The purchase sources and purities of the standard materials
for determination of the 15 targeted urinary metabolites
are shown in Table 1. The standard materials were
used without further purification. N-(tert-Butyldimethylsilyl)-
N-methyltrifluoroacetamide (MTBSTFA) for transforming the
metabolites into their tert-butyldimethylsilyl derivatives and isopropylphosphate
(diisopropylphosphate: 68.3%) as an internal
standard were purchased from Tokyo Kasei Kogyo (Tokyo, Japan)
and sodium disulfite, which was of analytical-reagent grade, from
Kanto Chemical (Tokyo, Japan). Other chemicals were obtained from Wako Pure Chemical (Osaka, Japan). Toluene and methylacetate
were of a grade for analysis of dioxins and for environmental
analysis, respectively. Acetonitrile was of a grade for analysis of
pesticide residue and polychlorinated biphenyl. All other chemicals
were of analytical-reagent grade. Isolute ENV+ (bulk; hydroxylated
polystyrene-divinylbenzene copolymers), a sorbent for extracting
metabolites from urine, was obtained from Biotage (Uppsala,
Sweden)