application of ir

SEMINAR ON APPLICATION OF INFRA-RED SPECTROSCOPY: 

SEMINAR ON APPLICATION OF INFRA-RED SPECTROSCOPY GUIDED BY: MR. DHARMENDRA A. BARIA ASSISTANT PROFFESOR PRESENTED BY : VAIPA G. PATEL M .PHARM (QA) SEM-I ROLL.NO . 2 DHARMAJ DEGREE COLLEGE OF PHARMACY

CONTENTS: 

CONTENTS Application of Infra-red spectroscopy Identification of functional group Identification by Fingerprinting Limit test of polymorphs Identification of drugs Determination of structures In Pharmacopoeial assay Detection & Identification of Impurity in Pharmaceutical substances

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Determining shape or symmetry of molecule Detection of water of sample Determination of air contaminates Quantitative analysis Infra-red emission spectroscopy Infra-red micro spectrometry Forensic application of Infra-red spectroscopy Application of IR spectroscopy to inorganic molecules

1) IDENTIFICATION OF FUNCTIONAL GROUPS:: 

1) IDENTIFICATION OF FUNCTIONAL GROUPS: The absence of specific characteristic absorption may be more informative than its presence. For e.g. the presence or absence of C=O stretching absorption.. ` In a situation where these functional groups interact with each other interact with one another or they shift from their original positions. For e.g. a)Glycine:H 2 N-CH 2 -COOH ( α-amino acetic acid i.e., an aliphatic amino acid) b)Pentane-2,4-dione, acetyl acetone: CH3COCH2COCH3- αβ - diketone c)Para hydroxy benzoic acid :HO-C6H4-COOH- a γ- hydroxy acid (aromatic)

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a functional group that give rise to many characteristic absorption can usually be identified more definitely than a functional group that gives rise to only one characteristic absorption. 0 || Esters (-C-OR): It affects group frequencies due to C=O str. And C-O str. And hence more readily identified than the ketones (C=O str.) 0 || Amides (-C-NH.H): It gives rise to group frequencies on account of (C=O str., N-H str., N-H def.) and therefore more easily identified than the esters.

2) Identification by Fingerprinting: 

2) Identification by Fingerprinting Infrared spectra contain many absorptions associated with the complex interacting vibrating systems in the molecule. the region that contains large number of unassigned vibrations is range from 900 cm-1 to 1400 cm-1 ,and this area is often called the ‟ finger print region”. To identify an unknown compound, compare its IR spectrum with standard spectra. IR-spectroscopy offers more characteristic, valid and qualified ‟proof of identity” than the comparison of any other physical property.

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Precautions: Sampling to be done under identical conditions. Same IR- spectrophotometer may be used for obtaining the various spectra. Experimental parameter like: slit-width, scan- speed etc., must be identical. An attempt should be made to obtain the maximum number of peaks in the ‟Finger print region” there by ascertaining the proof of identity more confidently.

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cetrizin.docx phenyl propanolamine.docx

3.Limit test of polymorphs : 

3.Limit test of polymorphs Polymorphs are same molecules differing only by crystalline forms. Eg . chloramphenicol palmitate suspension IP, BP, USP Chloramphenicol palmitate - 3 polymorphic forms Form A – least bioavailable & least activity. Form B Form C Limit of Chloramphenicol palmitate in Pharmacopoeia – NMT 10 % of form A which is found out by IR spectroscopy. In IP and USP - 1 parts of polymorph A and 9 parts of polymorph B are mixed and spectrum is recorded. Test must not have peak geater then standard.

