Measurement of Quantum Yields in Polychromatic ... - ACS Publications

Chapter 20

Measurement of Quantum Yields in Polychromatic Light: Dinitroaniline Herbicides 1

William M. Draper

Downloaded by UNIV OF MISSOURI COLUMBIA on March 8, 2013 | http://pubs.acs.org Publication Date: December 8, 1987 | doi: 10.1021/bk-1987-0327.ch020

Environmental Health Division, School of Public Health, University of Minnesota, Minneapolis,MN55455

General procedures are described for determina tion of wavelength-averaged quantum yields in near UV light (310-410 nm). Calculations are discussed and a computer program in BASIC language i s provided which allows rapid and accurate com putation of Ф. In this work the widely available Rayonet photoreactor fitted with fluorescent black light lamps is used to measure Фfor fluchloralin, isopropalin, and profluralin, im portant dinitroaniline herbicides. Study of these pesticides demonstrates the utility of the pro cedure as well as the sensitivity of Фto slight changes in molecular structure. The burgeoning interest i n mathematical modeling as a t o o l for predicting the fate of chemicals i n the environment has empha s i z e d the need for accurate measurement of rate constants for various chemical and photochemical processes. Models have been developed which allow accurate p r e d i c t i o n of aquatic environmen t a l photolysis rates for various seasons, l a t i t u d e s and water depths predictive c a p a b i l i t y of such models i s further enhanced by incorporating data on the attenuation of incident sunlight by endogenous substances i n the water column, i . e . , c h l o r o p h y l l , organic carbon, and suspended m a t e r i a l . The considerable success of these models i s achieved by detailed estimation of the rate of sunlight absorption by the substrate under hypothetical environmental conditions. The needed compound-specific inputs include molar e x t i n c t i o n c o e f f i c i e n t s , i n d i c a t i n g the e f f i c i e n c y with which incident l i g h t i s absorbed, and a disappearance quantum y i e l d (jj) which gauges the e f f i c i e n c y for conversion of absorbed l i g h t energy to phoT

n

e

'Current address: California Public Health Foundation, Berkeley, CA 94704 0097-6156/87/0327-0268$06.00/0 © 1987 American Chemical Society

In Photochemistry of Environmental Aquatic Systems; Zika, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

20.

