Air Systems - American

19

P a r t i t i o n of Organoelements in O c t a n o l / W a t e r / A i r Systems

Downloaded by UNIV LAVAL on July 13, 2016 | http://pubs.acs.org Publication Date: January 12, 1979 | doi: 10.1021/bk-1978-0082.ch019

STANLEY P. WASIK Chemical Thermodynamics Division, National Bureau of Standards, Washington, DC 20234

Introduction The ability of organic compounds to bioconcentrate in the marine environment was found to be dependent upon the partition behavior of molecules between l i p i d and aqueous phases (1,2). The organic/water partition coefficient is defined as the ratio of the concentration of a chemical in the organic solvent to its concentration in water under equilibrium conditions in an organic solvent/ water system. Neely, Branson, and Blau (1) demonstrated that bioconcentration factors for chlorobenzenes and chlorophenols in trout muscles from water containing low levels of these compounds could be successfully correlated with their partition coefficients in the n-octanol/water system. Dunn and Hansch (3) compiled hydrophobic interactions of a large number of organic compounds and showed that these interactions quantitatively correlated with partition coefficients of organic/water systems. Leo (4) suggested that hydrophobicity, as measured by the noctanol/water partition coefficient, is the most important parameter in bioaccumulation and biotransport. The role of hydrophobicity in non-biological transport may not be dominant but should, nonetheless, be important. Although values for the n-octanol/ water partition coefficient have been reported in the literature for over 10,000 compounds, there is a large number of environmentally significant molecules that are absent. One group of molecules for which the n-octanol/water partition coefficient have not been reported is the organometal compounds.

This chapter not subject to U.S. copyright. Published 1978 American Chemical Society Brinckman and Bellama; Organometals and Organometalloids ACS Symposium Series; American Chemical Society: Washington, DC, 1979.

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Partition of Organoelements

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Wasik and coworkers (5,6) reported a method f o r determining the w a t e r / a i r p a r t i t i o n c o e f f i c i e n t from measurements o f the c o n c e n t r a t i o n of the s o l u t e i n the head-space i n e q u i l i b r i u m w i t h the l i q u i d phase. I n t h i s paper, a r e presented, by a s i m i l i a r method, our measurements o f the n-octanol/water p a r t i t i o n c o e f f i c i e n t s of dimethylmercury i n d i s t i l l e d and sea water over a temperature range of 0-25°C. The apparatus i s described and the v a r i o u s f a c t o r s e f f e c t i n g the p r e c i s i o n and accuracy of the p a r t i t i o n c o e f f i c i e n t s a r e discussed.


