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Laser Excited Raman andFluorescence Spectra of SomeImportant PesticidesR. S. Vickers a , P. W. Chan a & Richard E. Johnsen ba Department of Electrical , Engineering Colorado StateUniversity , Fort Collins, Colorado, 80521b Pesticide Research Laboratory Department of Zoology andEntomology , Colorado State University , Fort Collins, Colorado,80521Published online: 06 Dec 2006.

To cite this article: R. S. Vickers , P. W. Chan & Richard E. Johnsen (1973) Laser Excited Ramanand Fluorescence Spectra of Some Important Pesticides, Spectroscopy Letters: An InternationalJournal for Rapid Communication, 6:2, 131-137, DOI: 10.1080/00387017308065439

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SPECTROSCOPY LETTERS, 6 (2) , 131-137 (1973)

LASER EXCITED RAMAN AND FLUORESCENCE

SPECTRA OF SOME IMPORTANT PESTICIDES

KEY WORDS: Raman, F luorescence , S p e c t r a ,

Organophosphates, Carbamates and

Chlor ina ted Hydrocarbons

R. S . Vickers and P . W. Chan

Department of E l e c t r i c a l Engineer ing

and

Richard E. Johnsen

P e s t i c i d e Research Laboratory Department of Zoology and Entomology

Colorado S t a t e U n i v e r s i t y F o r t C o l l i n s , Colorado 80521

INTRODUCTION

The d e t e c t i o n of r e s i d u a l p e s t i c i d e levels i n a i r and s o i l s by

remotely sens inn their Raman Spec t ra i s t h e o b j e c t i v e of a r e c e n t l y

i n i t i a t e d r e s e a r c h program i n t h e department .

s t e p i n t h e endeavor has been t o o b t a i n d a t a on t h e s p e c t r a l d i s t r i -

b u t i o n of s c a t t e r e d laser l i g h t from p u r e samples, under l a b o r a t o r y

c o n d i t i o n s .

A necessary pre l iminary

With such d a t a on hand, t h e v a r i o u s s c a t t e r i n g c r o s s - s e c t i o n s

can be c a l c u l a t e d , and t h e e v e n t u a l s e n s i t i v i t y of a p e s t i c i d e

131

Copyright 0 1973 by Morcel Dekker, Inc. All Rights Reserved. Neither this work nor any part may be reproduced or transmitted in any form or by ony means, electronic or mechanical, including photocopying, microfilming, and recording, or by any information storage and retrieval system, without permission in writing from the publisher.

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VICKERS ET AL.

detection system estimated.

excitation of a number of pesticides are reported, €rom which it can

be seen that both Raman and Fluorescence spectra are present to varying

deRrees.

SAMPLE PRRPARATIClI

In this paper, the results of argon laser

(1) Samples were chosen from the three major Desticide groups,

organophosphates, carbamates and chlorinated hydrocarbons. The majority

of the samples were pure pesticide (i.e., no solvents) and came in

either powdered or liquid form. The powders were compacted in a 3m

pellet press immediately before being exposed to the laser radiation

in order to provide a uniform surface with the minimum of chemical

deterioration. The liquids were used in their concentrated form and

were contained in a sample cell that had been washed with reagent grade

acetone. Further samples were prepared in a solution of acetone

(reagent grade, refluxed over KMnO for eight hours and distilled),

but were found to be unsuitable due to the strong Raman activity of

the acetone itself.

4

EXPERIMENTAL PROCEDURE

The laser source used in this experiment was a Coherent Radiation

52B CW argon laser operating at a power of 0 . 6 watts and a wavelength

of 5145; (19440 cm-l).

Turner scanning spectrometer was used to analyze the scattered radiation.

A scattering angle of 90' was chosen for the liquid samples in accordance

with accepted practice, and for the solid samples, the specularly

reflected beam was used with the sample pellet oriented 45' to the

laser beam. Considerable care was taken to duplicate the experimental

conditions from sample to sample.

A Jarrell-Ash Model 25-102 Czerny-

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SOME IMPORTANT PESTICIDES

-1 The spectra were taken over a range of 100 cm to 6980 cm-' from

A spectrum analyzer with 512 channels of the laser excitation line.

storage was used, thus giving 13.3 cm

An integration time of eight seconds per channel was used. The dark

current count was about ten per second and was considerably less than

the signal count. DesDite the exnerimental precautions, some differences

in the pellet surfaces and optical geometry were bound to exist, causing

differences in the relative photon count from sample to sample. The magni-

tude of the spectra shown should therefore not be taken as absolute in

the case of the solid samples.

-1 spectral range ner channel.

