Ppt

Fourier transform infrared spectroscopy

Presented by:IQRA MALIK

Presented to:Dr. Mohsin Ali Raza

Department of Metallurgy and

Materials Engineering , CEET

University of the Punjab

Fourier transform infrared spectroscopy (FTIR) is a technique which is used to obtain an infrared spectrum of  absorption, emission, photoconductivity or Rama scattering of a solid, liquid or gas.

An FTIR spectrometer simultaneously collects spectral data in a wide spectral range

Fourier Transform Infrared Spectroscopy (FTIR) is a powerful tool for identifying types of chemical bonds in a molecule by producing an infrared absorption spectrum that is like a molecular "fingerprint"

Introduction

Around 1800, Herschel studied the

spectrum of sunlight using the

prism. He measured the temperature

of each color, and found the highest

temperature was just beyond the

red, what now we call the ‘infrared’.

Developmental background

Infrared radiation lies between the visible and microwave portions of the electromagnetic spectrum Infrared waves have wavelengths longer than visible and Shorter than microwaves and have frequencies which are lower than visible and higher than microwave The infrared region is divided into near(closer to visible light),far(closer to microwave) and mid regions(b/w these two) Primary source of IR is thermal radiation(heat) Any object radiates in infrared. Even an ice cube emit infrared.

What is Infrared Radiation

The heart of FTIR is Michelson Interferometer

The basic Michelson Interferometer consists of a broad-band light source which emits light covering

the mid-IR range, a beam splitter made of KBr or CsI, Two front surface coated mirrors – one moving and

one fixed, and a detector.

THE MICHELSON INTERFEROMETER

Working principle:Light falls on a light sourceSome of the light is reflected some transmitted The reflected light goes to the fixed mirror and it reflected back to beam splitter and the transmitted light also reflected to beam splitter Both goes to detector and both interfere constructively and destructively and generate sinusoidal signal and generate interferrogram.

Fourier transform infrared spectroscopy is preferred over dispersive or filter methods of infrared spectral analysis for several reasons:

It is a non-destructive technique It provides a precise measurement method which requires no external calibration It can increase speed, collecting a scan every secondIt can increase sensitivity – one second scans can be co-added together to ratio out random noise It has greater optical throughput(because it do not require slits to achieve resolution). It is mechanically simple with only one moving part in a compoundFTIR instruments are computerized which makes them faster and more sensitive than the older dispersive instruments

FTIR AND DISPERSIVE IR SPECTROMETRY

Difference between Dispersive spectrometer and ftir

Dispersive Spectrometer FTIR

In order to measure an IR spectrumIt takes several minutesThe detector receives only a few % of the energy of original light source.

In order to measure an IR spectrumFTIR takes only a few seconds The detector receives up to 50% of the energy of original light source (much larger than the dispersion spectrometer )

Sample Analysis

The normal instrumental process is as follows:

The Source:: Infrared energy is emitted from a glowing black-body source.The Interferometer: The beam enters the interferometer where the “spectral encoding” takes place. The Sample: The beam enters the sample where it is transmitted through or reflected off the surface of the sample, depending on the type of analysis being accomplished. The Detector: The beam finally passes to the detector for final measurement. The detectors used are specially designed to measure the special interferrogram signal The Computer: The measured signal is digitized and sent to the computer where the Fourier transformation takes place. The final infrared spectrum is then presented to the user for interpretation and any further manipulation.

Sampling techniques

1. Liquid samples Neat sample Diluted solution Liquid cell2. Solid samples KBR pellets Neat sample Pressed films3. Gas samples Short path cell Long path cell

• It can identify unknown material(both organic or inorganic).

• It can identify quantity or consistency of sample. • It can identify the amount of components in a compound

What Information FTIR provides

The term Fourier Transform Infrared Spectroscopy (FTIR) refers to a fairly recent development in the manner in which the data is collected and converted from an interference pattern to a spectrum. Two types of analysis involve are:

Qualitative analysis: FTIR can be used to identify chemicals from paints, polymers, coatings, drugs, and contaminants.

It can identify chemical bonds (functional group)

Chemical bond in the spectra can be determined by interpreting the infrared spectrum

Chemical bond in the spectra can be determined by interpreting the infrared spectrum

Quantitative Analysis

Type of Analysis

Incoming material analysis for product quality control

• Incoming raw material matched to previously used production sample…

• Raw material analyzed kept in storage for future analysis…

Chemical Analysis:

Match spectra to known databasesi.e. identify an unknown compound

Unknown Green Contaminantfound in production line…

Spectra obtained by FTIR Analysis….

FTIR Green Contaminant Polymer Library Match….i.e. Green Contaminant – Polyamide 6,6 material…

Structural Ideas: Can determine what chemical groups are in a specific compound.

APPLICATIONS

Determination of degrees of crystallinity in polymers (e.g LDPE and HDPE)

Extent of thermal, UV or other degredation or depolymarization of polymers and paint coatings

Can also be used on satellites to probe the space

Thin film analysis , contamination analysis

In remote sensing, in parmaceuticals

•Universal technique •sensitivity 10-6 grams•fast and easy•relatively inexpensive•rich information•sensitive to “molecules”-anything that contains chemical bonds•vast majority of molecules in the universe absorb mid-infrared light, making it a highly useful tool

Advantages of FTIR (technique)

Cannot detect atoms or monoatomic ions - single atomic entities contain no chemical bonds

Cannot detect molecules comprised of two identical atoms symmetric-such as N2 or O2.

Aqueous solutions are very difficult to analyze- water is a strong IR absorber

Complex mixtures - samples give rise to complex spectra

Disadvantages of FTIR

Conclusion:

Infact it is the preferred method of spectroscopy so it is used for many future applications. FTIR spectroscopy is a powerful tool for biomedical and biological applications in future and is used for cancer detection.It produces hydrated polymer coating used to make contact lens and is also used for drug analysis and also has many applications in biochemical, food and agriculture.