Experimental Methods and C a l c u l a t i o n s Apparatus. A schematic diagram o f the apparatus and the e q u i l i b r a t i o n c e l l used to measure the w a t e r / a i r p a r t i t i o n c o e f f i c i e n t i s shown i n F i g u r e 1. The g l a s s e q u i l i b r a t i o n c e l l of volume V which contains a volume, V L , o f the aqueous s o l u t i o n and a s m a l l volume of the gas phase, V = V - V , i s contained i n a water bath where the temperature i s c o n t r o l l e d t o w i t h i n 0.01°C. The gas c i r c u l a t i n g pump was constructed from a s t a i n l e s s s t e e l bellows (7.6 χ 3 cm) by the NBS shop. The bellows was enclosed i n a s t a i n l e s s s t e e l j a c k e t and was d r i v e n by p u l s a t i n g compressed a i r w i t h a duty c y c l e of 3 seconds. The a i r - s o l u t e mixture was pumped i n t o the apparatus through the 1/16-inch tube connecting the check v a l v e w i t h the 4-port gas v a l v e . The two g l a s s check v a l v e s were made by the NBS g l a s s shop. The pump c i r c u l a t e d the a i r - s o l u t e vapor through a 6-port gas sampling v a l v e . By s w i t c h i n g t h i s v a l v e , a s m a l l sample volume of the gas phase ( V = 0.1 cm ) can be sent t o the gas chromatograph f o r a n a l y s i s without i n t e r r u p t i n g the c i r c u l a t i o n of the a i r s o l u t e mixture. The gas mixture i s then d i r e c t e d t o a 4-port gas v a l v e which i n the c l o s e d - p o s i t i o n passes the gas phase back to the pump, and i n the open p o s i t i o n d i r e c t s the gas mixture through the e q u i l i b r a t i o n c e l l and then back t o the pump. The components of the apparatus a r e connected together w i t h 1/16i n c h s t a i n l e s s s t e e l tubing and commercial tubing connectors. The t o t a l volume o f the pump, v a l v e s , and t u b i n g , V R , i s 85.25 cm . T h i s p a r t of the apparatus i s contained i n an a i r bath a t 100 + 0.05°C. The e q u i l i b r a t i o n c e l l used t o measure the o c t a n o l / a i r p a r t i t i o n c o e f f i c i e n t was constructed i n the form o f a U; the bottom p a r t of the U was a g l a s s r e c t a n g u l a r tube ( 4 x 1 x 1 cm) and the two s i d e arms were g l a s s tubes (1/4-inch 0D χ 3 cm). The c e l l was connected t o the 4-port v a l v e w i t h 1/16-inch tubing and commercial reducing f i t t i n g s . The n-octanol (saturated w i t h water) was weighed i n the c e l l and the volume o f the s o l u t i o n was c a l c u l a t e d from i t s d e n s i t y . The n-octanol was deposited on the bottom of the c e l l and the a i r - s o l u t e mixture c i r c u l a t e d above i t . The volume of the c e l l was 4.821 cm . T

c

t

L

3

s

3

3

Brinckman and Bellama; Organometals and Organometalloids ACS Symposium Series; American Chemical Society: Washington, DC, 1979.


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Figure 1. Schematic showing equilibration cell and apparatus for determination of water/air partition coefficients



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317

Before assembly, the s t a i n l e s s s t e e l p o r t i o n s of. the apparatus were cleaned w i t h t r i c h l o r o e t h y l e n e ; the g l a s s p a r t s were washed w i t h 10 percent (by weight) aqueous HF and r i n s e d s e v e r a l times w i t h d i s t i l l e d water. The chromatgraphic column was a Scot column (15 m χ 0.5 mm ID) prepared w i t h f i n e l y ground diatomaceous e a r t h on a fused support and coated w i t h a mixture o f m-bis-(m-phenoxylphenoxyl) benzene and Apiezon L. The e f f l u e n t gas was monitored by a hydrogen flame d e t e c t o r and an e l e c t r o n i c i n t e g r a t o r was used to measure the peak areas. Commercial n-octanol was p u r i f i e d by successive washings w i t h HC1, w i t h d i l u t e sodium b i c a r b o n a t e s o l u t i o n , and f i n a l l y w i t h d i s t i l l e d water. The n-octanol, d r i e d w i t h sodium s u l f a t e , was d i s t i l l e d under reduced pressure. The d i s t i l l e d sample was found by gas chromatography to be 99.97 mole percent n - o c t a n o l . The water used i n the p r e p a r a t i o n of s o l u t i o n s was doubly d i s t i l l e d over potassium permanganate. The p u r i t y o f the commercial diethylmercury and dimethylmercury was determined by gas chromato graphy t o be 99.4 mole percent. The compound was used without f u r t h e r p u r i f i c a t i o n . The a r t i f i c i a l sea water was prepared a c c o r d i n g to a r e c i p e g i v e n by Sverdrup e t §1 (7) and had a c h l o r i d i t y v a l u e o f 19.0 percent. The c h l o r i d i t y i s the t o t a l amount o f c h l o r i n e , bromine, and i o d i n e ( i n grams) contained i n 1 k g o f sea water where bromine and i o d i n e are replaced by chlorine. n-Octanol/Water P a r t i t i o n C o e f f i c i e n t . Consider a system composed o f two i m m i s c i b l e l i q u i d phases, n-octanol and water, and a gas phase, a i r , i n t o which v o l a t i l e s o l u t e vapor i s i n t r o d u c e d . L e t the e q u i l i b r i u m c o n c e n t r a t i o n o f the s o l u t e i n the a i r be CA» i n the o c t a n o l (saturated w i t h water) be C , and i n the water ( s a t u r a t e d w i t h o c t a n o l ) be C ^ . The octanol/water p a r t i t i o n c o e f f i c i e n t , K(o,w), i s d e f i n e d as the r a t i o 0 /0^ the w a t e r / a i r p a r t i t i o n c o e f f i c i e n t , K(w/a), as


