f/EPA
United States
Environmental Protection
Agency
Environmental Research
Laboratory
Duluth MN 55804
EPA-600 3-78-049
May 1978
Research and Development
A Rapid Method
for Estimating Log P
for Organic
Chemicals
-------
RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. 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 ECOLOGICAL RESEARCH series. This series
describes research on the effects of pollution on humans, plant and animal spe-
cies, and materials. Problems are assessed for their long- and short-term influ-
ences. Investigations include formation, transport, and pathway studies to deter-
mine the fate of pollutants and their effects. This work provides the technical basis
for setting standards to minimize undesirable changes in living organisms in the
aquatic, terrestrial, and atmospheric environments.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
-------
EPA-600/3-78-049
May 1978
A RAPID METHOD FOR ESTIMATING LOG P
FOR ORGANIC CHEMICALS
by
Gilman D. Veith
Environmental Research Laboratory - Duluth, MN 55804
Richard T. Morris
University of Wisconsin-Superior, WI 54880
ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
DULUTH, MINNESOTA 55804
-------
DISCLAIMER
This report has been reviewed by the Environmental Research Laboratory-
Duluth, U.S. Environmental Protection Agency, and approved for publication.
Mention of trade names or commercial products does not constitute endorsement
or recommendation for use.
ii
-------
FOREWORD
Many of the test protocols for screening organic chemicals for potential
harmful effects in the environment rely on correlations of known effects with
physical properties of the chemicals. The partition coefficient of a chemical
in an n-octanol/water system provides insight into the tendency of chemicals
to accumulate in lipoid tissues, to adsorb onto particulate matter coated with
natural organic material, and to resist biodegradation. Specific correlations
exist between the partition coefficient (expressed as Log P), the water
solubility, and the bioconcentration factor of organic chemicals in fish.
This report sets forth a rapid, inexpensive method for estimating Log P,
which will greatly enhance screening tests for evaluating the potential
hazards of chemicals in the environment.
iii
-------
ABSTRACT
A rapid, inexpensive technique based on reverse-phase high pressure
liquid chromatography has been developed to estimate the n-octanol/water
partition coefficient of organic chemicals. The system consists of a
preparative Micro-Pak C-10 Qy reverse-phase column eluted with a 15 percent
water/85 percent methanol solvent flowing at 2 ml/min at room temperature.
The chemicals are detected in the eluant with a standard ultraviolet detector
or a fraction collector system followed by appropriate analysis of the
fractions to determine the retention time of the chemical. A linear
calibration of the logarithm of retention time with the logarithm of the
partition coefficient (Log P) is attained by using a mixture of benzene,
bromobenzene, biphenyl, bibenzyl, pp'DDE, and 2,4,5,2',5' pentachlorobiphenyl
as reference standards of known Log P- Chemicals with Log P of approximately
3 elute in less than 10 min whereas those with Log P greater than 5 elute
after 20 min.
iv
-------
CONTENTS
Foreword iii
Abstract iv
Figures vi
Tables vii
Acknowledgments viii
1. Introduction 1
2. Conclusions 3
3. Recommendations 4
4. Experimental Procedures ; . . 5
Liquid chromatography conditions 5
Test solutions 6
Calibration mixture 6
5. Results and Discussion 7
Correlation of Log P and HPLC retention 7
Calculation of Log P 10
HPLC estimation of Log P 10
References 15
v
-------
LIST OF FIGURES
Number Page
1 Verification of the dependency of the HPLC relative retention
time on the Log P for 47 organic chemicals 9
2 Relationship between Log P and HPLC log retention time of the
calibration mixture ... 12
VI
-------
TABLES
Number Page
1 Retention data of a variety of chemicals obtained by using
gradient elution reverse-phase HPLC 8
2 HPLC retention times and partition coefficients for organic
chemicals used for calibration » 11
3 Comparison of estimated Log P values with reported Log P values
for 18 organic chemicals 14
VII
-------
ACKNOWLEDGMENTS
The assistance of Ned Austin in the early development of this technique
is sincerely appreciated and acknowledged. Also, we thank Donald I. Mount
for his encouragement and support of this work on rapid screening techniques.
viii
-------
SECTION 1
INTRODUCTION
The use of the n-octanol/water partition coefficients (expressed as Log
P) has become the cornerstone of predicting the biological effects of organic
chemicals from physical properties through the use of structure-activity
correlations (1, 2). The Log P value has become a critical physical property
for predicting toxicity to aquatic organisms (3), bioconcentration factors
for fish (4), and water solubility (5). Moreover, adsorption of chemicals
in sewage sludges and organic particulate matter and the biodegradability of
organic chemicals appear to be related to the Log P value.
