&EPA United States Environmental Protection Agency Environmental Research Laboratory Athens GA 30605 EPA 600 4 79 032 April 1979 Research and Development Determination of Octanol/Water Distribution Coefficients, Water Solubilities, and Sediment/Water Partition Coefficients for Hydrophobic Organic Pollutants ------- RESEARCH REPORTING SERIES Research reports of the Office of Research and Development. US. Environmental Protection Agency, have been grouped into nine series These nine broad cate- gories were established to facilitate further development and application of en- vironmental technology Elimination of traditional grouping was consciously planned to foster technology transfer and a maximum interface in related fields The nine series are. 1 Environmental Health Effects Research 2. Environmental Protection Technology 3. Ecological Research 4. Environmental Monitoring 5. Socioeconomic Environmental Studies 6 Scientific and Technical Assessment Reports (STAR) 7. Interagency Energy-Environment Research and Development 8. "Special" Reports 9 Miscellaneous Reports This report has been assigned to the ENVIRONMENTAL MONITORING series This series describes research conducted to develop new or improved methods and instrumentation for the identification and quantification of environmental pollutants at the lowest conceivably significant concentrations. It also includes studies to determine the ambient concentrations of pollutants in the environment and/or the variance of pollutants as a function of time or meteorological factors. This document is available'to the public through the National Technical Informa- tion Service, Springfield, Virginia 22161. ------- EPA-600/4-79-032 April 1979 DETERMINATION OF OCTANOL/WATER DISTRIBUTION COEFFICIENTS, WATER SOLUBILITIES, AND SEDIMENT/WATER PARTITION COEFFICIENTS FOR HYDROPHOBIC ORGANIC POLLUTANTS by Samuel W. Karickhoff and David S. Brown Environmental Processes Branch Environmental Research Laboratory Athens, Georgia 30605 ENVIRONMENTAL RESEARCH LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT U.S. ENVIRONMENTAL PROTECTION AGENCY ATHENS, GEORGIA 30605 ------- DISCLAIMER This report has been reviewed by the Environmental Research Laboratory, U.S. Environmental Protection Agency, Athens, Georgia, and approved for publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use. 11 ------- FOREWORD Environmental protection efforts are increasingly directed towards prevention of adverse health and ecological effects associated with specific compounds of natural or human origin. As part of this laboratory's research on the occurrence, move- ment, transformation, impact, and control of environmental con- taminants, the Environmental Processes Branch studies the microbiological, chemical, and physico-chemical processes that control the transport, transformation, and impact of pollutants in soil and water. Difficulties in determining octanol/water distribution coefficients, water solubilities, and sediment/water partition coefficients for certain organic pollutants produce discrep- ancies in studies by different investigators. This report discusses specific problems associated with each determination and suggests techniques that can eliminate potential sources of error. David W. Duttweiler Director Environmental Research Laboratory Athens, GA 111 ------- ABSTRACT Octanol/water distribution coefficients, water solubili- ties, and sediment/water partition coefficients are basic to any assessment of transport or dispersion of organic pollu- tants. In addition, these determinations are prerequisites for many chemical or biological process studies. In response to the accepted need for this type of data and in light of the widespread discrepancies in reported data, this report sets forth conventional methods of measurement and identifies pote i- tial sources of measurement error for these three physical properties. IV ------- CONTENTS Foreword iii Abstract iv 1. Introduction 1 2. Octanol/Water Distribution Coefficients 2 3. Water Solubility 7 4. Sediment/Water Partition Coefficients 10 References 14 v ------- SECTION 1 INTRODUCTION Octanol/water distribution coefficients, water solubili- ties/ and sediment/water partition coefficients involve the distribution of an organic solute between an aqueous phase and a second phase that might be loosely characterized as hydro- phobic (that is, octanol, organic crystals or liquid, or organ- ic components in the sediments). It is not surprising, then, that these three physical properties are highly correlated and have been interrelated quantitatively (Chiou, 1977; Leo, 1971; Briggs, 1973; Karickhoff, 1979). For hydrophobic solutes, these determinations are beset with difficulties that produce widespread discrepancies in studies by different investiga- tors. Contributing sources of error include: (1) low aqueous phase concentrations that may result in large analytical errors. (2) inadequate separation of crystalline, octanol, or sediment phases from the aqueous phase. (3) losses of solute