Development of a Solid-Phase Extraction Method Based on Biocompatible Starch Polyurethane Polymers for GC-MS Analysis of Polybrominated Diphenyl Ethers in Ambient Water Samples

A new solid-phase extraction (SPE) method for the extraction, enrichment, and analysis of eight polybrominated diphenyl ethers (PBDEs) in water was developed. The current approach involves using a cross-linked starch-based polymer as an extraction adsorbent and determining the PBDE analytes of interest using gas chromatography-mass spectrometry in negative chemical ionization mode (GC-NCI-MS). The starch-based polymer was synthesized by the reaction of soluble starch with 4,4'-methylene-bis-phenyldiisocyanate as a cross-linking agent in dry dimethylformamide. Various parameters impacting extraction efficiencies, such as adsorbent quantity, sample volumes, elution solvents and volumes, and methanol content, were carefully optimized. The 500 mg of starch-based polymer as an adsorbent used to extract 1000 mL of spiked water, presented high extraction recoveries of eight PBDEs. The linearity of the extraction process was investigated in the range of 1-200 ng L-1 for BDE-28, 47, 99, 100, and 5-200 ng L-1 for BDE-153, 154, 183, and 209, with coefficients of determination (r2) exceeding 0.990 for all PBDEs. The limits of detection (LODs) ranged from 0.06 to 1.42 ng L-1 (S/N = 3) and the relative standard deviation values (RSD) were between 3.6 and 9.5 percent (n = 5) under optimum conditions. The method was successfully used to analyze river and lake water samples, where it exhibited acceptable recovery values of 71.3 to 104.2%. Considering the excellent analytical performance and comparative cost advantage, we recommend the developed starch-based SPE method for routine extraction and analysis of PBDEs in water media.

A sensitive microextraction by packed sorbent-gas chromatography-mass spectrometry method for the assessment of polycyclic aromatic hydrocarbons contamination in Antarctic surface snow

For the first time an eco-friendly method involving microextraction by packed sorbent (MEPS) coupled to gas chromatography-mass spectrometry (GC-MS) was developed for the determination of the 16 US-EPA priority pollutant polycyclic aromatic hydrocarbons (PAHs) as indicators of anthropogenic contamination in snow samples collected in polar regions. MEPS was carried out by using C8 sorbent material packed in a barrel insert and needle (BIN) and integrated in the eVol® semi-automatic device. For optimization purposes a Face Centred Design and the multicriteria method of the desirability functions were performed to investigate the effect of some parameters affecting the MEPS extraction efficiency, i.e. the number of loading cycles and the number of elution cycles. The developed MEPS-GC-MS method proved to be suitable for PAHs analysis at ultra-trace level by extracting small sample volumes achieving detection limits for 16 PAHs in the 0.3-5 ng L^-1 range, repeatability and intermediate precision below 11% and 15%, respectively, and good recovery rates in the 77.6 (±0.1)-120.8 (±0.1)% range for spiked blank snow samples. Enrichment factors in the 64 (±7)-129 (±18) range were calculated. Finally, the proposed method was successfully applied to the determination of PAHs in surface snow samples collected in 2020-2021 from four locations of Northern Victoria Land, Antarctica. Local emission sources such as ships and research stations were found to influence PAHs concentrations in the surface snow.

Microorganisms as Bio-SPE Materials for Extraction of Pharmaceutical Drugs: Mechanism of Extraction

In solid-phase extraction (SPE), the extraction materials depend on the physicochemical interactions to obtain the target analytes from complex systems. However, many matrix interferences existing in real samples influence the extraction efficiency through these common interactions. Therefore, extraction materials based on more special interactions for biological systems need to be developed. In this work, live microorganisms including Escherichia coli and Staphylococcus aureus were considered as the potential biological SPE (bio-SPE) materials with their biological functions in the live state. To study the enrichment and selectivity of the bio-SPE, four antibacterial drugs and two non-antibacterial drugs were employed as the target analytes. The enrichment factor (EF) was used as the evaluation index. The results showed that when using chlorpheniramine (CPM) and ofloxacin (OFLO), the enrichment capacity of E. coli was better than that of S. aureus. When extracting a single analyte, the enrichment ability of E. coli for CPM was significantly higher than other analytes, and the EF was 8.5. In a mixture solution of antibacterial analytes, OFLO could be enriched mostly by E. coli. However, in the mixture solution of antibacterial and non-antibacterial analytes, CPM was enriched more than that of antibacterial analytes. In real rat plasma, bio-SPE using live E. coli could obviously extract CPM, while traditional liquid-liquid extraction could not. The confocal microscopy results showed that the extraction mechanism may not only depend on the surface adsorption of bacteria with analytes but also on the uptake into bacteria. This provides a valuable basis for the development of more biological separation materials based on biological interactions.

