Yan et al. extended the scope of β-cyclodextrin based CSPs toward the
enantiomer-selective separation of modern chiral pesticides (Yan et al. 2016).
Baseline separation was achieved for diclofop-methyl, fenoxaprop-ethyl,
tebuconazole and triticonazole (Rs > 1.5), and sufficient partial separation was
found for toxazole and lactofen.
The up-take and toxicological potential of neonicotinoid pesticides are today an
important research focus for environmental scientists due to the obvious linkage to
the decline of bee populations on a global bases (Fairbrother et al. 2014; Lundin et al.
2015; Sanchez-Bayo et al. 2016; Carreck 2017). Neonicotinoid pesticides are chiral
compounds. Thus, the enantiomeric profile may have the potential to contribute to a
better understanding of the mechanisms underlying the currently observed effects on
bee health (Chen et al. 2015). The transformation potential for the chiral
neonicotinoid cycloxaprid was investigated by a Chinese research group in spiking
laboratory experiments on soil samples (Liu et al. 2015a, b). A complete transformation pathway identifying 10 different transformation products was identified.
However, no specific toxicological potential was identified for neither of the hereidentified compounds. In soil and sediment samples, mainly non-stereoselective
transformation pathways were identified for cycloxaprid (Chen et al. 2017). However, enantiomer-selective analysis is only occasionally applied to the determination
of enantiomeric profiles in the search for the effect mechanisms of novel chiral
neonicotinoids (Chen et al. 2016a, b; Wu et al. 2016). A general update on the
mechanisms for uptake, distribution and toxicity for selected neonicotinoids is
recently published (Giorio et al. 2017).
Jarman and co-workers applied capillary electrophoresis for the enantiomerselective determination of modern pesticides in aqueous slurries of soil samples
(Jarman et al. 2005). The enantiomers of five chiral pesticides of environmental
interest, metalaxyl, imazaquin, fonofos (dyfonate), ruelene (cruformate) and
dichlorprop were separated and analysed by capillary electrophoresis (CE) with
cyclodextrin chiral selectors. For metalaxyl, imazaquin and fonofos, aqueous slurries
of soil samples from two sites in Georgia and one in Ohio were spiked with the
racemate of each pesticide at 50–60 mg/L of aqueous phase directly into the slurry,
and CE analyses were performed at various time intervals to determine enantiomer
fractions (EF). For metalaxyl enantioselective transformation was found. The halflife of the target active R-(+)-enantiomer was 17 days while that for the S-(À)enantiomer was 69 days in one soil samples. Transformation occurred more slowly
in the other two soils but was still selective for the R-(+)-enantiomer. Imazaquin and
fonofos exhibited non-selective enantiomer loss over their 3 months of incubation
time; this could have been due to abiotic or non-selective microbial reactions. CE is
shown to be a simple, efficient and inexpensive way to follow the transformation of
chiral pesticides in laboratory experiments as demonstrated here.
Pyrethroid pesticides belong today to the most used group of agrochemicals
worldwide. Recently, the environmental stability of selected pyrethroids was examined by means of enantiomer-selective analysis (Qin et al. 2006). Synthetic pyrethroids contain two or three asymmetric carbon atoms. Thus, this pesticide group
exhibits a large number of stereoisomers. Recent studies showed significant
210
8 Enantiomer-Specific Fate and Behaviour of Chiral Contaminants
enantiomer-selective separation of modern chiral pesticides (Yan et al. 2016).
Baseline separation was achieved for diclofop-methyl, fenoxaprop-ethyl,
tebuconazole and triticonazole (Rs > 1.5), and sufficient partial separation was
found for toxazole and lactofen.
The up-take and toxicological potential of neonicotinoid pesticides are today an
important research focus for environmental scientists due to the obvious linkage to
the decline of bee populations on a global bases (Fairbrother et al. 2014; Lundin et al.
2015; Sanchez-Bayo et al. 2016; Carreck 2017). Neonicotinoid pesticides are chiral
compounds. Thus, the enantiomeric profile may have the potential to contribute to a
better understanding of the mechanisms underlying the currently observed effects on
bee health (Chen et al. 2015). The transformation potential for the chiral
neonicotinoid cycloxaprid was investigated by a Chinese research group in spiking
laboratory experiments on soil samples (Liu et al. 2015a, b). A complete transformation pathway identifying 10 different transformation products was identified.
However, no specific toxicological potential was identified for neither of the hereidentified compounds. In soil and sediment samples, mainly non-stereoselective
transformation pathways were identified for cycloxaprid (Chen et al. 2017). However, enantiomer-selective analysis is only occasionally applied to the determination
of enantiomeric profiles in the search for the effect mechanisms of novel chiral
neonicotinoids (Chen et al. 2016a, b; Wu et al. 2016). A general update on the
mechanisms for uptake, distribution and toxicity for selected neonicotinoids is
recently published (Giorio et al. 2017).
Jarman and co-workers applied capillary electrophoresis for the enantiomerselective determination of modern pesticides in aqueous slurries of soil samples
(Jarman et al. 2005). The enantiomers of five chiral pesticides of environmental
interest, metalaxyl, imazaquin, fonofos (dyfonate), ruelene (cruformate) and
dichlorprop were separated and analysed by capillary electrophoresis (CE) with
cyclodextrin chiral selectors. For metalaxyl, imazaquin and fonofos, aqueous slurries
of soil samples from two sites in Georgia and one in Ohio were spiked with the
racemate of each pesticide at 50–60 mg/L of aqueous phase directly into the slurry,
and CE analyses were performed at various time intervals to determine enantiomer
fractions (EF). For metalaxyl enantioselective transformation was found. The halflife of the target active R-(+)-enantiomer was 17 days while that for the S-(À)enantiomer was 69 days in one soil samples. Transformation occurred more slowly
in the other two soils but was still selective for the R-(+)-enantiomer. Imazaquin and
fonofos exhibited non-selective enantiomer loss over their 3 months of incubation
time; this could have been due to abiotic or non-selective microbial reactions. CE is
shown to be a simple, efficient and inexpensive way to follow the transformation of
chiral pesticides in laboratory experiments as demonstrated here.
Pyrethroid pesticides belong today to the most used group of agrochemicals
worldwide. Recently, the environmental stability of selected pyrethroids was examined by means of enantiomer-selective analysis (Qin et al. 2006). Synthetic pyrethroids contain two or three asymmetric carbon atoms. Thus, this pesticide group
exhibits a large number of stereoisomers. Recent studies showed significant
210
8 Enantiomer-Specific Fate and Behaviour of Chiral Contaminants