from aqueous phase subsequent to phase separation — volatilization, photolysis, or handling losses including sorption to filters or containers. (4) incomplete equilibration — organic crystal/water and sorption equilibria commonly require hours or in some cases days to achieve. (5) the presence of solute impurities that are not analyt- ically distinguished from the "parent" compound. No general procedure for measuring these three physical properties is universally adaptable for all organic solutes. Numerous methods are available from the literature, but in most cases, they are tailored to meet time constraints or specific conditions of measurement or to suit specific compounds or sor- bents. This document discusses specific problems associated with each determination for hydrophobic solutes (that is, water solubility of a few parts per million or less) and suggests techniques that can eliminate or circumvent each of the diffi- culties or potential sources of error. ------- SECTION 2 OCTANOL/WATER DISTRIBUTION COEFFICIENTS The tendency of a neutral organic chemical to partition out of water into other environmental compartments containing hydrophobic constituents (that is, aquatic biota, sediments, or microorganisms) can be inferred from the octanol/water distri- bution coefficient (Kow) of the chemical. Although Kow provides an excellent base from which to estimate environmental partitioning behavior for most organic chemicals, the range in KOW (lo2 to lo6) nas perhaps the most utility for this purpose. Chemicals with Kow's less than 10^ will not partition into, or tend to accumulate in, any hydrophobic com- partment. Chemicals with Kow's in excess of 10° will tend to accumulate into any (or all) hydrophobic compartments. For chemicals outside this range, Kow can be categorized as < 10^ or > 106 with no further quantification. The procedure described here focuses on the range of Kow measurement, 10^ to 10^. Measurement of the Kow is an excellent first step in any sequence of physical measurements involving partitioning of hydrophobic compounds between water and a second phase. This physical measurement is useful because: (1) The measurement is fast; 15 minutes or less is required for system equilibration as opposed to a minimum of several hours for solubility or sorption measurements. (2) In most cases, a good estimate of the value of Kow can be easily computed from the works of Leo (1971 and 1975). This facilitates the measurement by estab- lishing the relative solvent volumes required for quantification of the solute in each phase. (3) For crystalline solutes, a three-phase measurement (octanol, water, solute crystals) provides a rapid measurement of water solubility. (4) Kow measurements also can be used to estimate solu- bility (Chiou, 1977; Hansch, 1968), sorption to sedi- ments (Briggs, 1973; Karickhoff, 1979), and biological accumulation (Southworth, 1978; Branson, 1975; Neely, 1974). ------- (5) Kow measurements can be used to identify elusive solute impurity problems that can affect other physi- cal measurements. The octanol/water distribution coefficient is the ratio of the equilibrium concentrations of the chemical in the two phases. By convention, the ratio of concentrations is ex- pressed as octanol over water. The concentrations are volume referenced (that is, mass or moles of chemical per unit volume of liquid) with the same units chosen for both phases. The standard temperature for measurement is usually 25°C. The basic technique for determination of Kow's was devel- oped by Hansch (1967) and Leo (1971). The following are exten- sions or refinements of this method for hydrophobic solutes. Reagent grade octanol is extracted once with 0.1 N NaOH, twice with distilled water, and distilled twice. This process removes the surfactant-type contaminants (primarily organic acids) that tend to create stable emulsions in water/octanol systems. The solutes are prepared in octanol at or near satu- ration concentrations for the solids or approximately 0.1M for liquids. (The 0.1M concentration is an arbitrary upper limit established to insure that the physical properties of the octanol phase not be altered significantly by the presence of the solute.) A small volume of this octanol solution (1 to 5 milliliters) is equilibrated with variable volumes of water (determined by the amount of compound required for analysis and thus the analytical sensitivity and water solubility of the compound). Equilibration is achieved by gentle shaking of the sample for approximately 15 minutes. For most solutes, the mixing is done in stainless steel centrifuge tubes with sealable caps. This minimizes solute losses by volatilization and handling (that is, sorption to vessels, etc.). Subsequent to equilibration, the samples are centrifuged at 10K for 10 minutes* (30 minutes if organic crys- tals are present), and the phases are sampled out of the cen- trifuge tubes. This phase sampling process is critical. A subsample of the octanol phase (usually one half or less of the total