The procedure may be repeated i number of times g i v i n g the expression

K ( W / A )

=

W

W

1 ) V

-

Λ

L ~ "

( 8 )

when i s the s o l u t e peak area a t the itîl e q u i l i b r i u m . l y i t can be shown that

V T R

A

/

l

A

i

"

[

C

±

T (K(w/a)V + V R L c D

+

1

]

_

Similiar-

Λ (

9

)

T

or

log^/A.)

=

[

( i - l)log

I^

V

+

V

+

«

( 1

°> R L c T h i s method f o r determining K(w/a) i s the " s o l u t e e x t r a c t i o n method." P a r t i t i o n C o e f f i c i e n t s a t D i f f e r e n t Temperature. I t i s p o s s i b l e to obtain K(w/a) a t various temperatures i n terms of the values a t some reference temperature, Τ . This can be done simply by measuring the r e l a t i v e s o l u t e p a r t i a l pressure i n the gas phase a t d i f f e r e n t temperatures of the e q u i l i b r a t i o n c e l l . Consider the system i n e q u i l i b r i u m w i t h the l i q u i d phase a t T T( K (

Q

P

V

T

P

R

Ο n

t

.

~RÏ~

=

V

T

P

c

Ο

+

.

K(w/a)V

L

Ο

~R¥~

+

R

T

/ π \

RT

ο

ο

where Ρ i s the p a r t i a l pressure of the s o l u t e and K(w/a) i s known fr8m e i t h e r a s o l u t e absorption or a s o l u t e extraction experiment. When the temperature of the l i q u i d phase i s changed to Τ τ

T

1

P

n

t

=

V

T R

τ Τ

P +

+

P

V

T c

I T

+ +

T

K ( W / A )

RT

V

T L (

1

2

)

R

where P^, i s the p a r t i a l pressure of the s o l u t e a t temperature Τ and K(w/a) i s the water/air p a r t i t i o n c o e f f i c i e n t . Combining T


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equations (11) and (12), s u b s t i t u t i n g Aq> /Ap f o r P /P^ and solving f o r K(w/a) ° ° T

T

V Τ K(w/a)

T

=

V A_ Τ (A^ /A^ - 1) + ^ - ( A /A^ - 1) + ο K(w/a) L R ο L ο T o ° T

τ

A

( χ 3 )

T

In determining K(w/a)x by t h i s method, a s m a l l c o r r e c t i o n should be made f o r V and due to the change i n d e n s i t y of the l i q u i d phase. T h i s method f o r determining K(w/a)m i s the "temperature v a r i a t i o n method." In d e r i v i n g equations ( 4 ) , ( 7 ) , and (13), the example was f o r a s i n g l e s o l u t e system. I n p r a c t i c e many s o l u t e s may be used i n the system as long as they are a t very low c o n c e n t r a t i o n s and can be separated by gas chromatography. N e i t h e r of these c o n d i t i o n s presents a s e r i o u s experimental problem. n-Octanol/Air P a r t i t i o n C o e f f i c i e n t . The o c t a n o l / a i r p a r t i t i o n c o e f f i c i e n t , K ( o / a ) , was measured by e i t h e r the s o l u t e a b s o r p t i o n , s o l u t e e x t r a c t i o n , or the temperature v a r i a t i o n method d e s c r i b e d above except t h a t the U-shaped e q u i l i b r a t i o n c e l l was used i n p l a c e of the bubble c e l l . The U-shaped c e l l was designed to keep V s m a l l and to be a b l e to weigh o c t a n o l conveniently.


