model describing the ionization efficiency of both phenols and benzoic acids. In a
further paper, this approach was applied to investigating the influence of different
mobile phases on the signal intensities in ESI, allowing to compare results obtained
under different chromatographic conditions [71].
A promising approach for investigating the fate of drugs after uptake by a plant
was the following. First experiments with rather high concentrations of the drug
were performed, and extracts from either the whole plant (or the whole cells in the
case of plant cell experiments) or the plant parts of interest were examined using
HPLC coupled to HR-MS
(n) . Thereby accurate masses could be determined (under
ideal circumstances allowing the proposal of an unambiguous sum formula), and
information on the molecular structure could be obtained from MS
n experiments.
Stable isotope labeling with HR-MS (i.e., spiking the nutrient solution with a
mixture of deuterated and non-deuterated drug) can be seen as an interesting
approach to further improve the workflow in the detection of drug-derived metabolites within the plant [63]. Combining the findings from HR-MS with knowledge
from plant biology or drug metabolism in mammals at best allowed proposing a
metabolic pathway for the investigated drug within the plant organism. Subsequently, to improve the applicability of this experimental approach also for actual
environmental samples (here the concentrations of both the parent drug and the drugrelated metabolites will be much lower), information from previous MS
n experiments was employed for setting up a multiple reaction monitoring (MRM) method
on a highly sensitive QqQ MS, thereby allowing the investigation of plants treated
with environmentally relevant concentrations of the drug. Examples for the successful application of this scheme can be found in the literature [35, 53].
As common for metabolomics research, two different approaches, namely, a
targeted and a non-targeted one, can be distinguished. Most of the studies published
so far investigating the uptake, translocation, and metabolization of drugs and
personal care products (PCPs) in plants clearly use a targeted approach. Based on
knowledge about regular plant metabolism, comparison with metabolic studies in
mammals and humans, and selective search for potential transformation products,
plant extracts are searched for drug-related metabolites. Only a few papers
employing a more untargeted approach can be found in the relevant literature (for
a good example, see [67]). Vilette et al. analyzed surface water and superficial sludge
(at the entrance of a tertiary treatment wetland) with respect to the presence of
micropollutants (HR-MS spectra were processed with common metabolomics software; sum formulas were proposed and entered into open-access data bases) and
compared these data with those from Salix alba growing on the edge of the wetland.
A total of 1,027 compounds were tentatively identified (level 3 according to
Schymanski) whereby 96 could be found in all 3 matrices (see also Fig. 2) [67].
502
F. Mlynek et al.
further paper, this approach was applied to investigating the influence of different
mobile phases on the signal intensities in ESI, allowing to compare results obtained
under different chromatographic conditions [71].
A promising approach for investigating the fate of drugs after uptake by a plant
was the following. First experiments with rather high concentrations of the drug
were performed, and extracts from either the whole plant (or the whole cells in the
case of plant cell experiments) or the plant parts of interest were examined using
HPLC coupled to HR-MS
(n) . Thereby accurate masses could be determined (under
ideal circumstances allowing the proposal of an unambiguous sum formula), and
information on the molecular structure could be obtained from MS
n experiments.
Stable isotope labeling with HR-MS (i.e., spiking the nutrient solution with a
mixture of deuterated and non-deuterated drug) can be seen as an interesting
approach to further improve the workflow in the detection of drug-derived metabolites within the plant [63]. Combining the findings from HR-MS with knowledge
from plant biology or drug metabolism in mammals at best allowed proposing a
metabolic pathway for the investigated drug within the plant organism. Subsequently, to improve the applicability of this experimental approach also for actual
environmental samples (here the concentrations of both the parent drug and the drugrelated metabolites will be much lower), information from previous MS
n experiments was employed for setting up a multiple reaction monitoring (MRM) method
on a highly sensitive QqQ MS, thereby allowing the investigation of plants treated
with environmentally relevant concentrations of the drug. Examples for the successful application of this scheme can be found in the literature [35, 53].
As common for metabolomics research, two different approaches, namely, a
targeted and a non-targeted one, can be distinguished. Most of the studies published
so far investigating the uptake, translocation, and metabolization of drugs and
personal care products (PCPs) in plants clearly use a targeted approach. Based on
knowledge about regular plant metabolism, comparison with metabolic studies in
mammals and humans, and selective search for potential transformation products,
plant extracts are searched for drug-related metabolites. Only a few papers
employing a more untargeted approach can be found in the relevant literature (for
a good example, see [67]). Vilette et al. analyzed surface water and superficial sludge
(at the entrance of a tertiary treatment wetland) with respect to the presence of
micropollutants (HR-MS spectra were processed with common metabolomics software; sum formulas were proposed and entered into open-access data bases) and
compared these data with those from Salix alba growing on the edge of the wetland.
A total of 1,027 compounds were tentatively identified (level 3 according to
Schymanski) whereby 96 could be found in all 3 matrices (see also Fig. 2) [67].
502
F. Mlynek et al.