phase) is withdrawn by pipet and added directly into an analysis cell or diluting solvent suitable for analysis. The remainder of the octanol phase (and interfacial solute crystals if present) is removed prior to aqueous phase sampling. A aqueous phase sample is then withdrawn by pipet and the pipet stem is wiped to remove any droplets of water containing traces of excess octanol (picked up from the water surface) prior to discharging the water into an extraction solvent or analysis *Centrifugation conditions are given in units of K (10^) rpm in a Sorvall ss-34 rotor. ------- cell. The extraction solvent should not be allowed to contact the exterior of the pipet stem. Some solutes (generally with Kow's in excess of 106 and solubilities less than 1 part per billion) require an aqueous phase volume greater than 40 ml for solute analysis. These solutes are phase-equilibrated in separatory funnels, and transferred to centrifuge tubes, which have been prerinsed with a portion of the aqueous phase, for the final phase separa- tion. After centrifugation, aliquots are withdrawn from each tube (as in the procedure described previously) and recombined for extraction and analysis. Additional distribution ratios should be determined at reduced concentrations (that is, water concentrations £ half the water solubility). This is accomplished by dilution of the stock octanol solutions prior to mixing with water. Generally, the distribution coefficient is relatively independent of the solute concentration. If the Kow differs significantly (more than one standard deviation for replicate determinations) at the two solute levels, an intraphase inter- fering equilibrium (solute association or dissociation) is suggested. Changes in speciation must be accounted for and experimental conditions controlled accordingly, such that the partition coefficient of individual chemical species can be determined (Leo., 1971) . Acid-base "protolyses" equilibria are indicated by pH changes in the aqueous phase as a function of solute concentration. Buffered solutions should be used cover- ing a pH range sufficient to resolve the octanol/water parti- tioning of individual species. If association (aggregation) effects are suggested, the monomer Kow can be determined by reducing the solute concen- tration below the aggregation threshold concentration, which is experimentally determined by consecutive dilution. All determinations should be done in triplicate. The analysis method should be tailored to the compound in question; chromatographic methods are preferred because of their compound specificity in isolating the parent compound, free from inter- fering impurities. Large errors in the octanol/water distribution coefficient can be incurred as a result of traces of more-water-soluble contaminants that are not analytically distinguished from the parent compound. This problem is especially apparent when the analysis involves radiolabels or DV absorption spectroscopy (which can be very nonspecific for many solutes), but becomes far less important when chromatographic analysis is used. Regardless, the presence of contaminants can be easily checked by subjecting the solute-containing octanol phase to consecu- ------- tive extractions with water. The Kow should remain constant under consecutive extraction. The presence of a more-water- soluble impurity is indicated by a significant increase in Kow. The impurity can be removed by exhaustive extraction with water (that is, until the Kow is unchanged by further extractions). Also, chromatographic analysis can potentially isolate the parent compound and thus determine the Kow of the parent species. Only in rare cases would one expect the pres- ence of an impurity to affect significantly the true Kow of a chemical species. THREE-PHASE MEASUREMENT For solutes that are crystalline in the pure state, a crys- talline third phase often appears when a near saturated solute- octanol solution is mixed with water. The solubility of hydro- phobic solutes is decreased substantially by the equilibrium water content (2.3M at 25°C) in the octanol phase. The quan- tity of crystallized solute produced in this way is more than the amount required to saturate the aqueous phase even at water-to-octanol volume ratios as large as 100. This three- phase system equilibrates rapidly (10 to 20 minutes). After centrifugation (10K, 30 minutes) the crystalline phase is largely at the interface of the two liquid phases. The two liquid phases can be sampled (free of crystalline contamina- tion) as described previously. If the saturation concentra- tions of the chemical do not exceed 0.1M in either phase, the three-phase KQW will not differ appreciably from that mea- sured at lower solute levels, unless solute association occurs. Also, aqueous phase solute concentrations are within a few percentage points of measured aqueous phase solubilities. Apparently the octanol dissolved in the aqueous phase (0.0045M at 25°C) does not significantly affect the water solubility of these hydrophobic