Helical multi-walled carbon nanotube-coated fibers for solid-phase microextraction determination of polycyclic aromatic hydrocarbons at ultra-trace levels in ice and snow samples

Polycyclic Aromatic Hydrocarbons (PAHs) detected in polar environment are recognized tracers of anthropogenic pollution. High sensitivity and selectivity are required for their analysis in ice and snow samples due to the presence at ultra-trace levels. In this study a solid-phase microextraction (SPME) gas chromatography-mass spectrometry (GC-MS) method for simultaneous determination of the 16 US-EPA priority pollutant PAHs in polar snow and ice samples was developed and validated. Helical multiwalled carbon nanotubes (HMWCNTs) were proposed for the first time as novel SPME coating. For optimization purposes a Central Composite Design and the multicriteria method of the desirability functions were applied to investigate the influence of extraction parameters, i.e. time and temperature as main factors. The optimal values were 68 °C for the extraction temperature and 60 min for the extraction time. The developed SPME-GC-MS method exhibited detection limits of 16 PAHs in the 0.1-1.2 ng/L range, a repeatability and an intermediate precision within 15% and 22% relative standard deviation, respectively, and good recovery rates in the 93.7 (± 0.1)-119.7 (± 0.2)% range for real spiked water sample, showing better analytical performance compared to commercial PDMS fibers. Enrichment factors in the 2670 (± 290)-142120 (± 580) range were calculated and a long fiber shelf-life with the possibility to reuse the fiber more than 200 times was achieved. Finally, the proposed method was successfully applied to the determination of PAHs in surface snow samples collected in April 2019 at Ny-Ålesund, Svalbard. Its application to the detection of PAHs in samples collected during monitoring campaigns in the polar regions is expected in the near future.

Facile synthesis of polydivinylbenzene coated magnetic polydopamine coupled with pressurized liquid extraction for the extraction and cleanup of polycyclic aromatic hydrocarbons in soils

Due to the trace levels of polycyclic aromatic hydrocarbons (PAHs) in soil and the complexity of soil matrices, effective sample pretreatment methods are of great significance to obtain accurate analytical results. In this paper, polydopamine (PDA) encapsulated Fe₃O₄ particles were used as seeds for in situ polymerization of divinylbenzene (DVB) to derive magnetic hybrid material Fe₃O₄@PDA@PDVB. Coupled with pressurized liquid extraction, Fe₃O₄@PDA@PDVB was investigated as a selective adsorbent for the extraction and cleanup of PAHs in soil. The prepared magnetic material was characterized and demonstrated to possess strong hydrophobicity and superparamagnetism. Under optimal conditions, Fe₃O₄@PDA@PDVB can effectively extract 15 PAHs from a 30% methanol solution within 2 min, and it is more selective for PAHs than for n-alkane in soil extracts. The matrix effect significantly decreased after extraction by the prepared material, which showed superiority to a silica gel column method (EPA 3630C Method). The developed method was linear (5-1000 ng g^-1) with coefficient of determination (R²) ranging from 0.9986-0.9998, and the limits of detection were 0.13-0.54 ng g^-1. Additionally, repetitive experiments indicated that the prepared material was reproducible and reusable with relative standard deviations below 8.4% and 8.6%, respectively. Finally, the new method was successfully employed to determine the concentrations of PAHs in genuine soil and standard reference material, and the results were comparable to those of widely utilized EPA methodology.

