IR seminar

Instrumental Methods Of Analysis: 

Instrumental Methods Of Analysis Revathi.S Infra Red Spectroscopy (IR) Presented By,

Synopsis : 

Synopsis Introduction InfraRed EMR IR Spectrocopy Principle Instrumentation Molecular Rotations Vibrational-Rotations Transition Fourier Transform IR Limitation Uses Application Conclusion

Introduction : 

Introduction Spectroscopy is the study of the interaction between matter and radiated energy . Spectrometry and spectrography are terms used to refer to the measurement of radiation intensity as a function of wavelength and are often used to describe experimental spectroscopic methods. Spectral measurement devices are referred to as spectrometers , spectrophotometers , spectrographs or spectral analyzers .

Infra Red: 

Infra Red Infrared light lies between the visible and microwave portions of the electromagnetic spectrum. Infrared light has a range of wavelengths, just like visible light has wavelengths that range from red light to violet . "Near infrared" light is closest in wavelength to visible light and "far infrared" is closer to the microwave region of the electromagnetic spectrum.

E-M radiation or EMR: 

E-M radiation or EMR Electromagnetic waves are produced by the motion of electrically charged particles. These waves are also called "electromagnetic radiation" because they radiate from the electrically charged particles . They travel through empty space as well as through air and other substances . The photons with the highest energy correspond to the shortest wavelengths . The full range of wavelengths (and photon energies) is called the "electromagnetic spectrum."

IR spectroscopy: 

IR spectroscopy Infrared (IR) spectroscopy is one of the most common spectroscopic techniques used by organic and inorganic chemists. Simply , it is the absorption measurement of different IR frequencies by a sample positioned in the path of an IR beam. The main goal of IR spectroscopic analysis is to determine the chemical functional groups in the sample . Different functional groups absorb characteristic frequencies of IR radiation. Using various sampling accessories, IR spectrometers can accept a wide range of sample types such as gases, liquids, and solids. Thus , IR spectroscopy is an important and popular tool for structural elucidation and compound identification.

Principle: 

Principle IR involves absorption phenomenon the absorption of radiation depends on increasing energy of vibration or rotation associated with covalent s change in the dipole moment of molecule. Hence in order to absorb IR radiation a molecule must go a net change in dipole moment due to its vibration or rotation motion. This means that nearly all molecules containing covalent bond will show some degree of selective IR absorption. Infra red spectra are usually plotter as % transmittance(%T) rather than as absorbance as the ordinate.

CONT…,,,: 

CONT…,,, This makes absorption band appear as dips in the curve than as maxima as in the case of UV-Vis. Each dip in the spectrum is called a band or peak and represented absorption of IR radiation at that frequency by the sample. The transmittance is 0% if all the radiation is absorbed and the transmittance is 100% for no absorption.

Instrumentation: 

Instrumentation 1. The Source: Infrared energy is emitted from a glowing black-body source. This beam passes through an aperture which controls the amount of energy presented to the sample (and, ultimately, to the detector). 2. The Interferometer: The beam enters the interferometer where the “spectral encoding” takes place . The resulting interferogram signal then exits the interferometer. 3. The Sample: The beam enters the sample compartment where it is transmitted through or reflected off of the surface of the sample, depending on the type of analysis being accomplished. This is where specific frequencies of energy, which are uniquely characteristic of the sample, are absorbed. 4. The Detector: The beam finally passes to the detector for final measurement. The detectors used are specially designed to measure the special interferogram signal. 5. 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 .

PowerPoint Presentation: 

Because there needs to be a relative scale for the absorption intensity, a background spectrum must also be measured. This is normally a measurement with no sample in the beam. This can be compared to the measurement with the sample in the beam to determine the “ percent transmittance .” This technique results in a spectrum which has all of the instrumental characteristics removed. Thus , all spectral features which are present are strictly due to the sample . A single background measurement can be used for many sample measurements because this spectrum is characteristic of the instrument itself.

PowerPoint Presentation: 

1. Source 2. Interferometer 3. Sample 4. Detector Interferogram FFT 5. Computer Spectrum Instrumentation of IR Spectroscopy

MOLECULAR ROTATIONS: 

MOLECULAR ROTATIONS Rotational transitions are of little use to the spectroscopist . Rotational levels are quantized,and absorption of IR by gases yields line spectra. However, in liquids or solids , these lines broaden into a continuum due to molecular collisions and other interactions.

VIBRATIONAL –ROTATIONS TRANSITIONS: 

VIBRATIONAL –ROTATIONS TRANSITIONS In general,a molecule which is an excited vibrational state will have rotational energy and can lose energy in a transition which alters both the vibrational and rotational energy content of the molecule. The total energy content of the molecule is given by the sum of the vibrational and rotational energies. For a molecule in a specific vibrational and rotational state,denoted by the pair of quantum numbers( ,J),we can write its energy as: E( ,J)=E( ) vib + E(J)rot

Fourier Transform Infrared Spectrometry: 

Fourier Transform Infrared Spectrometry FT-IR stands for Fourier Transform InfraRed , the preferred method of infrared spectroscopy. In infrared spectroscopy, IR radiation is passed through a sample. Some of the infrared radiation is absorbed by the sample and some of it is passed through (transmitted ). The resulting spectrum represents the molecular absorption and transmission, creating a molecular fingerprint of the sample . Like a fingerprint no two unique molecular structures produce the same infrared spectrum. This makes infrared spectroscopy useful for several types of analysis.

So, what information can FT-IR provide?: 

So, what information can FT-IR provide? • It can identify unknown materials • It can determine the quality or consistency of a sample • It can determine the amount of components in a mixture

FT-IR: 

FT-IR

Limitations of IR: 

Limitations of IR General • Minimal elemental information is given for most samples. • Background solvent or solid matrix must be relatively transparent in the spectral region of interest. • Molecule must be active in the IR region. (When exposed to IR radiation, a minimum of one vibrational motion must alter the net dipole moment of the molecule in order for absorption to be observed.) Accuracy In analysis of mixtures under favorable conditions, accuracy is greater than 1%. In routine analyses, it is ± 5%. Sensitivity and Detection Limits Routine is 2%; under most favorable conditions and special techniques, it is 0.01%.

General Uses: 

General Uses • Identification of all types of organic and many types of inorganic compounds • Determination of functional groups in organic materials • Determination of the molecular composition of surfaces • Identification of chromatographic effluents • Quantitative determination of compounds in mixtures • Determination of molecular conformation (structural isomers) and stereochemistry ( geometrical isomers ) • Determination of molecular orientation (polymers and solutions )

Common Applications: 

Common Applications • Identification of compounds by matching spectrum of unknown compound with reference spectrum (fingerprinting) • Identification of functional groups in unknown substances • Identification of reaction components and kinetic studies of reactions • Identification of molecular orientation in polymer films • Detection of molecular impurities or additives present in amounts of 1% and in some cases as low as 0.01% • Identification of polymers, plastics, and resins • Analysis of formulations such as insecticides and copolymers

References: 

References THERMO NICOLET, 5225 Verona Road • Madison, WI 53711-4495 • U.S.A. Lau, W.S. (1999). Infrared characterization for microelectronics http:// www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/Spectrpy/InfraRed/infrared.htm http://www.umsl.edu/~orglab/documents/IR/IR2.html