HPLC methods partition coefficients

Reynolds, D., Abraham, M. H. Rapid method for estimating octanol-water partition coefficient (logPocr) from isocratic RP-HPLC and a hydrogen bond acidity term (Aj.J. Liquid Chromatogr. 

Paschke, A., Manz, M., Schtiurmann, G. Application of different RP-HPLC methods for the determination of the octanol/water partition coefficient of selected tetrachlorobenzyltoluenes. Chemosphere 2001, 45, 721-728. 

Slater, B., McCormack, A., Avdeef A., Comer, J. E. pH-metric logP. 4. Comparison of partition coefficients determined by HPLC and potentiometric methods to literature values. J. Pharm. 

Haky, J.E., Young, A.M. (1984) Evaluation of a simple HPLC correlation method for the estimation of the octanol-water partition coefficients of organic compounds. J. Liq. Chromatogr. 7, 675-689. 

Lei, Y.D., Wania, F., Shiu, W.Y., Boocock, G.B. (2000) HPLC-based method for estimating the temperature dependence of n-octanol-water partition coefficients. J. Chem. Eng. Data 45, 738-742. 

Klein, W., Kordel, W., Weip, M., and Poremski, H.J. Updating of the OECD test guideline 107 partition coefficient-octanol/water OECD laboratory intercomparison test of the HPLC method, Chemosphere, 17(2) 361-386, 1988. Klemenc, A. and Low, M. Die Loslichkeit in Wasser und ihr Zusammenhang der drei Dichlorbenzole. Line Methode zur Bestimmung der Loslichkeit sehr wenig loslicher und zugleich sehr fluchtiger Stoffe, Rec. Trav. Chim. Pays-Bas, 49(4) 629-640, 1930. 

Liquid-liquid extraction is used extensively and successfully (6). If the analytes are acidic or basic, as is often the case when HPLC is the analytical method selected, appropriate ionization suppression can be employed to affect the desired extraction. Back extraction of the analytes into an appropriately buffered aqueous volume can then serve to isolate and concentrate. Anionic and cationic surfactants, or so-called ion-pairing reagents, can be added prior to extraction to increase the partition coefficients of the trace organic ionic compounds. 

Microemulsion electrokinetic chromatography, MEEKC (or MECC), is a relatively new technique which holds some promise of delivering octanol/water partition coefficients much more conveniently than the shake-flask method (Gluck, 1996 Ishihama, 1994). MEEKC is claimed to have all the advantages of an HPLC method but it is not suitable for solutes with pKas much below 7.0 (Adlard, 1995). It has been used over a log P range of -1.0 to +4.0. 

Eadsforth, C.V. (1986) Application of reverse phase HPLC for the determination of partition coefficients. Pest. Sci. 17, 311-325. Eadsforth, C.V., Moser, P.(1983) Assessment of reversed phase chromatographic methods for determining partition coefficients. Chemosphere 12, 1459-1475. 

Klein, W., Kordel, W., WeiP, M., Poremski, H J. (1988) Updating of the OECD test guidehne 107 Partition coefficient n-octanol/water OECD laboratory intercomparison test on HPLC method. Chemosphere 17, 361-386. 

Mirrlees MS, Moulton SJ, Murphy CT et al. (1976) Direct measurement of octanol-water partition coefficients by high-pressure liquid chromatography. J Med Chem 19 615-619 Pagliara A, Khamis E, Thrinh A et al. (1995) Structural properties governing retention mechanisms on RP-HPLC stationary phases used for lipophilicity measurements. J Liquid Chromatography 18 1721-1745 Slater B, McCormack A, Avdeef A et al. (1994) pH-Metric log P. 4. Comparison of Partition Coefficients Determined by Shake-Flask, HPLC and Potentiometric Methods. J Phar-maceut Sci 83 1280-1283... 

Donovan SF, Pescatore MC (2002) Method for measuring the logarithm of the octanol-water partition coefficient by using short octadecyl-poly(vinyl alcohol) high performance liquid chromatography columns. J Chrom A 952 47-61 Du CM, Valko K, Bevan C et al. (1998) Rapid gradient RP-HPLC method for lipophilicity determination s solvation equation based comparison with isocratic methods. Anal Chem 70 4228-4234... 

Equilibrium dialysis is used in a number of examples to analyse the ratio of lipid-bound to free analyte. Kramer et al. (1998) described the use of equilibrium dialysis by separating the liposome suspension and the water phase by a semi-permeable membrane. The analyte is dissolved in the water compartment of the system and diffuses into the liposome compartment. If equilibrium is reached, the remaining concentration of the analyte in the water compartment is determined by means of a quantification method (mainly HPLC or LCMS, fluorescence techniques) and the partition coefficient is calculated. Kramer et al. (1997) used a radio tracer substance as analyte to quantify the compound in both compartments using liquid scintillation counting. 

Reversed-phase high-performance liquid chromatography (RP-HPLC) is the usual method of choice for the separation of anthocyanins combined with an ultraviolet-visible (UV-Vis) or diode-array detector (DAD)(Hebrero et al., 1988 Hong et ah, 1990). With reversed-phase columns the elution pattern of anthocyanins is mainly dependent on the partition coefficients between the mobile phase and the Cjg stationary phase, and on the polarity of the analytes. The mobile phase consists normally of an aqueous solvent (water/carboxylic acid) and an organic solvent (methanol or acetonitrile/carboxylic acid). Typically the amount of carboxylic acid has been up to 10%, but with the addition of a mass spectrometer as a detector, the amount of acid has been decreased to as low as 1 % with a shift from trifluoroacetic acid to formic acid to prevent quenching of the ionization process that may occur with trifluoroacetic acid. The acidic media allows for the complete displacement of the equilibrium to the fiavylium cation, resulting in better resolution and a characteristic absorbance between 515 and 540 nm. HPLC separation methods, combined with electrochemical or DAD, are effective tools for anthocyanin analysis. The weakness of these detection methods is a lack of structural information and some nonspecificity leading to misattribution of peaks, particularly with electrochemical... 

The classical measurement of LogP is the shake flask method [17]. A known amount of drug is dissolved in a flask containing both octanol phase and aqueous buffer at controlled pH to ensure the existence of only nonionic form (at least two units from the drug pA) ). The flask is shaken to equilibrate the sample between two phases. There must be no undissolved substance present in both phases. After the system reaches its equilibrium, which is time- and temperature-dependent, the concentration of drug is analyzed by HPLC in both phases. Partitioning coefficient is calculated as... 

VII) The best or right n-octanol/water partition coefficients which were experimentally determined e.g. by the slow-stirring method or the HPLC method (in agreement with the OECD guideline) were used for establishing the QSAR. 

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