Th e composition ratios of cresol isomers are diff erent accord-ing to cresol-containaccord-ing products; it, therefore, seems very important to measure the concentra-tions of each isome
Trang 1© Springer-Verlag Berlin Heidelberg 2005
Introduction
Cresol is being used for an antiseptic, disinfectant, maggot-killing agent and cresol soap solu-tion Since various kinds of more powerful and odorless disinfectants have nowadays become available in practical use, the frequency in the use of cresol seems decreasing However, the cases of acute poisoning by cresol are still being reported at the present time
Th e toxic eff ects of cresol are due to its corrosive actions, resulting in the destruction of cell membranes and coagulation of proteins, and its suppressive action on the central nervous sys-tem [1] Th ere are three isomeric forms of cresol, vis., o-, m- and p-cresols; the toxicity of each
isomer is somewhat diff erent [2] Th e composition ratios of cresol isomers are diff erent accord-ing to cresol-containaccord-ing products; it, therefore, seems very important to measure the concentra-tions of each isomer of cresol to identify a causative cresol product used in its poisoning case Cresol, aft er being absorbed into human bodies, is metabolized into glucuronide- and/or sulfate-conjugated forms and excreted into urine Th e half-life of unchanged cresol in blood is
as short as about 1.5 h [3]; this means that it becomes undetectable several hours aft er emer-gency treatments However, the metabolites (conjugated forms) remain in the body for rela-tively a long time [4–6]; the detection of the conjugated form(s) sometimes becomes necessary
As methods for analysis of cresol, GC [4, 7–9], HPLC [5, 6, 10–14] and capillary electro-phoreisis [15] were reported In this chapter, procedures for HPLC and GC/MS analysis of cresol isomers and their conjugates are presented
HPLC analysis
Reagents and their preparation
• A 10-mg aliquot each of o-, m- and p-cresols (Aldrich, Milwaukee, WI, USA and other
manufacturers) is dissolved in 10 mL methanol separately (1 mg/mL)
• A 10-mg aliquot of 4-ethylphenola (internal standard, IS, Aldrich and other manufacturers)
is dissolved in 10 mL methanol (1 mg/mL)
• β-Glucuronidase: 10 mg of bovine liver glucuronidase (EC 3.2.1.31, type B-10, 11,000 units/mg solid, Sigma, St Louis, MO, USA) is dissolved in 1 mL distilled water
• Sulfatase: Aerobacter aerogenes sulfatase (EC 3.1.6.1, 19 units/mL, Sigma).
HPLC conditions
Instruments; pump: LC-10A; detectors: SPD-10A and RF-10A (all from Shimadzu Corp.,
Kyo-to, Japan); column: a Nova-Pak C18 stainless cartridge column (150 × 3.9 mm i.d., particle size
Trang 2582 Cresol
4 µm, Waters, Milford, MA, USA); guard column: Guard-Pak Nova-Pak C18 (Waters); mobile phaseb: acetonitrile/20 mM potassium dihydrogenphosphate buff er solution (pH 3.0, to be ad-justed with phosphoric acid) (1:4, v/v), containing 20 mM β-cyclodextrin (Sigma and other manufacturers); its fl ow rate: 1.0 mL/min; detection wavelength: 270 nm for the UV detector;
fl uorescence detector: Ex 270 nm and Em 305 nm; injection volume: 20 µL
Procedures
i Analysis of unconjugated forms
i A 100-µL volume of a specimenc is mixed with 10 µL of IS solution
ii A 100-µL volume of acetonitrile is added to the above mixture with stirringd
iii It is centrifuged at 12,000 g for 10 min
iv A 20-µL aliquot of the supernatant solution is injected into HPLC
v Various concentrations (not less than 4 plots) of a cresol isomer plus 10 µL of IS solution are added to blank specimens and processed in the same way to construct a calibration curve
Th e concentration of a cresol isomer in a test specimen is calculated with the curve
ii Analysis of the glucuronide-conjugated forms
i A 100-µL volume of a specimenc is mixed with 10 µL of IS solution
ii A 5-µL volume of 4 M sodium acetate buff er solution (pH 5.0) and 5 µL of β-glucuroni-dase solution are added to the above mixture and incubated at 37 °C for 2 h
iii Aft er cooling to room temperature, 100 µL acetonitrile is placed in the above mixture with stirring
iv Th e following procedure is achieved according to the iii–v steps of the above section
iii Analysis of the sulfate-conjugated forms e
i A 100-µL volume of a specimenc is mixed with 10 µL of the IS solution
ii A 5-µL volume of 2.5 M Tris-HCl buff er solution (pH 7.5) and 5 µL of sulfatase are added
to the above mixture and incubated at 37 °C for 2 h
iii Aft er cooling to room temperature, 100 µL acetonitrile is added to the above mixture with stirring
iv Th e following procedure is achieved according to the iii–v steps of the above section for ana-lysis of unconjugated forms
Assessment of the method
