APPLICATIONS OF UV-VISIBLE SPECTROMETRY FINAL.pptx

APPLICATION OF UV VISIBLE SPECTROSCOPY

1. APPLICATIONS OF VISIBLE AND UV SPECTROMETRY PRESENTED BY:- AARADHNA TRIPATHI M.PHARM (2422829 )

2. UV-VISIBLE SPECTROSCOPY LIGHT SOURCE ENTRANCE SLIT DISPERSION DEVICE EXIT SLIT SAMPLE DETECTOR

3. Molar composition of complexes concentration) A quantity In any mixture of M and X, [M]= –[MX [X]= Obviously, the co ncentration of the complex will change as f is varied. It will be zero when is either zero or unity and will have maximum value at some intermediate point. If the absorbance is measured at a wavelength, where the complex absorbs but M and X do not absorb, the value of at the point of maximum absorbance will correspond to the maximum concentration of MX n . This in turn, will be the value of the point where =0, since [M ]= Where K is the dissociation constant of complex. It can be easily shown that K . Now on putting , =0, this equation reduces to n= .   APPLICATION OF VISIBLE SPECTROMETRY [1]

4. B . MOLE RATIO METHOD Popular method worked out by Yoe and Jones. Mole reagents per mole, at wavelength 520nm   Absorbance

5. A series of solution are prepared containing a constant amount of metal ion but with increasing ratios of concentration of the metal ion to that of reagent (or vice versa). The curve of absorbance plotted against the concentration ratios rises linearly from the origin when both reactants are colorless and breaks sharply to an horizontal straight line at molar ratio of the components in the complex. However , a complex that undergoes appreciable dissociation in solution gives a continuous curve, which only become parallel to the mole ratio axis when a large excess of the variable component is added.

6. C. SLOPE RATIO METHOD This method , originally used with spectrophotometric measurements , is restricted to those cases where only a single complex is formed at a time. If the complex formation proceeds according to reaction., mM L=M m L n Then in presence of large excess and constant concentration of L, the concentration of the complex formed will be proportional to , the analytical concentration of M added. If the absorbance due to the other species besides M m L n is ignored, the absorbance of solution will be equal to  

7. MOLE RATIO METHOD This has been used to evaluate the instability constant of complexes. If the complex contains metal ion M and the reagent R in the ratio 1:n, the reaction may be written as follows: M nR ⇌ MR n 0 0 C n ( initial concentration) C nC C(1- ( Equilibrium concentration ) The instability constant of the complex is given by, K ins = Where C is the concentration of the complex in moles per litre and is the degree of dissociation. The value of can be evaluated from the conventional relationship, = Where E m is the maximum absorbance in the presence of a large excess of the reagent , E s is the value of metal when and reagent are present in the stoichiometric ratio (1:n).   DETERMINATION OF INSTABILITY CONSTANT

8. b ) Logarithmic method of Bent and French The stoichiometric ratio of metal to ligand in the case of weak complexes is frequently determined by logarithmic method of Bent and French. The General reaction is represented as M nRH ⇌ MR n ……….(1) Where M stands for metal, RH stands for reagent and n is an integral number . On applying law of mass to equilibrium , we get K= …………(2) Or, K = ………….(3) On taking logarithm of equation (3), we get log K [RH]= log  

9. DETERMINATION 0F THE P k VALUE OF AN INDICATOR ; Spectrophotometric study is well suited for the determination of the dissociation of acid- base indicator. STRUCTURE OF ORGANIC COMPOUND; Spectrophotometry is of much use in elucidating the structure of organic molecules. According to Hartley, compounds of similar structure have analogous absorption spectra. STRUCTURE OF INORGANIC COMPOUNDS; Absorption spectra has been widely used to solve many problems in inorganic chemistry. For instances, absorption spectral studies have revealed that deep blue colour of ferric thiocyanate is due to the presence of FeCN ions.  

10. STRUCTURE OF INORGANIC COMPLEXES GEOMETRICAL ISOMERISM PLANAR-TETRAHEDRAL EQUILIBRIUM OCTAHEDRAL-PLANAR EQUILIBRIUM Spectrophotometry has been used to distinguish between cis and trans isomers of complex, Equilibrium between the octahedral , tetrahedral, square planar, and the five coordinate configurations have been studied in recent years by Absorption spectroscopy .

