Development of the Space-Resolved Solid-Phase Microextraction Technique and Its Application to Biological Matrices

Sampling-rate calibration vs. equilibrium calibration for in vivo solid-phase microextraction: Analysis of neonicotinoids in bananas

In vivo solid-phase microextraction (in vivo SPME) is an emerging fascinating sample pretreatment technique, but its quantitative correction method is different from the traditional correction methods, which has become a bottleneck limiting its development. At present, the sampling-rate calibration and equilibrium calibration are mainly used, however, their characteristics and applicability are not clear. In this study, the sampling-rate calibration and equilibrium calibration were evaluated in the case of the determination of neonicotinoids in bananas by in vivo SPME. The factors that affect the sampling rate (Rs), such as the matrix states, sampling durations, and individual differences were studied, and they all had impacts on Rs. Conversely, the equilibrium distribution coefficient (Kfs) remained constant after extraction equilibrium and the individual differences were smaller. The highest accuracy and precision were achieved by equilibrium calibration, and the relative recoveries were in the range of 83.2 %-104.3 % with the relative standard deviations below 8.1 % compared to a standard QuEChERS-based method. The lower limits of quantification for 4 neonicotinoids in bananas were below 5 ng g-1, lower than the standard method and the maximum residue levels in China and the European Union. This work clarifies the characteristics, rules and performance of the sampling-rate calibration and equilibrium calibration, which is of crucial importance for the development and application of in vivo SPME. The developed method is convenient, sensitive, and accurate for the determination of pesticide residues, which is of great significance to guide the safe use of pesticides in the field and prevent products with excessive pesticide residues from entering the market.

Determination of phthalates in fish fillets by liquid chromatography tandem mass spectrometry (LC-MS/MS): A comparison of direct immersion solid phase microextraction (SPME) versus ultrasonic assisted solvent extraction (UASE)

Due to the increasing presence of plastic and plastic associated contaminants in the aquatic environments, the monitoring of this contamination in fish products and the understanding of possible human health implications is considered urgent. However, data are still relatively scarce, mostly due to the methodological challenges in the chemical analysis: these contaminants are ubiquitous and procedural contamination from the laboratory is frequent. In this work, we compared solid-phase microextraction (SPME) to ultrasonic assisted solvent extraction (UASE) as sample preparation methods for the liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) determination of phthalates in fish fillets. UASE was carried out with an acetone-hexane (1:1) solution and according to a reference procedure aimed to obtain the exhaustive extraction of the target analytes. SPME was carried out by applying C18 fibers in direct immersion mode and by using water/methanol 20:80 mixture to desorb the aliquot required for the analysis. Overall, SPME displayed an improved control of the background contamination and enabled lower LOQs. Precision, calculated as relative standard deviation (RSD) on replicates of a reference sample, was below 24% for both the method. Analysis of real samples purchased from Italian supermarkets showed that SPME might be an efficient tool for estimating the risk associated with fish consumption.

Detection technologies and metabolic profiling of bile acids: a comprehensive review

Bile acids (BAs) are important regulatory factors of life activities, which are involved in the regulation of glucose, lipid and energy metabolisms, and closely associated with intestinal hormones, microbiotas and energy balance. BAs abnormalities easily lead to inflammation and metabolic diseases, in turn, the progress of diseases could influence characteristics of BAs. Therefore, accurate detection of BAs contents is of great significance to disease prevention, diagnosis and treatment. At present, the most widely used enzymatic method in clinical practice is applicable to the detection of total bile acid (TBA). In laboratory research, different types of BAs can be accurately separated and quantified by liquid chromatography-mass spectrometry (LC-MS). The metabolic profiling of BAs based on detection technologies can completely and accurately monitor their types and contents, playing a crucial role in disease prevention, diagnosis and treatment. We herein reviewed the main detection technologies of BAs and the application of metabolic profiling in related diseases in recent years.

PLGA-based nanofibers with a biomimetic polynoradrenaline sheath for rapid in vivo sampling of tetrodotoxin and sulfonamides in pufferfish

PLGA nanofibers with PNA sheath modification achieve enhanced extraction performance and antibiofouling capacity for in vivo sampling in pufferfish.

