Size-dependent vector effect of microplastics on the bioaccumulation of polychlorinated biphenyls in tilapia: A tissue-specific study.

Microplastics play a significant role in interactions between organisms and hydrophobic organic contaminants (HOCs), leading to a joint toxic effect on aquatic organisms. This study extensively investigated the tissue-specific accumulation of polychlorinated biphenyls (PCBs) resulting from different sized microplastics in tilapia (Oreochromis mossambicus) using a passive dosing device. Based on biological feeding behavior considerations, 1 mm and 2 µm polystyrene (PS) microplastics with concentrations of 2 and 5 mg L-1 were investigated. A physiologically based toxicokinetic (PBTK) model was applied to evaluate the exchange kinetics and fluxes among the tissues. Moreover, an in vitro simulation experiment was conducted to theoretically validate the vector effect. The findings demonstrated that the effects caused by HOCs and microplastics on organisms were influenced by multiple factors such as size and surface properties. The mass transfer kinetics of HOCs in specific tissues were closely related to their adsorption capacity and position microplastics could reach. Specifically, although 2 µm microplastics exhibited high adsorption capacity for PCBs, they were only retained in the intestines and did not significantly contribute to the bioaccumulation of PCBs in gills or muscle. While 1 mm microplastics were ingested but just paused in the mouth and subsequently flew through the gills with oral mucus. Their vector effects increased the desorption of microplastic-bound PCB-118 in the gill mucus microcosm, thereby facilitating the mass transfer and accumulation of PCB-118 in gills and muscle. This study sheds new light on how the size-dependent vector generated by microplastics affects the tissue-specific accumulation of HOCs in aquatic organisms.

Unraveling the distribution characteristic of cyclic volatile methylsiloxanes in various environmental media of a wastewater treatment plant.

Cyclic volatile methylsiloxane (cVMS) is extensively used in consumer products and frequently detected in various environmental media, including water and air. In this study, we developed reliable and convenient methods to sample three cVMS compounds: octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6) in water and air samples collected from different tanks within a wastewater treatment plant (WWTP). The concentrations of D4, D5, and D6 in the water samples ranged from 0.40 to 8.0 µg L-1, 0.35 to 91 µg L-1, and 0.54 to 17 µg L-1, respectively. In the air samples, these concentrations varied from 0.34 to 20 µg m-3, 0.34 to 128 µg m-3, and 0.08 to 12 µg m-3, respectively. It is worth noting that the air-water distribution coefficient (Kaw) for these three cVMS exhibited a strong correlation with their water solubility. Moreover, fugacity fractions indicated a net evaporation process from water to the atmosphere. Furthermore, we investigated the distribution of cVMS between the gaseous and particulate phases. The results revealed a significant fraction, exceeding 72 %, of cVMS resided in the gas phase. D4 and D5 predominate in the gaseous phase, while D5 and D6 are the principal constituents within the particulate phase. The distribution coefficient characterizing the partitioning of cVMS compounds between the gaseous and particulate (Kp) exhibited a strong correlation with their corresponding octanol-air partitioning coefficients (Koa). These findings contribute to a better understanding of the distribution of cVMS in diverse environmental media and the underlying mechanism governing their dispersion.

Exploring the release of hazardous volatile organic compounds from face masks and their potential health risk.

Hazardous chemicals released from the petroleum-derived face mask can be inhaled by wearers and cause adverse health effects. Here, we first used headspace solid-phase microextraction coupled with GC-MS to comprehensively analyze the volatile organic compounds (VOCs) released from 26 types of face masks. The results showed that total concentrations and peak numbers ranged from 3.28 to 197 µg/mask and 81 to 162, respectively, for different types of mask. Also, light exposure could affect the chemical composition of VOCs, particularly increasing the concentrations of aldehydes, ketones, organic acids and esters. Of these detected VOCs, 142 substances were matched to a reported database of chemicals associated with plastic packaging; 30 substances were identified by the International Agency for Research on Cancer (IARC) as potential carcinogenic to humans; 6 substances were classified in the European Union as persistent, bioaccumulative, and toxic, or very persistent, very bioaccumulative substance. Reactive carbonyls were ubiquitous in masks, especially after exposure to light. The potential risk of VOCs released from the face masks were then accessed by assuming the extreme scenario that all the VOC residues were released into the breathing air within 3 h. The result showed that the average total concentration of VOCs (17 µg/m3) was below the criterion for hygienic air, but seven substances, 2-ethylhexan-1-ol, benzene, isophorone, heptanal, naphthalene, benzyl chloride, and 1,2-dichloropropane exceeded the non-cancer health guidelines for lifetime exposure. This finding suggested that specific regulations should be adopted to improve the chemical safety of face masks.