solutes. For hydrophobic solutes that are unstable in water and therefore cannot be equilibrated with water for long periods, the method provides a good means of getting a water solubility. For water-stable solutes, it pro- vides a quick estimate of the solubility. We have used these three-phase measurements only for polycyclic aromatic hydrocar- bons. This technique has not been tested for other families of compounds and has not been published. ALTERNATIVE METHODS The basic technique, as described earlier, is that of Leo (1971) and Hansch (1967). More recently, however, a new method of determining octanol/water partitioning utilizing high pres- sure liquid chromatography (HPLC) has been demonstrated by McCall (1975), Carlson (1975), and later by Mirrlees (1976), Veith (1978) and Dnger (1978). This method combines solute phase partitioning and analysis into a single step that permits a faster and, for many solutes, more precise determination of ------- hydrophobic/hydrophillic phase partitioning that can be direct- ly related to Kow. Briefly, the technique utilizes a chro- matographic column, the stationary phase of which contains functional groups (either as a coating substance or chemically bound on the surface) that simulate the octanol phase. In reverse phase liquid chromatography, the elution volume can be related to the partitioning of solute between the stationary and mobile phases. For solutes whose water solubilities are 1 ppm or greater, water (saturated with octanol) can be used as the mobile phase and octanol as the stationary phase coating, thereby providing a "direct" measurement of Kow. For com- pounds of lesser solubility, organo-water solutions (methanol/- water, acetonitrile/water) are used for elution and a station- ary phase matrix containing silanol groups is commonly used to simulate octanol. Solute partitioning in this system can be related to Kow through the use of calibration standards (com- pounds whose structure is similar to the compound to be mea- sured and whose Kow is known). With the continuous evolution of more sensitive liquid chromatographs, this technique pro- mises to become the most precise and reliable method of making partitioning measurements of this type. The technique poten- tially can circumvent the sources of error in Kow determina- tions described previously. To date, however, this technique is not available to all who need partitioning information and will not likely be so in the near future. ------- SECTION 3 WATER SOLUBILITY At first glance, determination of water solubility appears to be a simple task. In reality, solubility of crystalline hydrophobic compounds proves to be a most difficult physical property to measure. Hydrophobic liquids generally pose no real problem; water-solute equilibration is rapid (less than 8 hours) under gentle shaking. Equilibrium phase separation and solute analysis (and intrinsic problems typically encountered) are quite similar to those incurred in the water phase isola- tion and analysis of the octanol/water determination (discussed previously). Also, because hydrophobic liquids tend to be highly volatile in water, vapor phase methods of solute intro- duction and/or determination provide excellent solubility mea- surements (Farkas, 1965; McAuliffe, 1966 and 1969). Special measurement problems exist for polychlorinated bi- phenyls and polybrominated biphenyls because the components of these hydrophobic compounds may be crystalline in their pure form. The definition and measurement of water solubility for these compounds are discussed by Dexter (1978), Paris (1978), Schoor (1975), and Haque (1975). For hydrophobic crystalline compounds, the literature abounds with methods or recipes for measuring water solubili- ties, some of which go so far as detailing the effect on the measurement of size or shape of the container in which the com- pound is equilibrated (Campbell, 1930; Haque, 1975; Wauchope, 1972; Bowman, 1960; Mackay, 1975; Mackay, 1977; Biggar, 1967; Schoor, 1975). A real problem in solubility measurement centers around getting the crystalline material dissolved and equilibrated with the solution, and subsequently, isolating the solution phase, free of microcrystals or large solute aggregates. Handling problems (degradation, volatilization, sorption) asso- ciated with aqueous solutions of these materials are similar to those encountered in Kow determination and will not be read- dressed here. The time required for compound equilibration is primarily a function of the method used to introduce the crystals into the water. Some methods prescribe adding the crystalline compounds ------- to water as large "chunks" with subsequent stirring extending for days or even weeks; this is done specifically to minimize the formation of microcrystals that are difficult to remove effectively without perturbation of the solute concentration. Although this time-consuming process may prove necessary for some compounds, it is impractical for many applications and unsuitable for compounds that