In this method, the pretreatment procedures are very simple and thus enable rapid analysis of cresol isomers and their conjugates It does not include no condensation step; it means that there is no concern about low recovery rates due to loss of a test compound caused by evapora-tion However, a great diff erence in composition ratio of acetonitrile in the supernatant solu-tion may aff ect the peak area ratio of cresol to IS; it is preferable to fi x the composisolu-tion ratio of acetonitrile before injection into HPLC
> Figure 6.1 shows HPLC chromatograms for the authentic cresol isomers and related
compounds and for extracts of plasma or urine of a poisoning case Th e cresol isomers are
Trang 3completely separated from each other; in addition, the test peaks are not interfered with by phenol or xylenol being contained in the cresol soap solution commercially available
With the UV detector, the quantitative range for each cresol isomer is 1–100 µg/mL; the detection limit is 0.1 µg/mL For the urine specimen, the impurity peaks interfere with that of
p-cresol; it is diffi cult to measure p-cresol at low concentration (not higher than 1 µg/mL) by HPLC-UV detection
By using a fl uorescence detector, the specifi city and sensitivity are increased; the detection limit of cresol isomers by HPLC-fl uorescence detection is 0.01 µg/mL
Th e concentration of a conjugated form can be calculated by subtracting the amount of a free form of a cresol isomer from its total amount obtained aft er enzymatic hydrolysis
HPLC chromatograms for the authentic standard cresol isomers and related compounds
(10 µg/mL each) and for extracts of plasma and urine of a poisoning case 1: phenol; 2: p-cresol; 3: m-cresol; 4: o-cresol; 5: 4-ethylphenol; 6: 2,4-xylenol.
⊡ Figure 6.1
Trang 4584 Cresol
GC/MS analysis
Reagents and their preparation
o-, m- and p-Cresols and IS are prepared according to the section of reagents and preparation
of the HPLC analysis
GC/MS conditions
Instrument: an HP 6890 Series GC/MS instrument (Agilent Technologies, Palo Alto, CA, USA)
Condition 1: Column: HP-5 Trace Analysis (30 × 0.25 mm i.d., fi lm thickness 0.25 µm, Agilent Technologies); carrier gas: He (1.0 mL/min); column (oven) temperature: 50 °C (4 min)
→ 20 °C/min → 300 °C (3.5 min); injection volume: 1 µL (splitless); injection temperature:
300 °C; detector temperature: 280 °C
Condition 2: Column: DB-WAX (60 m × 0.32 mm i d., fi lm thickness 0.5 µm, J & W Scientifi c, Folsom, CA, USA); carrier gas: He (1.0 mL/min); column temperature: 200 °C; injection volume:
1 µL (splitless); injection temperature: 250 °C; detector temperature: 280 °C
Procedure
i An Oasis HLB (3 cc, 60 mg) cartridge (Waters, Milford, MA, USA) is activated by passing
3 mL methanol and 3 mL distilled water
ii A 0.1-mL volume of a specimenf is mixed with 0.9 mL distilled water and 10 µL IS solution, and poured into the activated cartridge
iii Th e test tube, which had contained the specimen, is rinsed with 1 mL distilled water; the rinsed water is also poured into the cartridge
iv Th e cartridge is washed with 1mL distilled water, and the water inside the cartridge is re-moved by aspiration under reduced pressure
v Th e target compound(s) and IS are eluted with 1 mL ethyl acetate
vi Th e organic eluate is condensedg into about 100 µL under a stream of nitrogen with warm-ing at 50 °C
vii A 1-µL aliquot of it is injected into GC/MS
Assessment of the method
> Figure 6.2 shows total ion chromatograms (TICs) for the authentic cresol isomers and
related compounds (10 µg/mL each) When non-polar and slightly polar columns (HP-1 or
HP-5) are used, p-cresol cannot be separated from m-cresol With use of a DB-WAX column,
such separation can be achieved ( > Figure 6.2, lower panal).
Th e relative recovery rate of cresol isomers as compared with that of IS was 98 %; their detection limit in the scan mode is about 1 ng on-column
Trang 5Poisoning cases, and toxic and fatal concentrations
Cresol poisoning case due to its percutaneous absorption: a male child was playing on a slide
in a park, and slid into a puddle with his buttocks getting wet with water probably containing
a large amount of cresol Aft er 30 min, he fell into a disturbance of consciousness, underwent treatments at an emergency hospital and was discharged 24 days aft er, because of improvement
of his conditions Th e time courses of plasma concentrations of cresol isomers and their conju-gates, measured by HPLC, are shown in > Figure 6.3 Th e plasma concentrations of free,
sul-fate-conjugated and glucuronide-conjugated forms for p-cresol 2 h aft er the accident were
15.7, 21.3 and 38.6 µg/mL, respectively; those for m-cresol 31.4, 17.0 and 82.9 µg/mL,
respec-tively Aft er 8 h, the concentrations of sulfate-conjugated forms were higher than those of the glucuronide-conjugated forms, and detectable for a long time Th e urinary concentrations at
an early stage of admission were 17.4, 102 and 709 µg/mL for the free, sulfate-conjugated and
glucuronide-conjugated forms of p-cresol, respectively; 12.0, 151 and 1,510 µg/mL for those of
m-cresol, respectively.
