In Situ Identification and Spatial Mapping of Microplastic Standards in Paramecia by Secondary-Ion Mass Spectrometry Imaging.

Microplastics (MPs) are universally present in the ecosystem and pose great threats to the environment and living organisms. Research studies have shown that small MPs (<50 µm in diameter) are especially toxic and account for more than half of all MPs collected in the Atlantic Ocean. Nevertheless, current methods for the detection and analysis of MPs are incapable of achieving rapid and in situ analysis of small MPs in the biota to ultimately enable the study of their biological effects. In this work, we report a method that allows rapid in situ identification and spatial mapping of small MPs directly from paramecia with high accuracy by acquiring chemical composition information using secondary-ion mass spectrometry (SIMS) imaging. Specifically, six types of common MPs (polymethyl methacrylate, polyvinyl chloride, polypropylene, polyethylene terephthalate, polyglycidyl methacrylate, and polyamide 6) with a diameter of 1-50 µm were simultaneously imaged with high chemical specificity at a spatial resolution of 700 nm. In situ spatial mapping of a group of MPs ingested by paramecia was performed using SIMS fragments specific to the plastic composition with no sample pretreatment, revealing the aggregation of MPs in paramecia after ingestion. Compared with existing methods, one additional advantage of the developed method is that the MPs and the organism can be analyzed in the same experimental workflow to record their fingerprint spectra, acquiring biochemical information to evaluate MP fate, toxicity, and the MP-biota interaction.

Magnetic stir cake sorptive extraction of trace tetracycline antibiotics in food samples: preparation of metal-organic framework-embedded polyHIPE monolithic composites, validation and application.

In this work, a novel Fe3O4@Cu3(btc)2-embedded polymerized high internal phase emulsion (Fe3O4@HKUST-1-polyHIPE) monolithic cake was synthesized, characterized and used as an adsorbent in the magnetic stir cake sorptive extraction (MSCSE) and determination of tetracycline antibiotics (TCs) in food samples by a combination of with high-performance liquid chromatography-fluorescence detection (HPLC-FLD). The prepared Fe3O4@HKUST-1-polyHIPE monolithic composites displayed a strong extraction ability and high column capacity due to enhanced interactions such as π-π interactions, hydrogen bonding, and electrostatic interactions. The extraction and desorption conditions were evaluated, and the calibration curves of four spiked TCs were linear (R2 ≥ 0.9991) in the range from 20 to 800 ng mL-1 for milk and egg samples, and 20 to 800 ng g-1 for chicken muscle and kidney samples. The limits of detection and the limits of quantification of the four TCs by using the proposed MSCSE-HPLC-FLD method were in the range of 1.9-4.6 and 5.5-13.9 ng mL-1 for milk and egg samples, and 1.8-3.7 and 5.3-13.0 ng g-1 for chicken muscle and kidney samples, respectively. The recoveries of the target TCs from spiked food samples were in the range from 86.6 to 110.7% with relative standard deviations lower than 7.0%. The proposed method was successfully applied for the determination of these four TCs in milk, egg, chicken muscle, and kidney samples.

Low-temperature plasma-probe mass spectrometry based method for determination of new psychoactive substances in oral fluid.

RATIONALE: Owing to the widespread abuse of new psychoactive substances (NPSs), developing a rapid, easily operable method to detect NPSs in oral fluid is of high priority. Their ease of collection and non-invasive nature make oral fluid samples suitable for on-site tests and forensic cases. Herein we report a rapid and sensitive method to screen and quantitate 11 new NPSs in oral fluid. METHODS: Low-temperature plasma-probe mass spectrometry (LTP-MS) was applied and, to improve the signal intensity, thermally assisted desorption was employed. Tandem mass spectrometry was performed to exclude false positive signals and to decrease noise at the m/z values of interest. RESULTS: Linearity was studied using matrix-matched calibration curves; all the analytes exhibited good linearity with R2 varying from 0.9907 to 0.9981. The estimated limits of detection (LODs) were in the range of 3.0-15.2 ng/mL, which are comparable to those of immunoassay; relative standard deviations (RSDs) are no greater than 23% at the studied concentration levels. CONCLUSIONS: The proposed LTP-MS-based method was promising in forensic and on-site applications to curb the abuse of NPSs.

High-internal-phase-emulsion polymeric monolith coupled with liquid chromatography-electrospray tandem mass spectrometry for enrichment and sensitive detection of trace cytokinins in plant samples.

High-internal-phase-emulsion polymers (polyHIPEs) show great promise as solid-phase-extraction (SPE) materials because of the tremendous porosity and highly interconnected framework afforded by the high-internal-phase-emulsion (HIPE) technique. In this work, polyHIPE monolithic columns as novel SPE materials were prepared and applied to trace enrichment of cytokinins (CKs) from complex plant samples. The polyHIPE monoliths were synthesized via the in-situ polymerization of the continuous phase of a HIPE containing styrene (STY) and divinylbenzene (DVB) in a stainless column, and revealed highly efficient and selective enrichment ability for aromatic compounds. Under the optimized experimental conditions, a method using a monolithic polyHIPE column combined with liquid chromatography-electrospray tandem mass spectrometry (LC-MS-MS) was developed for the simultaneous extraction and sensitive determination of trans-zeatin (tZ), meta-topolin (mT), kinetin (K), and kinetin riboside (KR). The proposed method had good linearity, with correlation coefficients (R (2)) from 0.9957 to 0.9984, and low detection limits (LODs, S/N = 3) in the range 2.4-47 pg mL(-1) for the four CKs. The method was successfully applied to the determination of CKs in real plant samples, and obtained good recoveries ranging from 68.8 % to 103.0 % and relative standard deviations (RSDs) lower than 16 %.

Development of high internal phase emulsion polymeric monoliths for highly efficient enrichment of trace polycyclic aromatic hydrocarbons from large-volume water samples.

In this work, polymerized high internal phase emulsion (polyHIPE) monoliths were prepared and applied as monolithic adsorbent materials for proconcentration of trace polycyclic aromatic hydrocarbons (PAHs) from large-volume water samples. The monolithic polyHIPE columns were prepared by in situ polymerization of the continuous phase of a high internal phase emulsion (HIPE) containing styrene (STY), divinylbenzene (DVB) and glycidyl methacrylate (GMA) in pipette tips, and the resulting STY/DVB/GMA polyHIPE monoliths exhibited highly interconnected porosity and large surface areas, making them excellent candidates as adsorbents for enrichment of trace aromatic compounds. The prepared STY/DVB/GMA polyHIPE monoliths were applied to the determination of trace PAHs in environmental water samples by combing with high performance liquid chromatography-fluorescence detection (HPLC-FLD). Under the optimized experimental conditions, the polyHIPE monoliths could effectively enrich trace 13 PAHs from 500mL of water samples, the mean recoveries at four spiked levels were ranged from 80.7% to 115.0% with the relative standard deviations (RSDs) lower than 14%, and the detection limits (LODs) were ranged from 4.0 to 228pg/L. In addition, the prepared polyHIPE monolith was stable enough for more than 200 replicate extraction cycles without measurable loss of performance on the enrichment of PAHs, and good column-to-column repeatability was obtained with RSD less than 13%. The proposed method was applied to simultaneous analysis of 13 PAHs in water samples with satisfactory recoveries.