Measuring Partition Coefficient

Measuring part CoefficientAbstractThis research laboratoryoratory study deals with the Analytical office of the Measurement of division Coefficient. Partition Coefficient is a really important step for perfect hearts. It finds use in Pharmaceutical Industry, Pollution abatement systems, Agro chemics, and chemic Industry. in that location argon many methods available for determining the Partition Coefficient, curiously Instrument methods akin, Chromato representy, Electrophoresis and so on The method adopt here is a simple, reliable and versatile atomic number 53, which utilizes basic principles of Chemical Analysis.The method employ was by step of pH and Colorimetric determination of the organic Ligand. The process used for partitioning was Shaking Flask method. The granted sample was reduce and buffered suitably and an aliquot was partiti adeptd with an equal quantity of the given oil. The pH of the sedimentary soma was sum of moneyd. The clear aqueous answer was further dilute appropriately and used for Colorimetric estimation employ a normalisation graph prepared. These data were used for computation of apparent Partition coefficient and then received Partition coefficient.Measuring Partition CoefficientChemistry is a material Science, dealingss with the study of corporeal and Chemical properties of the matter name in the universe. There are many disciplines in Chemistry dealing with different materials and properties, like Inorganic Chemistry, Organic Chemistry, Physical Chemistry, Pharmaceutical Chemistry, Analytical Chemistry etc. The Analytical Chemistry is a special branch of Chemistry dealing with the determination of Chemicals, quantity wise and quality wise. The Analytical Chemistry uses the cognition available in other branches of Chemistry, like Inorganic Chemistry, Organic Chemistry, Physical Chemistry, and many principles of Physics. The uses and finishings of Analytical Chemistry are wide, and practic all toldy, in e very(prenominal) aspects of clement life, uninflected Chemistry is involved in some way or other, say, in Clinical Chemistry, Pharmaceutical Chemistry, Forensic Chemistry, in commerce, in springer Department and so on. The measurement of Partition Coefficient is a typical analytical procedure using many theoretical principles of various branches of Chemistry. It de nones the differential amounts of the affections found at equilibrium conditions in the organic contour and the aqueous phase for a set of conditions like dumbness, pH, Temperature etc. This Lab study aims at and involves, in addition to learning partitioning technique, Electro Chemical application the pH measurement, subterfugeimetric measurement, computational techniques, and tally procedures. The partition coefficient study assumes signifi usher come out of the closetce, because it finds use in Pharmaceutical Chemistry for drug bearing, development, and delivery, Pesticide design, soil Chemistry, design ing of Chemical Plants by Chemical Engineers, and excessively for Chemists and Scientists working on Liquid Liquid symmetricalness data.METHODSSample preparation Sodium salicylate solution of 0.2 gram groyne per fifty ( breakwater) was taken for this study. From this stock standard solution quadruple Test samples, named A to D, were prepared. 10 ml of 0.2 mol standard solution was pipetted into from each iodin of the cardinal one C ml volumetric flasks marked A to D and diluted to the mark with four buffer solutions of different pH, and mixed thoroughly. So the immersion of the resultant diluted samples was 0.02 mol each.Partitioning Aliquots of 25 ml of the to a superior place diluted samples, 4 Nos, were taken in 4 separating funnels. Then, 25 ml of the given oil was added in each of the 4 separating funnels, marked A to D, and mixed thoroughly and gently by inverting and rotating for 10 minutes. Then the commixture in the separating funnels were allowed to settl e thoroughly. After the aqueous and organic layers became clear, the aqueous layers of the four separating funnels were drained into four glass beakers marked A to D.pH measurement of aqueous phase The pH of the four partitioned aqueous samples were measured using a pH meter.Determination of Salicylate intentness in the Aqueous phase For determining the Salicylate submergence, Colorimetric method was adopted where the absorbance of the Iron- Salicylate complex was measured. The procedure adopted for developing the standard and test samples is given below. zeal of Standard color Solutions Four different Standard solutions of Sodium Salicylate, namely, 0.00125mol, 0.0025 mol, 0.00375 mol and 0.005mol were prepared along with a blank.Five test tubes were taken. The first one was marked as 1 (Blank), and the others as 2,3,4, and 5.To the blank, 1 ml of water was added, and in the others, one ml each of the prepared standards were added. Then 2 ml of the given Ferric Nitrate was added to all the test