Tài liệu Drugs and Poisons in Humans - A Handbook of Practical Analysis (Part 49) docx

5.7
5.7
© Springer-Verlag Berlin Heidelberg 2005
II.5.7 p-Dichlorobenzene
by Kanako Watanabe
Introduction
Nowadays, p-dichlorobenzene ( paradichlorobenzene, 1,4-dichlorobenzene) is becoming more
popular than naphthalene as a moth repellant (insecticide) worldwide.  e discrimination be-
tween p-dichlorobenzene and naphthalene is usually di cult only by their smells and their
appearances. However, speci c gravities of their crystals are di erent; they are 1.152 and 1.5
for naphthalene and p-dichlorobenzene, respectively.  erefore, when the crystals sink in
NaCl-saturated water, it is estimated to be p-dichlorobenzene; while when they  oat in the
same solution, it may be naphthalene [1]. Camphor also gives a similar aromatic smell and
appearance, but its discrimination is even easier, because its speci c gravity is only 0.99; it
 oats in tap water.  e weight of p-dichlorobenzene being sold as a moth repellant is about 4 g;
the crystal mass of the same compound being used for a toilet mothball ranges from 40 to
200 g.  erefore, when a large amount of this compound is ingested, it is dangerous for life.
Like naphthalene, p-dichlorobenzene easily vaporizes from its solid into gas; in this chapter,
a method for headspace GC/MS analysis of p-dichlorobenzene is presented utilizing the vola-
tile property.
Reagents and their preparation
i. Reagents
p-Dichlorobenzene and p-dichlorobenzene-d
4
(product No. 32,933-9)
a
can be purchased from
Aldrich (Milwaukee, WI, USA). Other common chemicals used were of the highest purity
commercially available.
ii. Preparation
p-Dichlorobenzene and p-dichlorobenzene-d

4
solutions: 2-mg aliquot each is dissolved in
1 mL methanol to prepare stock solutions. A 1-µL volume of each stock solution is injected
into GC/MS to record each mass spectrum.
For spiked tests, the above each stock solution is diluted 10-fold with methanol; a di erent
volume of the p-dichlorobenzene solution (1–10 µL containing 0.2–2 µg) and 10 µL (contain-
ing 2 µg) of p-dichlorobenzene-d
4
(IS) are placed in each glass vial with a Te on-septum cap
containing 0.2 mL of blank whole blood.
444 p-Dichlorobenzene
GC/MS conditions
GC column
b
: an Rtx-1 fused silica medium-bore capillary column (30 m × 0.32 mm i. d.,  lm
thickness 0.25 µm, Restek, Bellefonte, PA, USA).
GC conditions; instrument: a GC-17A gas chromatograph (Shimadzu Corp., Kyoto, Japan);
column (oven) temperature: 50 °C (1 min) → 10 °C/min → 150 °C → 20 °C/min → 280 °C;
injection temperature: 250 °C; carrier gas: He; its  ow rate: 3 mL/min; injection mode: splitless
for 1 min a er injection, followed by the split mode.
MS conditions; instrument: a Shimadzu QP-5050 quadrupole mass spectrometer
c
(con-
nected with the above GC); ionization: positive ion EI; electron energy: 70 eV; emission cur-
rent: 60 µA; ion source temperature: 280 °C; accelerating voltage: 1.5 kV.
Procedure
i. A 0.2-mL volume of a whole blood specimen
d
, 10 µL (containing 2 µg) of IS solution and
0.8 mL distilled water are placed in a 7-mL volume glass vial with a Te on-septum screw

cap, capped and mixed gently.
ii.  e vial is heated at 80 °C for 30 min on a heat block or in a water bath. At the same
time, the 5-mL volume syringe
e
is also heated on the block.  e needle
f
size for the syringe
is 23 G. A er heating, a 1-mL volume of the headspace vapor is withdrawn into the heated
syringe, and carefully injected into GC/MS not to in uence the vacuum degree of the MS
instrument.
iii. Detection is made using ions at m/z 146 and at m/z 152 for IS in the SIM mode.
iv. Construction of a calibration curve: to 0.2 mL each of blank whole blood (not less than 3
vials) obtained from healthy subjects, 2 µg of IS and a di erent amount of p-dichloroben-
zene are added.  e calibration curve consists of peak area ratio of p-dichlorobenzene to IS
on the vertical axis and p-dichlorobenzene concentration on the horizontal axis.  e peak
area ratio obtained from a blood specimen is applied to the calibration curve to obtain its
concentration
g
. It is essential that the concentration to be analyzed is within the concentra-
tion range of the calibration curve.
Assessment of the method
> Figure 7.1 shows mass spectra of p-dichlorobenzene and IS. p-Dichlorobenzene contains
two chlorine atoms, which give characteristic isotopic peaks at m/z M + 2 and M + 4.  ere-
fore, the molecular base peak of p-dichlorobenzene found at m/z 146 is not interfered with by
any peak of other compounds, while that of p-dichlorobenzene-d
4
found at m/z 150 is inter-
fered with by a minor peak of non-labelled p-dichlorobenzene (
> Figure 7.1). However,
the relatively intense isotopic peak at m/z 152 appearing for p-dichlorobenzene-d