The effect of microplastics on the depuration of hydrophobic organic contaminants in Daphnia magna: A quantitative model analysis.

Microplastics are emerging pollutants that can absorb large amounts of hydrophobic organic contaminants (HOCs). However, no biodynamic model has yet been proposed to estimate their effects on HOC depuration in aquatic organisms, where the HOC concentrations are time-varying. In this work, a microplastic-inclusive biodynamic model was developed to estimate the depuration of HOCs via ingestion of microplastics. Several key parameters of the model were redefined to determine the dynamic HOC concentrations. Through the parameterized model, the relative contributions of dermal and intestinal pathways can be distinguished. Moreover, the model was verified and the vector effect of microplastics was confirmed by studying the depuration of polychlorinated biphenyl (PCB) in Daphnia magna (D. magna) with different sizes of polystyrene (PS) microplastics. The results showed that microplastics contributed to the elimination kinetics of PCBs because of the fugacity gradient between the ingested microplastics and the biota lipids, especially for the less hydrophobic PCBs. The intestinal elimination pathway via microplastics would promote overall PCB elimination, contributing 37-41 % and 29-35 % to the total flux in the 100 nm and 2 µm polystyrene (PS) microplastic suspensions, respectively. Furthermore, the contribution of microplastic uptake to total HOC elimination increased with decreasing microplastic size in water, suggesting that microplastics may protect organisms from HOC risks. In conclusion, this work demonstrated that the proposed biodynamic model is capable of estimating the dynamic depuration of HOCs for aquatic organisms. The results can shed light on a better understanding of the vector effects of microplastics.

Rapid detection and speciation of illicit drugs via a thin-film microextraction approach for wastewater-based epidemiology study.

High detection frequency of illicit drugs in water samples urges the development of rapid detection method for wastewater-based epidemiology (WBE) study. Here, we first developed a fast, convenient, and cost-effective method by combining thin-film microextraction (TFME) with gas chromatography-mass spectrometry (GC-MS) for sensing illicit drugs in wastewater sample. A divinylbenzene particle-loaded membrane was prepared by dip coating on a copper mesh. The sampling conditions of three illicit drugs were optimized and the performance of the proposed method was evaluated. The limit of detection was 5.5 2.0, and 1.1 ng L-1 for methamphetamine (MAMP), ketamine (KET), and methaqualone (MEQA), respectively, with acceptable precision (< 6.1 % for membrane to membrane reproducibility) and recovery from influent water (95 % - 111 %). Then, the proposed method was applied to study the occurrence and distribution of the target compounds in a wastewater treatment plant. The presence of methamphetamine, ketamine, and methaqualone was confirmed and their concentrations in the influent sample were 57 ± 8, 40 ± 4, and 75 ± 2 ng L-1, respectively. The speciation of the target compounds in different ponds was also investigated. Results showed that the content of organic matter and the pH of the sample significantly affected the binding state of the compounds. This work provides an efficient and accurate analytical protocol for WBE investigation of illicit drugs.

New insights into the photo-degraded polystyrene microplastic: Effect on the release of volatile organic compounds.

Excessive use of plastics leads to the ubiquity of plastic waste in the environment. Weathering can cause changes in the properties of plastics and lead to the release of various chemicals especially the volatile organic compounds (VOCs). Possible photodegradation pathway of polystyrene (PS) microplastics (MPs) was proposed and verified by the detection of VOCs. Headspace solid phase microextraction (HS-SPME) was employed to investigate the release behavior of VOCs from PS MPs exposed to simulated ultraviolet (UV). Results indicated that although the physicochemical properties of the PS MPs showed no significantly change after UV-irradiation, a variety of toxic VOCs, such as benzene, toluene, and phenol were detected from the irradiated MPs. UV irradiation progressively enhanced the release amount of VOCs with total concentration up to 66 µg g-1 after 30 d of exposure, about 2.4 times higher than that stored in the darkness (27 µg g-1). Some compounds (e.g., benzene and toluene) showed an upward trend over irradiation time, while others (e.g., styrene and 2-propenylbenzene) reduced over time. Results also found that the size of MPs could affect the release amounts but without consistent pattern for different VOCs detected in the headspace of the vial. In general, current study provided a new insight on the photo-aging process of MPs.

