20 research outputs found
Improved Separation of Complex Polycyclic Aromatic Hydrocarbon Mixtures Using Novel Column Combinations in GC × GC/ToF-MS
Complex mixtures of polycyclic aromatic hydrocarbons
(PAHs) are
difficult to resolve because of the high degree of overlap in compound
vapor pressures, boiling points, and mass spectral fragmentation patterns.
The objective of this research was to improve the separation of complex
PAH mixtures (including 97 different parent, alkyl-, nitro-, oxy-,
thio-, chloro-, bromo-, and high molecular weight PAHs) using GC ×
GC/ToF-MS by maximizing the orthogonality of different GC column combinations
and improving the separation
of PAHs from the sample matrix interferences, including unresolved
complex mixtures (UCM). Four different combinations of nonpolar, polar,
liquid crystal, and nanostationary phase columns were tested. Each
column combination was optimized and evaluated for orthogonality using
a method based on conditional entropy that considers the quantitative
peak distribution in the entire 2D space. Finally, an atmospheric
particulate matter with diameter <2.5 μm (PM<sub>2.5</sub>) sample from Beijing, China, a soil sample from St. Maries Creosote
Superfund Site, and a sediment sample from the Portland Harbor Superfund
Site were analyzed for complex mixtures of PAHs. The highest chromatographic
resolution, lowest synentropy, highest orthogonality, and lowest interference
from UCM were achieved using a 10 m × 0.15 mm × 0.10 μm
LC-50 liquid crystal column in the first dimension and a 1.2 m ×
0.10 mm × 0.10 μm NSP-35 nanostationary phase column in
the second dimension. In addition, the use of this column combination
in GC × GC/ToF-MS resulted in significantly shorter analysis
times (176 min) for complex PAH mixtures compared to 1D GC/MS (257
min), as well as potentially reduced sample preparation time
Long-Term Field Measurement of Sorption of Organic Contaminants to Five Types of Plastic Pellets: Implications for Plastic Marine Debris
Concerns regarding marine plastic pollution and its affinity
for
chemical pollutants led us to quantify relationships between different
types of mass-produced plastic and organic contaminants in an urban
bay. At five locations in San Diego Bay, CA, we measured sorption
of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons
(PAHs) throughout a 12-month period to the five most common types
of mass-produced plastic: polyethylene terephthalate (PET), high-density
polyethylene (HDPE), polyvinyl chloride (PVC), low-density polyethylene
(LDPE), and polypropylene (PP). During this long-term field experiment,
sorption rates and concentrations of PCBs and PAHs varied significantly
among plastic types and among locations. Our data suggest that for
PAHs and PCBs, PET and PVC reach equilibrium in the marine environment
much faster than HDPE, LDPE, and PP. Most importantly, concentrations
of PAHs and PCBs sorbed to HDPE, LDPE, and PP were consistently much
greater than concentrations sorbed to PET and PVC. These data imply
that products made from HDPE, LDPE, and PP pose a greater risk than
products made from PET and PVC of concentrating these hazardous chemicals
onto fragmented plastic debris ingested by marine animals
Identifying Bioaccumulative Halogenated Organic Compounds Using a Nontargeted Analytical Approach: Seabirds as Sentinels
<div><p>Persistent organic pollutants (POPs) are typically monitored via targeted mass spectrometry, which potentially identifies only a fraction of the contaminants actually present in environmental samples. With new anthropogenic compounds continuously introduced to the environment, novel and proactive approaches that provide a comprehensive alternative to targeted methods are needed in order to more completely characterize the diversity of known and unknown compounds likely to cause adverse effects. Nontargeted mass spectrometry attempts to extensively screen for compounds, providing a feasible approach for identifying contaminants that warrant future monitoring. We employed a nontargeted analytical method using comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC/TOF-MS) to characterize halogenated organic compounds (HOCs) in California Black skimmer (<i>Rynchops niger</i>) eggs. Our study identified 111 HOCs; 84 of these compounds were regularly detected via targeted approaches, while 27 were classified as typically unmonitored or unknown. Typically unmonitored compounds of note in bird eggs included tris(4-chlorophenyl)methane (TCPM), tris(4-chlorophenyl)methanol (TCPMOH), triclosan, permethrin, heptachloro-1'-methyl-1,2'-bipyrrole (MBP), as well as four halogenated unknown compounds that could not be identified through database searching or the literature. The presence of these compounds in Black skimmer eggs suggests they are persistent, bioaccumulative, potentially biomagnifying, and maternally transferring. Our results highlight the utility and importance of employing nontargeted analytical tools to assess true contaminant burdens in organisms, as well as to demonstrate the value in using environmental sentinels to proactively identify novel contaminants.</p></div
Polystyrene Plastic: A Source and Sink for Polycyclic Aromatic Hydrocarbons in the Marine Environment
Polycyclic
aromatic hydrocarbons (PAHs) on virgin polystyrene (PS) and PS marine
debris led us to examine PS as a source and sink for PAHs in the marine
environment. At two locations in San Diego Bay, we measured sorption
of PAHs to PS pellets, sampling at 0, 1, 3, 6, 9, and 12 months. We
detected 25 PAHs using a new analytical method with comprehensive
two-dimensional gas chromatography coupled to time-of-flight mass
spectrometry. Several congeners were detected on samples before deployment.