tend to be unstable in water over the required time frame. A much quicker and more facile proce- dure for introducing the crystalline material (Haque, 1975) involves "coating" the compound (in excess of the amount re- quired to saturate the water) out of a volatile solvent onto the walls of the container used for equilibration. Potential solvents include hexane, isooctane, methylene chloride, ethyl ether, etc. The vessel containing the compound (dissolved in a minimal amount of solvent) is rotated on its side, allowing the solvent to evaporate and thus plate the solute onto the con- tainer walls. The crystalline form varies with the choice of solvent. The best choice (achieved by trial and error) seems to be that which deposits the most translucent crystalline film on the container. Chalky films produce excessive microcrystal loading of the aqueous phase. After the crystalline compound has been "suitably" coated onto the container, membrane- filtered (0.2 micrometer pore size) water is added and the "solution" stirred or swirled gently under controlled tempera- ture conditions. After 24 hours of agitation, aliquots of aqueous phase from which microcrystals have been removed are analyzed periodically until a maximum solute concentration is achieved. Crystalline material can be removed from the aqueous phase by quiescent settling, centrifuging, or filtering. Quiescent settling requires no additional handling but is time consuming and may not be adequate for many compounds. Centrifugation should be in glass or stainless steel tubes that have been pre- rinsed with aliquots of the aqueous phase. Centrifugation time and speed are rather arbitrary; generally 30 minutes at 10K will suffice. It should be established that additional centri- fugation does riot remove appreciable compound from the "solu- tion" phase. If filtration is used, consecutive aliquots of filtrate should be analyzed until a constant solute response is obtained, indicative that the solute is not being further sorbed by the filter material. Suitable filter materials include glass microfiber filters—such as the Whatman, GF/F—or halocarbon membranes such as those manufactured by Chemplast, Inc., Wayne, NJ. (Two or more filters in series may be re- quired in some instances.) If filtration or centrifugation are used, care must be taken to avoid appreciable handling-induced temperature fluctuations in the aqueous samples. For many crystalline solutes whose solubilities are a few parts per billion or less, these conventional techniques give 8 ------- at best a coefficient of error of 0.2 to 0.3 in replicate determinations (coefficient of error = standard deviation/ mean). Measurement by two different techniques or in different laboratories commonly agree within a factor of 2. ALTERNATIVE METHODS Three Phase Measurement For many applications, the solubility determined in the octanol-water-crystalline system (described previously) is ade- quate. Although this technique remains untested for a wide variety of compounds, its speed and ease-of-use make it most attractive in lieu of the conventional alternatives. HPLC Method As in the case of KQW determination, a new HPLC method of measuring water solubilities of hydrophobic organic compounds has recently been reported (May and Wasik, 1978). In this pro- cedure, a saturated aqueous solution is prepared by passing water through a column filled with glass beads onto which the compound has been "plated" out of a volatile solvent (similar to the procedure described in conventional method). A measured aliquot of the saturated solution is passed through a resin column suitable for trapping the compound. The collected com- pound is then eluted from the resin with an organic solvent (or mixture of solvents) directly into the chromatograph for solute analysis. This method is fast and potentially circumvents all the difficulties commonly encountered with classical methods. The method has been tested on only a few polycyclic aromatic hydrocarbons; solubilities determined by this method tended to be 20 to 40% lower than those measured by conventional methods. The HPLC technique, however, may well prove to be the most accurate and precise method for this difficult determination. ------- SECTION 4 SEDIMENT/WATER PARTITION COEFFICIENT The sediment/water partition coefficient (Kp) is the slope of the linear portion of the equilibrium sorption iso- therm.