DRAPER

Quantum Yields in Polychromatic Light

269


ar,

tochemical reactions of the chromophore. ji d the absorption spectrum, of course, are e s s e n t i a l pieces of data for d e f i n i t i o n of the fate of environmental chemicals. To date very few a p p l i cable environmental quantum y i e l d s have been published i n the open literature. Unlike other physicochemical molecular properties a f f e c t i n g environmental behavior, there are no u s e f u l guidelines or even empirical r e l a t i o n s h i p s for prediction of |. Subtle changes i n molecular structure, as w i l l be demonstrated i n t h i s study, a l t e r the e f f i c i e n c y of competing photochemical and photophysical pro cesses. For most molecules quantum y i e l d s are less than 0.01 (_3) i n d i c a t i n g that the vast majority of electromagnetic energy absorbed does not a f f e c t a chemical r e a c t i o n of the substrate. The v a r i a t i o n of known quantum y i e l d s i s remarkable, however, ranging from greater than unity to less than 1 0 . Since there i s no a l t e r n a t i v e a v a i l a b l e to experimental measurement of jj, stan dardized and straightforward procedures and apparatus for jj measurement are needed by environmental chemists. The fundamentals of quantum y i e l d measurement have been described i n various sources (2, 4, 5). For purposes of environ mental modeling quantum e f f i c i e n c i e s i n s o l u t i o n are assumed to be wavelength-independent. I t i s generally accepted, however, that environmental ξ measurements should be r e s t r i c t e d to wavelengths greater than 280 nm. Use of monochromatic l i g h t s i m p l i f i e s | determination since only a s i n g l e e x t i n c t i o n c o e f f i c i e n t i s required and t h i s approach has gained the widest acceptance. $ measurement at 313 nm has been recommended (6) since most mole cules absorbing sunlight are r e a c t i v e at t h i s wavelength. T y p i c a l l y , medium pressure, high i n t e n s i t y mercury arc lamps are u t i l i z e d with the desired mercury l i n e or band i s o l a t e d by a monochrometer or f i l t e r system. C h a r a c t e r i s t i c s of the a v a i l a b l e lamps, preparation and use of chemical and glass f i l t e r s and other photochemical techniques are reviewed i n Reference 4. This chapter outlines a procedure for the determination of wavelength-averaged quantum y i e l d s , that i s , ξ measured i n polychromatic l i g h t . In t h i s case use of the Rayonet photoreactor equipped with fluorescent b l a c k l i g h t lamps emitting over the range of 310 to 410 nm was examined. The r a t i o n a l e for t h i s approach are the followingι (1) such photoreactors are widely a v a i l a b l e i n chemical laboratories* (2) determination of $ i n polychromatic l i g h t i s not d i f f i c u l t experimentally nor does i t require addi t i o n a l e f f o r t when compared to single-wavelength were converted from units of energy/time to l i g h t quanta/time for pur poses of c a l c u l a t i n g the rate of l i g h t absorption. An impression of the rates of photoprocesses i n the pho toreactor i n r e l a t i o n to natural sunlight i s gained on examining Figure 1. The i n t e n s i t y of UV-A r a d i a t i o n (320-400 nm) i s about 1.7 times the i n t e n s i t y of midday summer sunlight ( l a t i t u d e 40° N) U ) and about 3.7 times that of midday winter sunlight. Thus, molecules with p r i n c i p a l absorption i n the UV-A range are pre dicted to photodegrade at greater rates i n the laboratory photoreactor. In the UV-B range, that below 320 nm, the photoreactor has between 1.5 and 5.7 times the i n t e n s i t y of midday sunlight depending on the season. Light of wavelengths below 320 nm i s most l i k e l y to overlap the absorption spectrum of organic mole cules. Some environmental chemicals, i . e . , p o l y c y c l i c aromatic hydrocarbons, which absorb longer wavelength r a d i a t i o n may photodegrade more r a p i d l y i n sunlight. 2

2

C a l c u l a t i o n s . The c a l c u l a t i o n of quantum y i e l d s i s accomplished with the following formula (2) which r e l a t e s ξ to the d i r e c t photolysis h a l f - l i f e and the rate of l i g h t absorption. 20

r CO.693) C6.02 χ 1 0 ) • = 2.303 t j Σ ε Ζ λ

λ

d>



272

PHOTOCHEMISTRY OF ENVIRONMENTAL AQUATIC SYSTEMS

WAVELENGTH (nm)

Figure 1. Spectra f o r fluorescent lamps (0), midday summer sunlight (•) and winter sunlight (Δ) f o r l a t i tude 40 °N ( 1 ) . Reproduced from Ref. 7. Copyright 1985, Pergamon Press L t d .