After deployment, some concentrations decreased (1,3-dimethylnaphthalene
and 2,6-methylnaphthalene), while most increased [2-methylanthracene
and all parent PAHs (PPAHs), except fluorene and fluoranthene], suggesting
that PS debris is a source and sink for PAHs. When sorbed concentrations
of PPAHs on PS are compared to the five most common polymers [polyethylene
terephthalate (PET), high-density polyethylene (HDPE), polyvinyl chloride
(PVC), low-density polyethylene (LDPE), and polypropylene (PP)], PS
sorbed greater concentrations than PP, PET, and PVC, similar to HDPE
and LDPE. Most strikingly, at 0 months, PPAHs on PS ranged from 8
to 200 times greater than on PET, HDPE, PVC, LDPE, and PP. The combination
of greater PAHs in virgin pellets and large sorption suggests that
PS may pose a greater risk of exposure to PAHs upon ingestion
Relative Abundance of Individual Compounds, excluding PCBs.
<p>Each point represents one egg sample (n = 4), including non-detects. Non-detects are shown with a value of zero (multiple non-detects overlap). PCBs are included in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0127205#pone.0127205.s003" target="_blank">S1 Fig</a>.</p
Relative Abundance of Compound Classes.
<p>Each point represents detection in a single egg sample (n = 4). The abundance is the sum total of the normalized peak areas for all compounds in the class, in each sample. The line is the median abundance for the compound class. The source of each compound class is indicated in the legend. Non-detects are shown with a value of zero (multiple non-detects overlap).</p
Nontargeted Comprehensive Two-Dimensional Gas Chromatography/Time-of-Flight Mass Spectrometry Method and Software for Inventorying Persistent and Bioaccumulative Contaminants in Marine Environments
Analytical methods for contaminant monitoring are generally
targeted;
i.e., they measure defined lists of compounds. Routine monitoring
projects using targeted methods are not usually designed to screen
for unrecognized or novel contaminants and therefore miss compounds
within the region or population of study that cause, or have the potential
to cause, adverse biological impacts. We describe a nontargeted analytical
method utilizing direct sample introduction coupled to comprehensive
two-dimensional gas chromatography with time-of-flight mass spectrometry.
To test the capabilities of this instrumental method within the context
of marine contaminant surveys, we characterized a broad array of nonpolar,
persistent, and bioaccumulative contaminants in Atlantic common dolphin
(Delphinus delphis) blubber, including
compounds that are not typically monitored. Compound identifications
were made by searching a standard reference database, by contemporaneously
analyzing mass spectra from reference standards, and by de novo interpretation.
We identified a total of 271 compounds belonging to 24 classes; all
compounds but 1 were halogenated. Anthropogenic contaminants and halogenated
natural products were concurrently detected. A total of 86 compounds
were anthropogenic contaminants that are not routinely targeted in
environmental surveys, and 54 compounds were halogenated natural products.
A total of 112 spectra were identified de novo, demonstrating that
exclusive reliance on commercially available reference standards and
mass spectral libraries may miss a significant fraction of identifiable
compounds. We also cataloged 27 halogenated mass spectra that were
not able to be identified. Due to the volume and complexity of the
identification data, we developed custom software to organize and
provide shared access to the identified mass spectra and related information.