* For hydrophobia compounds, sorption isotherms are approximately linear at equilibrium aqueous solute concentra- tions below one-half of the distilled water solubility of the compound. This linear portion of the isotherm generally passes through the origin with no significant portion of irreversibly bound sorbate. Also, for dilute suspensions (< 1% dry weight solids) the Kp is relatively independent of sediment concen- tration. In general, a Kp determination should involve the mea- surement of at least two points on the linear portion of the isotherm. This is accomplished by equilibrating two aqueous concentrations of solute with a fixed concentration of sediment at a fixed temperature.' For these hydrophobic compounds, the choice of amounts of solute and/or sediment required is greatly facilitated by a computed Kp estimate (Karickhoff, 1979) whereby Kp = 0.6 Kow [O.C.] where Kow is a measured or computed octanol/water distribu- tion coefficient, and [O.C.] is the fractional mass of organic *By convention, sorption isotherms have sorbed concentrations of compound (computed relative to dry-mass sorbent) given by the ordinate and solution phase compound concentrations given on the abscissa. In expressing the compound concentrations in the two phases, units equivalent in mass are chosen for water and sediment. That is, if the sorbed compound concentration is expressed as microgram of sorbate per kilogram of sorbent, the solution concentration would be given as microgram of solute per liter of solution. tin soils system (in addition to batch suspension methods) sorption is commonly measured by passing a solute solution through a column packed with soil (Davidson, 1968). Although this technique could be used for sediment sorption, hydrophobic solutes (especially those with solubilities < 10 ppb) would pose a severe problem with conventional column techniques. 10 ------- carbon in the sediment. The choice of sediment concentrations is rather arbitrary, but one should choose large enough sedi- ment samples to insure adequate analytical precision and if possible allow sediment concentrations to approach naturally occurring levels. As was the case with solubility determination, many possi- ble recipes for sediment processing and sorption measurement are available. In general, natural sediments should be sieved to remove plant debris or pebbles larger than 2 mm. Samples should be air-dried and ground to uniform texture (free of clumps) and cool-stored (5 to 15°C) until used. Minimal characterization should include particle size distribution (at least sand, silt, and clay) and organic carbon content. If possible, organic carbon should be determined on each particle size isolate. For characterization procedures, one should con- sult Jackson (1956) and other soils procedures manuals (Ameri- can Society of Agronomy monograph series, Agronomy #9). For more hydrophillic chemicals (in particular, organic compounds with potentially ionizable functional groups) sorp- tion may be affected significantly by the hydrogen-ion concen- tration (pH), the redox potential (Eh), and the cation exchange capacity of the sediment. This introduces sediment collection, handling, and storage problems because these properties vary significantly with aeration and may change irreversibly upon drying. Sorption measurement can generally proceed by one of two mixing methods. (1) Direct mixing — Aliquots of aqueous stock solution of the hydrophobia compounds are mixed with sediment sus- pensions and shaken until equilibrium is achieved. Equilibration, as judged by sequential sampling is generally complete (to within experimental error) in 8 hours, but the sample should be allowed to mix for at least 24 hours, unless the compound shows significant attenuation losses over this period. (2) Compound plating — Many hydrophobic compounds (those having solubility less than 0.1 ppm) are difficult to prepare, handle, and store in aqueous solutions. Also these compounds tend to be highly sorbed, and thus when an aqueous solution of the compound is mixed with sediment, the aqueous phase solute concentration may drop to a small fraction of the initial concentration, and in the presence of the natural organic background, solute analysis in the aqueous phase may pose a severe analytical difficulty. These problems can often be circumvented by plating the compounds out of volatile solvents (as described in solubility determination) 11 ------- onto the containers in which sediment is to be equili brated. Sediment suspensions can then be added and gently swirled until equilibration is achieved. This step requires at least 24 hours under these condi- tions; 48 hours should be allowed if possible. Subsequent to compound- sediment equilibration (regardless of mixing procedure), the suspensions are phase separated, by filtering or centrifuging, and the compound concentration in each phase is determined. The degree of phase separation required may or may not be critical depending upon the magni- tude of the Kp. At equilibrium, the fraction of compound sorbed (F) is given by F ' P where p is the sediment concentration (expressed in equivalent mass units as described earlier) . After centrif ugation or fil- tration, a sediment concentration (remaining in the "water" phase) equal in magnitude to l/Kp will produce a factor of 2 error in the measured water phase concentration. For most compound/sediment systems, centrif ugation at 20K for 60 minutes or filtration through filters (0.2 ym or less in pore size) should suffice. In sampling and processing the aqueous phase component, many of the same experimental difficulties (attenuation and handling