In Situ Hydrothermally Grown TiO2@C Core-Shell Nanowire Coating for Highly Sensitive Solid Phase Microextraction of Polycyclic Aromatic Hydrocarbons

Nanostructured materials have great potential for solid phase microextraction (SPME) on account of their tiny size, distinct architectures and superior physical and chemical properties. Herein, a core-shell TiO₂@C fiber for SPME was successfully fabricated by the simple hydrothermal reaction of a titanium wire and subsequent amorphous carbon coating. The readily hydrothermal procedure afforded in situ synthesis of TiO₂ nanowires on a titanium wire and provided a desirable substrate for further coating of amorphous carbon. Benefiting from the much larger surface area of subsequent TiO₂ and good adsorption property of the amorphous carbon coating, the core-shell TiO₂@C fiber was utilized for the SPME device for the first time and proved to have better performance in extraction of polycyclic aromatic hydrocarbons. In comparison to the polydimethylsiloxane (PDMS) and PDMS/divinylbenzene (DVB) fiber for commercial use, the TiO₂@C fiber obtained gas chromatography responses 3-8 times higher than those obtained by the commercial 100 μm PDMS and 1-9 times higher than those obtained by the 65 μm PDMS/DVB fiber. Under the optimized extraction conditions, the low detection limits were obtained in the range of 0.4-7.1 ng L^-1 with wider linearity in the range of 10-2000 ng L^-1. Moreover, the fiber was successfully used for the determination of polycyclic aromatic hydrocarbons in Pearl River water, which demonstrated the applicability of the core-shell TiO₂@C fiber.

Hydrothermally grown and self-assembled modified titanium and nickel oxide composite nanosheets on Nitinol-based fibers for efficient solid phase microextraction

A novel titanium and nickel oxide composite nanosheets (TiO₂/NiOCNSs) coating was in situ grown on a Nitinol (NiTi) wire by direct hydrothermal treatment and modified by self-assembly of trichlorophenylsilane for solid phase microextraction (SPME). TiO₂/NiOCNSs were radially oriented and chemically bonded to the NiTi substrate with double-faced open access sites. Moreover the phenyl modified TiO₂/NiOCNSs (TiO₂/NiOCNSs-Ph) coating exhibited original surface supporting framework favorable for effective SPME. The extraction performance of TiO₂/NiOCNSs-Ph coated NiTi (NiTi-TiO₂/NiOCNSs-Ph) fiber was investigated for the concentration and detection of ultraviolet (UV) filters, polycyclic aromatic hydrocarbons (PAHs), phthalate acid esters and polychlorinated biphenyls coupled to HPLC with UV detection. The novel fiber exhibited better selectivity for UV filters and PAHs and presented greater extraction capability compared to commercial polydimethylsiloxane and polyacrylate fibers. Under the optimized conditions for SPME of UV filters, the proposed method presented linear ranges from 0.1 to 300μg/L with correlation coefficients of higher than 0.999 and limits of detection from 0.030μg/L to 0.064μg/L. Relative standard deviations (RSDs) were below 7.16% and 8.42% for intra-day and inter-day measurements with the single fiber, respectively. Furthermore RSDs for fiber-to-fiber reproducibility from 6.57% to 8.93% were achieved. The NiTi-TiO₂/NiOCNSs-Ph fiber can be used up to 200 times. The proposed method was successfully applied to the preconcentration and determination of trace target UV filters in different environmental water samples. The relative recoveries from 87.3% to 104% were obtained with RSDs less than 8.7%.

