Ftir, ndir and flame photometry
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Transcript of Ftir, ndir and flame photometry
FTIR, NDIR and flame photometry
P MANOJ713MN1117MINING DEPT NIT ROURKELA
SPECTRUM
INTERACTIONInteraction between Matter and Electromagnetic radiation
SPECTROSCOPY
Measuring and interpreting spectra arising from the interactionsEnergy used :1. EMR2. Particles of low de broglie wave length3. Acoustic / Pressure waves4. Mechanical
INSTRUMENTS
Spectrometer Correlates intensity with property of radiation
Spectroscope Spectrometer operating in Visible region
Spectrograph Disperses incoming radiation to different frequencies
DISPERSIVE SPECTROSCOPY
Interaction of monochromatic light with object, repeated for every wavelength
FTIR
Fourier Transform Infrared Spectroscopy
Shining of various wavelengths of light at once as combination to obtain data
Uses Michelson Interferometer setup
Michelson interferometer basically consists of 2 mirrors, a beam splitter with certain angle. When a light beam falls on beam splitter it transmits half the light to stationary mirror and reflects the other half to movable mirror. When the light hits both the mirrors it gets reflected. The two beams combine (Interference) and reach the detector with different path lengths where the intensity is measured.
INTERFEROGRAM
Plot between Intensity/Energy vs Path difference
DISCOVERY AND APPLICATION
In 1965, Cooley and Turkey were able to convert the interferogram to spectra by the application of Fourier analysis as function of Wavenumber (inverse of wavelength).
Used in gaseous pollutant monitoring of CO, VOC, N2O, CH4 etc. difference in the absorption.
Used in identifying pollutants in untreated wastewater before treatment for compounds like oils, grease etc.
NDIR
Non Dispersive Infrared sensor
It is a spectroscopic sensor used as gas detector
Infrared energy is allowed to pass through the atmospheric sampling chamber without deformation.
NDIR sensor uses 2 chambers, one for the sample and other is with reference gas (typically non-absorbing gas like Nitrogen).
Radiation from Infrared source (lamp) passes through the sample chamber where the absorption of the radiation takes place before reaching the other end where filter is fitted.
The filter blocks all other wavelengths except of the gases to be analysed.
Since the reference gas is non-absorbing, the detection end receives 100% signal while the analysed gas signal is attenuated due to absorption.
The difference in energies is used to measure absorption and correlate with the quantity of particular gas present by the sensor.
Gases : CO, CO2,HCHO, NO, SO2, H2O, CH4 and other hydrocarbons.
FLAME PHOTOMETRY
Flame atomic emission spectroscopy
Used for detection of metals (particularly Group 1 and 2) of periodic table. Detectors used are photovoltaic cells and photoemissive cells.
Principle
Every metals emits certain spectrum of light on application of thermal energy.
Steps involved are
Nebulization/vaporization,
Passing over flame and
Analysis of light produced.
Schematic diagram
Liquid salt of metal salt solution is vaporized to get metal salts which are moved towards flames getting vaporized to gaseous states.
The gases absorb to get to higher states which on de-excitation emit their characteristic spectra which can be used in identification.
I = K x C
I= intensity of light emitted
C= concentration of metal METAL Emission
wavelength(nm)Colour
Potassium 766 Violet
Lithium 670 Red
Calcium 620 Orange
Sodium 589 Yellow
Barium 554 Green