losses) discussed in the sections on Kow and solu- bility measurements, are encountered, and require similar tech- niques and precautionary measures. In general, handling should be minimized, vessels prerinsed, filters preequilibrated, etc. The sediment phase compound analysis can be a direct deter- mination (labeled compounds) or the compound can be isolated from the sediment for analysis. Many compounds are difficult to extract from natural sediments. Adequate recovery often requires prolonged use of continuous extraction or sonication of the sediment in the presence of the extraction solvent. ALTERNATIVE METHODS For the measurement of solubility and Kow, the most at- tractive recent methodology involved the use of "flow-through" HPLC integrated methods in lieu of the conventional techniques involving batch-equilibration followed by phase isolation and analysis. In the case of Kp measurement, however, no such technological breakthrough has occured. 12 ------- Alternative techniques that show promise include: (1) The previously described soil-column technique that uses high pressure (such as is availble to HPLC) and membranes or microporous glass fibers to adequatly remove the sediment fines from the flow-through water. (2) A flow-through suspension system (Grice, 1972) that involves the flowing (or circulating) of solute-con- taining solution through a suspended sediment retained in a column by membranes or filters. As with the pre- vious technique, the proper choice of membranes and the use of high pressures could adapt this technique to hydrophobic compounds. (3) A three-phase method (Hance, 1977) that involves the equilibration of compound in a three-phase system (water, sediment, and a water-immiscible organic sol- vent) . The sediment/water partition coefficient of the compound is derived from its measured concentra- tion in the organic phase, coupled with a knowledge of the distribution coefficient of the compound between water and the organic phase. Hance (1976) used this technique in low-moisture soil systems from which a water-phase sample could not easily be isolated for analysis. Potentially this method could be used to estimate sediment-water partitioning for hydrophobic compounds for which a direct water phase measurement of solute is not easily accessible analytically. 13 ------- REFERENCES Biggar, V., G. Dutt, and R. Riggs. 1967. Predicting and Mea- suring the Solubility of pp'DDT in Water. Bull. Environ. Contain. Toxicol. 2(2):90-100. Bowman, M., F. Acree, and M. Corbett. 1960. Solubility of Carbon-14 DDT in Water. J. Agri. Food Chem. 8(5):406-408. Branson, D., W. Neely, and G. Blau. 1975. Predicting a Bio- concentration Potential of Organic Chemicals in Fish from Partition Coefficients. Proc. Symp. on Structure-Activity Correlations, in Studies of Toxicity and Bioconcentration with Aquatic Organisms. Burlington, Ontario. G. Veith and D. Koneasewich, eds. International Joint Comm. pp. 99-118, Briggs, G. 1973. A Simple Relationship Between Soil Sorption of Organic Chemicals and Their Octanol/Water Partition Coefficients. Proc. 7th British Insecticide and Fungicide Conf. 11:475-478. Campbell, A. 1930. An Apparatus for the Determination of Solubility. J. Chem. Soc. London, Part I. pp. 179-180. Carlson, R., R. Carlson, and H. Kopperman. 1975. Determina- tion of Partition Coefficients by Liquid Chromatography. J. Chromatog. 107:213-223. Chiou, C., V. Freed, D. Schmedding, and R. Kohnert. 1977. Partition Coefficient and Bioaccumulation of Selected Organic Chemicals. Environ. Sci. Technol. 11(5):475-478. Davidson, J. M. and P. Santelmann. 1968. Displacement of Fluometuron and Diuron Through Saturated Glass Beads and Soil. Weed. Sci. 16:544-548. Dexter, R. and S. Pavlou. 1978. Mass Solubility and Aqueous Activity Coefficients of Stable Organic Chemicals in the Marine Environment: Polychlorinated Biphenyls. Marine Chem. 6:(in press). Farkas, E. 1965. New Method for Determination of Hydrocarbon- in-Water Solubilities. Anal. Chem. 37(9):1173-1174. 14 ------- Grice, R. and M. Hayes. 1972. A Continuous Flow Method for Studying Adsorption and Desorption of Pesticides in Soils and in Soil Colloid Systems. Proc. llth Br. Weed Control Conf. pp. 784-790. Hamaker, J. and J. Thompson. 1972. Adsorption. Chapter 2 in Organic Chemicals in the Soil Environment, Vol. I. C. A. Goring and J. Hamaker, eds. Marcell Dekker, Inc., New York. pp. 49-143. Hance, R. 1976. The adsorption of Atraton and Monuron by Soils at Different Water Contents. Weed Res. 17:197-201. Hansch, D. and S. M. Anderson. 1967. The Effect of Intra- molecular Hydrophobic Bonding on Partition Coefficients. J. Org. Chem. 23:2583. Hansch, C., J. Quinlan, and G. Lawrence. 1968. The Linear Free-Energy Relationship Between Partition Coefficients and the Aqueous Solubility of Organic Liquids. J. Org. Chem. 33:347-350. Haque, R. and D. Schmedding. 1975. A Method of Measuring the Water Solubility of Hydrophobic Chemicals: Solubility of Five Polychlorinated Biphenyls. Bull. Environ. Contain. Toxicol. 