The samples chosen were as follows:

Organophosphate Group

Par a thion (liquid)

Guthi on (pellet)

Ethion (pellet)

0,O-diethyl 0-p-nitrophenyl phosphoro- thioate

0,O-dimethyl S-4-oxo-1,2,3-benzotri- azin-3(4H)-yl methyl phosphorodithioate

O,O,O',O'-tetraethyl S,S' methylene bisphosphorodithioate

Carbamate Group

Furadan Q 2,3-dihydro-2,2-dimethyl-7-benzofuranyl (pellet) methyl carbamate

Baypon (pellet)

o-isopropoxyphenyl methyl carbamate

Chlorinated Hydrocarbon Group

Endosulfan (Thiodan) 6,7,8,9,10,1O-hexachloro-l,5,5a,6, (pellet) 9,9a-hexahydro-6,9-methano-2,4,3-

benzodioxathiepin 3-oxide

Dieldrin (pellet)

Lindane (pellet)

1,2,3,4,5,5-hexachlorocyclohexane, gamma isomer

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VICKERS ET AL.

t e c h n i c a l grade of b iphenyl c h l o r i - n a t e d t o c o n t a i n 5455 by weight of c h l o r i n e . C o n s i s t s of numerous compounds v a r y i n g from t r i c h l o r o - t o oc tachloro- d e r i - v a t i v e s o f b iphenyls i n c l u d i n g isomers

Aroclo @ ( p e l l e t )

0,P' DT)T ( p e l l e t )

1-(0-chloropheny1)-1-(p-chloropheny1)- 2 , 2 , 2 - t r i c h l o r o e t h a n e

RESULTS

F i g u r e 1 shows t h e s a e c t r a o f t h r e e a e s t i c i d e s of t h e organo-

phosphate group: E t h y l P a r a t h i o n i n l i q u i d form, Guthion ( p e l l e t ) and

Ethion ( p e l l e t ) .

E th ion i s rather s t r o n g , b o t h Guthion and P a r a t h i o n have s t r o n g

f l u o r e s c e n c e s p e c t r a spread over a wide s p e c t r a l range. Thus it would

It can be seen t h a t a l though t h e Raman spectrum of

appear d i f f i c u l t t o make u s e of t h e Raman e f f e c t f o r t h e i d e n t i f i c a t i o n

of t h e s e two subs tances . The broad f l u o r e s c e n c e s p e c t r a are n o t

b- z 3 0

z 0

0 I

W 2 a J

w [L

100 1000

WAVE NUMBER I cm-')

FIG. 1

0

Laser-induced s v e c t r a of t h r e e organophosphates . (The b a s e l i n e of t h e three t r a c e s are d i s p l a c e d a r b i t r a r i l y f o r c l a r i t y . This a l s o a p p l i e s t o Figs. 2 and 3 . )

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SOME IMPORTANT PESTICIDES

convenient f o r i d e n t i f i c a t i o n purposes. The s p e c t r a of two carbamates,

F u r a d a p and Bavgon, are shown i n F igure 2 . The Raman s p e c t r a a r e very

similar because of t h e s t r u c t u r a l s i m i l a r i t y of t h e two molecules .

However, Baygon shows very s t r o n g f l u o r e s c e n c e background wi th t h e

peak a t a wave number s h i f t of 3046.8 cm-l and 3061.9 cm-1,(2) which

a l s o corresponds t o t h e s t r o n g Raman peaks of t h e benzene r i n g of

t h e molecules. For F u r a d a D t h e Raman spectrum i s very l a r g e compared

wi th its f luorescence background, and i t would appear t h a t Raman

s c a t t e r i n g should b e a f e a s i b l e i d e n t i f i c a t i o n technique. F i n a l l y

t h e s p e c t r a of t h e c h l o r i n a t e d hydrocarbon group i s shown i n

Figure 3. Lindane and Aroclo P show clear Raman Spec t ra whereas t h e

spectra of Thiodan and D i e l d r i n are f luorescence dominated. Rather

s u r p r i s i n g l y t h e spectrum o f t h e 0,P' isomer of DDT shows l i t t l e o r

I 1

100 1000 7 0 W A V E NUMBER (cm-' )

0

FIG. 2 Laser-induced s p e c t r a of two carbamates.

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VICKERS ET AL.

AROCLOR

L INDANE

I000 WAVE NUMBER ( C m - ' )

FIG. 3 Laser-induced spec t r a of f i v e ch lor ina ted hydrocarbons.

no Raman l i n e s . The in t ense fluorescence resonance occurred a t

3800 cm-' and can be used f o r i d e n t i f i c a t i o n .

CONCLUSION

In this work t h e Raman and fluorescence spec t r a of s eve ra l c l a s ses

of pes t i c ides have been s tudied .

na ture , i t does i n d i c a t e the f e a s i b i l i t y of using l a s e r induced Raman

OK f luorescence spec t r a f o r monitoring p e s t i c i d e l eve l s .

s t age of the experimental program w i l l inc lude measurement of Raman

cross-sections f o r var ious pes t i c ides and s tud ie s with d i f f e r e n t

pes t i c ide concentrations i n s o i l s , t o e s t a b l i s h the s e n s i t i v i t y of the

method.

While the work is of a preliminary

T h e next

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SOME IMPORTANT PESTICIDES

REFERENCES

(1) Johnsen, R. E . and Hantsbarger , W. M., Handbook of I n s e c t i c i d e s , Colorado S t a t e U n i v e r s i t y Press, 1966, 57 pp.

( 2 ) Herzberg, G . , I n f r a r e d and Raman Spec t ra of Polyatomic Molecules , Van Nostrand, NY (1945).

Received December 28, 1972

Accepted January 8 , 1973

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