c

c

Results Values f o r K(w/a), K ( o / a ) , and K(o/w) f o r dimethyImercury i n d i s t i l l e d and sea water are given i n t a b l e s I and I I , r e s p e c t i v e l y . Absolute values of K(w/a) and K(o/a) i n d i s t i l l e d water were determined u s i n g the s o l u t e a b s o r p t i o n method a t two tempera t u r e s , 15.42 and 5.38°C. Values of K(w/a) and K(o/a) at other temperatures were obtained u s i n g the temperature v a r i a t i o n method. Absolute values of K(w/a) and K(o/a) i n sea water were determined a t two temperatures 18.42 and 6.42°C. The remaining K(w/a) and K(o/a) were obtained u s i n g the temperature v a r i a t i o n method. The numbers i n parentheses are the standard d e v i a t i o n s of the p a r t i t i o n c o e f f i c i e n t s . No K(o/w) values f o r dimethyImercury are reported i n the l i t e r a t u r e . I n order to compare K(o/w) v a l u e s measured i n t h i s work w i t h l i t e r a t u r e v a l u e s , we determined K(o/w) f o r benzene (132), toluene (482), and ethylbenzene (1420) i n d i s t i l l e d water at 25°C. The values may be compared w i t h those v a l u e s measured Hansch et a l ( 8 ) , e.g., benzene (135), toluene (490), and e t h y l benzene (1413). Discussion The main cause of the spread i n the K(w/a) and K(o/a) v a l u e s a r i s e from d i s p e r s i o n s i n the peak area measurements by the e l e c t r o n i c i n t e g r a t o r . This spread was reduced by t u r n i n g the c i r c u l a t i n g pump o f f before sample i n j e c t i o n i n t o the gas


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TABLE I

Dime thy Imercury P a r t i t i o n C o e f f i c i e n t s i n D i s t i l l e d Water K(w/A) K(o/W) K(o/A)

Temp. (°C)

Number o f Observations

5.38

6

12.41(.050)

1800(6.2)

145.0(.76)

8.02

6

10.5K.041)

1590(5.4)

151.4(.78)

10.40

8

9.11(0.41)

1435(5.4)

157.1(.91)

13.10

7

7.82(.038)

1272(4.8)

162.6(.99)

15.42

6

6.80(.049)

1160(3.9)

170.6(1.08)

18.62

6

5.71(.031)

1004(3.9)

175.8(1.1)

20.00

9

5.25(.032)

950(3.6)

180.9(1.2)

24.48

6

4.13(.028)

790(3.4)

191.3(1.3)

TABLE I I

DimethyImercury P a r t i t i o n C o e f f i c i e n t s i n Sea Water Temp. (°C)

Number o f Observations

K(w/A)

6.42

7

8.52(.041)

1720(9.1)

201.9(1.4)

10.02

6

6.82(.034)

1466(6.2)

215.0(1.4)

13.08

7

5.68(.030)

1282(5.2)

225.7(1.5)

15.64

7

4.90(.022)

1151(5.1)

234.9(1.5)

18.42

8

4.15(.021)

1010(5.0)

243.4(1.7)

20.00

6

3.82(.017)

950(4.4)

248.7(1.6)

25.00

6

2.88(.011)

760(3.6)

263.9(1.6)

K(o/W)

K(o/A)



