturing different wavelengths of light.

Photodiode

Sensor in the diode array with 2 nm bandwidth.

Agilent 8453 Spectrophotometer

Instrument measuring samples from 190-1100 nm.

Standard Curve

Graph relating absorbance to concentration using standards.

Caffeine Stock Solution

0.00100 M solution prepared for UV analysis.

Spectral Scan

Data collected from scanning the standard solution.

Unknown Determination

Process of finding concentration of an unknown sample.

Extrapolation

Estimating unknown values from known data points.

e Value

Molar absorptivity coefficient for a substance.