Sample preparation and instrumental methods for illicit drugs in environmental and biological samples: A review.

Detection of illicit drugs in the environmental samples has been challenged as the consumption increases globally. Current review examines the recent developments and applications of sample preparation techniques for illicit drugs in solid, liquid, and gas samples. For solid samples, traditional sample preparation methods such as liquid-phase extraction, solid-phase extraction, and the ones with external energy including microwave-assisted, ultrasonic-assisted, and pressurized liquid extraction were commonly used. The sample preparation methods mainly applied for liquid samples were microextraction techniques including solid-phase microextraction, microextraction by packed sorbent, dispersive solid-phase extraction, dispersive liquid-liquid microextraction, hollow fiber-based liquid-phase microextraction, and so on. Capillary microextraction of volatiles and airborne particulate sampling were primarily utilized to extract illicit drugs from gas samples. Besides, the paper introduced recently developed instrumental techniques applied to detect illicit drugs. Liquid chromatograph mass spectrometry and gas chromatograph mass spectrometry were the most widely used methods for illicit drugs samples. In addition, the development of ambient mass spectrometry techniques, such as desorption electrospray ionization mass spectrometry and paper spray mass spectrometry, created potential for rapid in-situ analysis.

Impact of different modes of adsorption of natural organic matter on the environmental fate of nanoplastics.

Recently, the exposure of nanoplastics (NPs) in the environment has received extensive attention. Research concerning their fate and transport in the aquatic environment is very important and urgent. In this study, the influence of two sources of natural organic matter (NOM) on the behaviour of NPs were investigated in view of the complexity of NOM. Humic acid (HA), Suwannee River humic acid (SRHA) and Upper Mississippi River NOM (MRNOM) were chosen to represent pedogenic NOM, while bovine serum albumin (BSA) was on behalf of aquagenic NOM. The results showed that NOM could reduce the aggregation and sedimentation of NPs, exhibiting excellent stabilization effect. The stability effect was affected by the concentrations and the sources of NOMs. For pedogenic NOMs, the stabilization effect was caused by adsorption modes with different microscopic morphologies through specific functional groups, while it was induced by the mode of steric stabilization in the presence of BSA. Spectroscopic method and micromorphology study further provided a new insight into exploring the possible mechanism of the interaction between NPs and NOMs.

Screening New Persistent and Bioaccumulative Organics in China's Inventory of Industrial Chemicals.

Over a third of the world's annual chemical production and sales occur in China. Thus, knowledge of the properties of the substances produced and emitted there is important from a global perspective. The chemical Inventory of Existing Chemical Substances of China (IECSC) lists over 45 000 chemicals. When compared to the North American and European chemical inventories, 6916 substances were found to be unique to the IECSC. We retrieved structural information for 14 938 organic chemicals in the IECSC and determined their overall environmental persistence , bioaccumulation factor (BAF), and long-range transport potential (transfer efficiency) using in silico approaches with the goal of identifying new chemicals with properties that might lead to global contamination issues. Overall, 10% of the 14 938 chemicals were unique to the IECSC and their environmental persistence and BAF were statistically higher than the values for the rest of the IECSC chemicals. We prioritized 27 neutral organic compounds predicted to have prolonged environmental persistence, and high potential for bioaccumulation and long-range transport when compared with polychlorinated biphenyls as a benchmark. We also identified 69 organofluorine compounds with three or more perfluorinated moieties, unique to the IECSC. Screening approaches and results from this study help to identify and prioritize those to be considered in further environmental modeling and monitoring assessments.

Development of a solid-phase microextraction method for fast analysis of cyclic volatile methylsiloxanes in water.

