UV VIS Flashcards
the study of the absorption and emission of light and other radiation by matter
SPECTROSCOPY
the measurement of the interactions between light and matter, and the reactions and measurements of radiation intensity and wavelength
SPECTROMETRY
the quantitative measurement of the reflection or transmission properties of a material as a function of wavelength
SPECTROPHOTOMETRY
this is when particles are moved from their normal room temperature state, or ground state, to one or more higher-energy excited states.
ABSORPTION OF RADIATION
normal room temperature state
ground state
is produced when excited particles (atoms, ions or molecules) relax to lower energy levels by giving up their excess energy as photons
electromagnetic radiation
electromagnetic radiation is produced when excited particles (atoms, ions or molecules) relax to lower energy levels by giving up their excess energy as
photons
causes of emission
(1) bombardment with electrons or elementary particles, which leads to emission of X-radiation
(2) exposure to an electric current or intense heat source producing UV, visible or IR radiation
(3) irradiation with a beam of electromagnetic radiation
(4) an exothermic chemical reaction that produces chemiluminescence
principle of uv vis
irradiation with a beam of electromagnetic radiation
this is when electromagnetic radiation is transmitted at all angles from the original path; usually observed when atomic or molecular particles are small relative to the wavelength of the radiation
SCATTERING
a parallel beam of radiation is bent as it passes by a sharp barrier or through a narrow opening
DIFFRACTION OF RADIATION
type of energy that is commonly known as light
ELECTROMAGNETIC RADIATION
aka white light
ELECTROMAGNETIC RADIATION
ELECTROMAGNETIC RADIATION is propagate in 2 fields known as
Electric and Magnetic Field Oscillation
ELECTROMAGNETIC RADIATION (PROPERTIES) Models
sinusoidal wave model
particle model
distance from basic to highest point
amplitude
time in sec where 2 minima passes through the same
point
period
no. of oscillators in sec
frequency
- distance between 2 successive crest/trough
wavelength
reciprocal of wavelength
wavenumber
- electromagnetic radiation transport into a
speed of light
wavelength and frequency
indirect
wavelength and energy
indirect
frequency and energy
direct
constant value of speed of light
3.00x108 m/s
The energy of a photon absorbed or emitted during a transition from one molecular energy level to another is given by the equation:
QUANTUM Theory
Study of discrete particles
QUANTUM THEORY
Planck’s constant
6.62x10-34 Js
1 electron volt (eV) =
1.6 x 10^-19 J
1 joule (J) =
10^7 ergs
an electronic transition spectroscopic technique in which the interaction between incident radiation and electrons results in the promotion of one or more of the outer or the bonding electrons from a ground state into a higher-energy state
Ultraviolet-visible (UV-Vis) spectroscopy
Ultraviolet-visible (UV-Vis) spectroscopy is an electronic transition spectroscopic technique in which the interaction between
____________ and __________ results in the promotion of one or more of the outer or the bonding electrons from a ________________ into a ____________
incident radiation and electrons; ground state into a higher-energy state
Radiation in the wavelength range _____________ nm is passed through a solution of a compound.
200–700
The electrons in the bonds within the molecule become excited so that they occupy a __________________ and in the process absorb some of the energy passing through the solution.
higher quantum state
The more loosely held the electrons are the ________ the wavelength
longer
extended system of double bonds that causes absorption of light at UV-visible region
CHROMOPHORES
CONTINUUM SOURCE (continuous)
tungsten halogen for visible
deuterium arc for UV
xenon arc for both
CONTINUUM SOURCE (pulsed)
xenon flash lamp
used to disperse the light into its constituent wavelengths, which are further selected by the slit
MONOCHROMATOR
is rotated so that a range of wavelengths is passed through the sample as the instrument scans across the spectrum
MONOCHROMATOR
have multiple exit slits, each of which allows a different wavelength to pass through it
POLYCHROMATOR
conventional rectangular cells
fiber-optic-based immersion probes
automated sample changers
micro-well plate configurations
flow cells
Sampling area
generate an electric current that is directly proportional to the intensity of the radiant energy incident upon them
Photoelectric detectors
photosensitive semiconductor devices
photomultipliers
detector
DIODE-ARRAY INSTRUMENTS
HPLC DETECTORS
FIBER-OPTIC-BASED MODULAR SYSTEMS
ALTERNATIVE DETECTOR CONFIGURATIONS
the optical configuration is reversed from that in a conventional spectrophotometer, and the light beam passes through the sample before being dispersed by the polychromator
DIODE-ARRAY INSTRUMENTS
gives the benefit of fast, full spectral data with no moving parts that can wear out
DIODE-ARRAY INSTRUMENTS
high-stability, low signal-to- noise ratio output at high transmittance levels through a small-aperture flow cell
HPLC DETECTORS
flexible and easy to use allow measurements to be performed on micro- plates
customized systems
FIBER-OPTIC-BASED MODULAR SYSTEMS (adv)
there might be room light interference
custom-built systems do not have additional shuttering,
stray light filtering light levels transmitted directly down fibers from high-intensity sources such as Xenon flash lamps may cause photodegradation
FIBER-OPTIC-BASED MODULAR SYSTEMS (dis)
the width of the band of light at one-half the peak maximum (or full width at half maximum
SPECTRAL BANDWIDTH
is adequate To have an accurate result.
2 nm
source of electromagnetic radiation that would be flashed through the sample to know the absorbance and transmittance. May later on affect the resolution (how accurate the data the instrument will produce).
light beam
radiant energy at wavelengths other than those indicated by the monochromator setting and all radiant energy that reaches the detector without having passed through the sample or reference solutions
STRAY LIGHT
any scattered radiation from imperfections in the dispersing medium
light leaks in the system incorrect wavelength calibration incorrect optical alignment reduced source output
reduced detector response
STRAY LIGHT - CAUSES
Relationship between a specific absorbance and the absorbance of the solution
OPTIMUM WORKING PHOTOMETRIC RANGE
is the photometric range in this spectrum of molar absorptivities at different concentrations
center plateau
suspended particles scatter light by the __________ effect, causing a ____________ in the measured intensity that __________ as the wavelength decreases
Tyndall; decrease; increase
property of light wherein light can be scattered in cases of colloidal solution.
Tyndall effect
the concentration of a chemical solution is directly proportional to its absorption of light
BEER’S LAW
each layer of equal thickness of the medium absorbs an equal fraction of the energy traversing it
LAMBERT’S LAW
SPECTRAL BANDWIDTH
STRAY LIGHT
OPTIMUM WORKING PHOTOMETRIC RANGE
INSTRUMENTAL FACTORS
FLUORESCENCE AND LIGHT SCATTERING
SAMPLE-BASED FACTORS
CARE OF CELLS
ALIGNMENT AND FILLING OF CELLS CELL CORRECTIONS
SAMPLING FACTORS CONSIDERATIONS