20. DRAPER


273

In t h i s expression J i s dimensionless, the h a l f - l i f e has units of seconds and the twentieth-power term i n the numerator i s a conversion factor with u n i t s of moles/photon. The i n t e g r a l overlap of the lamp emission and the chromophore e l e c t r o n i c spectrum, ΣεχΖχ, defines l i g h t absorption i n photons mole" s e c " , εχ i s the average e x t i n c t i o n c o e f f i c i e n t for a given wavelength i n t e r v a l with Ζ χ equaling the lamp output over t h i s same band. The f i r s t - o r d e r disappearance of the substrate y i e l d s a l i n e a r semilogarithmic plot with slope equal t o k" and t | equal to 0.693/k. Linear regression i s used to obtain the best estimate of the substrate h a l f - l i f e . At the high chemical d i l u t i o n s used i n t h i s procedure (ppb l e v e l s ) conversion of the substrate i s not c r i t i c a l since only a minute f r a c t i o n of the incident r a d i a t i o n i s absorbed and competition for l i g h t or quenching of excited states by photoproducts i s not s i g n i f i c a n t . As outlined above the near UV i r r a d i a n c e experienced by samples i n the photoreactor i s t y p i c a l l y 10,280 microwatts/cm . The actual i n t e n s i t y of l i g h t emitted, however, varies with the temperature of the arc w a l l , current, age of the lamps and other factors (4) necessitating the use of chemical actinometers. For measurement of wavelength-averaged quantum y i e l d s i t i s necessary to assume that the wavelength d i s t r i b u t i o n of the l i g h t source i s i n v a r i a n t . Thus, Ζχ values given i n Table I are each corrected by the same factor as followsχ 1

1


1

2

t l , t r i f l u r a l i n (10,280) (2)

Ζχ ( a c t u a l ) = Ζχ (10,280) χ 4 , t r i f l u r a l i n (actual)

The numerator i s the expected actinometer h a l f - l i f e for an i r r a diance of 10,280 microwatts/cm while the denominator i s the observed actinometer h a l f - l i f e . Expected t r i f l u r a l i n h a l f - l i v e s calculated according to Equation 1 with quantum y i e l d s stated above and spectral data compiled i n Table I, are 44 and 9.7 min utes for aqueous and toluene s o l u t i o n s , respectively. 2

Rapid and Accurate C a l c u l a t i o n of For speed and accuracy i n c a l c u l a t i o n of wavelength-averaged quantum y i e l d s a short computer program i n BASIC language has proven useful (Figure 2). This program u t i l i z e s several simple arrays for storing variables and for inputting experimental data. In the array named LAMP (statement #70) values of Ζχ are assigned for the 15 wavelength i n t e r v a l s between 310 and 410 nanometers. The WAVE array declared i n statement #230 prompts the operator to input εχ values for the reactant which are assigned to memory l o c a t i o n s i n EXTINCT. A fourth and f i n a l array, 0VLAP, performs an arithmetric operation y i e l d i n g the spectral overlap. Up to t h i s point the program as sumes the radiant energy to be 10,280 microwatts/cm , so-called "standard" conditions. As described above the actual rate of l i g h t absorption i s obtained by a c o r r e c t i o n factor (statement #580) using experimental and standard h a l f - l i v e s for the t r i f l u r a l i n actinometer. The program outputs the following information! photon irradiance (ΣΖχ)$ εχΖχ,· and The use of a microcomputer allows c a l c u l a t i o n of | and confirmatory c a l c u l a t i o n s i n a short period of time. 2

Σ


274


Table I. Typical Spectral

Irradiance Values and D i n i t r o a n i l i n e Herbicide Absorption Spectra Extinction

Wavelength


(nm)

Photon Irradiance (Photons cm-

2

-

297.5 300 302.5 305 307.5

Coefficients

ÇL m o l e 1

sec" )

-1

0

-1

cm )

F l u c h l o r a l i n Isopropalin P r o f l u r a l l n T r i f l u r a l i n 3,820