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Sometimes Nujol Mull is used to measure absorbance. Absorbance of standard and test is measured at 858 and 840 cm -1 Ratio of peak height at these frequencies should not be greater than that of standard preparation. USP`95 in case of nadolol mentions to determine % of racemates by spectroscopy. Absorption is measured at 7.9 µm ( Aa ) and 8 ( Ab ). Racemate should be in between 40-60 % as per USP

4) Identification of drugs:: 

4) Identification of drugs: Ibuprofen in IP, BP and USP identified by IR- because it contains COOH group so, chemical tests are not useful for identification. Steroids are difficult to be distinguished from ketones by any chemical test.U . V. spectrum is same as the chromophoric part is same in both. But IR spectrum can give complete difference between steroids and ketones . Steroid identified are Cortisone acetate, Dehydro cortisone acetate, Ethysterone , Prednisolone , Prednisone, Progesterone All the sulpha drugs in BP’93 are identified Other compounds identified are Ethambutol , Ibuprofen Cholecalciferol , Disodium EDTA. In IP and USP spectrum of the test and standard are compared. Impurity is also identified by IR spectroscopy.

5) Determination of structures: : 

5) Determination of structures: The frequency range used is 1400-4000 cm -1 . IR spectra are are characteristic for molecular structures and molecular grouping. Thus IR spectra is used for checking the synthesis as well as in dealing with the unknown structures of unknown products. Absorption frequency of C=N ( nitrile ) is 2200 cm -1 ,C=O is 1715 cm -1 ,amine is 3400 cm -1 and ortho , meta, para isomers in a aromatic compound is 700-850 cm -1 . Compound containing C=O group give strong predictable peak at around 1715 cm -1 but attachment C=O group make predictable change in peak. Primary amine gives a duplet and secondary amine gives a singlet. When molecule has hydrogen bonding peak becomes very broad. E,Z isomers or Geometric isomers can be distinguished and confirmed by IR spectroscopy.

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H R’ H H C C C C R H R R ’ 970 cm -1 710 cm -1 trans cis In ‟ trance forms” bending is difficult because of bulky groups on both sides and so energy is high and frequency is high. ‟ cis forms” undergoes bending and so energy is low and frequency is low. Frequency of trans alkene is 970 cm -1 and that of cis form is 710 -1 that`s why IR spectroscopy proved to be the best method for cis , trans isomer differentiation.

6) In pharmacopoeial assay: : 

6) In pharmacopoeial assay: It is not a proper method for quantitative analysis because Sensitivity is very low. Base line is always flocculating. e.g : Diethyl toluamide : Measure absorbance in a 1 mm thick cell using CS2 as a solvent at 14.1 µm & 14.4 µm. Concentration of unknown is calculated by formula. Cu = (Au 14.1 – Au 14.1 ) × Cs (As 14.1 – As 14.4) * Thotepa for injection Measure absorbance at 10.75 µm in a 0.1 mm thick cell using CS2 as a solvent. Concentration is measured by formula. CU = AU /A S* CS

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Acetazolamide : Measure absorbance in a 0.1 mm thick cell at 7.38 µm using pyridine as a solvent. Concentration is determined by formula. CU =A U /A S *C S In IR spectroscopy blank is never 100% as in U.V Propoxyphene HCL capsule: Measure absorbance in 1 mm thick cell at 5.80 µm using CHCL3 as a solvent & comparison of test with standard.

7) Detection &identification of impurity in pharmaceutical substances: : 

7 ) Detection &identification of impurity in pharmaceutical substances: When a compound is containing impurity, it reduces sharpness of individual bands, cause appearance of extra band or peak. Conditions for detection of impurity are most favourable when impurity possesses a strong band in IR region where main substance do not possess absorption band in that region. e.g. Small quantity of ketone in hydrocarbon can be detected as a band near 1720 cm -1 ,characteristic of ketone .

8) Determining shape or symmetry of molecule: : 

8) Determining shape or symmetry of molecule: e.g. NO 2 (nitrogen dioxide) If linear, should show two bands & if nonlinear than show three bands. IR spectra of NO 2 gives 3 bands in 750, 1323, 1616 cm -1 region showing it is a bend structure & not a linear. 9) Detection of water in sample A small quantity of water held will show three characteristic band in 3600-3200 cm -1 , 1650-1620 cm -1 & 600-450 cm -1 regions. If water is held coordinated to metal ion additional band in 880-650 cm -1 region is observed .

