CC LEC - LESSON 5 - ANALYTIC TECHNIQUES Flashcards
transmitted via electromagnetic waves that are characterized by their frequency and wavelength
energy
energy is characterized by their (2)
frequency and wavelength
this measure instruments without consideration of wavelength
photometric instrument
radiant energy that passes through an object will be partially _____, _____ and ______.
reflected, absorbed and transmitted
this refers to the distance between two successive peaks
wavelength
wavelength is expressed in
nanometer (nm)
this is described as the photons of energy travelling in waves
electromagnetic waves
the relationship of wavelength and energy is described by what
planck’s formula
what is planck’s formula
E = hv
in the formula E = hv, h refers to what
planck’s constant and is equivalent to 6.62 x 10 ^ -27 erg sec
in the formula E = hv, v refers to what
frequency
state the relationship between wavelength and energy
frequency is inversely proportional to the wavelength, therefore energy of electromagnetic radiation is inversely proportional to wavelength.
where are short wavelength and highly energetic radiation waves situated in the spectrum
left
where are long wavelength radiofrequencies situated in the spectrum
right
where are visible light situated in the spectrum
in between
what can be concluded with the planck’s formula in regards with the frequency and wavelength of electromagnetic radiation
the greater the frequency the shorter the wavelength and vice versa.
a method of clinical analysis based on the comparisons of colors produced by an unknown and a standard solution when reacted with similar chemical reagents.
colorimetry
two primary consideration in colorimetric analysis
quantity of color and intensity of color
this form of colorimetry involves the comparison of an unknown solution with a series of colored standard solutions using the naked eye. the unknown then, is diluted until its color matches the standard.
visual colorimetry
this form of colorimetry refers to measurement is done by an instrument which measures light intensity by converting light energy to electric energy.
photoelectric colorimetry
this is the isolation of discreet portions of the spectrum for the purposes of measurement.
photoelectric colorimetry
principle of photoelectric colorimetry
selected light passing through a solution to a greater or lesser extent strikes a photocell or phototube which generates current registered by a galvanometer.
types of photoelectric colorimeter (2)
filter photometer and spectrophotometer
the selection of wavelength of color of this type of photoelectric colorimeter is accomplished by placing a colored glass filter in the path of the light beam
filter photometer
other name of filter photometer
abridged spectrophotometer
this type of of photoelectric colorimeter involves measurement of of the light transmitted by a solution to determine the concentration of the light absorbing substances in the solution.
spectrophotometer
two type of spectrophotometer
single bean and double beam
simplest type of absorption of spectrometer
single beam
it is designed to make one measurement at a time at one specified wavelength.
single beam
an instrument that splits the monochromatic light into two components - one beam passes through the sample and the other through a reference solution or bank.
double beam
this uses two photodetectors for the sample beam and reference beam
double beam in space
uses one photodetector and alternatively passes the monochromatic light through the sample cuvet and then a reference cuvet using a chopper or rotating sector mirror.
double beam in time
the absorbance reading from the sample must be blanked using an appropriate reference solution that does not contain the compound of interest.
single beam
permit automatic correction of sample and reference absorbence. these are necessary when the absorption spectrum for sample is obtained.
double beam
basic components of spectrophotometer (7)
- light source
- entrance slit
- monochromator
- exit slit
- sample cell / cuvet
- photodetector
- meter or read our device
provides polychromatic light and must generate sufficient radiant energy or power to measure the analyte of interest.
light / radiant source
form of radiant energy provided by the light source that may pass through the monochromator.
visible and non visible light
two type of light source
continuum and line source
this emits radiation that changes in intensity
continuum source
types of continuum source
tungsten lamp, deuterium lamp and xenon lamp
this type of continuum source is commonly used as light source in the visible and near infrared region.
tungsten lamp
this type of continuum source that provides UV radiation in analytic spectrometers
deuterium lamp
this type of continuum source covers both UV and visible region
xenon lamp
this emits limited radiation and wavelength
line source
types of line source (3)
mercury and sodium vapor, hollow cathode lamp (atomic absorption spectroscopy) and laser
alternatives for tungsten lamp (6)
- mercury arc
- deuterium lamp
- hydrogen lamp
- xenon lamp
- merst glower
- globar
factors for light source
- range
- spectral distribution within the range
- source of radiant production
- stability of radiant energy
- temperature
minimizes unwanted or stray light and prevents the entrance of scattered light into the monochromator system
entrance slit
this refers to any wavelengths outside the band transmitted by the monochromator, it does not originate from the poly chromatic light source
stray light
stray light causes what
absorbance error
a system for isolating radiant energy of a desired wavelength and excluding that of either wavelength
monochromator
types of monochromator
- prisms
- diffraction grafting
- filters
- holographic graftings
this is a wedge shaped piece of glass or quartz which separates white light into continuous spectrum
prism
made by cutting grooves or slits into an aluminized surface of a flat piece of crown glass - wavelength are bent as they pass a sharp corner.
diffraction grafting
least expensive, not precise but useful type of monochromator
filters
controls the width of the light beam
exit slit
allows only a narrow fraction of the spectrum to reach the sample cuvette
exit slit
the total range of wavelengths transmitted
bandpass