1,920

1,,400

3,480

1,790

1.,280

2,980

3,340

1,660

1,,210

2,500

2,920

1,,570

1.,150

2,290

2,590

1,,480

ι,,090

2, 140

2,190

310

3.9 Ε + 13

1,,410

1,,040

2,010

1,960

312.5

7.5 Ε + 13

1,,370

ι.,020

1.,850

1,840

315

1.2 Ε + 14

L ,350

985

1,730

317.5

1.9 Ε + 14

1.,330

997

320

2.6 Ε + 14

1,,310

1.,000

323.1

6.3 Ε + 14

1.,360

997

ι,750 ι,,650 ι,,580 ι,,540

330

1.6 Ε + 15

1,450

1,000

1,460

340

3.1 Ε + 15

1.,580

997

1.,540 1.,650

350

4.0 Ε + 15

1»,720

985

1.,820

1,740

360

3.6 Ε + 15

!» ,910

991

2,020

1,960

370

2.4 Ε + 15

1,,980

967

2,,200

2,140

380

1.4 Ε + 15

2,030

1,,030

2,,350

2,290

390

6.3 Ε + 14

1,,960

1,,050

2,,400

2,340

400

2.8 Ε + 14

1,,840

1,,060

2,,350

2,340

410

9.6 Ε + 13

1,,690

1,,050

2,,280

2,310

1,,450

1,030

2,,210

2,230

1,,230

995

2,,070

2,080

859

915

1,,810

1,860

577

811

1,490

1,460

366

663

1,,070

1,100

211

510

725

680

-

375

466

450

282

328

270

196

207

150

-

420 430 440 450 460 470 480 490 500 a

Total near UV intensity of 10,280 microwatts/cm

b

UV-visible

2

spectra recorded i n a c e t o n i t r i l e


1,630 1,580 1,530

1,580

20.

DRAPER


275


10 20 30 40 50

PRINT "WHAT IB THE NAME OF THE COMPOUND?" INPUT COMPOUND* PRINT "WHAT IS THE H A L F - L I F E FOR",COMPOUND*,"IN SECONDS?" INPUT THALF PRINT "WHAT IS THE H A L F - L I F E FOR THE TRIFLURALIN ACTINOMETER WITH TO LUENE AS SOLVENT?" 60 INPUT EXHALF 70 DIM LAMP(16) 80 LAMP(l) == 3.9E + 13 90 LAMP(2) = 7.5E + 13 100 LAMP(3) = 1.2E + 14 110 LAMP(4) = 1.9E + 14 120 LAMP(5) = 2.6E + 14 130 LAMP(6) = 6.3E + 14 140 LAMP(7) = 1.6E + 15 150 LAMP(8) = 3 . I E + 15 160 LAMP(9) = 4.0E + 15 170 LAMP(10) = 3.6E + 15 180 L A M P ( l l ) = 2.4E + 15 190 LAMP(12) = 1.4E + 15 200 LAMP(13) = 6.3E + 14 210 LAMP(14) = 2.8E + 14 220 LAMP(15) = 9.6E + 13 230 DIM WAVE(16) 240 WAVE(l) = 310 250 WAVE(2) = 312.5 260 WAVE(3) = 315 270 WAVE(4) = 317.5 280 WAVE(5) = 320 290 WAVE(6) = 323.1 300 WAVE(7) = 330 310 WAVE(8) = 340 320 WAVE 15 THEN GOTO 470 420 PRINT "ENTER THE",COMPOUND*,"EXTINCTION COEFFICIENT FOR WAVELENGTH" 430 440 450 4ά>0 470 480 490 500 510 520 530 540 550 560 570 580 590 600 610 62

PRINT WAVE(I),"NANOMETERS." INPUT E X T I N C T ( I ) 1 = 1 + 1 GOTO 410 SUM = 0 I = 1 DIM 0VLAP(16) IF I > 15 THEN GOTO 550 OVLAP(I) - LAMP(I) * E X T I N C T ( I ) SUM = SUM + OVLAP(I) 1 = 1 + 1 GOTO 500 ΚA = (2.303 * SUM) / 6.02E + 20 PHI = 0.693 / (THALF * KA) STDHALF = 584.6 CFAC = EXHALF / STDHALF TRUFLUX = 10280 / CFAC CSUM = SUM / CFAC CPH1 = PHI * CFAC PRINT "THE LIGHT INTENSITY IN THE PHOTOREACTOR IS",TRUFLUX,"MICROWA TTS PER SQUARE CENTIMETER." 630 PRINT "THE RATE OF LIGHT ABSORPTION BY" ,COMPOUND*,"IS",CSUM, "PHOTON S PER MOLE PER SECOND." 640 PR1NT "THE QUANTUM YIELD FOR",COMPOUND*,"IS",CPHI"." 650 END

Figure 2. Microcomputer program i n BASIC language f o r rapid and accurate c a l c u l a t i o n of wavelengthaveraged quantum y i e l d s .