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chromatograph. A group of 30 observations of dimethyImercury peak areas was found to have a c o e f f i c i e n t of v a r i a t i o n of 0.75 percent w i t h the pump on w h i l e the same number of observations gave a v a r i a t i o n of 0.15 percent w i t h the pump o f f . The pump was conveniently turned o f f by stopping the supply of compressed a i r to the pump. I n the methods described above f o r measuring K(o/a) and K(w/a), the term (Α/Αχ - 1) appears i n equations ( 4 ) , ( 7 ) , and (13). The e r r o r , p a r t i c u l a r l y i n the K(w/a) c a l c u l a t i o n s , may be l a r g e f o r s m a l l values of A/A^. This e r r o r may be reduced by choosing the volume of the l i q u i d phase such t h a t A/A^ i s l a r g e . In p r a c t i c e , s e v e r a l e q u i l i b r a t i o n c e l l s of d i f f e r e n t volumes should be a v a i l a b l e f o r t h i s use. T h i s e r r o r may a l s o be reduced by the proper choice of the method used f o r measuring K(w/a). For i n s t a n c e , the volume of the e q u i l i b r a t i o n c e l l used i n t h i s study was 114.2 cm w i t h the l i q u i d volume, V L , equal to 112.2 cm . Using the s o l u t e a d s o r p t i o n method f o r dimethylmercury i n d i s t i l l e d water a t 16.02°C i t was found that A/A = 10.217 (K(w/a) = 6.00). An e r r o r of 0.50 percent i n A/AJL r e s u l t e d i n a 0.549 percent e r r o r i n K(w/A). Under the same experimental c o n d i t i o n s the s o l u t e e x t r a c t i o n method gave A/A^ = 1.098, r e s u l t i n g i n an e r r o r of 5.31 percent i n K(w/a). I f , under the same experimental con d i t i o n s , a s o l u t e w i t h K(w/a) = 0.10 was measured u s i n g the s o l u t e e x t r a c t i o n method; A/A^ would equal 6.00 r e s u l t i n g i n an e r r o r of 0.7% i n K(w/a) whereas the s o l u t e a b s o r p t i o n method would g i v e A/A^ = 1.20 and an e r r o r of 3.5 percent. I n g e n e r a l , the s o l u t e a b s o r p t i o n method i s p r e f e r r e d f o r K(w/a) values g r e a t e r than u n i t y , w h i l e the s o l u t e e x t r a c t i o n method i s p r e f e r r e d f o r K(w/a) values l e s s than u n i t y . A p o s s i b l e systematic e r r o r i s t h a t a s i g n i f i c a n t f r a c t i o n of the s o l u t e vapor could be adsorbed on the surface of the apparatus r a t h e r than i n the gas phase. To evaluate t h i s e f f e c t , the e x t r a c t i o n f a c t o r (equation 10, where V = 0, V = V ) f o r the dry apparatus was examined f o r dimethylmercury over a 1000f o l d c o n c e n t r a t i o n range by repeatedly e x t r a c t i n g the gas i n VR. V Τ The slope l o g Γ + 1] of the p l o t log(A../A.) versus i - 1 was Τ R l i n e a r and equal to the c a l c u l a t e d v a l u e . Two such experiments a t a i r bath temperature of 100°C and 50°C gave the same r e s u l t s . These experiments i n d i c a t e t h a t surface a d s o r p t i o n was a n e g l i g i b l e f a c t o r i n the K(w/a) and K(o/a) measurements and t h a t the hydrogen flame d e t e c t o r was l i n e a r over the s o l u t e c o n c e n t r a t i o n range measured. The same experiments were repeated w i t h methane as the s o l u t e and gave s i m i l i a r r e s u l t s . In an i d e n t i c a l experiment w i t h diethyImercury as the s o l u t e i t was observed t h a t the s o l u t e peak area d i d not o b t a i n a constant value but decreased w i t h time. Two i m p u r i t y peaks; one i d e n t i f i e d by gas chromatography as η-butane and one as 3