10)Determination of air contaminants:   : 

10) Determination of air contaminants: IR absorption procedure is the most sensitive, rapid, highly specific method for the determination of atmospheric contaminants. This can be used for analysis of mixture of gases CONTAMINANTS Conc. ppm Found ppm Relative errors % Carbon monoxide 50 49.1 1.8 Methyl ethyl ketone 100 98.3 1.7 Methyl alcohol 100 99.0 1.0 Ethylene oxide 50 49.9 0.2 chloroform 100 99.5 0.5

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Above table demonstrates the potential of infrared spectroscopy for the analysis of the mixture of gases. The other potential application of infrared filter photometer is the quantitative determination of various chemicals in the atmosphere . Determination of stars dust by IR rays

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11. Quantitative analysis: all quantitative spectrophotometric measurement are governed by Beer`s law. In IR spectrophotometric , deviation to beer`s law are more due to Week intensity of light source. Week detection by detectors. By employing wider slit width .

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Another error is encountered by fixing the baseline. For quantitative determination selection of suitable solvent for liquid cell method is Usually CHCL 3 , CCL4, CS2, Pyridine can also be used(10%). All these errors can be reduced by applying various technique:

1.Internal standard method: : 

1.Internal standard method: Pellets from the disc technique can be used in qualitative measurements. Known wt of KBr+test sub->absorbance->calibration curve. The disc are weighed and the thickness of pellets should be uniform which is not possible, this can be overcome by using the internal standard method. Known wt of KBr -KCNs + test sub(10% of total wt) The ratio of the thiocyanate absorption at 2125 cm -1 to a chosen absorption band of test substance is plotted against concentration of the test substance

2) Difference method:: 

2) Difference method: A series of standard is prepared with concentration extending from just above to just below the concentration of the unknown. The unknown is placed in sample beam, the standard one after another, are placed in the difference beam (using the same cell) and the differences, are plotted against concentration. The concentration of the unknown is that concentration on the curve where the difference is zero. 12) near infrared spectroscopy: (4000-14000 cm -1 or 0.74-2.5 µm) It is used for quantitative determination of species, such as water, protein, low molecular weight hydrocarbon &fats in products of the agricultural, food, petroleum & chemical industries.

A) Near-IR Absorption spectroscopy: : 

A) Near-IR Absorption spectroscopy: It is less useful for identification and more useful for quantitative analysis of compound containing functional group that are made up of hydrogen bonded to C, N, O. Determination of water in glycerol, hydrazine, organic films & fuming nitric acid. The quantitative determination of phenols, alcohols, organic acid & hydro peroxides (7100 -1 ) and esters, ketones & carboxylic acids (3300-3600 cm -1 ) Identification and determination of of 1º & 2º amine in the presence of 3º amine in mixtures.

B) Near-IR Reflectance spectrometry:: 

B) Near-IR Reflectance spectrometry: for the routine quantitative determination of constitutes in finely ground solids. for the determination of protein, moisture, starch oil, lipids & cellulose in agricultural products such as grains & oilseeds. 13) Far – infrared spectroscopy: determination of the structure of inorganic & metal organic species e.g. Heavy metal iodides generally absorbs in region below 100 cm -1 . while the bromides & chlorides have bands at higher frequencies. provided information about lattice energy of crystals & transition energies of semi conducting materials. Pure rotational absorption by gases is observed in the far infrared region, provided the molecules have permanent dipole moments. Example include H2O, HCL & ASH3.

14) Infra-red Emission spectroscopy:: 

14) Infra-red Emission spectroscopy: Upon being heated, molecules that absorb infra-red radiations are also capable of emitting characteristic infrared wavelengths. For example uses of a Fourier transform spectrometer for the identification of microgram quantities of pesticides. Use for the interferometric technique for the remote detection of components emitted from industrial stacks (waste). 15) Infra-red micro spectrometry: Used for sample having physical dimension in the 10 to 500 µm range. It consists of two microscope, one an ordinary optical microscope & the other an infrared device with reflection optics that reduce the size of the infrared beam to about that of the sample.

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current application include: Identification of polymer contaminants. Imperfections in polymer films & industrial layers of laminated polymer sheath. Identification of contaminants on electronic components. Identification of tiny samples of fibres, paints & explosive in criminalistics . Characterisation of single fibres in the textile industry.