Several methods can be used for measuring or estimating P. The obvious
method is to mix the chemical with n-octanol and water, shake the biphasic
system to assure equilibrium, and measure the concentration of the chemical
in the two phases. The value of P is calculated as the ratio of the
concentration in the octanol and the concentration in the water. This
method can be laborious because emulsions are formed and analytical methods
are needed for each chemical in at least one of the phases. The use of
radiolabeled chemicals simplifies the analytical problems, but it may greatly
increase the cost of the measurement. Also, chemicals with Log P of 4 and
greater (10,000 times more in the octanol than water) cannot be measured with
the same precision as chemicals that distribute more evenly, and highly lipid
soluble chemicals are those of great concern in environmental hazard assessment.
Another drawback to measuring P is that the measurement cannot be done
reliably when dealing with mixtures of chemicals of unknown identity, such as
would be encountered in complex effluents, because the bulk of the organic
constituents may alter the solvent-system behavior.
If the structure of a chemical is known, Log P can be estimated from
substituent constants as discussed by Hansch and Fujita (7). This is probably
the best initial step in determining Log P since it can be done without
experimentation and is quite reliable for many common organic chemicals.
However, for some functional groups the substituent-constant approach is
not yet completely reliable (Personal Communication, 1977, A. Leo, Pomona
College, Claremouht, Calif.) Moreover, the structure of the chemicals must
be known, which precludes this approach from use in assessing potential
hazards of complex effluents, landfill leachates, or other uncharacterized
mixtures of chemicals.
The objectives of this study were to determine if Log P and the high
pressure liquid chromatography (HPLC) reverse-phase retention time are
related by using a wide variety of industrial chemicals, and, if so, to
develop a method for estimating Log P by using HPLC, The results are
-------
summarized in this report, and a method of estimating Log P is suggested
which alleviates some of the problems discussed above. The constraints on
this research were that the method be inexpensive, require less than 1 hr
of laboratory time, and provide an acceptable measure of Log P-
-------
SECTION 2
CONCLUSIONS
The logarithm of the retention time (Log RT) of organic chemicals on a
permanently bonded (C-18) reverse-phase high pressure liquid chromatography
system is linearly related to the logarithm of the n-octanol/water partition
coefficient (Log P). The relationship is summarized by the equation Log
P = 5.106 Log RT - 1.258 with a correlation coefficient 0.975.
By using a calibration mixture, the Log P of other organic chemicals
were estimated with a mean accuracy of 22.8 percent compared to Log P
values reported in the literature. The technique permits estimation
of Log P in a maximum of 25 min and does not require a knowledge of
the structure of the chemical for the estimate.
-------
SECTION 3
RECOMMENDATIONS
1. The correlation between the estimates of Log P from the technique presented
in this report and the Log P values from direct measurement is presently
limited by the number of chemicals tested, particularly high lipophilic
chemicals. Additional work is needed to expand the correlation and set
confidence intervals for estimates of Log P by this indirect method.
2. The relationship between the dissociation constant of organic chemicals
and the estimation of Log P by this indirect method is needed to evaluate
the comparatively large discrepancies between estimated and literature
Log P values for such chemicals.
-------
SECTION 4
EXPERIMENTAL PROCEDURES
Reverse-phase liquid chromatography is a separation process in which
chemicals are injected onto a column of fine particles coated with a
nonpolar (water-insoluble) oil and then eluted with a polar solvent such as
water or methanol. Recent developments in this field have produced a
permanently bonded reverse-phase column in which long-chain hydrocarbon groups
are chemically bonded to the column packing material resulting in a much more
reproducible separation. The chemicals injected are moved along the column
by partitioning between the mobile phase and the stationary hydrocarbon phase.
Provided the residual polar groups on the packing can be kept at a minimum,
mixtures of chemicals can be eluted in order of the hydrophobicity, with water-
soluble chemicals eluted first and the oil-soluble chemicals last in proportion
to their hydrocarbon/water partition coefficient. These experiments were
intended to determine the relationship of the retention time on this reverse-
phase column and the n-octanol/water partition coefficient.
