3 research outputs found
Combining a Deconvolution and a Universal Library Search Algorithm for the Nontarget Analysis of Data-Independent Acquisition Mode Liquid ChromatographyâHigh-Resolution Mass Spectrometry Results
Nontarget
analysis is considered one of the most comprehensive
tools for the identification of unknown compounds in a complex sample
analyzed via liquid chromatography coupled to high-resolution mass
spectrometry (LCâHRMS). Due to the complexity of the data generated
via LCâHRMS, the data-dependent acquisition mode, which produces
the MS<sup>2</sup> spectra of a limited number of the precursor ions,
has been one of the most common approaches used during nontarget screening.
However, data-independent acquisition mode produces highly complex
spectra that require proper deconvolution and library search algorithms.
We have developed a deconvolution algorithm and a universal library
search algorithm (ULSA) for the analysis of complex spectra generated
via data-independent acquisition. These algorithms were validated
and tested using both semisynthetic and real environmental data. A
total of 6000 randomly selected spectra from MassBank were introduced
across the total ion chromatograms of 15 sludge extracts at three
levels of background complexity for the validation of the algorithms
via semisynthetic data. The deconvolution algorithm successfully extracted
more than 60% of the added ions in the analytical signal for 95% of
processed spectra (i.e., 3 complexity levels multiplied by 6000 spectra).
The ULSA ranked the correct spectra among the top three for more than
95% of cases. We further tested the algorithms with 5 wastewater effluent
extracts for 59 artificial unknown analytes (i.e., their presence
or absence was confirmed via target analysis). These algorithms did
not produce any cases of false identifications while correctly identifying
âź70% of the total inquiries. The implications, capabilities,
and the limitations of both algorithms are further discussed
In Vivo Passive Sampling of Nonpolar Contaminants in Brown Trout (<i>Salmo trutta</i>)
Equilibrium
passive sampling through in vivo implantation can help
circumvent complex extractions of biological tissues, provide more
accurate information on chemical contaminant burden based on the fugacity
of a chemical in an organism rather than conventional normalization
to lipid content, and improve the assessment of contaminant bioaccumulation
potential. Here, we explored the feasibility of in vivo implantation
for the passive sampling of neutral hydrophobic contaminants through
the insertion of a silicone tag into brown trout (<i>Salmo trutta</i>). Implanted fish from the upper reaches of the River Alna (Oslo,
Norway) were relocated to a polluted section of the river for a 28
day caged exposure. âWhole fishâ lipid-silicone distribution
coefficients (<i>D</i><sub>lipâsil</sub>) were calculated
for chlorinated compounds measured in whole fish and in silicone tags
of 13 fish. <i>D</i><sub>lipâsil</sub> ranged from
13.6 to 40.0 g g<sup>â1</sup> for polychlorinated biphenyl
congeners 28â156 (CB28 and CB156), respectively, and are in
close agreement with literature in vitro lipid phase and tissue-based
lipid-silicone partition coefficients. After dissection a further
of eight fish, muscle and liver samples were analyzed separately.
Muscle-based <i>D</i><sub>lipâsil</sub> values similar
to the whole fish data were observed. However, lipid-normalized concentrations
in the liver tended to be lower than in muscle for most compounds
(by up to 50%). Values of whole fish <i>D</i><sub>lipâsil</sub> for brominated diphenyl ethers determined for three fish were in
the range of 8.6â51 g g<sup>â1</sup> and in agreement
with chlorinated substances. Finally, fugacity ratios calculated from
equilibrium concentrations in fish-implanted and water-exposed silicone
provided information on the bioaccumulation for chlorinated compounds
as well as for some polycyclic aromatic hydrocarbons. Equilibrium
passive sampling through in vivo implantation can allow the comparison
of a chemicalâs activity or fugacity in biotic as well as abiotic
environmental compartments and at different trophic levels up to humans
PAH Accessibility in Particulate Matter from Road-Impacted Environments
Snowmelt, surface
runoff, or stormwater releases in urban environments
can result in significant discharges of particulate matter-bound polycyclic
aromatic hydrocarbons (PAHs) into aquatic environments. Recently,
more-specific activities such as road-tunnel washing have been identified
as contributing to contaminant load to surface waters. However, knowledge
of PAH accessibility in particulate matter (PM) of urban origin that
may ultimately be released into urban surface waters is limited. In
the present study, we evaluated the accessibility of PAHs associated
with seven distinct (suspended) particulate matter samples collected
from different urban sources. Laboratory-based infinite sink extractions
with silicone rubber (SR) as the extractor phase demonstrated a similar
pattern of PAH accessibility for most PM samples. Substantially higher
accessible fractions were observed for the less-hydrophobic PAHs (between
40 and 80% of total concentrations) compared with those measured for
the most-hydrophobic PAHs (<5% of total concentrations). When we
focused on PAHs bound to PM from tunnel-wash waters, first-order desorption
rates for PAHs with log <i>K</i><sub>ow</sub> > 5.5 were
found in line with those commonly found for slowly or very slowly
desorbing sediment-associated contaminants. PAHs with log <i>K</i><sub>ow</sub> < 5.5 were found at higher desorbing rates.
The addition of detergents did not influence the extractability of
lighter PAHs but increased desorption rates for the heavier PAHs,
potentially contributing to increases in the toxicity of tunnel-wash
waters when surfactants are used. The implications of total and accessible
PAH concentrations measured in our urban PM samples are discussed
in a context of management of PAH and PM emission to the surrounding
aquatic environment. Although we only fully assessed PAHs in this
work, further study should consider other contaminants such as OPAHs,
which were also detected in all PM samples