Cyclic volatile methylsiloxanes (cVMS) are widely used in consumer products and commonly detected in the environment. There are challenges in the analysis of cVMS because of their ubiquitous use which can introduce high background contamination. The current study introduces a sample preparation method based on headspace of solid-phase microextraction (SPME) for monitoring the cVMS in waters. Efforts were made to reduce the background contamination during sample preparation and instrument analysis. A laboratory prepared MIL-101 coating was prepared using polysulfone instead of polydimethylsiloxane as adhesive to avoid the contamination. The extraction performance of the MIL-101 fiber was optimized and evaluated. The optimized extraction time and temperature were 60 min and 40 °C, respectively. The method quantification limits of the MIL-101 fiber for octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5) and dodecylcyclohexasiloxane (D6) in water were 0.15 ng mL-1, 0.14 ng mL-1, and 0.27 ng mL-1, respectively. The extraction efficiency of the proposed MIL-101 fiber was comparable to the commercial polydimethylsiloxane/divinylbenzene fiber. The developed method was applied to analyze the cVMS in wastewater treatment plant and the concentrations in the barscreen and in the aeration tank ranged from 0.73 to 3.3 ng mL-1 and 7.74-85.1 ng mL-1, respectively. The MIL-101 fiber was also applied to study the photodegradation of the cVMS in water under simulated sunlight. Approximately 25%, 20%, and 45% of D4, D5, and D6, respectively, were degraded after 10 h exposure.

Joint effect of nanoplastics and humic acid on the uptake of PAHs for Daphnia magna: A model study.

Nanoplastics (NPs) are emerging pollutants which can adsorb large amounts of hydrophobic organic compounds (HOCs) and be ingested by aquatic organisms. NPs interact with dissolved organic matter (DOM) and result in significant impacts on the bioaccumulation of HOCs in the actual environment. For the first time, the joint effects of two complex matrices on the bioaccumulation of polycyclic aromatic hydrocarbons (PAHs) to Daphnia magna (D. magna) were studied by modeling calculation. The complex matrices, nano-sized polystyrene (PS) and/or humic acid (HA), were under environmentally realistic concentrations. A biodynamic model was modified and the uptake fluxes from all exposure pathways were quantified using the experimental data. A flux estimation showed that the bioaccumulation amounts at equilibrium were mostly dependent on dermal uptake (≥99.3 % of the total). The PS matrix would retard the intestinal uptake process in D. magna, especially for the less hydrophobic PAHs; while the HA or the HA-PS matrix would facilitate the mass transfer of PAHs from the matrix to lipids in the gut. Moreover, the biota matrix accumulation factor (BMAF) were calculated to verify the biodynamic model. This work is helpful to clarify the bioaccumulation effects of PAHs in complex environmental systems.

Microplastic Impacts on Microalgae Growth: Effects of Size and Humic Acid.

Research has already demonstrated the toxic effects of microplastics (MPs) on different biota. However, the underlying toxic mechanism of MPs remains to be elucidated, especially the effect of particle size and the presence of dissolved organic matter in water. This study investigated the impact on Scenedesmus obliquus exposed in five types of polystyrene particle suspensions with different sizes and surface charges, in the presence and absence of humic acid (HA). Results indicated that the 50% growth inhibition rate of S. obliquus showed no significant difference between the five types of MPs, but the toxic mechanism varied with particle size. Larger size MPs caused adverse effects by blocking the light transport and affecting photosynthesis, while smaller ones destroyed the cell wall by adsorbing onto the algae surface. Also, the addition of HA significantly alleviated the toxicity of smaller size MPs, but not of the larger ones. Scanning electron microscopy images and the reactive oxygen species assay demonstrated that the HA could form a corona on the surface of MPs, reduce the affinity to microalgae, and minimize the adverse effect. Together, these findings identified important factors in determining the toxicity of MPs, providing valuable data for risk assessment of MPs.

Sorption properties of hydrophobic organic chemicals to micro-sized polystyrene particles.