LIQUID CHROMATOGRAPHY CONDITIONS
The liquid chromatograph was a Varian 4200 instrument equipped with two
5,000-pai. pumps and a high pressure stopflow,injector. The column was a Varian
Micropak-'C-10 analytical reverse phase column (250 mm x 2 mm I.D.) or a
Preparative Micropak—'C-H column (250 mm x 8 mm I.D.), which consists of a
stainless tube filled with 10-y Lichrosorb to which octadecylsilane is
permanently bonded. The detector was a 254-nm ultraviolet detector with a
8-yl cell volume and 1-cm path length. The detector was interfaced with a
Hewlett-Packard computer for retention-time determination. For chemicals
that cannot be detected by the ultraviolet detector, a fraction collector
was used to collect fractions at 1.0-min intervals for analysis by gas
chromatography, liquid scintillation, or other suitable techniques.
The analytical column was operated at 50 C with a constant temperature
bath. The solvent was programmed from 22 percent methanol in water initially
to 75 percent methanol in water at a rate of 2 percent/min. The solvent
flow rate was maintained at 20 ml/min at a pressure of approximately 2,500 psi.
The preparative column was operated at ambient temperature. The column
was eluted isocratically with a mixture of water and methanol (15:85, v/v)
which was pumped through the column at 2.0 ml/min at a pressure of
approximately 1,200 psi.
-------
TEST SOLUTIONS
Chemicals to be tested were dissolved in a mixture of acetone and
cyclohexane (3:1, v/v), which was found to be suitable for compounds over a
wide range of water solubility. Because only the retention time of the
chemical,' which is independent of concentration in dilute solutions, is
used in this method, the quantity of individual chemicals in the solution
was adjusted to give a chromatographic peak of at least 25 percent of the
recorder scale.
CALIBRATION MIXTURE
Six chemicals for which Log P has been reported were used to calibrate
the elution time in units of Log P- The calibration mixture includes
benzene, bromobenzene, biphenyl, bibenzyl, pp'DDE, and 2,4,5,2',5'
pentachlorobiphenyl. The Log P values selected from the literature for
these chemicals were 2.13, 2.99, 4.09, 4.81, 5.69, and 6.11, respectively.
(References for Log P values are given in Table 1.)
-------
SECTION 5
RESULTS AND DISCUSSION
CORRELATION OF LOG P AND HPLC RETENTION
Previous work at this laboratory (6) has shown that the reported values
of Log P for a wide variety of organic chemicals are correlated to the
retention volume of the chemical in the reverse-phase HPLC column. The data
obtained by using the gradient elution with the analytical column (2 mm I.D.)
are summarized in Table 1. In this table, the retention volume, K, is
corrected for minor column variations by using phenol as an internal standard
and setting its retention equal to 1.00. The log K values are presented
relative to the K value of phenol.
The Log P values were taken from Leo, Hansch, and Elkins (8) except for
those of the PCB. Because thesS formulations (the Aroclor's) consist as
mixtures, the log K values are presented .as ranges of values obtained
for the major component peaks observed in the HPLC chromatograms. The Log P
values for PCB's are those provided by Chiou et al. (5) for PCB's having
three to six chlorine atoms per molecule. The Log P values used for the
Aroclor's were: Aroclor 1016 and Aroclor 1242, 5.58; Aroclor 1248, 6.11;
and Aroclor 1254, 6.72 (Table 1). Although these values are only approximations,
the possible deviation must be small since the entire range for these PCB's
is small.
The data in Table 1 were analyzed by a family regression procedure as
illustrated in Figure 1. The data can best be summarized by power function
of Log P = a(log K) , where a and b are constants with r2 for the correlation
equal to 0.870. Although this variance may seem somewhat large, the
correlation includes ketones, aldehydes, phenols, aromatic amines, ethers,
aromatic hydrocarbons, and a variety of chlorinated hydrocarbons that span
over six orders of magnitude of lipophilic properties. The relationship
between Log P and log K is best approximated with a power function because
of the solvent gradient used with the analytical column to optimize resolution.
The solvent gradient increases the methanol concentration during the analysis,
and the retention of highly lipophilic chemicals is less than that which
would have resulted by using a constant solvent composition.