Correlation analysis based on the hydropathy properties of non-steroidal anti-inflammatory drugs in solid-phase extraction (SPE) and reversed-phase high performance liquid chromatography (HPLC) with photodiode array detection and their applications to biological samples

In the present work we analyzed the hydrophobicity and hydrophilicity properties of several non-steroidal anti-inflammatory drugs (NSAIDs) by investigating the structural changes of the dynamic hydrogen bond network in order to predict the extraction recovery of NSAIDs from biological fluids set by solid phase extraction (SPE). This work allows investigating the relationship between theoretical descriptors and experimental data using a parameter free method with a strong correlation (Pearson correlation 0.95, p-value 0.0003). The identification and quantification of analytes in human plasma were carried out by high performance liquid chromatography coupled with photodiode array detection (HPLC-PDA) using a Kinetex Evo C₁₈ (150 x 4.6 mm I.D) protected by a guard column and a mixture of acetonitrile and 10 mM phosphate buffer (pH 2.5) (50:50, v/v) as mobile phase at isocratic conditions. Accuracy (BIAS%) ranged within -2.33% and + 8.05% while precision (RSD%) was less than 5.73%.The mean extraction recovery of the carprofen (IS) was 84.1% and the recovery of NSAIDs from human plasma ranged between 81.9% to 86.6%. LODs and LOQs for all the investigated NSAIDs were 0.003 and 0.01 μg/mL, respectively. The method was validated according to the ICH guide line in the range 0.010-20.0 μg/mL.

Degree of time dependency of kinetic coefficient as a function of adsorbate concentration; new insights from adsorption of tetracycline onto monodispersed starch-stabilized magnetic nanocomposite

The realization that the observed kinetic coefficient (k_obs) varies with time in most real-time adsorption system, as against the constant value conceived in the most widely-applied adsorption kinetic models, have attracted much attention in recent time. Understanding the factors that control the extent/degree of time dependency (otherwise known as fractal-like kinetics), is therefore central in taking manipulative advantage of this phenomenon in critical adsorption applications. This study therefore deployed non-fractal-like and fractal-like kinetic approach to study the adsorption of tetracycline on monodispersed starch-stabilized magnetite nanocomposite (MSM). MSM was synthesized by in-situ coprecipitation of magnetite in the presence of starch, and successfully characterized with classical solid-state techniques. Isotherm studies indicated that MSM has heterogenous surface adsorption sites. Equilibrium and kinetic data indicated the existence of π-cation interaction as the underlying mechanism, while pH study revealed that tetracycline was adsorbed in its zwitterion form. Though the non-fractal kinetic models exhibited some level of relevance in explaining the tetracycline adsorption interactions, the best fitting of the fractal-like pseudo second order model to the adsorption kinetic data, indicated that the real-time adsorption kinetics occurred in fractal-like manner. The study also revealed that the degree of time dependency of k_obs had negative correlation with the initial tetracycline concentration. Apart from developing a low-cost strategy for addressing tetracycline water pollution, the result of this study serves a positive step towards gaining manipulative control of adsorption mechanism in potential application of MSM for targeted drug delivery and controlled release of tetracycline antibiotics.

Characteristics, source, and potential ecological risk assessment of polycyclic aromatic hydrocarbons (PAHs) in the Songhua River Basin, Northeast China

The concentration characteristics, sources, and potential ecological risk assessment of 16 PAHs were investigated in the surface water from the Songhua River Basin, Northeast China. A total of 48 river water samples, including 16 from the main streams and 32 from the tributaries, were collected. Samples were separated into dissolved phases and suspended particle matter (SPM) via filtration with 0.47 μm glass fiber filters. Each phase was analyzed for PAHs. The total PAH concentration in the dissolved phase in the water ranged from 32.5 to 108 ng L^-1 and from 0.3 to 62.3 μg g^-1 (dry weight) in the suspended particle matter (SPM). The total PAH concentration in the main stream was lower than in the tributaries; the volume of annual runoff of rivers had a significant effect on the ƩPAH in the rivers. The 2- and 3-ring PAHs dominated in both the dissolved phase and SPM, indicating a relatively recent local source of PAHs in the study area. The concentrations of PAHs in the Songhua River Basin are lower when compared with the values previously reported in the literature from other rivers around the world. The sources of PAHs were assessed by diagnostic ratios and principal component analysis (PCA), and the ecological risk of the PAHs was assessed based on the risk quotient (RQ). The diagnostic ratios and PCA indicated that the main sources of PAHs originated from pyrogenic and petrogenic sources, and pyrogenic sources had a greater impact. The ecological risk assessment indicated that the PAHs presented low ecosystem risk in the Songhua River Basin.

Theoretical and experimental studies on the separation of cinnamyl acetate and cinnamaldehyde by adsorption onto a β-cyclodextrin polyurethane polymer

CAc and CA were separated using CDPU as adsorbent, and the mechanism was proposed through DFT calculations and experimental analyses.