276


Method V a l i d a t i o n . In studies reported elsewhere (2) s a t i s f a c t o r y measurements of jj have been obtained by t h i s procedure when r e s u l t s were compared to published single-wavelength quantum y i e l d s determined at 313 or 366 nm or those measured i n s u n l i g h t . This i s the case even without the use of a chemical actinometer, e.g., assuming a constant l i g h t i n t e n s i t y of 10,280 microwatts/cm i n the operating photoreactor. ξ values for substrates which absorb the emitted r a d i a t i o n poorly ( i . e . , DOE and methoxychlor) as well as molecules with e f f i c i e n t long-wavelength UV chromo phores C t r i f l u r a l i n ) were determined with equal accuracy demon s t r a t i n g the u t i l i t y of the procedure and the accuracy of the a v a i l a b l e emission spectrum. Downloaded by UNIV OF MISSOURI COLUMBIA on March 8, 2013 | http://pubs.acs.org Publication Date: December 8, 1987 | doi: 10.1021/bk-1987-0327.ch020

2

D i n i t r o a n i l i n e Quantum Y i e l d s . The d i n i t r o a n i l i n e s are a s t r u c t u r a l l y diverse group of p e s t i c i d e s used i n large volume for s e l e c t i v e pre-emergence weed c o n t r o l i n cotton, soybeans and corn. Electron-withdrawing substituents (e.g., n i t r o groups) i n the 2and 6- p o s i t i o n are required for high h e r b i c i d a l a c t i v i t y while f u n c t i o n a l i t y at other p o s i t i o n s seems l e s s c r i t i c a l (9). For t h i s study d i n i t r o a n i l i n e s with minor modifications i n the N-alkyl and para-ring substituents were examined (Figure 3). The photochemical r e a c t i v i t y of t h i s herbicide c l a s s i s well known and has been studied i n aqueous media U ) > vapor phase (10), organic solvents (_11) and on s o i l surfaces (_12, J3). Photoreduced (e.g., amines and azobenzene and azoxybenzene dimers), 21-dealkyl a t e d and c y c l i z e d d e r i v a t i v e s appear to be the predominant photochemical transformation products. In p r a c t i c a l a p p l i c a t i o n these p e s t i c i d e s must be s o i l incorporated due i n large part to t h e i r photochemical i n s t a b i l i t y . I n t e r e s t i n g l y , the d i n i t r o a n i l i n e s are potent p h o t o s t a b i l i z e r s capable of protecting photol a b i l e i n s e c t i c i d e s on surfaces (14). The substituted d i n i t r o a n i l i n e herbicides absorb well into the v i s i b l e region due to extended p i - e l e c t r o n systems. The X for each (Table I.) i s i n the 380-400 nm range where e x t i n c t i o n c o e f f i c i e n t s ( l o g i g ) are 3.0-3.4 for the p i to p i * e l e c t r o n i c t r a n s i t i o n . These e l e c t r o n i c spectra afforded excellent chromo phores for absorption of the emitted b l a c k - l i g h t r a d i a t i o n . F l u c h l o r a l i n , i s o p r o p a l i n and p r o f l u r a l i n each photodegraded r a p i d l y i n the laboratory photoreactor (Figure 4). The disap pearance of both i s o p r o p a l i n and f l u c h l o r a l i n showed l i t t l e deviation from an exponential curve, while photolysis of the l e a s t photolabile herbicide, p r o f l u r a l i n , unexplicably showed greater experimental e r r o r . The data depicted i n Figure 4 represent pho t o l y s i s of a s i n g l e substrate i n s o l u t i o n . The low a n a l y t i c a l concentrations of the chromophores (25 ppb) and the a b i l i t y to resolve the reactants and photoproducts chromatographically, however, allowed simultaneous measurement of quantum y i e l d s for mixtures. Under s i m i l a r experimental conditions t r i f l u r a l i n ex h i b i t e d a h a l f - l i f e of 52-68 minutes (7). Over the period of the photolysis experiment no change i n concentration was observed for solutions held i n the dark. m a x


20.