Having demonstrated a strong correlation between Log P and the HPLC relative
retention time, the secondary objectives of developing a simple method for cal-
culating Log P from retention times and reducing the cost of the analysis were
pursued. The use of phenol as an internal standard was judged too tedious, and
the non-linear correlation resulting from the gradient elution increased both
the cost and the complexity of the analysis. The use of isocratic elution
-------
TABLE 1. RETENTION DATA OF A VARIETY OF CHEMICALS OBTAINED
BY USING GRADIENT ELUTION REVERSE-PHASE HPLC
Chemical
Hydroquionone
m- Amino ph eno 1
Resorcinol
Catechol
Phenol
o-Amino phenol
4-Methoxyphenol
Aniline
Benzyl Alcohol
o-Toludine
4-Nitrophenol
o-Anisidine
Benzaldehyde
3-Methylphenol
2 -Ph eny 1 e thano 1
4-Methylphenol
Indole
o-Chloroaniline
Benzene
n-Methylaniline
Acatophenone
Cinnamyl Alcohol
4-Chlorophenol
Anisole
2 s 4-Dimethylphenol
Dimethylphthalate
1-Naphthol
3-Methyl-4-Chlorophenol
2 s 4-Dichlorophenol
Pentachloro phenol
4-Phenylphenol
Diethylphthalate
Naphthalene
2,4, 5-Trichlorophenol
Diphenylamine
Diphenyl ether
Anthracene
n,n-Dibutylphthalate
p,p '-Methoxyclor
Endrin
p,p'-DDD
p,p'-DDT
Hexachlorobenzene
Aroclor 1016
Aroclor 1242
Aroclor 1248
Aroclor 1254
K (phenol=1.00)
0.27
0.36
0.36
0.73
1.00
1.00
1.17
1.18
1.40
1.82
1.83
2.00
2.18
2.25
2.27
2.33
2.45
2.48
2.50
2.90
3.18
3.32
3.73
4.00
4.00
5.42
6.46
7.04
8.73
10.42
11.46
12.45
12.65
14.27
14.36
18.50
22.33
24.45
39.81
39.82
41.70
44.69
52.50
35.50-51.30
25.50-60.29
35.50-60.28
35.50-69.20
Log K
(phenol=0.00)
-0.564
-0.439
-0.439
-0.138
0.000
0.000
0.067
0.073
0.146
0.260
0.263
0.301
0.338
0.352
0.357
0.368
0.390
0.395
0.398
0.464
0.503
0.521
0.571
0.602
0.602
0.734
0.810
0.848
0.941
1.018
1.059
1.095
1.103
1.154
1.157
1.267
1.344
1.388
1.600
1.600
1.620
1.650
1.72
1.55-1.71
1.55-1.78
1.55-1.78
1.55-1.84
Log P
0.59
0.17
0.80
0.95
1.46
0.62
1.34
0.98
1.10
1.32
1.91
0.95
1.48
1.96
1.60
1,94
2.25
1.92
2.13
1.82
1.58
1.95
2.39
2.11
2.36
2.11
2.98
3.10
3.08
5.01
3.37
3.15
3.37
3.72
3.50
4.21
4.45
5.15
4.20
4.56
6.02
6.19
6.18
5.58
5.58
6.11
6.72
-------
Benzene
Phenol ». •
Methoxychlor
Naphthalene
Figure 1.
-0.5 0.0 0.5 IO 1.5
Log K (PhenohO.OO)-HPLC
Verification of the dpendency of the HPLC relative retention time on the Log P for
47 organic Chemicals.
2.0
-------
resulted in a linear correlation and the development of a simple calibration
mixture to replace the internal standard. Although the analysis time increases
when the isocratic elution is used, substantial savings are possible because
it eliminates the need for one of the HPLC pumps and the electronic solvent
programming module (approximately 50 percent of the instrument costs). Finally,
preparative scale reverse-phase columns produce linear calibration curves with
shorter overall retention times at pressures of only 1,200 psi. This column
offers the additional advantage of a larger loading capacity which is needed
for analysis of complex effluents.
