Fourier Transform Infrared Spectrometer (FTIR)
Principal:
Molecules are formed by chemical bonding of atom which FT/IR determine molecular structure vibration and rotational energy OR Identification of chemical function groups.
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When IR beam goes to beam splitter. It is divided in two directions; one IR beam goes to movable mirror and other goes to stationary mirror. Movable mirror move around 21cm. Both IR beam return to beamsplitter thus it have different wavelength, these IR beam goes to detector through sample and detector send electronic signal to computer.
Calibration of FTIR:
Calibration done by the using calibrated polystyrene film which have 36 µm thickness and check the below parameter.
- Resolution performance
- Verification of wave number
Resolution performance:
Step 1= Record
the spectrum of a secondary polystyrene film of 36 micro meter thickness the
film has a reference number and a validity certificate traceable.
Step 2= Check the
percent absorbance at the absorption minimum at 2870.0 cm-1 and absorption maximum
at 2849.5 cm-1. The difference percent absorbance between the two should be greater
than 0.33 The difference between the percent absorbance at the absorption
minimum at 1589.0 cm-1 and the absorption maximum at 1583.0 cm-1 should be greater
than 0.08.
When:
Maximum : at about 2849.5 cm-1
Minimum : at about 2870 cm-1
Transmittance : Grater than 6%
for prism instrument
Transmittance : Grater than 18% for
grating instrument and
Maximum : at about 1583 cm-1
Minimum : at about 1589 cm-1
Transmittance : Grater than 6%
for prism instrument
Transmittance
: Grater than 12% for grating instrument
Verification of wave number scale:
Step 1= The wave
number scale verified by using traceable serialized secondary polystyrene
standard of 36 micrometer thickness which has transmittance minimum absorption
Maximum at the wave number in cm-1 as shown below
Step 2= Transmission
minim and acceptable tolerances of polystyrene film.
3060.0 (±1.0) cm-1
2849.5 (±1.0) cm-1
1942.9 (±1.0) cm-1
1601.2 (±1.0) cm-1
1583.0 (±1.0) cm-1
1154.5 (±1.0) cm-1
1028.3 (±1.0) cm-1
The frequency for calibration as every three
month.Additional information about FTIR
Question: Why using KBr and NaCl for blank.?
Answer: Its nature does not interfere with sample.It has know peak.Before testing it must be heat at 80°C for 3 hrs. because released moisture.
Question: Why using polystyrene film for calibration of FTIR.?
Answer: Because it shows an accurate result any condition & any temperature.
Question: What mean by Fourier transform.?
Answer: Fourier transform of the time domain transitional signal yield the corresponding frequency. Spectrum this is high resolution technique yielding M/Z ratio to about one thousand of Dalton.
Question: What is the
purpose of FTIR?
Answer: Fourier Transform
Infrared Spectroscopy also known as FTIR Spectroscopy, It is an analytical technique
used to identify organic, polymeric, and, in some cases, inorganic materials. FTIR infrared light to scan of test samples and show chemical properties.
Question:What is in the
fingerprint region?
Answer:The region to
the right-hand side of the diagram (from about 1500 to 500 cm-1) usually
contains a very complicated series of absorption. These are mainly due to all
manner of bending vibrations within the molecule. This is called the fingerprint
region.
Question:What is the functional group
region IR?
Answer: The functional group region runs from 4000
cm-1 to 1450 cm-1, and the fingerprint region from 1450 cm-1 to 500 cm-1. ... The
functional group region contains relatively few peaks.
These are typically associated with the stretching vibrations of functional
groups.
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