The nontargeted analytical method and data reporting system, in combination
with the analysis of a high-trophic-level sentinel species, demonstrates
a framework for creating an inventory of persistent and bioaccumulative
contaminants in marine environments, with the future goal of suggesting
new compounds for further investigation by targeted monitoring and
risk assessment
Comprehensive Screening Links Halogenated Organic Compounds with Testosterone Levels in Male <i>Delphinus delphis</i> from the Southern California Bight
While environmental
pollutants have been associated with changes
in endocrine health in cetaceans, efforts to link contaminant exposure
with hormones have largely been limited to a list of known, targeted
contaminants, overlooking minimally characterized or unknown compounds
of emerging concern. To address this gap, we analyzed a suite of potential
endocrine disrupting halogenated organic compounds (HOCs) in blubber
from 16 male short-beaked common dolphins (<i>Delphinus delphis</i>) with known maturity status collected from fishery bycatch in the
Southern California Bight. We employed a suspect screening mass spectrometry-based
method to investigate a wide range of HOCs that were previously observed
in cetaceans from the same region. Potential endocrine effects were
assessed through the measurement of blubber testosterone. We detected
167 HOCs, including 81 with known anthropogenic sources, 49 of unknown
origin, and 37 with known natural sources. The sum of 11 anthropogenic
and 4 unknown HOC classes were negatively correlated with blubber
testosterone. Evidence suggests that elevated anthropogenic HOC load
contributes to impaired testosterone production in mature male <i>D. delphis</i>. The application of this integrative analytical
approach to cetacean contaminant analysis allows for inference of
the biological consequences of accumulation of HOCs and prioritization
of compounds for future environmental toxicology research
Environmental Tobacco Smoke as a Source of Polycyclic Aromatic Hydrocarbons in Settled Household Dust
Environmental tobacco smoke is a major contributor to
indoor air
pollution. Dust and surfaces may remain contaminated long after active
smoking has ceased (called ‘thirdhand’ smoke). Polycyclic
aromatic hydrocarbons (PAHs) are known carcinogenic components of
tobacco smoke found in settled house dust (SHD). We investigated whether
tobacco smoke is a source of PAHs in SHD. House dust was collected
from 132 homes in urban areas of Southern California. Total PAHs were
significantly higher in smoker homes than nonsmoker homes (by concentration:
990 ng/g vs 756 ng/g, <i>p</i> = 0.025; by loading: 1650
ng/m<sup>2</sup> vs 796 ng/m<sup>2</sup>, <i>p</i> = 0.012).
We also found significant linear correlations between nicotine and
total PAH levels in SHD (concentration, <i>R</i><sup>2</sup> = 0.105; loading, <i>R</i><sup>2</sup> = 0.385). Dust
collected per square meter (g/m<sup>2</sup>) was significantly greater
in smoker homes and might dilute PAH concentration in SHD inconsistently.
Therefore, dust PAH loading (ng PAH/m<sup>2</sup>) is a better indicator
of PAH content in SHD. House dust PAH loadings in the bedroom and
living room in the same home were significantly correlated (<i>R</i><sup>2</sup> = 0.468, <i>p</i> < 0.001) suggesting
PAHs are distributed by tobacco smoke throughout a home. In conclusion,
tobacco smoke is a source of PAHs in SHD, and tobacco smoke generated
PAHs are a component of thirdhand smoke
Leached Compounds from Smoked Cigarettes and Their Potential for Bioaccumulation in Rainbow Trout (Oncorhynchus mykiss)
Cigarette butts are one of the most prevalent forms of
litter worldwide
and may leach toxic compounds when deposited in aquatic environments.
Previous studies demonstrated that smoked cigarette leachate is toxic
toward aquatic organisms. However, the specific bioavailable chemicals
from the leachate and the potential for human and wildlife exposure
through the food chain were unknown. Using a nontargeted analytical
approach based on GC×GC/TOF-MS, 43 compounds were confirmed to
leach from smoked cigarettes when exposed to a water source. Additionally,
the bioaccumulation potential of organic contaminants in an edible
fish, rainbow trout (Oncorhynchus mykiss), was assessed through direct exposure to the leachate of smoked
cigarettes at 0.5 CB/L for 28 days. There was a significant reduction
in fish mass among the exposed rainbow trout vs the control group
(χ2 (1) = 5.3, p = 0.021). Both
nontargeted and targeted chemical analysis of representative fish
tissue identified four tobacco alkaloids, nicotine, nicotyrine, myosmine,
and 2,2′-bipyridine. Their average tissue concentrations were
466, 55.4, 94.1, and 70.8 ng/g, respectively. This study identifies
leached compounds from smoked cigarettes and demonstrates the uptake
of specific chemicals in rainbow trout, thus suggesting a potential
for accumulation in food webs, resulting in human and wildlife exposure