4
is usable,
because it is not interfered with by any peak.  us we have decided to use peaks at m/z 146 and
152 for p-dichlorobenzene and IS, respectively.
> Figure 7.2 shows SIM chromatograms a er headspace extraction of whole blood, to
which p-dichlorobenzene and IS had been added.  e detection limit of p-dichlorobenzene in
whole blood was about 50 ng/mL.
445p-Dichlorobenzene
Mass spectra of p-dichlorobenzene and p-dichlorobenzene-d
4
(IS).
⊡ Figure 7.1
SIM chromatograms for p-dichlorobenzene and IS after their headspace extraction from a whole
blood sample. The amounts of IS and p-dichlorobenzene spiked into 0.2 mL whole blood were
2 µg and 200 ng, respectively.
⊡ Figure 7.2
446 p-Dichlorobenzene
 e extraction e ciency of headspace extraction of p-dichlorobenzene was tested; 10–15 %
of total compound spiked into blood was distributed in the gaseous phase in the vial under
heating at 80 °C for 30 min.
In this method, in spite of the use of a medium-bore capillary column in the splitless mode,
as much as 1 mL gas is injected into GC/MS. Usually, such conditions cause remarkable broad-
ening of a peak to be detected, but it was not the case for p-dichlorobenzene at 50 °C of the
oven temperature (
> Figure 7.2).  e author et al. examined various initial oven temperatures
by using a trapping device (see Chapter 5 of general nature of this book); it was con rmed that
an entire amount of p-dichlorobenzene contained in the headspace gas injected was completely
trapped inside the column at 50 °C.
Poisoning cases and fatal concentrations
Case 1 [2]: a 74-year-old female ingested a mothball (p-dichlorobenzene ingested, 160–200 g)

and fell into clouding of her consciousness and severe constipation. When an enema was given
to her, strongly aromatic-smelled feces were excreted. Neither gastrolavage, intestinal lavage
nor administration of an adsorbent was performed. On day 13, she died of dysfunctions of the
liver and kidney.
Case 2 [3]: a 85-year-old female ingested 40 pieces of Neoparasol
®
(p-dichlorobenzene
140 g) due to senile dementia. At a clinic nearby, gastrolavage was performed, but she fell into
respiratory suppression, bradycardia and a shock state, and was sent to a general hospital. She
was treated with gastrolavage, purgative administration, enforced diuresis, oxygen inhalation
and administration of Alotec
®
(metaproterenol sulfate) and Inovan
®
(dopamine hydrochlo-
ride). On day 4, hemoperfusion was performed and she was discharged on day 34.
Case 3 [4]: a 73-year-old male kept Neoparaace
®
(p-dichlorobenzene) in a warm kotatsu
(Japanese quilt-covered frame with a heat source inside) to dry it up for 3 days, because it had
gotten wet with water.  erefore, a strongly irritable smell took place inside the kotatsu and
around it. When he was resting with his legs inside the kotatsu, he fell into dyspnea suddenly
and was sent to a hospital. Upon his arrival, there was a mild clouding of his consciousness, but
no orientation disturbance. He showed tachypnea, cyanosis in every part of his body, and crep-
itations audible for both lungs by auscultation. PaO
2
was as low as 34.1 mmHg even under
oxygen inhalation; PaCO
2
was 58.7 mmHg. Severe lung edema was observed for both lungs by

X-ray photography. Under arti cial respiration, diuretic and steroid drugs were administered.
By these treatments, his respiratory conditions were rapidly improved, and he could get out of
the arti cial respiration 25 h a er the entrance into ICU. Although there were slight increases
of liver transminases and high values of blood sedimentation and CRP, he was discharged
without any severe sequela about 1 month a er admission.
 ere is no literature on toxic and fatal blood concentrations of p-dichlorobenzene. Human
oral lethal dose is estimated to be 0.5–5 g/kg; the minimal lethal dose for adults estimated to
be 25 g.  ere was a case, in which a 2-month-old baby had died a er ingestion of 3–6 g of
p-dichlorobenzene [3].
447p-Dichlorobenzene
Notes
a) Stable-isotopic p-dichlorobenzene is commercially available from Aldrich. Its price is not
expensive.
b) Any type of non-polar dimethylsilicone capillary columns can be used, irrespective of their
manufacturers.
c) Any type of GC/MS, including sector, quadrupole and ion-trap types, can be used.
d) Urine specimens seem also analyzable with the same procedure, although the author has
not tested it yet.
e) Either a usual 5-mL volume glass syringe or a gas-tight syringe can be used.
f)  e author et al. are using a special type of 23 G needles, which has a tip being cut coni-
cally; this shape of the tip prevents the needle from being clogged by septum debris.
g)  e quantitation using a stable-isotopic IS is most desirable. When it is not available, the
external calibration method can be used by spiking known amounts of p-dichlorobenzene
into 0.2 mL each of blank whole blood, followed by treatments according to the same pro-
cedure.
References
1) Ukai T (ed) (1999) Manual of Treatments in Acute Poisoning. 3rd edn. Jiho Inc., Tokyo, pp 154–155 (in Japanese)
2) Japan Poison Information Center (1995) Poisoning data card No. 56, p-dichlorobenzene. Jpn J Toxicol 8:209–
210 (in Japanese)
3) Nishi K (ed) (1999) Emergency Manual for Poisoning. Iyaku Journal, Osaka, pp 246–247 (in Japanese)

4) Tamagawa R, Ito H, Kamihira A et al. (1995) A case of lung edema caused by inhalation of p-dichlorobenzene.
Jpn J Toxicol 8:450–451 (in Japanese)