5 research outputs found
Preparation of a Particle-Loaded Membrane for Trace Gas Sampling
A divinylbenzene (DVB) particle-loaded
membrane with high extraction
capacity was prepared using the bar coating method. The prepared membrane
was evaluated in terms of morphology, effect of particle ratio, and
membrane size on extraction efficiency, as well as linear calibration
curve and limit of detection. The SEM (scanning electron microscope)
images showed that the DVB particles were uniformly distributed in
the PDMS base, ensuring the repeatability of the membranes. The extraction
amount was quantified by gas chromatography–mass spectrometry
coupled with a thermal desorption unit. Results showed that the extraction
efficiency of the prepared membrane increased about 2 orders of magnitude
for benzene sampling as the particle ratio increased from 0% to 30%,
and the extraction amount was linearly proportional to the size of
the membrane. A comparison with a pure PDMS membrane and DVB/PDMS
fiber for outdoor air sampling showed that the extraction efficiency
of the DVB/PDMS membrane was significantly enhanced, especially for
volatile and polar compounds. The limit of detection was about 0.03
ng/mL for benzene in air, and the linear dynamic range extended to
100 ng/mL. An equilibrium calibration method was proposed for low-level
air pollutant sampling using this high capacity membrane, and a displacement
effect was not observed. To demonstrate the power of the technique,
the developed approach was applied to monitor both spot and time weighted
average (TWA) concentrations of benzene in outdoor air. A high spot
concentration of benzene was observed in morning and afternoon rush
hours, with TWA concentrations of 10.7 ng/L measured over the 11-h
monitoring period
Bioinspired Polydopamine Sheathed Nanofibers for High-Efficient in Vivo Solid-Phase Microextraction of Pharmaceuticals in Fish Muscle
In this study, electrospun nanofibers
were used as solid-phase
microextraction (SPME) fiber coatings after substituting the water-soluble
sheath of the emulsion electrospun polystyrene (PS)@Plurinic F-127
core–sheath nanofibers with biocompatible and water-stable
polydopamine (PDA) and subsequently being appropriately cross-linked
with glutaraldehyde (GA) to enhance the strength of the electrospun
architecture. The novel custom-made PS@PDA-GA coating was wettable
in aqueous solutions and thus exhibited much higher extraction efficiency
than the nonsheathed PS nanofiber coating and the thicker polydimethylsiloxane
(PDMS) coating. The novel coating also possessed excellent stability
(relative standard deviations (RSDs) less than 7.3% for six sampling-desorption
cycles), interfiber reproducibility (RSDs less than 14.3%), and antibiofouling
ability, which were beneficial for in vivo sampling. The PS@PDA-GA
fiber was used to monitor pharmaceuticals in dorsal-epaxial muscle
of living fish, and satisfactory sensitivities with the limits of
detection in the range of 1.1 (mefenamic acid) to 8.9 (fluoxetine)
ng·g<sup>–1</sup> and comparable accuracies to liquid
extraction were achieved. In general, this study explored a convenient
and effective method to sheath nanofibers for high-efficient in vivo
SPME of analytes of interest in semisolid tissues
Study on the Diffusion-Dominated Solid-Phase Microextraction Kinetics in Semisolid Sample Matrix
Solid-phase microextraction (SPME)
kinetics in semisolid samples
should be different from that in aqueous and gaseous samples, as convection
is negligible in semisolid samples but dominates mass transfer in
bulk phases of aqueous and gaseous samples. This study developed a
mathematical model for describing SPME kinetics in semisolid samples
by considering the diffusion of analytes in two compartments, i.e.,
the fiber coating and the ever-increasing diffusion domain in the
sample matrix. The mathematical model predicted that SPME and the
desorption of preloaded analytes from the fiber would be isotropic
in semisolid samples, while SPME in semisolid samples would not follow
the first order kinetics as in aqueous and gaseous samples. The predictions
were proven true in the experiment of four pharmaceuticals in agarose
gel. In return, it was observed in the experiment that SPME kinetics
would deviate more significantly from the first order kinetics for
the analytes with higher partition coefficients between the fiber
and the sample matrix, which was well explained by the mathematical
model developed in this study. In addition, SPME kinetics predicted
by the model coincided well with the experimental results when the
diffusion coefficients were at reasonable levels, which demonstrated
that the model could be satisfactory for describing SPME kinetics
in semisolid samples. The illustration of the nonfirst order SPME
kinetics in semisolid samples can be valuable for evaluating the applicability
of the existing pre-equilibrium calibration methods in semisolid samples
<i>In Vivo</i> Tracing Uptake and Elimination of Organic Pesticides in Fish Muscle
Bioconcentration
factors (BCFs) measured in the laboratory are
important for characterizing the bioaccumulative properties of chemicals
entering the environment, especially the potential persistent organic
pollutants (POPs), which can pose serious adverse effects on ecosystem
and human health. Traditional lethal analysis methods are time-consuming
and sacrifice too many experimental animals. In the present study, <i>in vivo</i> solid-phase microextraction (SPME) was introduced
to trace the uptake and elimination processes of pesticides in living
fish. BCFs and elimination kinetic coefficients of the pesticides
were recorded therein. Moreover, the metabolism of fenthion was also
traced with <i>in vivo</i> SPME. The method was time-efficient
and laborsaving. Much fewer experimental animals were sacrificed during
the tracing. In general, this study opened up an opportunity to measure
BCFs cheaply in laboratories for the registering of emerging POPs
and inspecting of suspected POPs, as well as demonstrated the potential
application of <i>in vivo</i> SPME in the study of toxicokinetics
of pollutants
Polyelectrolyte Microcapsules Dispersed in Silicone Rubber for in Vivo Sampling in Fish Brains
Direct detection
of fluoxetine and its metabolite norfluoxetine
in living fish brains was realized for the first time by using a novel
solid-phase microextraction fiber, which was prepared by mixing the
polyelectrolyte in the oligomer of silicone rubber and followed by
in-mold heat-curing. The polyelectrolyte was finally encased in microcapsules
dispersed in the cured silicone rubber. The fiber exhibited excellent
interfiber reproducibility (5.4–7.1%, <i>n</i> =
6), intrafiber reproducibility (3.7–4.6%, <i>n</i> = 6), and matrix effect-resistant capacity. Due to the capacity
of simultaneously extracting the neutral and the protonated species
of the analytes at physiological pH, the fiber exhibited high extraction
efficiencies to fluoxetine and norfluoxetine. Besides, the effect
of the salinity on the extraction performance and the competitive
sorption between the analytes were also evaluated. Based on the small-sized
custom-made fiber, the concentrations of fluoxetine and norfluoxetine
in the brains of living fish, which were exposed to waterborne fluoxetine
at an environmentally relevant concentration, were determined and
found 4.4 to 9.2 and 5.0 to 9.2 times those in the dorsal-epaxial
muscle. The fiber can be used to detect various protonated bioactive
compounds in living animal tissues