Phenyl-functionalization of titanium dioxide-nanosheets coating fabricated on a titanium wire for selective solid-phase microextraction of polycyclic aromatic hydrocarbons from environment water samples

A novel titanium dioxide-nanosheets coating on a titanium wire (TiO2NS-Ti) was in situ fabricated by one-step electrochemical anodization in ethylene glycol with ammonium fluoride and followed by phenyl-functionalization for selective solid-phase microextraction (SPME). The fabricated TiO2NS coating exhibits higher specific surface area and more active sites, it also provides an ideal nanostructure and a robust substrate for subsequent surface modification. These characteristics were useful for efficient extraction. The SPME performance of phenyl-functionalized TiO2NS-Ti (ph-TiO2NS-Ti) fiber was evaluated by using ultraviolet filters, polychlorinated biphenyls and polycyclic aromatic hydrocarbons (PAHs) as model compounds coupled to high performance liquid chromatography with UV detection (HPLC-UV). It was found that the ph-TiO2NS-Ti fiber exhibited high extraction capability, good selectivity and rapid mass transfer for PAHs. The main parameters affecting extraction performance were investigated and optimized. Under optimized conditions, the proposed fiber showed good extraction efficiency comparable to those of commercial polydimethylsiloxane and polyacrylate fibers toward PAHs. The calibration graphs were linear over the range of 0.05-300 µg L(-1). The limits of detection of the proposed method were 0.008-0.043 µg L(-1) (S/N=3). Single fiber repeatability varied from 3.51% to 5.23% and fiber-to-fiber reproducibility ranged from 4.43% to 7.65% for the extraction of water spiked with 25 µg L(-1) each analyte (n=5). The established SPME-HPLC-UV method was successfully applied to selective concentration and sensitive determination of target PAHs from real environmental water samples with recoveries from 86.2% to 112% at the spiking level of 10 µg L(-1) and 50 µg L(-1). The relative standard deviations were below 9.45%. Furthermore, the ph-TiO2NS-Ti fiber can be fabricated in a reproducible manner, and has high stability and long service lifetime.

In vivo and ex vivo SPME: a low invasive sampling and sample preparation tool in clinical bioanalysis

Solid phase microextraction (SPME) is well-established technology in bioanalysis. Current review discusses the features of SPME, which determine the non- or low-invasiveness of the method in biomedical analysis. In the first section we analyze the factors, which have significant influence on the SPME sampling device performance in the view of sampling safety and efficiency. In the later sections applicability of various SPME approaches for analysis of easily accessible samples routinely used for analysis (e.g., urine, blood) as well as limited availability samples (tissues) is discussed. Moreover, the examples of sampling alternative matrices such as hair, saliva, sweat or breath are presented. The advantages and limitation of the technology in the view of future development of SPME are also reviewed.

Microextraction techniques for the determination of volatile and semivolatile organic compounds from plants: a review

Vegetables and fruits are necessary for human health, and traditional Chinese medicine that uses plant materials can cure diseases. Thus, understanding the composition of plant matrix has gained increased attention in recent years. Since plant matrix is very complex, the extraction, separation and quantitation of these chemicals are challenging. In this review we focus on the microextraction techniques used in the determination of volatile and semivolatile organic compounds (such as esters, alcohols, aldehydes, hydrocarbons, ketones, terpenes, sesquiterpene, phenols, acids, plant secondary metabolites and pesticides) from plants (e.g., fruits, vegetables, medicinal plants, tree leaves, etc.). These microextraction techniques include: solid phase microextraction (SPME), stir-bar sorptive extraction (SBSE), single drop microextraction (SDME), hollow fiber liquid phase microextraction (HF-LPME), dispersive liquid liquid microextraction (DLLME), and gas purge microsyringe extraction (GP-MSE). We have taken into consideration papers published from 2008 to the end of January 2013, and provided critical and interpretative review on these techniques, and formulated future trends in microextraction for the determination of volatile and semivolatile compounds from plants.

In vivo solid-phase microextraction for tissue bioanalysis

Conventional in vitro or ex vivo bioanalytical quantitative sample preparation methods for the determination of compounds in biological tissues are often coupled with challenges in obtaining an assay representative of the system of interest. The rising interest in in vivo microsampling bioanalytical methods is due to the unique advantages they offer over their in vitro counterparts. In vivo solid-phase microextraction (SPME), a diffusion-based microsampling tool, has been successfully applied in recent studies to various biological systems. This review presents recent trends in tissue bioanalysis using in vivo SPME as a sample preparation tool. Efforts were made to discuss the various bioapplications of the method while highlighting possible strategies for improved sensitivity where needed. In vivo SPME devices currently employed for the various applications have also been described. In addition, we highlight selectivity of a new class of biocompatible coatings that can potentially improve the coverage of metabolites for untargeted metabolomics.

