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^–1 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