19 Synthetic Pyrethroids: Residue Methodology and
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Applications
1
D. A. GEORGE, J. E. HALFHILL, and L. M. McDONOUGH Yakima Agricultural Research Laboratory, Agricultural Research Service, U.S. Department of Agriculture, Yakima, Wash. 98902
The shortcomings of DDT [ l , l , l - t r i c h l o r o - 2 , 2 - b i s = (p-chlorophenyl )ethane] and other chlorinated hydrocarbons has stimulated research into the development of other broad spectrum insecticides that could provide high insecticidal activity combined with low mammalian toxicity and moderate persistence. Compounds related to natural pyrethrum (synthetic pyrethroids) have been developed in recent years that show promise of meeting these requirements. Natural pyrethrum (Fig. 1) i s an ester with synthetic variations of both the acid and alcohol portion of the molecule providing promising insecticides. Field studies indicate that Bioethanomethrin® [(5-benzyl3-furyl)methyl trans-(+)-3-(cyclopentylidenemethyl)-2,2dimethylcyclopropanecarboxylate] and FMC 33297 [m-phenoxybenzyl cis,trans-(±)-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane= carboxylate] (Fig. 2), showed promise of controlling insects of certain vegetable crops. Consequently, we investigated methods of detecting their residues. We report here a direct method u t i l i z i n g gas chromatography and electron capture detection for FMC 33297. In addition, we developed a method based on derivatives of the alcohol and acid moieties of the saponified pyrethroid molecule for both pyrethroids (1). This latter method should work equally well with other synthetic pyrethroids (Fig. 3). The sample i s saponified, the alcohol moiety i s extracted with methylene chloride, the water portion i s then a c i d i f i e d , and the acid moiety i s extracted with methylene chloride. Trichloroacetyl chloride with pyridine i s used to form a trichloroacetate ester from the alcohol and trichloroethanol 1/ This paper reports the results of research only. Mention of a pesticide in this paper does not constitute a recommendation for use by the U.S. Department of Agriculture nor does i t imply registration under FIFRA as amended.
201
Elliott; Synthetic Pyrethroids ACS Symposium Series; American Chemical Society: Washington, DC, 1977.
SYNTHETIC
202
CHRY3ANTHEMATE3
PYRETHROIDS
PYRETHRATES
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3 PYRETHRIN I
Ο
PYRETHRIN Π
8
CINERIN I
CINERIN Π
JASMOLIN 1
JASMOLIN
Figure 1.
Π
Natural pyrethrums: chrysanthemates and pyrethrates
Figure 2. Synthetic pyrethroids Bioethanometrin and FMC 33297
Elliott; Synthetic Pyrethroids ACS Symposium Series; American Chemical Society: Washington, DC, 1977.
19.
GEORGE
with
pyridine
ester
with
increases
with
The the
the
derivatized both
at
8 microns,
a
capture
products
5.68
used
to
form
compound
t h e nanogram gas
an
in
the
range
chromatograph
detector.
support at
to
by a
the
( F i g . 4).
is
pyrethroids,
is
trichloro
sensitivity
spectra
frequency
of
use of
are determined
an electron
infrared
vibrational
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This
the derivatives
equipped
203
and dicyclohexylcarbodiimide
the acid.
derivatives when
Residue Methodology
E T A L .
expected
microns
the aromatic
structures
The carbonyl ether
and the carbon-chloride
for the
trichloroacetate
stretching
bands
for
stretching frequency
are near
14
is
a n d 17
microns. The the
esters
carbonyl
C-O-C the
from
the acid
stretching
t r i p l e t
at
8.7,
carbon-chloride
moiety
frequency
8.9,
and 9.1
stretching
for both
at
5.78
pyrethroids
microns,
microns
a
( F i g . 5).
frequencies
are at
show
strong Again,
14
a n d 18
microns. The
high
structures ion
was f o u n d
331.9773). was base from was
be m/e
The molecular
324.0445
peak
of
the trichloroacetate
corresponding
the molecule. at
m/e
to
of
2
The
ester
peak
of
of
the trichloroethanol
(calculated
m/e
337.9200)
ester,
i o n from
the
loss
of
2
in
atoms
electron
ion ester
of
a method
in
greater
detector;
of
5 to
50
sensitivity
of
the
m/e
183.0808.
corresponding
for determining was u s e d .
t h e compound
the result nanograms. with
at
peak of
to
163.0058.
molecule
make
the loss
The
was m / e
The base
to
was f o u n d
m/e
derivative
derivative
ester,
was d e v e l o p e d
the complete
the molecule
capture
at
ester
345.9765).
is
a
residues
The 2
sensitive
standard
However,
we
to
curve
obtained
the derivatization
method.
Studies emulsifiable
lentils
as
oz/acre)
a 14
collected were
concentrate
spray
2 times
a n d 21 after
h r , and a f t e r
samples
The
m/e
the loss
m/e
ester
the molecule,
was f o u n d
3
which
sensitivity
10-fold
168
2
addition,
chlorine
(10
of
C0 CH CC1 ,
FMC 3 3 2 9 7
were
to
( F i g . 7).
the trichloroethanol
An
at
the trichloroacetate
corresponding
peak
to
ester
324.0449).
was f o u n d
(calculated
base
Residue
m/e
corresponding
The
a
m/e
the trichloroethanol
trichloroacetate
a
(calculated
the trichloroethanol
the loss
346.9764
trichloroacetate
with
molecular
Bioethanomethrin
ion for the trichloroacetate
was m / e
ion of
337.9185
the
expected
The
2
molecular
molecular
In
the
(C0 CH CCl3).