3

x

L

C

T

c

1

1



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p o s s i b l y ethane increased i n time. Lowering the a i r - b a t h temperat u r e from 100° to 50°C slowed the thermal decomposition of d i e thy Imercury but d i d not stop i t . These experiments were done i n the absence of l i g h t i n order to r u l e out well-known photodecomposition processes ( 9 ) . The methods described i n t h i s paper f o r measuring K(w/a) and K(o/a) a r e a p p l i c a b l e to compounds having a vapor pressure g r e a t e r than 0.10 T o r r . For compounds w i t h vapor pressures l e s s than 0.1 Torr a d s o r p t i o n of the s o l u t e on the w a l l s of the apparatus would probably lead to erroneous values of K(w/a) and K(o/a). I n any case, f o r compunds having low vapor pressures o r compounds that adsorb s t r o n g l y on s u r f a c e s , the procedure described above should be used to determine the extent of s u r f a c e adsorption. Using Neely jet a l (1) l i n e a r r e g r e s s i o n equation t o c o r r e l a t e the o c t a n o l p a r t i t i o n c o e f f i c i e n t w i t h b i o c o n c e n t r a t i o n of chlorohydrocarbons i n t r o u t muscle we c a l c u l a t e d a b i o c o n c e n t r a t i o n f a c t o r of twenty f o r dimethylmercury i n f r e s h water. T h i s presumes that the l i p o p h i l i c i t i e s of dimethylmercury and the chlorohydrocarbons e i t h e r occur by s i m i l i a r processes o r t h a t the molecular d i f f e r e n c e s are not that important i n r a t e - d e t e r m i n i n g uptake s t e p s . The K(o/w) values f o r dimethylmercury a r e approximately 37 percent g r e a t e r i n sea water than f r e s h water which would i n d i c a t e that the b i o c o n c e n t r a t i o n f a c t o r i s g r e a t e r i n sea water than i n f r e s h water.


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Literature Cited 1. Neeley, W. Β., Branson, D. R., and Blau, G. Ε., Environ. S c i . Technol. 8, 1113 (1974). 2. Branson, D. R., et al., Proceedings of Symposium Structure Activity Correlations in Studies of Toxicity and Bioconcentration with Aquatic Organisms, Canada Center for Inland Waters, Burlington, Ontario, Canada (1975).


3.

Dunn, W., and Hansch, C . , J. Pharm. S c i . 61, 1 (1972).

4. Leo, A. J., Symposium on Nonbiological Transport and Trans formation, National Bureau of Standards, Gaithersburg, MD (1976). 5. Wasik, S. P . , Brown, R. L., and Minor, J. I., J. Environ. Sci. Health A11(1), 99 (1976). 6. Brown, R. L., and Wasik, S. P . , J. of Res. National Bureau of Standards 78A, 453 (1974). 7. Sverdrup, H. V . , Johnson, M. W., and Fleming, R. Η . , The Oceans Prentice-Hall, Inc., Englewood C l i f f s , New Jersey (1942). 8. Hansch, C . , Quinlan, J. Ε . , and Lawrence, G. L., J. Organic Chem. 33, 347 (1968). 9. Rebbert, R. E., and Steacic, E . W. R., Can. J. Chem. 31, 631 (1953).

Discussion F. E . BRINCKMAN (National Bureau of Standards): By doing the linear free energy relationship as a function of temperature one can generate a thermodynamic property, in this case, the heat of solution. This is a very important concern for organometal chem i s t s who do not have such information for these kinds of species. Experimentally, what kind of v o l a t i l i t y do you need i f you want to do a system as a function of salinity and temperature; for example, one of these organotin species which has ionic properties and strongly solvates in water? WASIK: We have other methods of determining these partition coefficients. This is what we c a l l our volatile solute method. Roughly, i t ' s good for solutes of a boiling point less than 200 . Above 200 we have to use l i q u i d chromatography as a detector. Q

G. E . PARRIS (Food and Drug Administration): People who do partition coefficients, such as octanol-water, where they put the


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WASIK


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two phases i n d i r e c t c o n t a c t , a r e u s u a l l y concerned about there being some water s o l u b i l i t y i n o c t a n o l and some o c t a n o l s o l u b i l i t y i n water. How much d i f f e r e n c e does i t make doing i t i n d i r e c t l y where you a c t u a l l y measure (or can get a c a l c u l a t e d v a l u e ) f o r w a t e r - o c t a n o l , as opposed t o w a t e r - s a t u r a t e d o c t a n o l versus o c t a n o l - s a t u r a t e d water?


