Aprea et al. [5] used pentafluorobenzyl bromide (PFBBr) for transformation of
3PBA into pentafluorobenzyl ester, which was further determined by gas chromatography with an intermediate polarity capillary column and an electron-capture
detector. PFBBr as a strong lachrymator should be handled with special care.
Yoshida et al. used N-trimethylsilylimidazole (TMSI) with trimethylchlorosilane
(TMCS) for derivatization of hydroxylated alcohols and N-(tert-butyldimethylsilyl)N-methyltrifluoroacetamide (MTBSTFA) for efficient derivatization of carboxylic
metabolites of several synthetic pyrethroids [20].
Recently, Schettgen et al. [9] modified and widened the scope of their original
method [11] by adding new metabolites, namely: ClF3CA (BIF), CPBA
(4-chloro-α-isopropyl benzene acetic acid), and MPB (2-methyl-3-phenylbenzoic
acid). Effective sample cleanup was achieved by extraction to hexane and
re-extraction to 0.1 M NaOH. Gas chromatography with tandem mass spectrometry
was used for separation and quantitative analysis. The limit of quantification for all
metabolites was 0.01 ng/mL when 10 mL of urine was processed.
3.2 Gas Chromatography
Gas chromatography (GC) methods were the first developed for determination of
synthetic pyrethroid metabolites in human urine. Up to now this technique dominates over others for this group of analytes. Although acidic metabolites need to be
derivatized before gas chromatography separation, GC-MS remains the method of
choice when considering the determination of pyrethroid metabolites in urine. Due
to the high separation power, equipment availability, reasonable purchase, and
maintenance cost, GC-MS serves as a reliable method.
Typical nonpolar capillary columns, such as DB-5 ms (5%-phenyl-95%dimethylpolysiloxane, 30 m  0.25 mm  0.25 μm) [7, 20, 26], HP-5 ms
(60 m  0.25 mm  0.25 μm) [6, 9], VF-5 ms low-bleed column
(30 m  0.25 mm  0.25 μm) [24], XLB column (60 m  0.25 mm  0.25 μm
film thickness), [22, 25] as well as medium polarity HP-35 (cross-linked 35%
diphenyl-dimethylpolysiloxane, 60 m  0.25 mm  0.25 μm) [11], DB-608
(30 m  0.25 mm  0.25 μm) [28], and relatively polar column Rtx 65 (crosslinked 65%-phenyl-35%-dimethylpolysiloxane 30 m  0.25 mm  1 μm) [10], were
used for separation of respective derivatives of synthetic pyrethroid metabolites.
In two published methods, electron-capture detector (ECD) was used
[5, 28]. High sensitivity of ECD toward halogen-containing molecules allows for
detection of hexafluoroisopropyl esters and pentafluorobenzyl esters of pyrethroid
metabolites. Despite the high sensitivity of the detector, these methods were not used
further in biomonitoring studies possibly due to the lack of specificity in comparison
to MS detection. Both quadrupole and ion-trap mass spectrometers operated in
single-ion mode (SIM), as well as multiple reaction monitoring (MRM), offered
sufficient sensitivity.
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B. Wielgomas et al.
3PBA into pentafluorobenzyl ester, which was further determined by gas chromatography with an intermediate polarity capillary column and an electron-capture
detector. PFBBr as a strong lachrymator should be handled with special care.
Yoshida et al. used N-trimethylsilylimidazole (TMSI) with trimethylchlorosilane
(TMCS) for derivatization of hydroxylated alcohols and N-(tert-butyldimethylsilyl)N-methyltrifluoroacetamide (MTBSTFA) for efficient derivatization of carboxylic
metabolites of several synthetic pyrethroids [20].
Recently, Schettgen et al. [9] modified and widened the scope of their original
method [11] by adding new metabolites, namely: ClF3CA (BIF), CPBA
(4-chloro-α-isopropyl benzene acetic acid), and MPB (2-methyl-3-phenylbenzoic
acid). Effective sample cleanup was achieved by extraction to hexane and
re-extraction to 0.1 M NaOH. Gas chromatography with tandem mass spectrometry
was used for separation and quantitative analysis. The limit of quantification for all
metabolites was 0.01 ng/mL when 10 mL of urine was processed.
3.2 Gas Chromatography
Gas chromatography (GC) methods were the first developed for determination of
synthetic pyrethroid metabolites in human urine. Up to now this technique dominates over others for this group of analytes. Although acidic metabolites need to be
derivatized before gas chromatography separation, GC-MS remains the method of
choice when considering the determination of pyrethroid metabolites in urine. Due
to the high separation power, equipment availability, reasonable purchase, and
maintenance cost, GC-MS serves as a reliable method.
Typical nonpolar capillary columns, such as DB-5 ms (5%-phenyl-95%dimethylpolysiloxane, 30 m  0.25 mm  0.25 μm) [7, 20, 26], HP-5 ms
(60 m  0.25 mm  0.25 μm) [6, 9], VF-5 ms low-bleed column
(30 m  0.25 mm  0.25 μm) [24], XLB column (60 m  0.25 mm  0.25 μm
film thickness), [22, 25] as well as medium polarity HP-35 (cross-linked 35%
diphenyl-dimethylpolysiloxane, 60 m  0.25 mm  0.25 μm) [11], DB-608
(30 m  0.25 mm  0.25 μm) [28], and relatively polar column Rtx 65 (crosslinked 65%-phenyl-35%-dimethylpolysiloxane 30 m  0.25 mm  1 μm) [10], were
used for separation of respective derivatives of synthetic pyrethroid metabolites.
In two published methods, electron-capture detector (ECD) was used
[5, 28]. High sensitivity of ECD toward halogen-containing molecules allows for
detection of hexafluoroisopropyl esters and pentafluorobenzyl esters of pyrethroid
metabolites. Despite the high sensitivity of the detector, these methods were not used
further in biomonitoring studies possibly due to the lack of specificity in comparison
to MS detection. Both quadrupole and ion-trap mass spectrometers operated in
single-ion mode (SIM), as well as multiple reaction monitoring (MRM), offered
sufficient sensitivity.
56
B. Wielgomas et al.