2
FMC 33297
of
the
(calculated
The base
149.1323,
confirm ( F i g . 6).
331.9789
ion of
be m/e
found
the
to
ester
to
C H 0 Cl3 2
spectra formed
found
171.0804,
of
mass
the derivatives
for the trichloroacetate
derivative
3
resolution
of
the
selected
days
the
at
of
before
first
of
harvest.
spray
2nd t r e a t m e n t randomly
Bioethanomethrin
the rate at at
0 h r ,
700
g
Foliage 66
applied
residues
h r , and
0 h r a n d 72
throughout
was
Ai/hectare
the plot,
hr.
The
placed
Elliott; Synthetic Pyrethroids ACS Symposium Series; American Chemical Society: Washington, DC, 1977.
204
SYNTHETIC
2 R CH -O-C-CCl.
c i c-coci
2
R -CH 0H o
1"1)\ OH , MeOH / U-ΛΙΙ / - --^ 2) H,0 \
Q
R -C-O-CH^R
λv
Λ
Ζ
+
+
PYRETHROIDS
Ô
0
C-CH OH
c
ι R -COOH
R -C-0-CH -Cl 2
pyridine - DCC
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Figure 3.
Derivative step (DCC is dicyclohexylcarbodiomide)
WAVENUMBfl (CM>
0.00
—
Ί IΓ T
.1 ο
11
.20
II
S
f
w
f
30
— 1
.40 .5 0 60 .70 1.00 25
30
40
3000
2.5 3.0
5.0
60
2000
4.0
5
0
70
β ϋ
1300
6.0
7
ΙΟ 0
l? 0
4
0
1000 8 0 0
0
80
10.0 12 0
ιβ 0
600
14
0
WAVELENGTH (MICRONS)
Figure 4.
6Ο
Infrared spectra of trichloroacetate ester derivatives
Elliott; Synthetic Pyrethroids ACS Symposium Series; American Chemical Society: Washington, DC, 1977.
16 0
18
0
3
19.
GEORGE
in
plastic
samples
bags,
were
subsamples 200 The
foliage to
extract
liquid
of
Baker s
through The
in
lentils
and
the residue
The
acetonitrile
as
compare were
168-hr by
hexane
were
Table
to
0.6
Table
in
50 m l o f
analyzed.
between
foliage
time.
determined of
loss
Immediately Control
Recoveries
the harvest
Residues
between
sampling
was
with
in
g
1.5%
was t h e
and
same
to
dryness,
acetonitrile.
t h e same
from
after to
was
manner
zero
of
samples
after
No
1.0
residue ppm)
and
residues
foliage of
700
at g
oz/acre).
found
(ppm)±/
Trichloroethanol ester derivative
1
0.350
0.447
.035
.066
168
.000
.000
Treatment
2
0
.647
.689
72
.000
.000
corrected
the no
to
66
were
residues
derivative
on l e n t i l
derivative
0
0.1
an a p p l i c a t i o n
ester
(hr)
of
ester
Trichloroacetate
and
sampling
the
showed
derivative.
Bioethanomethrin (10
derivatives
by t h e end o f
( i n the range ester
the 2
the 7-day
spraying,
o r check
Treatment
Results
(20
passed
and the residue
during
Residues
treatment
subjecting
l e n t i l s .
intervals
Ai/hectare
1/
hexane
and chromatographed
ppm a n d d e c l i n e d
various
Interval
methylene
column
hexane
Extraction
84.2% f o r t h e t r i c h l o r o a c e t a t e
I.
oxide
was e v a p o r a t e d
was e v a p o r a t e d
for the trichloroethanol in
analyzed.
the
and then
was e l u t e d
the extract
The r a t e I.
method.
found
anhydrous until
hexane,
g
sample.
sampling
averaged 80.3%
solution
in
either
through
an aluminum
After
also Then
favorably.
0.4
with
in
Bioethanomethrin
were
residues
shown
with
up by e v a p o r a t i n g
was p a r t i t i o n e d
the foliage The
is
in
50
2 minutes
was r e f r i g e r a t e d
the residue
frozen
hexane.
for the foliage.
redissolved
The
thoroughly;
blended
and f i l t e r e d
0536).
the column,
and mixed
for analysis,
chromatography
acetonitrile
the laboratory.
was c l e a n e d
Analyzed
T
at
chopper
The f i l t r a t e
redissolving
it
a
chloride,
sulfate.
chloride,
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removed
ml methylene
sodium
as
and frozen
put through
were
205
Residue Methodology
E T A L .
to
100% b a s e d
on
recoveries.
Elliott; Synthetic Pyrethroids ACS Symposium Series; American Chemical Society: Washington, DC, 1977.
206
SYNTHETIC
PYRETHROIDS
WAVENUMSER (CM"') 0.00 J
ο
11
.20
Κv Λ if 1 Λι II >
rw
1
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30 .40 .5 0 .60 .70 1.00
CO CD
.0 12.0 14.0 16.0 18.0
(MICRONS)
Infrared spectra of trichloroethyl derivatives
lOOi 80 60 >I-
40
LA