WASIK: We d i d the experiment where we determined the octano l - a i r p a r t i t i o n c o e f f i c i e n t i n o c t a n o l s a t u r a t e d w i t h water and i n o c t a n o l ; there was about 2% d i f f e r e n c e . The o c t a n o l - a i r p a r t i t i o n c o e f f i c i e n t can a l s o be measured by gas chromatography by measuring the r e t e n t i o n time of the s o l u t e . PARRIS: I s t h i s f i g u r e of 2% t y p i c a l i n view of the heats of s o l v a t i o n f o r d i f f e r e n t types of molecules or do you t h i n k i t might v a r y w i d e l y ? WASIK: solute.

Of course

i t would vary w i d e l y a c c o r d i n g t o the

J . S. THAYER ( U n i v e r s i t y of C i n c i n n a t i ) : What a r e the prope r t i e s o f o c t a n o l that make i t a d e s i r a b l e s o l v e n t f o r use i n t h i s p a r t i c u l a r study? WASIK: From the p h y s i c a l chemical s t a n d p o i n t , i t ' s a poor choice. We would have been b e t t e r o f f w i t h something l e s s v o l a t i l e and l e s s s o l u b l e . Water i s f a i r l y s o l u b l e i n o c t a n o l . But I t h i n k people j u s t kept measuring i t and measuring i t , and i t s c o n v e n t i o n a l use grew. Once you measure the octanol-water part i t i o n c o e f f i c i e n t of a parent compound then you can p r e d i c t the octanol-water c o e f f i c i e n t f o r d e r i v a t i v e s . I f you know a coeff i c i e n t f o r benzene, you could p r e d i c t that i t would be f o r x y lenes and butylbenzene because they show a d d i t i v e p r o p e r t i e s . You don't a c t u a l l y have t o measure a l o t of compounds as long as you measure the parent compound. A. J . CANTY ( U n i v e r s i t y of Tasmania): Your comment j u s t then and the p a r t i t i o n c o e f f i c i e n t f o r dimethylmercury r e l a t e t o some work that we have been doing i n v e s t i g a t i n g b o d i l y d i s t r i b u t i o n of phenyl compounds. You would expect a s i m i l a r r e l a t i o n s h i p of p a r t i t i o n c o e f f i c i e n t s f o r diphenyImercury t o dimethylmercury. We f i n d that i n t r a p e r i t o n e a l i n j e c t i o n of diphenyImercury, compared w i t h monophenyImercury, shows a 10 t o 20 times h i g h e r c o n c e n t r a t i o n i n f a t t y t i s s u e which would correspond f a i r l y w e l l w i t h your partition coefficients. M. L. GOOD ( U n i v e r s i t y of New O r l e a n s ) : Are these head-space experiments the same techniques that you use f o r determining the v o l a t i l e m a t e r i a l s from a b a c t e r i a l m e t h y l a t i o n procedure?


326

ORGANOMETALS AND

WASIK:

ORGANOMETALLOIDS

L i k e Dr. Brinckman does?

GOOD: Yes.


WASIK: the system.

I b e l i e v e h i s head-spaces a r e i n e q u i l i b r i u m w i t h Do you c i r c u l a t e the v o l a t i l e gases?

BRINCKMAN: We have done both s t a t i c and c i r c u l a t i o n measure ments. Our problem i s d e t e c t o r s e n s i t i v i t y . With some m i c r o organisms, p a r t i c u l a r l y the ρlasmid-altered microorganisms, such as we have acquired from P r o f e s s o r Simon S i l v e r ' s l a b o r a t o r y (Washington U n i v e r s i t y , S t . L o u i s ) , the IS. c o l i which are good methylators of mercury, we might do d i r e c t measurements. You have t o dedicate the apparatus because the experiments r e q u i r e some p e r i o d o f time and s t e r i l e c o n d i t i o n s . A l s o , one experiences s u r f a c e e f f e c t s from the v e s s e l . WASIK: One of the most important things about t h i s type of p a r t i t i o n c o e f f i c i e n t measurement i s t h a t these a r e a t i n f i n i t e d i l u t i o n , and from that you can measure a c t i v i t y c o e f f i c i e n t s which g i v e you more freedom t o make new c o r r e l a t i o n s . RECEIVED

November 3,

1978.


Air Systems - American

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