tubes. Then 5 ml of water was added into all the five test tubes. All the test tubes were move gently to mix the contents thoroughly and waited for some metre for the over(p) development of the color. The five solutions represented 0.0000 mol, 0.00125mol, 0.0025 mol, and 0.00375 mol and 0.005mol Salicylic back breaker tightness respectively.Preparation of Calibration Graph The Colorimeter (Spectrophotometer) was set at the wave duration of 624 nm. Placed the blank in the cuvete in the colorimeter and adjusted the absorbance as zero. Then the other standard solutions were placed one by one and noted the absorbance readings. Calibration Graph was plotted, plotting intentness of salicylic sulphurous in X axis of rotation and Absorbance at the y axis.Preparation of Test samples 10 ml of each of the four Partitioned aqueous layers were diluted with water to 50 ml, indeed making a diluted sample. From these, 1 ml solution each were placed in four test tubes, marked A, B, C, D. Then, 2 ml ferric Nitrate and 5 ml water were added in all the four test tubes and treated convertible to the Standard tubes.Measurement of Salicylic bitter assiduousness of the test samples The absorbance of all the four test samples were measured similar to the standards. The Salicylic acid concentration of the test samples were arrived from the Calibration graph. The concentration arrived was of the diluted samples. So the concentration of the partitioned aqueous phase was multiplied 5 times to stomach the concentration of the salicylic acid. This gives the Cw , i.e., the concentration of the salicylic acid in the partitioned aqueous solution.Determination of CO The Cw was subtracted from the concentration of the buffered solution, i.e., 0.02 mol, to get the CO.Determination of total heat Ion concentration From the pH of the four partitioned aqueous solutions, Hydrogen Ion concentrations were work out.CALCULATIONSStep 1. Calculation of H+ and 1/H+ from the pH Model calculation for Experiment A pH = 2.35.pH is the negative logarithm to base 10 of Hydrogen ion concentration.So Hydrogen ion concentration is the antilog of 2.35= 0.00447Reciprocal of Hydrogen ion concentration = 1/H+ =1/0.00447 = 223.9 withal H+ and 1/H+ are calculated for other experiments and tabulated below.ExperimentpH of the buffer addedResultant pHH+1 / H+A2.02.350.00447223.9B2.83.220.0006031660C3.33.850.0001417079D4.04.020.000095510471Step 2a. Calculation of the concentration of salicylate added to each separating funnel The salicylic acid concentration of the sample taken = 0.2 gm. mol/Liter. 10 ml of this solution was diluted with buffer to 100 ml. So the concentration of the diluted solutions, added to eachseparating funnel, taken for the Partition experiment were 0.210/100 = 0.02 gm mol/L each.Step 2b. Calculation of Cw and Co The partitioned concentration of salicylic acid in water and oil, denoted by S (aq) and S (org) are Cw and Co in the formula respectively. 25 ml of the Solution A ( 0.02 gm mol Sodium Salicylate, buffered with buffer of 2.0 pH) was partitioned with 25 ml of oil. After separation of the phases, the pH was measured in the aqueous phase. Then the aqueous phase was diluted five fold for colorimetric estimation. The absorbance obtained for experiment A was 0.065 and the corresponding concentration obtained for experiment A from the calibration graph = 0.00054. So the concentration of this full-strength Partitioned aqueous solution, S(aq) , is five times of the value determined calorimetrically = 0.00054x 5 = 0.0027. This is CWThe concentration of salicylic acid in the organic phase is the concentration of the diluted solution taken for the Partition experiment, minus concentration of the undiluted Partitioned aqueous solution, i.e. CO = (0.02- CW) = (0.02 -0.0027) = 0.0173gm mol/L.Apparent partition coefficient P = CO / CW = 0.0173/0.0027 = 6.41/P = 1/6.4=0.156CW, CO, P and 1/P for other experiments were also calculated l ike wise and tabulated below.The calibration graph of this study is attached separately.Exp AbsorbanceSalicylate ducking in aqueous phase of the diluted aliquot, from calibration GraphSalicylate Concentration in aqueous phase the undiluted aliquot, CW i.e. (S(aq) )Salicylate Concentration in Organic phaseCO i.e. (S(org) ) =0.02- S(aq)A0.0650.000540.00270.0173B0.1380.001160.00580.0142C0.2210.002180.01090.0091D0.2670.00250.01250.0075Calculation of P and 1/PExp S(aq) i.e. CWS(org) i.e. COP = (CO / CW )1/PA0.00270.01736.40.156B0.00580.01422.450.408C0.01090.00910.831.200D0.01250.00750.61.667Step 3. Preparation of 1/H+ vs. 1/P Graph and Calculation of P and Ka A graph was plotted with 1/H+ in X axis and 1/P in Y axis. The slope, Ka/P was estimated from the graph = 0.0001518. The intercept, 1/P, was at 0.13, and hence, P = 1/0.13 = 7.69.Ka = (Ka/P) x P = 0.0001518 x 7.69 = 0.001167 pKa = log of 0.001167 = 2.93DISCUSSIONThe study results show a definite trend of higher ingress of the orga nic acid, i.e., Salicylic