DRAPER

277


FLUCHLORALIN R ^ C ^ . R g - C ^ C I , R 3 « C F


ISOPROPALIN

R , , R " C H , R » CH(CH > 2

3

7

3

3

PROFL U R ALI Ν R j • C Hg^.Rg- C H , R « C F 3

TRIFLURALIN

e

R,, Rg C H 3

? f

7

R -CF 3

3

3

2

3

3

Figure 3. Chemical structures for substituted d i n i t r o a n i l i n e herbicides.

f i g u r e A. Photodecomposition of d i n i t r o a n i l i n e herbicides i n water: i s o p r o p a l i n (Δ), f l u c h l o r a l i n (•) and p r o f l u r a l i n ( 0 ) .


278


Replotting the photodecomposition data on semilogarithmic scale revealed f i r s t - o r d e r reaction k i n e t i c s (Figure 5.) with no evidence of departure from l i n e a r i t y over several h a l f - l i v e s . C o r r e l a t i o n c o e f f i c i e n t s for these l i n e s varied between -0.95 and -1.0. Photochemical k i n e t i c data and outputs from the microcomputer program are summarized i n Table I I . As can be seen, the near UV radiant energy i n the photoreactor varied l i t t l e from experiment to experiment, but usually was s u b s t a n t i a l l y lower than the stan dard 10,280 microwatts/cm . These irradiance values are based on 5 or 6 consecutive ~one-actinometer-half-life measurements with the chemical actinometer during the photolysis experiments. The importance of the para-CF^ group to the d i n i t r o a n i l i n e chromophore i s evident from these data (and Table I ) — Σεχ Ζχ for both f l u c h l o r a l i n and p r o f l u r a l i n greatly exceed that of isopropal i n with a para-CH(CH-Q9 substituent. An i n t e r e s t i n g and not e a s i l y predicted r e s u l t i s that isopropalin i s the most photo chemically reactive of the analogs. Isopropalin u t i l i z e s absorbed radiant energy 4 to 6 times more e f f i c i e n t l y than i t s para-CFi analogs. I t appears from t h i s l i m i t e d survey of d i n i t r o a n i l i n e structure-photoreactivity that the electron-donating parasubstituent, while l i m i t i n g l i g h t absorption, greatly enhances the chemical r e a c t i v i t y of the r e s u l t i n g e l e c t r o n i c a l l y - e x c i t e d state.


2

1.5

TIME

(min)

Figure 5. Semilogarithmic plots for photodecomposition of d i n i t r o a n i l i n e herbicides: isopropalin (Δ), f l u c h l o r a l i n (•) and p r o f l u r a l i n ( 0 ) .


20.

Table I I .

Trifluralina H a l f - l i f e (sec)

Experimental Light intensity (microwatts/cm ) 2

Light Absorption Rate (photons mole-1 s e c ) - 1

0

Quantum Yield

1,752

744

8,077

2.53 Ε 19

0.0041 (0.0037)

Isopropalin

912

747

8,045

1.43 Ε 19

0.014 (0.013)

Profluralin

2,658

732

8,210

2.81 Ε 19

0.0024 (0.0013)

Fluchloralin


Photodecomposition Kinetics, Rates of Light Absorption and Quantum Yields for D i n i t r o a n i l i n e Herbicides

Half-life (sec)

