F1. SPECTROCHEMICAL METHODS Flashcards
- Measurements based on light and other forms of electromagnetic radiation.
- Provided the most widely used tools for the
elucidation of modern atomic theory
SPECTROCHEMICAL MEHTODS
any analytical method that uses light for measurement of chemical concentrations.
Spectrophotometry
- originally the study of the interaction between radiation and matter as a function of wavelength (λ)
- historically, referred to the use of visible light dispersed according to its wavelength
Spectroscopy
Light can be thought of as a?
wave or particle
distance between crests
of a wave (m)
wavelength
the number of oscillations per
second (Hz)
frequency
Spectral Distribution of Radiant Energy
- < 200 nm
- 200-400 nm
- 400-800 nm
- > 800 nm
- X-Ray
- UV
- Visible light
- IR
Beer-lambert law is also known as?
- Beer’s law
- Lambert-beer law
- Beer-Lambert-Bouguer law
empirical relationship that relates the absorption of light to the properties of the material through which the light is travelling.
BEER-LAMBERT LAW
Beer-Lambert Law is a logarithmic dependence between?
1. ____ of light through a substance;
2. product of ____ of the substance; and
3. ____ the light travels through the material.
- transmission/ transmissivity (T)
- absorption coefficient
- distance
is a plastic ware wherein we will put a sample, and light will pass through it.
Cuvette
fraction of incident light at a specified wavelength that passes through a sample.
Transmittance
unitless measure of the transmittance of an optical element for a given length at a given wavelength
Optical density
- The type of spectroscopy depends on the ____ measured.
- Normally, the quantity that is measured is an ____, either of energy absorbed or produced.
- physical quantity
- intensity
involves interactions of matter with electromagnetic radiation, such as light.
ELECTROMAGNETIC SPECTROSCOPY
Electromagnetic spectroscopy can be classified into:
- Emission spectroscopy
- Absorption spectroscopy
- Scattering spectroscopy
- study of electromagnetic radiation spectra given off by atoms or molecules that undergo a transition to a lower energy level.
- deals with visible light and shorter wavelengths
is less likely to happen with long wavelengths.
EMISSION SPECTROSCOPY
fluorescence/ phosphorescence
Examples of Emission spectroscopy:
- fluorescence spectroscopy/ fluorometry, spectrofluorometry
- flame emission spectroscopy
- x-ray fluorescence spectroscopy
- stellar spectroscopy
- study of electromagnetic radiation spectra absorbed by atoms or molecules that change energy levels
- range of the electromagnetic spectra in which a substance absorbs
- used to determine the concentration of chemical compounds in samples
- usually positioned between a radiation source and the observer.
- specific chemical compounds have a specific absorption spectrum that acts as a
ABSORPTION SPECTROSCOPY
- atoms
- fingerprint
absorption of infrared radiation
Vibrational spectroscopy
technique for determining the concentration of a particular metal element in a sample
Atomic absorption
absorption of ultraviolet and visible light
UV/ Visible spectroscopy
- Measures the absorption of gamma rays by atoms bound in a solid as a function of gamma-ray energy.
- not an analytical technique
- means to understand certain microscopic processes in matter
Mossbauer spectroscopy
- subset of spectroscopy
- deals with the infrared region of the electromagnetic spectrum
- special use in forensic analysis in both criminal and civil cases, enabling identification of polymer degradation for example.
- most widely used method of applied spectroscopy
INFRARED SPECTROSCOPY
Infrared spectroscopy is widely used in both research and industry as a simple and reliable technique for
measurement
quality control
dynamic measurement
A reference is used for two reasons:
- prevents fluctuations in the output of the source affecting the data
- allows the effects of the solvent to be cancelled out
- measures the amount of light that a substance scatters at certain wavelengths, incident angles, and polarization angles.
- much faster than the absorption/emission process
One of the most useful applications of light scattering spectroscopy
SCATTERING SPECTROSCOPY
Raman spectroscopy
- used in condensed matter physics and chemistry
- to study ____, ____, & ____ modes in a system
- raman spectroscopy
- vibrational, rotational, & low-frequency
Raman spectroscopy relies on ____ or ____,
of monochromatic light, usually from a laser in the visible, near infrared, or near ultraviolet range
inelastic scattering or raman scattering
involves interactions with electron beams
ELECTRON SPECTROSCOPY
- involves inducing the Auger effect with an electron beam.
- In this case the measurement typically involves the kinetic energy of the electron as variable.
Auger spectroscopy
- involves the interaction of charged species with magnetic and/or electric fields, giving rise to a mass spectrum.
- determination of the elemental composition of a sample or molecule
- also used for elucidating the chemical structures of molecules
MASS SPECTROMETRY
consists of ionizing chemical compounds to generate charged molecules or molecule fragments and measurement of their mass-to-charge ratios
calculated from the motion of the ions as they transit through electromagnetic fields.
MS principle
mass-to-charge ratio
MS instruments consist of three modules:
1. splits the sample molecules into ions
2. sorts the ions by their masses by applying electromagnetic fields
3. measures the value of an indicator quantity and thus provides data for calculating the abundances of each ion present
[has both qualitative and quantitative uses]
these include?
- source
- mass analyzer
- detector
- identifying unknown compounds
- determining the isotopic composition of elements in a molecule
- determining the structure of a compound by observing its fragmentation
other uses of MS?
- quantifying the amount of a compound in a sample
- studying the fundamentals of gas phase ion chemistry (the chemistry of ions and neutrals in a vacuum)
involves the frequency of sound
Acoustic spectroscopy
involves the frequency of an external electrical field
Dielectric spectroscopy
involves the frequency of an external mechanical stress,
e.g. a torsion applied
to a piece of material
Mechanical spectroscopy
- quantifiable study of electromagnetic spectra
- more specific than the general term electromagnetic spectroscopy
- deals with visible light, near ultraviolet, and near-infrared
SPECTROPHOTOMETRY
is a photometer (a device for measuring light intensity) that can measure intensity as a function of the color, or more specifically, the wavelength
spectrophotometer
