differences in aquatic toxicity between enantiomers from the same diastereomers of
pyrethroids. Therefore, the comprehensive understanding of the ecotoxicological
effect and fate of pyrethroid insecticides is mandatory for the regulation and development of new products. Thus, the authors examined the enantiomer compositions
of selected pyrethroids in field sediment samples taken from various locations in
southern California. Enantioselective transformation was frequently observed for
cis-bifenthrin, permethrin and cyfluthrin under field conditions. In addition, long
incubation experiments under laboratory-controlled conditions using single enantiomers of cis-bifenthrin, cis-permethrin and cypermethrin were conducted. The halflives for individual enantiomers were calculated with 277–770 days for cisbifenthrin enantiomers, 99–141 days for cis-permethrin enantiomers and 52–135
days for cypermethrin enantiomers, respectively. The enantiomer selectivity for soil
degradation was found to be dependent on inherent compound properties as well as
experimental conditions. A recent review of the environmental behaviour of synthetic pyrethroids may be consulted for further detailed information on this pesticide
group (Gan 2008).
The simultaneous enantiomer-selective separation of three modern chiral pesticides is reported by Wang et al. (2008). A new HPLC-UV-based analytical method
(CSP: amylose-tris(3,5-dimethylphenylcarbamate ¼ AD column) for the EF determination of paclobutrazol, myclobutanil and uniconazole in soil and water was
developed. The enantiomers were identified by a circular dichroism detector. Validation involved complete resolution of each of the two enantiomers, plus the
determination of linearity, precision and limit of detection (LOD). The pesticide
enantiomers were isolated by solvent extraction from soil and C 18 solid-phase
extraction from water. The two enantiomers of the three pesticides could be
completely separated on the AD column using n-hexane and 2-propanol as mobile
phase. The linearity and precision results indicated that the method was reliable for
the quantitative analysis of the enantiomers. LODs were 0.025, 0.05 and 0.05 mg/kg
for each enantiomer of paclobutrazol, myclobutanil and uniconazole, respectively.
Recovery and precision data showed that the pretreatment procedures were satisfactory for enantiomer extraction and clean-up. This method can be used for optical
purity determination of technical material and analysis of environmental residues,
but in this case with a more sensitive detection system.
The pesticide salithion was separated into enantiomers with HPLC and Chiralpak
AD as CSP (Zhou et al. 2009) for subsequent effect assessment. HPLC-based
separation on Chiracel OJ was applied for the enantiomer-selective separation of
several triazole fungicides. The influence of column temperature was studied for the
optimisation of the resolution, as well as the type and percentage of organic modifier
in the mobile phase with thermodynamic methods. The retention factors for the
enantiomers of all investigated compounds decreased as the temperature increased.
The natural logarithms of the selectivity factors (ln α) of hexaconazole,
tebuconazole, flutriafol, propiconazole and difenoconazole depended linearly on
the inverse of temperature (1/T ), while the corresponding values for triadimefon
and diniconazole kept unchanged in the studied temperature range 10–35
C. Van’t
Hoff plots afforded thermodynamic parameters, such as the apparent change in
8.2 Transformation/Accumulation of Chiral Xenobiotics in Higher Organisms
211
pyrethroids. Therefore, the comprehensive understanding of the ecotoxicological
effect and fate of pyrethroid insecticides is mandatory for the regulation and development of new products. Thus, the authors examined the enantiomer compositions
of selected pyrethroids in field sediment samples taken from various locations in
southern California. Enantioselective transformation was frequently observed for
cis-bifenthrin, permethrin and cyfluthrin under field conditions. In addition, long
incubation experiments under laboratory-controlled conditions using single enantiomers of cis-bifenthrin, cis-permethrin and cypermethrin were conducted. The halflives for individual enantiomers were calculated with 277–770 days for cisbifenthrin enantiomers, 99–141 days for cis-permethrin enantiomers and 52–135
days for cypermethrin enantiomers, respectively. The enantiomer selectivity for soil
degradation was found to be dependent on inherent compound properties as well as
experimental conditions. A recent review of the environmental behaviour of synthetic pyrethroids may be consulted for further detailed information on this pesticide
group (Gan 2008).
The simultaneous enantiomer-selective separation of three modern chiral pesticides is reported by Wang et al. (2008). A new HPLC-UV-based analytical method
(CSP: amylose-tris(3,5-dimethylphenylcarbamate ¼ AD column) for the EF determination of paclobutrazol, myclobutanil and uniconazole in soil and water was
developed. The enantiomers were identified by a circular dichroism detector. Validation involved complete resolution of each of the two enantiomers, plus the
determination of linearity, precision and limit of detection (LOD). The pesticide
enantiomers were isolated by solvent extraction from soil and C 18 solid-phase
extraction from water. The two enantiomers of the three pesticides could be
completely separated on the AD column using n-hexane and 2-propanol as mobile
phase. The linearity and precision results indicated that the method was reliable for
the quantitative analysis of the enantiomers. LODs were 0.025, 0.05 and 0.05 mg/kg
for each enantiomer of paclobutrazol, myclobutanil and uniconazole, respectively.
Recovery and precision data showed that the pretreatment procedures were satisfactory for enantiomer extraction and clean-up. This method can be used for optical
purity determination of technical material and analysis of environmental residues,
but in this case with a more sensitive detection system.
The pesticide salithion was separated into enantiomers with HPLC and Chiralpak
AD as CSP (Zhou et al. 2009) for subsequent effect assessment. HPLC-based
separation on Chiracel OJ was applied for the enantiomer-selective separation of
several triazole fungicides. The influence of column temperature was studied for the
optimisation of the resolution, as well as the type and percentage of organic modifier
in the mobile phase with thermodynamic methods. The retention factors for the
enantiomers of all investigated compounds decreased as the temperature increased.
The natural logarithms of the selectivity factors (ln α) of hexaconazole,
tebuconazole, flutriafol, propiconazole and difenoconazole depended linearly on
the inverse of temperature (1/T ), while the corresponding values for triadimefon
and diniconazole kept unchanged in the studied temperature range 10–35
C. Van’t
Hoff plots afforded thermodynamic parameters, such as the apparent change in
8.2 Transformation/Accumulation of Chiral Xenobiotics in Higher Organisms
211