![handle is hein.journals/injlegame114 and id is 1 raw text is: *3
K. Minakata - O. Suzuki - S. Saito - N. Harada
A new diquat derivative appropriate for colourimetric measurements
of biological materials in the presence of paraquat
Received: 21 June 1999 / Accepted: 28 September 1999
Abstract A new colourimetric method is described for
the quantification of diquat using a yellow-coloured de-
rivative produced by heating diquat in alkaline solution at
80°C. The absorption maximum of the yellow derivative
is 420 nm and the molar absorption coefficient is 2.76 x
104 (0.15 in 1 gg diquat/ml with 1 cm light path). The ab-
sorption at 420 nm shows a linear concentration depen-
dence in the range 0.1-10 gg/ml and fading of the colour
is about 5% after 1 h. Under the same conditions, paraquat
does not produce any coloured products. The concentra-
tion of diquat in the solution containing both diquat and
paraquat can be determined by the absorption of diquat
derivative at 420 nm without interference from paraquat.
By adding sodium dithionite to the solution the concentra-
tion of paraquat can be determined by the absorption of
paraquat radicals at 600 nm without interference from di-
quat, because the yellow derivative does not react with
dithionite. This yellow diquat derivative can be extracted
completely with cyclohexanol by saturating the solution
with Na2SO4. The absorption maximum in cyclohexanol
shifts to 440 nm with the same molar absorbance and the
same half-band width as in water. Fading of the colour is
less than 5% after 24 h in cyclohexanol. Perchloric acid
(3%) and trichloroacetic acid (4.5%) which are often used
for deproteinization of tissue homogenates, do not inhibit
production of the coloured derivative at pH 13.5 or ex-
traction of the derivative with cyclohexanol. This method
is suitable for a quick determination of small amounts of
diquat in tissues, since the extraction with cyclohexanol
not only concentrates the derivative rapidly but also quite
efficiently eliminates the coloured substances in tissue ho-
mogenates. The detection limit of diquat is 0.02 gg/ml for
blood and 0.05 gg/g for liver when 1 ml or 1 g is used for
K. Minakata (®) O. Suzuki
Department of Legal Medicine, Hamamatsu University School of
Medicine, 3600 Handa, Hamamatsu 431-3192, Japan
Tel./Fax: +81-53-4352239
S. Saito N. Harada
University of Shizuoka, Hamamatsu College, 3-2-3, Nunohashi,
Hamamatsu 432, Japan
analysis. In three human cases of fatal intoxication, both
paraquat and diquat were quantified using 50 pl of serum.
In non-toxic dosing of diquat to rats for 14 days, the di-
quat level was highest in the spleen followed by the kidneys.
Key words Diquat Paraquat Colourimetry Tissue
concentration Cyclohexanol
Introduction
The toxicity of the herbicide paraquat (PQ, 1, 1'-dimethyl-
4, 4'-dipyridylium) is higher than that of diquat (DQ, 1,
1'-ethylene-2, 2'-dipyridylium) for mammals e.g. the
acute oral LD50 of PQ is 30 mg/kg whereas that of DQ is
100 mg/kg in guinea-pigs [1, 2]. To lower the toxicity of
herbicides, commercial products containing equimolar
amounts of PQ and DQ have been used in Japan since
1986. Although equimolar amounts of PQ and DQ were
ingested in cases of poisoning, the molar ratio of DQ/PQ
contained in the tissues of the victims varied from 0.08 to
8 indicating differences in the pharmacokinetics of PQ
and DQ [3]. It would therefore be desirable to establish a
simple method of measuring the concentrations of PQ and
DQ in tissues. Because of high aqueous solubility, PQ and
DQ are usually determined by liquid chromatography
(LC) [4, 5]. The colourimetry of PQ radicals produced
with alkaline dithionite [6] is a simple method and still ap-
plicable to the quantification of PQ at fatal levels [7]. The
optical density (OD) of the PQ radical at 600 nm is 0.0855
for 1 gg/ml [6], however, the alkaline dithionite reaction
is not suitable for the colourimetric quantification of DQ
because the DQ radical produced is unstable and the ab-
sorption is too weak,i.e. the OD at 430 nm is 0.0255 for
1 gg DQ/ml [6]. Therefore, we tried to establish a new
colourimetric method for the quantification of DQ, and
found that DQ changed to a yellow-coloured derivative
when heated at 80 °C in alkaline solution which has
higher molar absorptivity as well as higher stability than
the DQ radical or the red DQ derivative reported previ-
ously [8]. The extraction of the derivative into organic
Int 7 Legal Med (2000) 114 : 1-5
© Springer-Verlag 2000](ViewImageLocal?handle=hein.journals/injlegame114&div=1&collection=&method=preview&ext=.png&size=3)
What Is HeinOnline?
Contact us for annual subscription options:
Already a HeinOnline Subscriber?
profiles profiles most
Contact us for annual subscription options:
Already a HeinOnline Subscriber?
profiles profiles most
Contact us for annual subscription options:
Already a HeinOnline Subscriber?
profiles profiles most