TICs by GC/MS for the authentic cresol isomers and related compounds (10 µg/mL each in ethyl acetate) using different GC columns.
⊡ Figure 6.2
Trang 6586 Cresol
Cresol poisoning case due to its oral intake: a female ingested about 80 mL of cresol soap
solution for suicidal purpose, underwent treatments, such as gastrolavage and hemophoresis and was remitted Th e time courses of plasma concentrations of cresol isomers and their con-jugates, measured by HPLC, are shown in > Figure 6.4 Th e plasma concentrations 3.5 h aft er ingestion were 16.3, 19.6 and 78.5 µg/mL for the free, sulfate-conjugated and
glucuronide-con-jugated forms of p-cresol, respectively; 37.4, 18.7 and 147 µg/mL for those of m-cresol,
respec-tively Th e concentrations of glucuronide-conjugated forms were higher than those of sulfate-conjugated forms until several hours aft er ingestion; but the former concentrations become
lower than the latter aft er 26 h (> Figure 6.4).
Phenol and p-cresol endogenously exist in humans, because they are produced during
metabolic decomposition of tyrosine by enteric bacteria [11] When plasma and urine
speci-mens from 5 healthy subjects were analyzed, p-cresol sulfate-conjugate was found in plasma
and urine at concentrations of 0.4 ± 0.3 and 31.0 ± 14.4 µg/mL, respectively; the concentration
of p-cresol glucuronide-conjugate in urine was 1.3 ± 0.9 µg/mL Th e endogenous p-cresol
con-centrations in plasma are relatively low and give no problems upon analysis in acute poisoning;
but with urine specimens, appreciable amounts of the endogenous p-cresol sulfate-conjugate
should be taken into consideration
Although there are numerous reports dealing with cresol poisoning, the reports describing cresol concentrations are not so many; they are listed in > Table 6.1 [3–7, 14, 16–21].
Case 3 shows a high blood cresol concentration; but her cause of death was exsanguina-tions due to being stabbed in her abdomen Case 5 died aft er treatments for 4 days; cresols were measured for the serum, which had been sampled about 24 h aft er ingestion, and were ex-pressed as a total amount of phenols, but free phenol could not be detected Th e victim in Case
6 with blood cresol concentration at only 10 ng/mL was suff ering from severe liver cirrhosis,
Time courses of plasma concentrations of cresol isomers and their conjugates in a
cresol-poisoned patient after percutaneous absorption.
⊡ Figure 6.3
Trang 7Time courses of plasma concentrations of cresol isomers and their conjugates in a
cresol-poisoned patient after its oral intake.
⊡ Figure 6.4
⊡ Table 6.1
Cresol poisoning cases
Case
No.
Age Sex Amount
of intake (mL)
Route Blood or plasma
concentration*
Time after intake (h)
Presence/
absence
of therapy
Out-come
Ref
unconju-gated form
conju-gated form
–
Trang 8588 Cresol
and was thus considered exceptional as a fatal case Th e blood concentrations of unconjugated cresol in fatal poisoning cases are 71–190 µg/mL
In the survived Cases 7–14, the blood specimens were sampled at the fi rst medical exami-nation; the plasma concentrations of unconjugated cresol were 9.5–58 µg/mL
Notes
a) 4-Ethylphenol to be used as IS may contain phenol and p-cresol as impurities Th e contents
of the impurities should be carefully checked before use
b) By adding β-cyclodextrin to the mobile phase, the separation of p-cresol from m-cresol can
be realized
c) As a specimen, blood, plasma or urine can be used When organ tissue is used, 1 g of it is put in 4 mL of cold distilled water, minced into small pieces with surgical scissors and homogenized with cooling with ice Th e homogenate can be used as a specimen; but the cresol glucuronide-conjugates may be hydrolyzed by the coexisting glucuronidase, result-ing in a higher concentration of the unconjugated cresols durresult-ing the procedure
d) Without stirring, the surface layer of the specimen solution may be coagulated, hindering the solution from well-mixing
e) To analyze the sulfate-conjugated forms of cresol isomers in organ tissues, the eff ect of endogenous glucuronidase should be excluded by adding saccharolactone as an inhibitor
of the enzyme
f) As a specimen, blood, plasma or urine can be used
g) Th e organic eluate should not be evaporated to dryness, because it causes very low recovery rates due to evaporation of free cresol isomers
References
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by high-performance liquid chromatography In: Takatori T (ed) Proceedings of the 14th Meeting of the Inter-national Association of Forensic Sciences, Vol 2 Shunderson Communications, Ottawa, pp 258–261
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an English abstract)
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J Toxicol 9:101–105 (in Japanese with an English abstract)