Preparation of functionalized graphene and ionic liquid co-doped polypyrrole solid phase microextraction coating for the detection of benzoates preservatives

Ordered mesoporous hairbrush-like nanocarbon assembled microfibers for solid-phase microextraction of benzene series in oilfield sewage

The development of advanced functional nanomaterials for solid-phase microextraction (SPME) remains an imperative aspect of sample pretreatment. Herein, we introduce a novel SPME fiber consisting of graphene fibers modified with ordered mesoporous carbon nanotubes arrays (CNTAs) tailored for the determination of benzene series in oilfield wastewater, which is synthesized by an ionic liquid-assisted wet spinning process of graphene nanosheets, followed by a precisely controlled growth of metal-organic framework and subsequent pyrolysis treatment. The resulting robust microfiber structure resembles a "hairbrush" configuration, with a crumpled graphene fiber "stem" and high-order mesoporous CNTAs "hairs". This unique architecture significantly enhances the SPME capacity, as validated by gas chromatography-mass spectrometry. The hairbrush-like nanocarbon assembled microfibers possess structural characteristics, a high specific surface area, and numerous binding sites, offering efficient enrichment of benzene series compounds in oilfield wastewater, including benzene, ethylbenzene, m-xylene, p-xylene, and toluene. Our analysis demonstrates that these microfibers exhibit broad linear ranges (0.2-600 μg L-1), low detection limits (0.005-0.03 mg L-1), and excellent repeatability (3.2-5.5% for one fiber, 2.1-6.7% for fiber-to-fiber) for detection. When compared to commercial alternatives, these hairbrush-like nanocarbon-assembled microfibers exhibit significantly enhanced extraction efficiency for benzene series compounds.

Application of Response Surface Methodology to Optimize Solid-Phase Extraction of Benzoic Acid and Sorbic Acid from Food Drinks

An experimental design was applied for the optimization of the extraction process of two preservatives, benzoic and sorbic acids (BA, SA), from food drinks. A simple, rapid, and reliable solid-phase extraction (SPE) method for the simultaneous extraction of these two preservatives and their determination by liquid chromatography with a diode array detector was considered. Box−Behnken design (BBD) was applied to both steps of the SPE process: (i) the sample percolation to ensure the retention of the totality of the acids by the silica-based C18 sorbent; (ii) the elution step to ensure desorption of the totality of the acids from the cartridge. Thus, the volume, pH, and flow rate of the sample, and the percentage of MeOH, volume, and flow rate of the elution solvent, were optimized. Sample volume and pH have a significant influence (p < 0.0001 and p = 0.0115) on the percolation yield. However, no effect was recorded for the flow rate (p > 0.05). Flow rate also has no significant effect on the elution efficiency. The proposed new solid-phase extraction method, which can be easily applied to routine monitoring of preservatives BA and SA in juice and soft drink samples, included 0.5 g of C18 sorbent, 1 mL of food drink adjusted to pH 1 and percolated at 4.5 mL min−1, and 1 mL of a solvent mixture composed of methanol/acidified water (pH = 2.6) (90:10, v/v) used in the elution step at a flow rate of 4.5 mL min−1. Validation of the SPE method and the technique of analysis were evaluated, namely, the accuracy, precision, detection, and quantification limits and linearity. Recovery percentages of benzoic and sorbic acids were above 95% with relative standard deviations lower than 1.78%. Detection and quantification limits were 0.177 and 0.592 µg mL−1, and 0.502 and 0.873 µg mL−1 for benzoic acid and sorbic acid respectively. Optimal conditions were applied to commercial fruit juices and soft drinks and a minimal matrix effect was observed. This method was compared with other SPE methods using oxidized activated carbon and multiwalled carbon nanotubes as adsorbents. The yields determined with these last two were low compared to those determined with our method.

Template-directed synthesis of three-dimensional metal organic framework 199-derived highly porous copper nano-foam fiber for solid-phase microextraction of some antibiotics prior to their quantification by High performance liquid chromatography

The in-situ preparation of three-dimensional MOF-199 (3D MOF-199) derived from the electrochemically prepared highly porous nano Cu foam on the surface of a flexible copper wire is reported. The 3D-Cu foam coating was used as a precursor and template for fabrication of MOF-199. The microextraction ability of the in-situ prepared 3D-MOF-199 fiber was evaluated using the prepared fiber for solid phase microextraction (SPME) of selected antibiotics including amoxicillin, azithromycin, ciprofloxacin, cefixime and gentamicin coupled to high-performance liquid chromatography with UV detection. Under the optimized condition, the calibration curves were linear in the range of 1-100 µg L ^- 1 (r² above 0.9921) for both water and urine matrices. Limits of detection and limits of quantification were 0.14-0.62 µg L ^- 1 and 0.53-2.17 µg L ^- 1 in the selected matrices, respectively. In addition, the repeatability of the method was evaluated by considering the relative standard deviation (RSD%). The intra-day and inter-day RSDs of the method with the single fiber was in the range of 2.8% to 4.9% and from 3.1% to 4.9%, respectively. Furthermore, the fiber-to-fiber reproducibility ranged from 2.9% to 5.5%. The enrichment factors were also in the range of 32 to 55. Finally, the method was successfully used for analysis of amoxicillin, azithromycin, ciprofloxacin, cefixime and gentamicin in urine samples. Relative recoveries for spiked urine samples were in the range of 90-105%.

Temperature and time-controlled hydrothermal growth and sorption selectivity of titania nanowires on titanium fiber for highly efficient solid-phase microextraction

Two kinds of TiO₂ nanowires (TiO₂NWs) with different orientation were in-situ grown on Ti substrates by controlling temperature and time during the hydrothermal process. The adsorption performance was evaluated by using typical aromatic compounds as model analytes coupled to HPLC with UV detection. The results demonstrated that the TiO₂NWs coating grown at higher temperature within longer time had better affinity towards PAHs. For this purpose, the key experimental factors affecting the adsorption performance of the TiO₂NWs coating fabricated at 200 °C for 10 h were further investigated and optimized for the extraction of PAHs. Under the optimized conditions, the proposed method presented linear responses in the concentration ranges of 0.05 to 200 μg·L^-1 PAHs with correlation coefficients more than 0.998. LODs (S/N=3) were 0.008 to 0.034 μg·L^-1. Moreover, RSDs for the single fiber repeatability of the intra-day and the inter-day analyses were less than 5.6% (n=5) and 5.8%, respectively. RSDs for the fiber-to-fiber reproducibility were between 5.1% and 6.5%. Finally, the proposed method was successfully applied to the selective preconcentration and determination of trace PAHs in environmental water samples. In addition, The fabricated Ti fiber can be used at least 200 times due to its high mechanical and chemical stability.