It has been reported that microplastics (MPs) have strong affinity for hydrophobic organic chemicals (HOCs) and can be ingested accidentally by aquatic organisms, posing a potential threat to the environment. To date, the sorption data used in modelling to clarify the mechanism were mostly obtained in varied sampling durations and regions from different works, which might cause inevitable deviation in modelling results. The current study aimed to illustrate the sorption properties of HOCs to the micro-sized polystyrene (PS). The sorption behaviors of HOCs to the PS were investigated at a certain pre-equilibrium status, and the theoretical analysis was taken into consideration. A bottle-shaped passive dosing system was designed to measure the concentration ratio of HOCs in different phases of the exposure suspension at a certain time (logaMP), including polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) with logKow ranging from 3.17 to 10.20, between water and PS MPs with different dimensions (diameters of 100 nm, 1 µm and 2 µm, respectively). The calculated logaMP ranged from 3.73 to 8.34, and a positive correlation was found between logaMP and log1r0 (r0 is the MP radius). The results indicated that HOCs would diffuse into the PS particles, but the mass transfers inside the particles were slow and would be negligible in some environmental cases. Under theoretical considerations, the diffusion through the boundary layer of the particle was considered as the dominating process because it was fast, and the contributions of absorbed amounts on the particle surface were larger for smaller PS particles (i.e. 100-nm PS). This study could provide applicable data for further exploring the effects of micro-sized plastics on the HOCs in environmental samples.

Investigating the toxicities of different functionalized polystyrene nanoplastics on Daphnia magna.

Nanoplastics (NPs) spread widely with water and air current, and they can accumulate in aquatic organisms, even penetrating biofilms, which may cause persistent toxicity and potential hazards. This current study aimed to reveal the toxicological mechanism of different functionalized polystyrene (PS) NPs on Daphnia magna (D. magna) by investigating toxicity endpoints in individual level and biochemical level. In this study, acute toxicity, behavioral parameters and biomarker responses of D. magna was measured in the exposure of different functionalized PS NPs (plain PS, PS-p-NH2, PS-n-NH2 and PS-COOH). The results indicated that when exposed to the plain PS, ROS induction would activate MAPKs, thereby causing lethality and adverse behavior effects on D. magna; while the functionalized PS NPs were less toxic than the plain PS, especially for PS-p-NH2 which was severely flocculated after exposure, thus showing no immobilization at the investigated concentrations. Also, the antioxidant system was mainly stimulated due to the direct interaction with the cell surface receptor, which was different from the plain PS. Consequently, this work suggests significant effects of functional groups on NPs for environmental toxicity studies, and provides a better understanding of the toxicological mechanism on the toxicity of PS NPs toward D. magna.

Development of a novel solid phase microextraction calibration method for semi-solid tissue sampling.

Accurate quantitative analysis using in vivo solid phase microextraction (SPME) for semi-solid tissue can be challenging due to the complexity of the sample matrix. In this paper, a comprehensive study was carried out on the extraction kinetics of SPME in the semi-solid sample, and subsequently proposed a new theoretical model to interpret the kinetic extraction process. Theoretically derived mathematical expressions well described the experimental desorption time profiles of the SPME process. Modelling experiments were also carried out to study the effect of sample tortuosity and binding matrix on the parameters affecting the extraction kinetics. Seven polyaromatic hydrocarbons (PAHs) and eight polychlorinated biphenyls (PCBs) in agarose gel and in real fish tissue were used for these experiments. The experimental data showed excellent agreement with theoretical prediction while providing excellent interpretation of the effect of tortuosity and binding matrix. Based on the theoretical model, an on-fiber standard calibration method with fewer internal standards was developed. The newly developed calibration method was used to quantify PAHs and PCBs in agarose gel and fish tissue. By using the proposed calibration method, a large number of organic compounds can be quantified with fewer internal standards. Current study provides the theoretical foundation for in vivo SPME quantitative semi-solid tissue analysis in the future.

Quantification of the combined toxic effect of polychlorinated biphenyls and nano-sized polystyrene on Daphnia magna.

It has been reported that nanoplastics (NP) could cause serious toxicity and accumulative effects on aquatic organisms as well as interact with organic pollutants and influence potential hazards when exposed to biota. The current study aimed to quantitatively investigate the combined acute toxic effect of polychlorinated biphenyls (PCBs) and nano-sized polystyrene (PS) plastic on aquatic organisms based on analyte speciation. First, the combined acute toxicity of PCB-18 and 100 nm PS to Daphnia magna (D. magna) in water was evaluated. Then, speciation analysis of the exposure system was conducted by measuring the sorption coefficients (logKNP) of PCBs to nano-sized PS (ranging from 5.28 to 6.56), which demonstrated the PS could substantially decrease the free concentrations of PCBs. The results showed that a low concentration of the PS could decrease the toxicity to D. magna., which might be originated from the decreased free concentration of PCB-18. However, when the PS concentration was high enough, an opposite effect was observed because the PS dominated the lethality instead of PCB-18. The current study is helpful to clarify the PCB occurrence in ecosystems and provide an in-depth understanding of the eco-toxicological effects of nanoscale plastics.

