enantioselectivity of such antiviral compound is an important factor that should be
considered when studying environmental effect of chiral pesticides. The configuration of dufulin enantiomers was determined in this study based on their circular
dichroism spectra. The S-(+)-dufulin and R-(À)-dufulin enantiomers were separated
and identified using a ChiralPaK IA column (CSP: amylose tris(3,5-dimethylphenylcarbamate)) and NP-HPLC/MS. The degradation of the racdufulin and the corresponding enantiomers followed first-order reaction kinetics
with reasonable linearity. The enantioselective photolysis of rac-dufulin was found
to be enantiomer-selective, showing a faster transformation of R-(À)-dufulin, compared to S-(+)-dufulin. This finding indicates that the combination of
phototransformation and enantiomer-selective adsorption/desorption processes
may result in the enantiomer selectivity of this observed process. S-(+)-dufulin
was also hydrolysed faster than the R-enantiomer. The same research group follow
up on these first results with a study on the enantiomer-selective distribution of
difulin in four different soil types (Zhang et al. 2014a, b, c). Also here, the
enantiomeric signature of the difulin enantiomers was determined on a ChiralPak
IA HPLC column and detected with mass-selective detection. Four local types of soil
(Guiyang silty loam, Nanning silty clay, Hefei silty clay and Harbin silty clay) were
investigated under sterile and non-sterile conditions. The dufulin enantiomer distribution was found to be stable and near racemic in the selected soils. No interconversion was observed during the incubation of enantiomerically pure S-(+)- or R(À)-dufulin under non-sterile conditions. The half-life (τ 1/2 ) confirmed that the
degradation of dufulin in sterile soils was slower compared to non-sterile soils.
These results suggest that dufulin transformation can be primarily attributed to
microbial activity in soils used for agricultural cultivation. Furthermore,
enantiomerically pure S-(+)-difulin degraded more rapidly than the corresponding
R-enantiomer.
The levels and elimination properties of the triazole pesticide penconazole
(IUPAC: 1-[2-(2,4-dichlorophenyl)pentyl]-1,2,4-triazole) was investigated in vegetables (Wang et al. 2014). The enantioselective dissipation of penconazole in
cucumber, tomato, head cabbage and pakchoi was investigated by field experiments.
A sensitive method for the enantiomeric analysis of penconazole was established on
the basis of the buffered QuEChERS sample preparation technique followed by
RP-HPLC/MS and a Lux Cellulose-2 column (Phenomenex: CSP: Cellulose tris
(3-chloro-4-methylphenylcarbamate)). Methanol and 2-mM ammonium ethanoate
buffer solution containing 0.1% methanoic acid (70:30, v/v) were used as mobile
phase at a 0.2 mL min
À1
flow rate isocratic elution. The study of the enantiomerselective dissipation in head cabbage and pakchoi showed the preferential transformation of (À)-penconazole, resulting in an enrichment of the (+)-penconazole.
However, the enantiomer-selective behaviour was not observed in cucumber and
tomato.
For the enantiomer-specific analysis of flufiprole in vegetables and fruits, a new
selective analytical method is reported (Tian et al. 2015). The enantiomer separation
was conducted on RP-HPLC with a Lux Cellulose-2 (Phenomenex, CSP: tris
(3-chloro-4-methylphenylcarbamate)) and mass-selective detection. The effects of
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8 Enantiomer-Specific Fate and Behaviour of Chiral Contaminants
considered when studying environmental effect of chiral pesticides. The configuration of dufulin enantiomers was determined in this study based on their circular
dichroism spectra. The S-(+)-dufulin and R-(À)-dufulin enantiomers were separated
and identified using a ChiralPaK IA column (CSP: amylose tris(3,5-dimethylphenylcarbamate)) and NP-HPLC/MS. The degradation of the racdufulin and the corresponding enantiomers followed first-order reaction kinetics
with reasonable linearity. The enantioselective photolysis of rac-dufulin was found
to be enantiomer-selective, showing a faster transformation of R-(À)-dufulin, compared to S-(+)-dufulin. This finding indicates that the combination of
phototransformation and enantiomer-selective adsorption/desorption processes
may result in the enantiomer selectivity of this observed process. S-(+)-dufulin
was also hydrolysed faster than the R-enantiomer. The same research group follow
up on these first results with a study on the enantiomer-selective distribution of
difulin in four different soil types (Zhang et al. 2014a, b, c). Also here, the
enantiomeric signature of the difulin enantiomers was determined on a ChiralPak
IA HPLC column and detected with mass-selective detection. Four local types of soil
(Guiyang silty loam, Nanning silty clay, Hefei silty clay and Harbin silty clay) were
investigated under sterile and non-sterile conditions. The dufulin enantiomer distribution was found to be stable and near racemic in the selected soils. No interconversion was observed during the incubation of enantiomerically pure S-(+)- or R(À)-dufulin under non-sterile conditions. The half-life (τ 1/2 ) confirmed that the
degradation of dufulin in sterile soils was slower compared to non-sterile soils.
These results suggest that dufulin transformation can be primarily attributed to
microbial activity in soils used for agricultural cultivation. Furthermore,
enantiomerically pure S-(+)-difulin degraded more rapidly than the corresponding
R-enantiomer.
The levels and elimination properties of the triazole pesticide penconazole
(IUPAC: 1-[2-(2,4-dichlorophenyl)pentyl]-1,2,4-triazole) was investigated in vegetables (Wang et al. 2014). The enantioselective dissipation of penconazole in
cucumber, tomato, head cabbage and pakchoi was investigated by field experiments.
A sensitive method for the enantiomeric analysis of penconazole was established on
the basis of the buffered QuEChERS sample preparation technique followed by
RP-HPLC/MS and a Lux Cellulose-2 column (Phenomenex: CSP: Cellulose tris
(3-chloro-4-methylphenylcarbamate)). Methanol and 2-mM ammonium ethanoate
buffer solution containing 0.1% methanoic acid (70:30, v/v) were used as mobile
phase at a 0.2 mL min
À1
flow rate isocratic elution. The study of the enantiomerselective dissipation in head cabbage and pakchoi showed the preferential transformation of (À)-penconazole, resulting in an enrichment of the (+)-penconazole.
However, the enantiomer-selective behaviour was not observed in cucumber and
tomato.
For the enantiomer-specific analysis of flufiprole in vegetables and fruits, a new
selective analytical method is reported (Tian et al. 2015). The enantiomer separation
was conducted on RP-HPLC with a Lux Cellulose-2 (Phenomenex, CSP: tris
(3-chloro-4-methylphenylcarbamate)) and mass-selective detection. The effects of
214
8 Enantiomer-Specific Fate and Behaviour of Chiral Contaminants