11. QUANTITATIVE ANALYSIS 4% 2% 1% 1.00 0.75 0.50 0.25 25 50 75 100 TRANSMITTANCE   WAVELENGTH   ABSORBANCE   Fig. Absorption curves for Hexanol at different concentrations

12. Determination of molecular weights This is another important applications of spectrophotometry. When a compound reacts with reagent to form a derivative having a characteristic absorption in another wavelength region, the molar absorptivity of the derivative is almost the same as that of reagent . For example , Amines Pictrates show maxima at 380 nm having =13,500 which is same as that of Picric acid. Then ,on applying Beer’s law, we get A=a c t Where c is the concentration in grams per litre, and the absorptivity a is calculated in litre per gram centimetre . The molecular weight can be calculated by applying the following relation; =a  

13. Detection of Impurities UV absorption spectroscopy is one of the best methods for determination of impurities in organic molecules . APPLICATION OF UV SPECTROSCOPY [2] 5000 4000 3000 2000 1500 1000 400 STANDARD PCM PCM WITH IMPURITY  

14. UV spectroscopy is useful in the structure elucidation of organic molecules, the presence or absence of unsaturation, the presence of hetero atoms. From the location of peaks and combination of peaks, it can be concluded that whether the compound is saturated or unsaturated, hetero atoms are present or not etc. Structure elucidation of organic compounds

15. UV absorption spectroscopy can be used for the quantitative determination of compounds that absorb UV radiation. This determination is based on Beer’s law which is as follows. A = log I / I t = log 1/ T = – log T = abc = εbc Where : ε -is extinction co-efficient, c- is concentration, and b- is the length of the cell that is used in UV spectrophotometer QUANTITATIVE ANALYSIS

16. 4. QUALITATIVE ANALYSIS UV absorption spectroscopy can characterize those types of compounds which absorbs UV radiation. Identification is done by comparing the absorption spectrum with the spectra of known compounds. 0.0 0.2 0.4 0.6 0.8 1.0 1.2 240 250 260 270 280 290 →WAVELENGTH(nm) ABSORBANCE UV SPECTRA’S OF IBUPROFEN

17. CHEMICAL KINETICS Kinetics of reaction can also be studied using UV spectroscopy. The UV radiation is passed through the reaction cell and the absorbance changes can be observed. DETECTION OF FUNCTIONAL GROUPS This technique is used to detect the presence or absence of functional group in the compound . Absence of a band at particular wavelength regarded as an evidence for absence of particular group.

18. MOLECULAR WEIGHT DETERMINATION Molecular weights of compounds can be measured spectrophotometrically by preparing the suitable derivatives of these compounds. For example, if we want to determine the molecular weight of amine then it is converted in to amine picrate. Then known concentration of amine picrate is dissolved in a liter of solution and its optical density is measured at λ max 380 nm.  After this the concentration of the solution in gm moles per liter can be calculated by using the following formula. C = "c" can be calculated using above equation, the weight "w" of amine picrate is known. From "c" and "w", molecular weight of amine picrate can be calculated. And the molecular weight of picrate can be calculated using the molecular weight of amine picrate  

19. AS HPLC DETECTOR A UV/Vis spectrophotometer may be used as a detector for HPLC. FIG. A typical HPLC chromatogram profile with UV spectra of MFP using Monascus purpureus (FTC5391). (a) Chromatogram before lactonization and the UV spectrum of 11.92 RT peak related to yellow pigment and (b) chromatogram after lactonization. The MFP was produced by submerged fermentation using Hiroi-PDA (sucrose (100 g/L), yeast extract (3 g/L), casamino acid (5 g/L), NaNO3 (2 g/L), KH2PO4 (1 g/L), MgSO4·7H2O (0.5 g/L), KCl (0.5 g/L), FeSO4 (0.01 g/L), potato starch (4 g/L), dextrose (20 g/L), and agar (15 g/L)) MKL: monacolin K lactone form, MKA: monacolin K acid form [3].

20. 1. Sharma. Y.R. Elementary Organic Spectroscopy. First edition S.Chand Publisher; 2010. 2. Chatwal G.R. Instrumental methods of chemical analysis. First edition. Himalaya Publisher; 2010. 3 . J. Y. Kim, H.-J. Kim, J.-H. Oh, and I. Lee, “Characteristics of Monascus sp. isolated from Monascus fermentation products,” Food Science and Biotechnology,vol.19,no.5,pp.1151–1157, 2010. REFERENCE