Effect of salinity and humic acid on the aggregation and toxicity of polystyrene nanoplastics with different functional groups and charges.

Studies regarding the effect of environmental factors on the environmental behaviour and potential toxicity of nanoplastics (NPs) are limited but important. In this study, four polystyrene NPs with different functional groups and charges (PS, PS-COOH, n-PSNH2, p-PSNH2) were selected to investigate the effect of humic acid (HA) and salinity on their aggregation behaviour and toxicity. The results showed that salinity significantly accelerated the aggregation of the four NPs, while HA mainly exerted a stabilizing effect on the three negatively charged NPs. In contrast, the positively charged p-PSNH2 aggregated significantly at first but remained stable as HA concentration further increased. The joint effect mainly depended on their concentration ratio. The aggregation phenomena can be explained by the Derjaguin - Landau - Verwey - Overbeek (DLVO) theory. Also, the acute toxicity of NPs on Daphnia magna was affected by the surface charge of NPs, and the positively charged p-PSNH2 showed the lowest toxicity among the selected NPs. Furthermore, the presence of HA effectively alleviated the toxicity of PS and p-PSNH2, as the survival rates increased from 15% to 45%-95% and 100% respectively. Our results demonstrate that the surface properties of NPs significantly influence their aggregation and toxicity.

Effect of dissolved organic matter on pre-equilibrium passive sampling: A predictive QSAR modeling study.

Pre-equilibrium passive sampling is a simple and promising technique for studying sampling kinetics, which is crucial to determine the distribution, transfer and fate of hydrophobic organic compounds (HOCs) in environmental water and organisms. Environmental water samples contain complex matrices that complicate the traditional calibration process for obtaining the accurate rate constants. This study proposed a QSAR model to predict the sampling rate constants of HOCs (polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and pesticides) in aqueous systems containing complex matrices. A homemade flow-through system was established to simulate an actual aqueous environment containing dissolved organic matter (DOM) i.e. humic acid (HA) and (2-Hydroxypropyl)-ß-cyclodextrin (ß-HPCD)), and to obtain the experimental rate constants. Then, a quantitative structure-activity relationship (QSAR) model using Genetic Algorithm-Multiple Linear Regression (GA-MLR) was found to correlate the experimental rate constants to the system state including physicochemical parameters of the HOCs and DOM which were calculated and selected as descriptors by Density Functional Theory (DFT) and Chem 3D. The experimental results showed that the rate constants significantly increased as the concentration of DOM increased, and the enhancement factors of 70-fold and 34-fold were observed for the HOCs in HA and ß-HPCD, respectively. The established QSAR model was validated as credible (RAdj.2=0.862) and predictable (Q2=0.835) in estimating the rate constants of HOCs for complex aqueous sampling, and a probable mechanism was developed by comparison to the reported theoretical study. MAIN FINDING OF THE WORK: The present study established a QSAR model of passive sampling rate constants and calibrated the effect of DOM on the sampling kinetics.

Improving the Sensitivity of Solid-Phase Microextraction by Reducing the Volume of Off-Line Elution Solvent.

Solid-phase microextraction (SPME) coupled with liquid chromatograph (LC) is widely used to detect polar and ionic organic compounds, including various pharmaceuticals and endogenous bioactive compounds. In this study, a small-sized insert tube for use in the commercial autosampler vial was designed for eluting the extracted analytes from SPME fibers for LC analysis. By using this custom-made insert tube as an alternative to the commercial insert tube, the volume of the elution solvent was reduced by four-fifths. Even though smaller fractions of the analytes were eluted from the fiber coatings, the analyte concentrations in the elution solutions were substantially increased by using the custom-made insert tube. Therefore, larger amounts of the analytes could be injected to LC and higher signal-to-noise ratios could be achieved, even at smaller injection volumes. Since the elution in the custom-made insert tube was nonexhaustive, four strategies were developed to figure out the extracted amounts in the fiber coatings. In combination with the sampling-rate calibration method, these strategies were successfully used to determine the concentrations of fluoxetine in living tilapias. This study provides a simple but effect way for improving the analytical sensitivity when coupling SPME with LC.