Determination of pharmaceutical residues in fish bile by solid-phase microextraction couple with liquid chromatography-tandem mass spectrometry (LC/MS/MS)

The present study investigates possible uptake and bioconcentration of different classes of pharmaceuticals residues (organic contaminants) in fish bile using a simplified analytical methodology based on solid phase microextration (SPME). The use of solid phase microextraction (SPME), as a simple analytical tool, to screen for target pharmaceuticals in fish bile samples was validated in rainbow trout (Oncorhynchus mykiss) following short-term laboratory exposures to carbamazepine and fluoxetine. While fish bioconcentrated both fluoxetine and carbamazepine from exposure water, fluoxetine accumulated to a greater degree in bile than carbamazepine. Good agreement was obtained for both analytes in bile samples between SPME and traditional liquid (solvent) extraction approaches (R(2) > 0.99). The field application of SPME sampling was further demonstrated in fathead minnow (Pimephales promelas), a small-bodied fish caged upstream and downstream of a local wastewater treatment plant where fluoxetine, atorvastatin, and sertraline were detected in fish bile at the downstream location. SPME is a promising analytical tool for investigating the bioconcentration of trace contaminants in fish bile, facilitating detection of trace environmental contaminants otherwise undetectable due to low concentrations in the environment and biological tissues as well as the complexity of the sample matrices.

ZnO nanorod coating for solid phase microextraction and its applications for the analysis of aldehydes in instant noodle samples

Zinc oxide (ZnO) nanorods based solid-phase microextraction (SPME) coating was directly prepared on stainless steel wires using in situ hydrothermal growth method. This coating has high surface-to-volume ratio with a diameter in the range of 300-500 nm and a thickness of about 3-5 μm. A guiding tube was introduced into the laboratory-made SPME fiber to protect the ZnO nanorods coating from shaving, which significantly improved the method repeatability and prolonged the service life of the coating. The extraction properties of the prepared fiber were investigated using headspace SPME (HS-SPME) coupled to gas chromatography (GC) for the determination of aldehydes in instant noodle samples. The extraction efficiency of the coating for the five aldehydes was comparable to that of a commercial 85 μm Carboxen/Polydimethylsiloxane fiber, which has been reported to have best affinity towards aldehydes among all commercial fibers. The linear ranges of the proposed HS-SPME-GC method were from 0.05 to 5 μg g⁻¹ (hexanal, nonanal and decanal) and 0.1-5 μg g⁻¹ (heptanal and octanal), with the correlation coefficients from 0.990 to 0.999. The method developed was successfully applied to the determination of five aldehydes in instant noodle samples, and the recoveries were found to be 70.5-129% at the spiking level of 2 μg g⁻¹.

Solid-phase microextraction coupled to LC-ESI-MS/MS: evaluation and correction for matrix-induced ionization suppression/enhancement for pharmaceutical analysis in biological and environmental samples

Solid-phase microextraction (SPME) coupled to liquid chromatography with electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) has been widely used to analyze biological fluids, tissues, and environmental matrixes for a variety of organic compounds including pharmaceuticals. However, effects of the sample matrix coextracted by SPME on tandem mass spectrometry analysis have not been systematically investigated. In this study, we characterized the complexity of matrix effects (ME) by analyzing SPME extracts of fish muscle and brain tissue, blood, and bile, as well as tap water, surface water, and the influent and effluent from a wastewater treatment plant. Significant enhancement or suppression of ionization (>15%) was observed with all biological and environmental samples. Intrasample ME variability was assessed through comparison of multiple samples from the same sample matrix, while intersample variability between different experimental subjects or varying sample treatment, storage, and sampling conditions were evaluated. To correct for ME, an isotopic internal standard (IIS) method was developed, with the strengths and limitations of the approach discussed. This study provides a framework for applying SPME within complex sample systems where the influences of ME are inevitable, thus ensuring more accurate quantitation of analytes during biological and environmental analysis.