16) Forensic application of Infrared spectroscopy:: 

16) Forensic application of Infrared spectroscopy: With the technology of FTIR spectroscopy (Fourier transform infrared spectroscopy) machines & integrated computer databases of known IR absorbance graphs, nearly any substances can be identity 1) Analysing alcohol with infrared spectroscopy The Analyte : Breath (suspected to contain alcohol) The Identity test: The breath is tested with a mechanism similar to a breathalyser. The difference is that a breathalyser relies on chemical oxidation & therefore requires a dangerous reagent, while a mechanism using an –IR test (for example, a CMI INTOXILIZER ) uses the unique response of alcohol to infrared radiation. mechanism compares radiation from the breath in one chamber , in a second chamber, which contain air.

2)Analysing drugs with infrared spectroscopy: 

2)Analysing drugs with infrared spectroscopy The Analyte : Drugs (perhaps heroin, LSD, or cocaine…..) The Identity test: sample of drug is put in to an IR testing machine. The drugʼs various chemical components respond uniquely to the infrared light. The machine prints out a graph, a chemist compares to known graphs, either by peak properties or using a computer database, probably both. The identity of drug is confirmed. 3) Analysing fibres with infrared spectroscopy: The Analyte : Synthetic fibres (possibly polyesters, nylon, or acrylic….) The Identity test: the fibre are put in to a machine that shines infrared light , chemical structure of compounds reacts to the light; different compounds absorb different wavelengths.

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The machine prints out a graph, comparing the graph to known graphs. The known graph may be a list of wavelengths, or an integrated, international computer database 4) Analysing paint with infrared spectroscopy The Analyte : paint (from a car, or on a weapon or someoneʼs clothing) The Identity test: Colours, layers, textures & other physical properties are recorded using a microscope as well as the naked eye. paint are analysed by IR . The results can be compared to IR results of known paint.

17) Application of IR spectroscopy to inorganic molecules : 

17) Application of IR spectroscopy to inorganic molecules the infrared spectra of relatively simple, purely inorganic compounds containing only a few atoms specifically, inorganic salts containing polyatomic (complex) ions are quite distinctive & can be used to rapidly identify the ions. Following are some e.g.:  in Inorganic salt KNO 2. a total of 3(4)-6=6 normal modes of vibration associated with this material. KNO 2 consists of K + & NO2 -1 ions. so to consider the vibrational modes of the cation & anion independently . the potassium ions are monoatomic , they have no vibration [3(1)-3=0], so we need only consider the nitrile anions.

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We thus anticipate 3 normal vibrations modes for NO2 -1 & they should all be infrared active. This bands are observed in the IR spectrum of KNO2 -1 : the symmetric stretch at 1250 cm -1 & the bending vibrations at 830 cm -1 The frequencies of these vibrations are about the same regardless of counter ion, substantiating the independence of the anion & cation in the crystal

Thermal vision: 

Thermal vision

REFERENCE: : 

REFERENCE: Douglas A. skoog , F James Holler, Timothy A. Nieman , ‟Principle of instrumental analysis”, Thomson Asia Pvt. Ltd., Singapore, 2004, Fifty Edition, P. -411 to 426. Sharma B.K., ‟Instrumental method of chemical analysis”, Krishna prakashan Media, U.P., 2005, Twenty forth edition, P.-S-313 to s-315. Ashutoshkar , ‟Pharmaceutical Drug Analysis”, Minerva Press, New Delhi, 2001, First Edition, P.-414 to 422. William Kemp, ‟Organic Sectroscopy ”, Palgrove , New york.2002, Third Edition, P.-55 to 58. Kasture A,V., Wadodkar S.G., Mahadik K.R., More H.N., ‟Pharmaceutical Analysis- Instrumental Methods”. Beckett A.H., Stenlake J.B., “Practical Pharmaceutical Chemistry”, CBS Publishers, Delhi, Third Edition, Vol – II, P.-340,341.

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Thank you