5.6
II.5.6 Naphthalene
by Kanako Watanabe
Introduction
Naphthalene (naphthalin) is being widely used as a moth repellant (insecticide), and being sold
at supermarkets and general stores. Since one package of the compound usually contains as
much as 1.8–5 g of naphthalene, the accidental ingestion of such a product by a small infant
may cause fatality. However, recently, p-dichlorobenzene products, to be dealt with in the next
chapter, have become more popular as a moth repellant.
Naphthalene exists in the form of colorless crystals at room temperature, but easily sublimes into its gas with an aromatic odor exerting the repellant effect for insects.
In this chapter, a method for headspace GC/MS analysis of naphthalene is presented utilizing its volatile property.
Reagent and their preparation
i. Reagents
Naphthalene can be purchased from Sigma (St. Louis, MO, USA); stable-isotopic naphthalene-d8 a
(internal standard, IS) from Aldrich (Milwaukee, WI, USA). Other common chemicals used are
of the highest purity commercially available.
ii. Preparation
Naphthalene and naphthalene-d8 (IS) solutions: 2-mg aliquot each is dissolved in 2 mL methanol to prepare stock solution separately. A 1-µL aliquot of each stock solution is injected into
GC/MS to measure each mass spectrum.
For spiked tests, the above each stock solution is diluted 10-fold with methanol; a different
volume of the naphthalene solution (1–10 µL containing 0.1–1 µg) and 10 µL (containing
1 µg) of naphthalene-d8 (IS) solution are placed in each glass vial with a Teflon-septum cap
containing 0.2 mL of blank whole blood.
GC/MS conditions
GC column b: an Rtx-1 fused silica medium-bore capillary column (30 m × 0.32 mm i. d., film
thickness 0.25 µm, Restek, Bellefonte, PA, USA).
GC conditions; instrument: a GC-17A gas chromatographc (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 flow rate: 3 mL/min; injection mode: splitless
for 1 min after injection, followed by the split mode.
© Springer-Verlag Berlin Heidelberg 2005
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Naphthalene
MS conditions; instrument: a Shimadzu QP-5050 quadrupole mass spectrometerc (connected with the above GC); ionization: positive ion EI; electron energy: 70 eV; emission current: 60 µA; ion source temperature: 280 °C; accelerating voltage: 1.5 kV.
Procedure
A 0.2-mL volume of a whole blood specimend, 10 µL (containing 1 µg) of IS solution and
0.8 mL distilled water are placed in a 7-mL volume glass vial with a Teflon-septum screw
cap, capped and mixed gently.
ii. The 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 syringee is also heated on the same block. The needlef size for the syringe
is 23 G. After heating, a 1-mL volume of the headspace vapor is withdrawn into the heated
syringe, and carefully injected into GC/MS not to influence the vacuum degree of the MS
instrument.
iii. Detection is made using ions at m/z 128 for naphthalene and at m/z 136 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, 10 µL IS solution and a different amount of naphthalene are added. The mixture is treated according to the above procedure. The calibration
curve consists of peak area ratio of naphthalene to IS on the vertical axis and naphthalene
concentration on the horizontal axis. The peak area ratio obtained from a blood specimen
is applied to the calibration curve to obtain a naphthalene concentrationg.
i.
Assessment of the method
> Figure 6.1 shows mass spectra of naphthalene and IS. By this method, most reliable identification of naphthalene can be achieved. The molecular ions constituted the base peaks; the
peaks at m/z 128 and 136 are not interfered with each other. > Figure 6.2 shows SIM chromatograms for naphthalene and IS, which had been extracted by the headspace method. The
detection limit of naphthalene in the SIM mode was about 100 ng/mL in whole blood.
The efficiency (recovery) of naphthalene was tested; about 25–30 % of total naphthalene,
which had been added to blank whole blood, were distributed in the headspace gas in the 7-mL
volume vial after 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 broadening of a peak to be detected. However, it is not the case in the present method; each peak
appears in a sharp shape ( > Fig. 6.2). The author adopted a relatively low temperature (50 °C)
of the column (oven) upon injection of the headspace vapor, and confirmed that an entire
amount of naphthalene contained in the headspace gas injected was completely trapped inside
the column at 50 °C.
It should be kept in mind that naphthalene is contained in gasoline, kerosene and heavy oil
[1] and also in tobacco smoke [2].
Naphthalene
⊡ Figure 6.1
Mass spectra of naphthalene and naphthalene-d8 (IS).