acid, into the organic layer at a dismount pH and vice versa. This is in accordance with the theory, which implies, at a turn away pH, the H+ ion concentration testament be higher, which exit in performance enhance association of the ions, R- + H+ RH, to form unionized molecule that lavatory attain the organic phase. So the unionized acid result be predominantly in the organic layer. At higher pH, the H+ ions will be low and there will be the tendency of the acid to ionize in the aqueous phase, RH R- + H+ , olibanum preventing the acid to enter the organic phase. So the ionized acid ion will be predominantly in the aqueous layer. This is established in this experiment CO, the concentration of salicylic acid in organic phase is highest, 0.0173mol, in Experiment A, where the pH is the worst, 2.35 and lowest, 0.0075 mol, in Experiment D where the pH is the highest ,4.02. Consequently the Apparent Partition coefficient P which is the ratio of CO / CW is highest in Experiment A and lowest in Experiment D. This shows, the pH of the solutions affect the partitioning.The accuracy of the study depends some(prenominal) on the accuracy of pH measurement and the measurement of absorbance. The linearity of the graph- 1/H+ vs. 1/P depends on both the measurements. But the wreathe was not perfectly linear as expected.The potential sources of errors . While carrying out the Chemical Analysis, one has to be aware of the potential sources of errors. Alexeyev (p 48) classifies the errors in duodecimal Analysis as Systematic errors, random errors and mistakes. The systematic errors are errors of the method, errors of utensil reagents, and Operative errors. Random errors do happen duringany analysis and one has to be vigilant and careful to avoid them. Mistakes are crude errors caused by careless noting of the readings in the instruments, parallax error, improper labeling of the various test samples ending with wateriness piece of musi c tabulating the readings etc.The possible systematic errors in this study are errors of the method, say non uniform pH among the four test in the colorimetric estimation. Lyalikov.Y (p 40) warns, many colored compounds are sensitive to Hydrogen Ion concentration. Changes in pH not only affects extinction, but change spectrophotometer squirm of the substance as well, Lyalikov.Y (41). The calibration curve obtained is not cracking as expected, showing the colored complex did not obey Beer Lambert Law, which states, absorbance is comparative to molar extinction coefficient, , depth of the solution layer, L, and concentration, C. (A= x L x C). It was expected at least to be a smooth curve of a definite pattern . But the curve is not very smooth indicating some error, whitethorn be varying final pH of the colored solutions. doable errors of apparatus leaking separating funnel. Possible errors of reagents accuracy of the buffers.Operative errors Possible non uniform mixing during part itioning, incorrect and non uniform draining from pipettes. It was expected that the curves of Calibration graph and that of 1/H+ vs. 1/P to be straight lines. But they are not straight as expected. The reason whitethorn be due to some or a combination of the preceding(prenominal) cited errors.Comparison of the result with Literature The literature value for Ka of salicylic acid as given by Harris, Daniel. C. (p 183) is Ka = 1.07 x 103. The result obtained in this Lab study is 0.001167. This is higher than the value reported in three-figure Chemical Analysis by about 9%The phenomenon of partitioning The chemical substances uncover different solubility in different solvents. Solvents may be classified into two groups, Aqueous and Non aqueous, in other words polar and non polar. Similarly the chemicals may be classified as Hydrophilic and Hydrophobic. Hydrophobic substances can also be termed as lipotropic. A hydrophilic substance will easily dissolve in an aqueous solvent and a aquaphobic (Lipophilic) substance will easily dissolve in non aqueous (Organic) solvent. If a substance is in contact with both the Hydrophilic and Hydrophobic Solvents, the substance will get distributed in both the solvents and the proportion of distribution will be according to the nature of the substance with respect to its Hydrophilic or hydrophobic nature and this property is termed as the Partition coefficient.Partition coefficient finds application in Pharmaceutical industry, agrochemical Industry, Pollution studies and for designing of Chemical Process by Chemical Engineers.Drugs are meant to be ingressed into human body. The partition coefficient finds use in drug design, as it is a measure of the hydrophobicity of the drug concerned. If the partition coefficient is high, it denotes high hydrophobicity ( high lipophilicity) and such a drug will easily enter the lipid regions of the variety meat and outride for longer time and hence may prove toxic. On the other hand a l ow Partition coefficient denotes a hydrophilic nature