CALCULATION OF LOG P
The calibration mixture is chromatographed on the preparative column, and
a calibration curve is prepared daily to eliminate small differences due to
flow rate or temperature and to follow the retention properties of the column
during prolonged use. The calibration is made by plotting the Log P versus
the logarithm of the absolute retention time (Log RT)- Figure 2 presents the
data from Table 2 in the form of the calibration curve. The relationship
between Log P and log RT can be fitted equally well by using a linear or a
parabolic function when these data are plotted. However, the linear regression
is more convenient to use in daily calculations, and differences between the
linear and exponential models appear only if Log P is estimated by extrapolating
beyond the range of Log P values used in the calibration.
The data in Figure 2 can be summarized with the equation Log P = 5.106
Log RT - 1.258, with a correlation coefficient of 0.975. The relative
standard deviations of the slope, intercept, and correlation coefficient of
seven calibration curves during a 2-week period were approximately 1 percent,
14 percent, and 0.1 percent, respectively. It must be emphasized that this
correlation is limited in regard to being representative of the organic
chemicals encountered. The calibration mixture was selected largely on the
basis of Log P values reported in the literature, and the correlation appears
to be linear over five orders of magnitude of this chemical property. Although
the accuracy of the estimates might be more convincing if several hundred
chemicals were presented in the correlation, it would be unmanageable to
prepare such a calibration mixture and use it daily in the calibration of
the liquid chromatograph.
HPLC ESTIMATION OF LOG P
To determine the accuracy of the calibrated liquid chroma tographic method
of estimating Log P by comparison with data reported in the literature, the
retention times of 18 chemicals, including the standards, were determined, and
the Log P values'were calculated from, the regression equation. Table 3 presents
the results of these estimates. The data show that Log P can be estimated with
a mean -accuracy of .22.5+20.1 percent, of the values reported in the literature.
obtained by using other methods. The percent error in Table 3 was calculated
assuming that the literature value is the correct value for Log P. The mean
absolute error in Log P for this set of chemicals was 0.64. This error is
approximately twice the error that can be expected by calculation with the
10
-------
TABLE 2. HPLC RETENTION TIMES AND PARTITION COEFFICIENTS
FOR ORGANIC CHEMICALS USED FOR CALIBRATION
Chemical
Benzene
Bromobenzene
Biphenyl
Bibenzyl
pp'DDE
2,4,5,2' ,5' penta-
chlorobiphenyl
Retention
time (min)
4.12
7.09
8.85
15.87
21.98
31.58
Log RT
0.615
0.851
0.947
1.201
1.342
1.499
Log P (ref.)
2.13
2.99
3.76a
4.813
5.69
6.11
(7)
(5)
(7)
(7)
(5)
(5)
Mean of Log P values reported.
11
-------
-------
substituent constants approach (Leo, personal communication); However, the
structure of the chemical need not be known to estimate the lipophilic
properties with the HPLC method.
Table 3 also shows that some of the greatest relative errors are observed
with polar chemicals which dissociate in water. The data indicate that the
dissociation of ionizable polar groups is more significant than adsorption
interactions since chemicals such as m-chlorobenzoic acid, 2,4,5-trichlorophenol,
and diphenylomine elute more rapidly than would be expected from their respective
Log P values. One explanation of this observation is that these chemicals
are dissociated in the unbuffered solvent and behave, in part, as ions in the
elution. This may be corrected by selecting a series of buffer solvents for
organic acids and bases which assure that the chemical would be in the
un-ionized form. However, considerable research is required before a
rationale involving buffer systems can be evaluated with a broad range of
chemicals.
