5.45.4
© Springer-Verlag Berlin Heidelberg 2005
II.5.4 Permethrin
by Naoto Matsumoto
Introduction
Pyrethroids are the general term for insecticide pyrethrins and their analogs ( cinerins and
jasmolins) being included in the  owers of pyrethrum or chrysanthemum. Trace concentra-
tions of pyrethroids exert rapid toxic e ects on insects, but are rapidly metabolized for detoxi-
 cation in warm-blooded animals; they are insecticides with very high safety for humans.
On the basis of clari cation of chemical structures of the e ective components of the pyre-
thrum, many of new synthetic pyrethroids were developed. Nowadays, the natural pyrethroids
are almost replaced by the synthetic ones.  ey are not only being used for household insecti-
cides, but also being used in agriculture worldwide.  ey count about 1/3 of the total insecti-
cides, and are even increasing at the present time.
Products containing pyrethroid insecticides are numerous; their toxicities for humans
are generally low. However, since phenotrin, permethrin and empenthrin are ubiquitous as
powders, emulsions and moth repellants for clothes, there are possibilities of their accidental
and suicidal ingestion.
Permethrin
a
(> Figure 4.1) [3-phenoxybenzyl(1RS)-cis, trans-3-(2,2-dichlorovinyl)-2,2-
dimethylcyclopropane-1-carboxylate] is one of the pyrethroids with the lowest toxicities and
being used very widely; the author et al. [1] experienced an actual case of ingestion of a large
amount of permethrin-containing emulsion (Adio
®
, Agros, Tokyo, Japan) and measured the
concentrations of its cis and trans isomers in blood and gastric juice. In this chapter, a method
of HPLC analysis for permethrin in serum is presented.
Structure of permethrin.
⊡ Figure 4.1
Reagents and their preparation

UV 210 nm.
Procedure
i. Permethrin is a lipophilic compound. When a plastic blood-collecting tube containing a
serum-separating agent is used for sampling a small amount of blood, permethrin is easily
adsorbed to the serum-separating agent ( polyole n or polystyrene), causing low recoveries
of this compound. For samplings of blood specimens, usual glass blood-collecting tubes
should be used.
ii. A 100-µL volume of serum and 200-µL acetonitrile are placed in a 500-µL volume polypro-
pylene tube, vortex-mixed for 10 s, sonicated for 1 min and centrifuged at 15,000 g for
1 min.
iii. A 100-µL volume of the supernatant solution is injected into HPLC using an auto injector.
iv. When it is within several hours a er ingestion, there is a possibility of the presence
of permethrin in gastric juice; in such cases, gastric juice and/or gastrolavage  uid should
be obtained. Either of them is diluted 100–1,000 fold with water/methanol (1:1) for analy-
sis; a 100-µL of the solution is processed in the same way as that of the above serum speci-
men.
v. Construction of a calibration curve: a 10-µL volume each of the standard permethrin solu-
tions (1–10 µg/mL) is placed in a 1.5-mL volume sample tube and evaporated to dryness
under a stream of nitrogen or by leaving it at room temperature. A 1-mL volume of serum
is added to each residue and vortex- mixed for 10 s; a 100-µL each of the spiked sera at
various concentrations is processed according to the above procedure.  e external cali-
bration method is used for quantitation using peak areas
f
.
Assessment and some comments on the method
Since the toxicity of permethrin is low, its poisoning cases are few; the reports on chromatog-
raphic analysis of permethrin in human blood are very limited [1].  ere are reports on anal-
ysis by HPLC or GC (GC/MS) for permethrin in foods (oil [2], milk [3] and grain [4]), chemi-
cal products (shampoo and lotion [5]), biological specimens (rat plasma and urine [6–8]) and
environmental water [9].

HPLC chromatograms for extracts of sera obtained from a permethrin-poisoned patient 3 h and
3 months after admission.
⊡ Figure 4.2
428 Permethrin
For more sensitive analysis, the condensation of permethrin using Sep-Pak C
18
[6] (Waters,
Milford, MA, USA) or Extrelut (Merck, Darmstadt, Germany) extraction becomes necessary.
Poisoning case, and toxic and fatal concentrations
A 59-year-old male [1] attempted suicide by ingesting 600 mL of 20 % permethrin emulsion
(Adion
®
) and sent to a hospital under clouding of his consciousness. He had had a past history
of mania-depression and renal dysfunction. Upon the  rst examination, his consciousness
level was 100 (JCS), and incontinent diarrhea with whitish water-like stools, which gave a in-
secticide-like smell, was observed.  e laboratory tests showed high values of BUN and creati-
nine probably due to metabolic acidosis and renal dysfunction. By treatments, such as endotra-
cheal intubation, gastrolavage, administrations of activated charcoal and magnesium citrate
and transfusion, his conditions were improved; a er 15 h, his consciousness became clear and
the metabolic acidosis was improved. On day 11, he was transferred to the psychiatric depart-
ment.
 e concentrations of permethrin isomers were: trans-form 96 ng/mL and cis-form 118 ng/
mL upon admission; trans-form 253 ng/mL and cis-form 615 ng/mL reaching the maximum
levels a er 3 h; the levels decreased therea er.  e areas under the curves (AUC) of perme-
thrin at 24 h a er ingestion were 2,700 and 6,280 ng
·
h/mL for trans- and cis-forms, respec-
tively; the trans/cis ratio of the AUC was 0.43 (trans/cis concentration ratio for the Adion
®


for the unsaturated carbonyl compounds ( Woodward rule).  e more conjugated double
bonds give more shi of absorbance toward a longer wavelength (from UV to visible
ranges). UV absorption spectra of compounds having phenyl groups like permethrin
show λ
max
at 260 °C 280 nm; there is a trend that lower absorbance of a compound is
obtained for a lower ratio of phenyl group(s) to the molecular size. When a detection
wavelength is set at 200–220 nm, the absorbance becomes higher. However, in this range
of wavelengths, the absorbance due to an impurity compound having a single double-
bond appears; such absorbance due to impurities interferes with that of a target com-
pound.  erefore, it is not necessary to set a detection wavelength at λ
max
of the com-
pound; it is more important to avoid the interference by absorbance of impurity com-
pounds, and it is most preferable to select a wavelength, which is highly speci c to a target
compound.
f) For quantitation of a compound by HPLC, the internal or external calibration method is
being utilized using peak heights or peak areas. Peak heights are very susceptible to degra-
dation of a separation column or a guard column, and to the increase of dead volumes due
to undesirable piping; peak areas are much more resistant to these problems and thus give
better reproducibility.
g) When deproteinization is performed by using a water-soluble organic solvent for the
pretreatment of a biomedical specimen such as serum, followed by centrifugation to
obtain clear supernatant extract to be directly injected into reversed phase HPLC, there is
a possibility of deformation of a peak shape (leading and/or decrease in the number of
theoretical plates).  is phenomenon is due to the solvent of a specimen to be injected into
HPLC; it appears when the elution ability of the solvent is higher than that of the mobile
phase.  e solvent makes a part of a compound eluted faster. In this method, the deprotein-
ization with acetonitrile gave 67 % acetonitrile extract solution.  erefore, such e ect may
appear, when the content of acetonitrile in the mobile phase is lower than 67 % (using