CHEM: SPECTROCHEMICAL METHODS Flashcards by arabella erivera

Measurements based on light and other forms of electromagnetic radiation.

SPECTROCHEMICAL MEHTODS

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• Provided the most widely used tools for the
elucidation of modern atomic theory.

SPECTROCHEMICAL MEHTODS

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is any analytical method that uses light for measurement of chemical concentrations.

Spectrophotometry (spectroscopy)

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was originally the study of the interaction between radiation and matter as a function of wavelength (λ)

SPECTROSCOPY

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referred to the use of visible light dispersed according to its wavelength,
e.g. by a prism

SPECTROSCOPY

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• Dispersion of light as it travels through a triangular prism

SPECTROSCOPY

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can be thought of as a wave or particle.

Light

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, is the distance between crests of a wave (m)

wavelength

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, is the number of oscillations per second (Hz)

frequency

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• Spectral Distribution of Radiant Energy

SPECTROSCOPY

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• Extremely high-resolution spectrum of the Sun showing thousands of elemental absorption lines

SPECTROSCOPY

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• also known as Beer’s law or the Lambert–Beer law or the Beer–Lambert–Bouguer law

BEER-LAMBERT LAW

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• is an empirical relationship that relates the absorption of light to the properties of the material through which the light is travelling.

BEER-LAMBERT LAW

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• The law states that there is a logarithmic
dependence between the transmission (or
transmissivity), T, of light through a substance and the product of the absorption coefficient of the substance, α, and the distance the light travels through the material
- A = abc

BEER-LAMBERT LAW

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is a plastic ware wherein we will put a sample and light will pass through it.

Cuvette

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is the fraction of incident light at a specified wavelength that passes through a sample.

Transmittance

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is a unitless measure of the transmittance of an optical element for a given length at a given wavelength

Optical density

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• involves interactions of matter with
electromagnetic radiation, such as light.

can be classified into:
- Emission spectroscopy
- Absorption spectroscopy
- Scattering spectroscopy

ELECTROMAGNETIC SPECTROSCOPY

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• is the study of electromagnetic radiation spectra given off by atoms or molecules that undergo a transition to a lower energy level.

EMISSION SPECTROSCOPY

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• Such a process is called fluorescence or, under certain conditions, phosphorescence.

• Generally, emission spectroscopy deals with visible light and shorter wavelengths, since fluorescence is
less likely to happen with long wavelengths.

EMISSION SPECTROSCOPY

• Examples:

Fluorescence spectroscopy or fluorometry or
spectrofluorometry
Flame emission spectroscopy
X-ray fluorescence spectroscopy
Stellar spectroscopy

• is the study of electromagnetic radiation spectra absorbed by atoms or molecules that change energy levels; the atoms usually positioned between a radiation source and the observer.

ABSORPTION SPECTROSCOPY

can be used to determine the concentration of chemical compounds in samples

Absorption spectroscopy

absorption of infrared radiation,

Vibrational spectroscopy

is a 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. This is not an analytical technique; it is a means to understand certain microscopic processes in matter.

Mossbauer spectroscopy

is the subset of spectroscopy that deals with the infrared region of the electromagnetic spectrum

(IR spectroscopy)

is widely used in both research and industry as a simple and reliable technique for measurement, quality control and dynamic measurement.

Infrared spectroscopy

• It is of special use in forensic analysis in both criminal and civil cases, enabling identification of polymer degradation for example. • It is perhaps the most widely used method of applied spectroscopy

Infrared spectroscopy

produced and split into two separate beams.

beam of infrared light

are both reflected back towards a detector, however first they pass through a splitter which quickly alternates which of the two beams enters the detector

beams

are then compared and a printout is obtained.

two signals

• measures the amount of light that a substance scatters at certain wavelengths, incident angles, and polarization angles.

SCATTERING SPECTROSCOPY

One of the most useful applications of light scattering spectroscopy

Raman spectroscopy

is much faster than the absorption/emission process.

scattering process

• is a spectroscopic technique used in condensed matter physics and chemistry to study vibrational, rotational, and other low-frequency modes in a system.

RAMAN SPECTROSCOPY

• It relies on inelastic scattering, or Raman scattering, of monochromatic light, usually from a laser in the visible, near infrared, or near ultraviolet range.

RAMAN SPECTROSCOPY

• involves interactions with electron beams. • Auger 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.

ELECTRON SPECTROSCOPY

• involves the interaction of charged species with magnetic and/or electric fields, giving rise to a mass spectrum. • is an analytical technique for the determination of the elemental composition of a sample or molecule.

MASS SPECTROMETRY

• It is also used for elucidating the chemical structures of molecules, such as peptides and other chemical compounds. consists of ionizing chemical compounds to generate charged molecules or molecule fragments and measurement of their mass-to-charge ratios

MASS SPECTROMETRY

a sample is loaded onto the MS instrument, and its compounds are ionized by different methods (e.g., by impacting them with an electron beam), resulting in the formation of charged particles (ions). • The mass-to-charge ratio of the particles is then calculated from the motion of the ions as they transit through electromagnetic fields.

MASS SPECTROMETRY

consist of three modules: an ion source, which splits the sample molecules into ions; a mass analyzer, which sorts the ions by their masses by applying electromagnetic fields; and a detector, which measures the value of an indicator quantity and thus provides data for calculating the abundances of each ion present

MS instruments

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

• is the quantifiable study of electromagnetic spectra.

SPECTROPHOTOMETRY

• It is more specific than the general term electromagnetic spectroscopy in that spectrophotometry 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