Compound

279


DRAPER

a

Toluene solutions

b

The values given i n parentheses were derived from simultaneous i r r a d i a t i o n of the three pesticides i n a single solution. The i n i t i a l concentration of each compound was 25 ppb and the average l i g h t intensity (n = 4) was 7,570 microwatts/cm . 2

Conclusion Measurement of wavelength-averaged quantum y i e l d s i n systems l i k e that described here o f f e r s a number of advantages to the environ mental photochemist. Determinations are experimentally s t r a i g h t forward, provide an optimum degree of experimental control and y i e l d data which i s r e a d i l y amenable to mathematical modeling. Moreover, since near UV δ are generally invariant with wavelength, the wavelength-averaged ξ should be indistinguishable from s i n g l e wavelength J measured at 313 nm or other wavelengths i n t h i s por t i o n of the spectrum. Acknowledgment Michael K i e r s k i provided assistance i n preparation of the computer program. I thank Betty Romani f o r typing numerous d r a f t s of the chapter. Funding by the National I n s t i t u t e of Environmental Health Sciences [Grant R23ES03524) and the 3M Foundation i s grate f u l l y acknowledged. L i t e r a t u r e Cited 1. 2. 3.

Zepp, R. G.j C l i n e , D. M., "Rates of d i r e c t photolysis i n aquatic environment," Environ. S c i . Technol. 1977, 11, 359-366. Zepp, R. G., "Quantum y i e l d s for reaction of pollutants i n d i l u t e aqueous s o l u t i o n , " Environ. S c i . Technol. 1978, 12, 327-329. H a r r i s , J. C.j In Handbook of Chemical Property Estimation Methods, Lyman, W.j Reehl, W.j Rosenblatt, D., Eds. McGraw-Hillι New York, 1982j Chapter 8.




2 8 R0

4. Calvert, J. G.; Pitts, J. N., Jr. Photochemistry, Wiley; New York, 1966. 5. Moses, F. G.; Liu, R. S. H.; Monroe, Β. M., "The merry-go– round quantum yield apparatus," Mol. Photochem. 1969, 1, 245-249. 6. Zepp, R. G.; Baughman, G. L.; Schlotzhauer, P. F.; "Comparison of photochemical behavior of various humic substances in water: I. Sunlight induced reactions of aquatic pollutants photosensitized by humic substances," Chemosphere 10, 119 (1981). 7. Draper, W. M., "Determination of wavelength-averaged, near UV quantum yields for environmental chemicals," Chemosphere, 1985, 14, 1195-1203. 8. Mill, T.; Mabey, W. R.; Lan, B. Y.; Baraze, Α., "Photolysis of polycyclic aromatic hydrocarbons in water," Chemosphere, 1981, 10, 1281-1290. 9. Jager, G., In Chemistry of Pesticides, Büchel, K. H., Ed. John-Wiley: New York, 1983; Chapter 4. 10. Woodrow, J. E.; Crosby, D. G.; Seiber, J. N. "Vapor-phase photochemistry of pesticides," Residue Rev. 1983, 85, 111-125. 11. Sullivan, R. G.; Knoche, H. W.; Markle, J. C., "Photolysis of trifluralin; characterization of azobenzene and azoxybenzene photodegradation products," J. Agric. Food Chem. 1980, 28, 746-755. 12. Plimmer, H. R., "Photolysis of TCDD and trifluralin on silica and soil, "Bull. Environm. Contam. Toxicol. 1978, 20, 87-92. 13. Parochetti, J. V.,· Dec, G. W., Jr., "Photodecomposition of eleven dinitroaniline herbicides," Weed S c i . , 1978, 26, 153-156. 14. Dureja, P.; Casida, J. Ε.,· Ruzo, L. O., "Dinitroanilines as photostabilizers for pyrethroids," J. Agric. Food Chem. 1984, 32, 246-250. RECEIVED May 27, 1986


Measurement of Quantum Yields in Polychromatic ... - ACS Publications

Recommend Documents