⊡ Figure 6.2
SIM chromatograms for naphthalene and IS headspace-extracted from whole blood. The
amounts of IS and naphthalene spiked to 0.2 mL blood were 1 µg and 50 ng, respectively.
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Naphthalene
Poisoning case and fatal concentrations
A 6-month-old male [3] opened two packages of naphthalene (commercial name: Neopas®) and
seemed to ingest a part of the total amount (18 g) of the compound, because an appreciable amount
of its crystals were found attached around his mouth and to the face and scalp hair. At 3 h later, he
was cheerful and showed no symptoms upon arrival at a hospital. His skin was immediately
washed, and various treatments, such as gastrolavage, administration of activated charcoal and a
purgative (magnesium citrate) and enforced diuresis, were given to him. On the 5th day of admission, exanthemas, followed by blisters and erosions, appeared in his back; they were improved by
the oral administration of Predonine® (prednisolone) together with the topical deterging. On day
6, hemolysis appeared together with the decrease of hemoglobin value from 12.7 to 10.6 g/dL.
During careful monitoring of his conditions, no abnormalities were observed for his neurological,
hepatic and renal functions. On day 14, he was discharged with complete recovery. In this case, the
real amount of naphthalene ingested by him seemed much smaller than that estimated.
When a large amount of naphthalene is taken orally, vomiting takes place in every case;
there appears abdominal spasm associated with diarrhea. When naphthalene is absorbed into
the body, central nervous system symptoms, such as headache, vertigo, unconsciousness, convulsion and coma appear. Naphthalene is metabolized into α- and β-naphthols and naphthoquinone, which cause severe hemolysis, followed by hemoglobinemia, methemoglobinemia
and then renal dysfunction after several days [4, 5].
Oral fatal doses estimated are 1–2 g for infants and 5–15 g for adults with great variations
among individuals [3].
The number of reports describing the concentrations of naphthalene in blood and tissues
in its poisoning cases is very limited. Ijiri et al. [6] reported a case, in which a neurotic mother
had given her 2-month-old male baby milk mixed with 6 g naphthalene; he had died 30 min–
1 h later. The concentrations of naphthalene in blood, the liver and kidney were 0.55, 0.12 and
0.03 µg/g or mL, respectively.
Notes
a) Stable-isotopic naphthalene is commercially available from Aldrich and Sigma (product
No. 17,604-4). Its price is not expensive. In MS techniques, the use of a stable-isotopic
compound is most desirable for quantitation; this is called “isotope dilution technique”.
b) Any type of non-polar dimethylsilicone capillary columns can be used, irrespective of their
manufacturers. An Rtx-Volatiles fused silica capillary column (30 m × 0.32 mm, film thickness 1.5 µm) was also tested, but the Rtx-1 column gave better results.
c) Any type of GC/MS instruments including sector, quadrupole and ion-traps types can be
used.
d) Since whole blood can be analyzed by this method, urine seems also analyzable with the
same procedure.
e) Either a usual 5-mL volume glass syringe or a gas-tight syringe can be used.
f) The tip of the usual injection-syringe needle is being cut obliquely and sharply. This can be
used in this method. However, the author is using a special type of 23 G needles, which has
a tip being cut conically; this needle is advantageous, because such a tip prevents the needle
from being clogged by septum debris.
Naphthalene
g) It is possible to make quantitation analysis without IS using an external calibration curve.
Also in place of the stable-isotopic compound, 1-methylnaphthalene or 2-methylnaphthalene can be used as IS.
References
1) Bertsch W, Holzer G (1995) Analysis of accelerants in fire debris by gas chromatography/mass spectrometry.
In: Yinon J (ed) Forensic Applications of Mass Spectrometry. CRC Press, Boca Raton, pp 129–169
2) Schmeltz I, Tosk J, Hoffmann D (1976) Formation and determination of naphthalenes in cigarette smoke. Anal
Chem 48 645–650
3) Japan Poisoning Information Center (ed) (2000) Poisoning Accidents and their Countermeasures with Special
Reference to Actual Cases, revised ed. Jiho Inc., Tokyo, pp 65–68 (in Japanese)
4) Nishi K (ed) (1999) Emergency Manual for Poisoning. Iyaku Journal, Osaka, pp 244–245 (in Japanese)
5) Ukai T (ed) (1999) Manual of Treatments in Acute Poisoning, 3rd edn. Jiho Inc., Tokyo, pp 156–157 (in
Japanese)
6) Ijiri I, Shimosato K, Ohmae M et al (1987) A case report of death from naphthalene poisoning. Jpn J Legal Med
41:52–55
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