and hence the drug will stay longer in the aqueous regions rake stream and will not readily ingress into the tissues. So the absorption, excretion and cleverness of the drugs into the body organs are related to the Log P value of a drug. An modal(a) Partition coefficient is preferred while designing the drugs by the Pharmacologists. Earll. see enumerates the optimum Partition Coefficient, as Log P, for different types of drug applications. best systema nervosum centrale penetration around Log P = 2 +/- 0.7 (Hansch)Optimum viva absorption around Log P = 1.8Optimum Intestinal absorption Log P =1.35Optimum Colonic absorption Log P = 1.32Optimum Sub lingual absorption Log P = 5.5Optimum Percutaneous Log P = 2.6 ( low mw)The drug has to be intentional accordingly for each of the application. The Formulation and dosing forms, as given by Earll. find outLow Log P (below 0) InjectableMedium (0-3) Oral in high spirits (3-4) Transd ermalVery High (4-7) Toxic build up in fatty tissuesThe drug has to go into human body done different routes, say, mouth, skin, Blood etc all having different pH. So the drug has to be designed taking into consideration of the effect of pH. Mark Earll gives the pH of the various separate of the body Stomach 2, Kidneys 4.2 (variable), Small Intestine Fed 5.0 Fasted 6.8, Duodenal mucus 5.5, Plasma 7.4.According to Chemie.DE breeding service GMBH, The Hydrophobic drugs are preferentially distributed to hydrophobic compartments such as lipid bilayers of cells while hydrophilic drugs preferentially are found in hydrophilic compartments such as blood serum. The Partition coefficient of the drug determines the Absorption. Distribution, Metabolism and excretion of the drugs. When a drug is admitted orally, it passes through the alimentary canal and has to be absorbed through the lipid layers of the epithelial tissue layer of the small intestine. So the drug should be sufficiently Lipophil ic as to pass through the lipid layers. At the same time it should not be too lipophilic, otherwise, it will stay permanently in the epithelial calls and will not enter the blood stream for run to the required location. Similarly the drug has to be metabolized and excreted after its function is over. This also depends on the Hydrophobicity. Similarly the other forms of drug administration are also need to be studied in this aspect. So control of the Hydrophobicity (lipophilicity) while developing the drug is important. Here is the use of Partition coefficient measurement, which is a measure of the hydrophobicity.Partition coefficients find use in designing pesticides. One has to design the insecticide in such a way it has got a very high partition coefficient , i.e. , having high hydrophobicity, ratherhigh lipophilic tendency, so that the insecticide easily penetrates into the organisms and stay permanently causing high toxicity, thus proving its efficacy in killing the pests. But, the adverse consequence is, the pollution aspect, vide Chemie.DE information service GMBH.In partition studies, Octanol/ water system is normally used. Earll. Mark states, Octanol was chosen as a simple model of a phospholipid membrane however it has shown serious shortcomings in predicting Blood-brain barrier or skin penetration.Berthold says,The most needed liquid- liquid partition coefficient is the octanol-water partition coefficient. Ko/w is accepted as a good reference parameter for solute hydrophobicity. Indeed, Ko/w can be rapidly estimated using capillary electrophoresis with a micellar or micro emulsion solution and/or RPLCLeahy, Taylor and tolerate of ICI have proposed, in addition to octanol, chloroform, cyclohexane and propylene glycol dipelargonate (PGDP) for modeling biological membranes, notes Earll. Mark.For determining the Partition Coefficient, there are many other slavish methods, like, HPLC. Paper Chromatography, Thin layer chromatography and Electrophoresis. Berthod. A and Carda-Broch. S. enumerates the various analytical Techniques. They are Shake-flask method, HPLC method, Micro emulsion electro energizing capillary electrophoresis, Counter-current chromatography (CCC), Co current CCC, Micellar electro kinetic capillary chromatography (MEKC), Micro emulsion electro kinetic capillary chromatography (MEEKC)ReferencesAlexeyev, V. (1969). Quantitative Analysis. capital of the Russian Federation Mir Publishers.Berthod.A, Carda-Broch.S (2004) Determination of liquid-liquid partition coefficients by separation methods. Journal of Chromatography A, 1037 3-14Chemie.DE information service. GMBH. cyclopaedia of Chemistry, Partition coefficient, Retrieved January 28, 2010, from http//www.chemie.de/lexikon/e/Partition_coefficientEarll, Mark. A guide to Log P and pKa measurements and their use. Retrieved January 28, 2010, from www.raell.demon.co.uk/chem/logp/logppka.htmHarris, Daniel C. Quantitative Chemical Analysis. Google Books.Lyalikov, Y. (1 968). Physicochemical Analysis. Moscow Mir Publishers.