13
-------
TABLE 3. COMPARISON OF ESTIMATED LOG P VALUES
WITH REPORTED LOG P VALUES FOR 18 ORGANIC CHEMICALS
Chemical Reported Log
o-Toluidine
Benzaldehyde
Nitrobenzene
p-Nitrophenol
Dime thy Iphthalate
Benzene
Indole
m-Chlorobenzoic acid
Bromobenzene
Methoxychlor
Naphthalene
Diphenylamine
2,4, 5-Tr ichlorophenol
Biphenyl
Anthracene
p , p ' -DDE
2, 4, 5, 2', 5' PCB
Hexachlorobenzene
1.32
1.48
1.86
1.91
2.11
2.13
2.25
2.68
2.99
4.20
3.41
3.50
3.72
3.76
4.45
5.69
6.11
6.18
Estimated Absolute
P Log P deviation
1.63
2.33
1.82
1.35
3.40
2.39
1.66
0.89
2.92
3.82
3.17
2.37
2.39
3.75
3.45
5.83
6.44
7.42
Mean Standard Deviation
0.31
0.85
0.04
0.56
1.29
0.26
0.59
1.79
0.07
0.42
0.24
1.13
1.33
0.01
1.00
0.14
0.33
1.24
0.64+0.54
Percentage
deviation
23.5
47.7
2.2
29.3
61.1
12.2
26.2
66.8
2.3
10.0
7.0
30.4
35.6
0.3
22.5
2.5
5.4
20.1
22.5+20.1
14
-------
REFERENCES
1. Gould, R. F., editor. 1972. Biological Correlations - The Hansch Approach.
Adv. Chem. Ser. #114. American Chemical Society, Washington, D.C.
2. Veith, G. D., and D. E. Konasewich. 1975. Structure-Activity Correlations
in Studies of Toxicity and Bioconcentration with Aquatic Organisms.
International Joint Commission Publication, Windsor, Ont. 347 p.
3. Carlson, R. M., H. L. Kopperman, and R. E. Carlson. Structure Activity
Relationships Applied. See Reference 2. p. 57-72.
4. Neely, W. G., D. R. Branson, and G. E. Blau. 1974. The Use of the
Partition Coefficient to Measure the Bioconcentration Potential of
Organic Chemicals in Fish. Environ. Sci. Technol. j^, 1113-1115.
5. Chiou, C. T., V. H. Freed, D. W. Schmedding, and R. L. Kohnert. 1977.
Partition Coefficient and Bioaccumulation of Selected Organic Chemicals.
Environ. Science & Technol. 11(5): 475-478.
6. Veith, G. D., and N. Austin. 1976. Detection and Isolation of Bioaccumulable
Chemicals in Complex Effluents. In p. 297-302. Identification and
Analysis of Organic Pollutants in Water (L. H. Keith, [eidtor]) Ann
Arbor Science Publishers, Inc., Ann Arbor, Michigan.
7. Hansch, C., and T. Fujita. 1964. A Method for the Correlation of Biological
Activity and Chemical Structure. J. Am. Chem. Soc. 86: 1616-1626.
8. Leo, A., C. Hansch, and D. Elkins. 1976. Partition Coefficients and
Their Uses. Chem. Rev. 71: 525-616.
15
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
REPORT NO.
EPA-600/3-78-049
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
A Rapid Method for Estimating Log P for
Organic Chemicals
5. REPORT DATE
May 1978 issuing date
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Oilman D. Veith
Richard T. Morris*
8. PERFORMING ORGANIZATION REPORT NO,
9. PERFORMING ORGANIZATION NAME AND ADDRESS
10. PROGRAM ELEMENT NO.
IBA608
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
ENVIRONMENTAL RESEARCH LABORATORY-DULUTH MN
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
DULUTH, MINNESOTA 55804
55804
13. TYPE OF REPORT AND PERIOD COVE RED
In House
14. SPONSORING AGENCY CODE
EPA/600/03
15. SUPPLEMENTARY NOTES
*University of Wisconsin-Superior, WI 54880
16. ABSTRACT
A rapid, inexpensive technique based on reverse-phase high pressure
liquid chromatography has been developed to estimate the n-octanol/water
partition coefficient of organic chemicals. The system consists of a
preparative Micro-Pak C-10 reverse-phase column eluted with a 15 percent
water/85 percent methanol solvent flowing at 2 ml/min at room temperature.
The chemicals are detected in the eluant with a standard ultraviolet detector
or a fraction collector system followed by appropriate analysis of the
fractions to determine the retention time of the chemical. A linear
calibration of the logarithm of retention time with the logarithm of the
partition coefficient (Log P) is attained by using a mixture of benzene,
bromobenzene, biphenyl, bibenzyl, pp'DDE, and 2,4,5,2',5' pentachlorobiphenyl
as reference standards of known Log P. Chemicals with Log P of approximately
3 elute in less than 10 min whereas those with Log P greater than 5 elute
after 20 min.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
Chromatography
Chemical Detection
partition coefficients
hazard evaluation
n-octanol/water
Log P
lipid solubility
99A
68D
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
24
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION is OBSOLETE
U.S. GOVERNMENT PRINTING OFFICE: 1978-767-140/1306
------- |