14:13-18. Jackson, M. L. 1956. Soil Chemical Analysis-Advanced Course. Univ. of Wisconsin Press, Madison. Karickhoff, S., D. Brown, and T. Scott. 1979. Sorption of Hydrophibic Pollutants on Natural Sediments. Water Research 13(2):241-248. Leo, A. 1975. Calculation of Partition Coefficients Useful in the Evaluation of the Relative Hazards of Various Chemicals in the Environment. Proc. Sym. on Structure-Activity Correlations in Studies of Toxicity and Bioconcentration with Aquatic Organisms, Burlington, Ontario. G. Veith and D. Konasewich, eds. International Joint Comm. pp. 151-176. Leo, A., C. Hansch, and D. Elkins. 1971. Partition Coeffi- cients and Their Uses. Chemical Rev. 71(6):525-616. Mackay, D. and W. Shiu. 1975. The Determination of the Solu- bility of Hydrocarbons in Aqueous Sodium Chloride Solutions. Canadian J. Chem. Eng. 53:239-242. May, W. and S. Wasik. 1978. Determination of the Aqueous Solubility of Polynuclear Aromatic Hydrocarbons by a Coupled Column Liquid Chromatographic Technique. Anal. Chem. 50(1):175-179. 15 ------- McAuliffe, C. 1966. Solubility in Water of Paraffin, Cyclo- paraffin, Olefin, Acetylene, Cycloolefin and Aromatic Hydrocarbons. J. Phys. Chem. 70 (4) :1267-1275. McAuliffe, C. 1969. Solubility in Water of Normal Cg and Alkane Hydrocarbons. Science. 163:478-479. McCall, J. 1975. Liquid-liquid Partition Coefficients by High Pressure Liquid Chroma tography. J. Med. Chem. 18(6) :549-552. Methods of Soil Analysis. 1965. Agronomy 9f Parts 1 and 2. American Society of Agronomy. C. Black, ed. Madison, Wisconsin. Mirrlees, M. , S. Moulton, C. Murphy, and P. Taylor. 1976. Direct Measurement of Octanol-Water Partition Coefficients by High-pressure Liquid Chroma tography. J. Medicinal Chem. 19(5) :615-619. Neely, W. , D. Branson, and G. Blau. 1974. Partition Coeffi- cient to Measure Bioconcentration Potential of Organic Chemicals in Fish. Environ. Sci. Technol. 8:1113-1115. Paris, D. F., W. C. Steen, and G. W. Baughman. 1978. Role of Physico-chemical Properties of Aroclor 1016 and 1242 in Determing Their Fate and Transport in Aquatic Environ- ments. Chemosphere. 7 (4) :319-325. Schoor, W. 1975. Problems Associated with Low-solubility Compounds in Aquatic Toxicity Tests: Theoretical Model and Solubility Characteristics of Aroclor 1254 in Water. Water Res. 9:937-944. Southworth, G. , J. Beauchamp, and P. Schmieder . 1978. Bio- accumulation Potential of Polycyclic Aromatic Hydrocarbons in Daphnia Pulex. Submitted to Water Research. Unger, S. H., J. Cook, and J. Hollenberg. 1978. Simple Procedure for Determining Octanol-Aqueous Partition, Distribution, and lonization Coefficients by Reversed-phase High-pressure Liquid Chroma tography. J. Pharm. Sci. 67(10) :1364-1367. Veith, G. D., and R. T. Morris. 1978. A Rapid Method for Estimating Log P for Organic Chemicals. Report EPA- 600/3-78-049, U.S. Environmental Protection Agency, Duluth, MN. 15 p. Wauchope, R. and F. Getzen. 1972. Temperature Dependence of Solubilities in Water and Heats of Fusion of Solid Aromatic Hydrocarbons. J. Chem. Eng. Data. 17(1):38-41. 16 ------- TECHNICAL REPORT DATA (Please read Instructions on the reverse before completing) 1. REPORT NO. EPA-600/4-79-032 3. RECIPIENT'S ACCESSION-NO. 4. TITLE AND SUBTITLE Determination of Octanol/Water Distribution Co- efficients, Water Solubilities, and Sediment/ Water Partition Coefficients for Hydrophobic 5. REPORT DATE April 1979 issuing date 6. PERFORMING ORGANIZATION CODE I?. AUTHOR^) Organic Pollutants Samuel W. Karickhoff and David S, Brown 8. PERFORMING ORGANIZATION REPORT NO 9. PERFORMING ORGANIZATION NAME AND ADDRESS Environmental Research Laboratory-Athens, GA Office of Research and Development U.S. Environmental Protection Agency Athens, GA 30605 10. PROGRAM ELEMENT NO. 1BB770 11. CONTRACT/GRANT NO. 12. SPONSORING AGENCY NAME AND ADDRESS Environmental Research Laboratory-Athens, GA Office of Research and Development U.S. Environmental Protection Agency Athens, GA 30605 13. TYPE OF REPORT AND PERIOD COVERED 14. SPONSORING AGENCY CODE EPA/600/01 15. SUPPLEMENTARY NOTES 16. ABSTRACT Octanol/water distribution coefficients, water solubilities, and sediment/water partition coefficients are basic to any assessment of transport or dispersion of organic pollutants. In addition, these determinations are prerequisites for many chemical or biological pro- cess studies. In response to the accepted need for this type of data and in light of the widespread discrepancies in reported data, this report sets forth conventional methods of measurement and identifies potential sources of measurement error for these three physical pro- perties. 7, KEY WORDS AND DOCUMENT ANALYSIS DESCRIPTORS b.lDENTIFIERS/OPEN ENDED TERMS c. cos AT i Field/Group Solubility Sorption Sediments Measurement Octanol/water 07D 8. DISTRIBUTION STATEMENT Release to Public 19. SECURITY CLASS (ThisReport) Unclassified 21. NO. OF PAGES 23 20. SECURITY CLASS (Thispage) Unclassified 22. PRICE EPA Form 2220-1 (9-73) 17 ft U.S. Gownnwnl Printing Office 1479 — &S7-O60/SM3 ------- |