CNT-TiO2 coating bonded onto stainless steel wire as a novel solid-phase microextraction fiber

Recent applications of organic molecule-based framework porous materials in solid-phase microextraction for pharmaceutical analysis

Sample preparation is an indispensable part of detection of complex samples in pharmaceutical analysis. Solid-phase microextraction (SPME) has obtained a lot of attention due to its advantages of time saving, less solvent and easily automation. A variety of functional materials are used as sorbents in SPME to carry out selective and high extraction. This review centers around the recent applications of organic molecule-based framework porous materials, such as metal organic frameworks (MOFs) and covalent organic frameworks (COFs), as SPME coating materials mainly focus on pharmaceutical analysis in food, environment, and biological samples. Four representative extraction devices are introduced, including on-fiber SPME, in-tube SPME, thin film SPME, stir bar SPME. The application prospect of other organic porous materials as sorbents for pharmaceutical analysis are also discussed, such as hyper crosslinked polymers (HCPs) and conjugated microporous polymers (CMPs). The progresses and discusses are provided to offer references for further research focusing on application and development of organic molecule-based framework porous materials in the field of SPME.

[Recent advance of new sample preparation materials in the analysis and detection of environmental pollutants]

To successfully analyze complex samples and detect trace targets, sample pretreatment is essential. Efficient sample pretreatment techniques can remove or reduce interference from the sample matrix. It can also enrich analytes, thereby improving analytical accuracy and sensitivity. In recent years, various sample preparation techniques, including SPE, magnetic dispersion SPE, pipette tip SPE, stir bar extraction, fiber SPME, and in-tube SPME, have received increasing attention in environmental analysis and monitoring. The extraction efficiency mainly depends on the type of adsorbent material. Therefore, the development of efficient adsorbents is a crucial step toward sample preparation. This review summarizes and discusses the research advances in extraction materials over recent years. These extraction materials contain inorganic adsorbents, organic adsorbents, and inorganic-organic hybrid materials such as graphene, graphene oxide, carbon nanotubes, inorganic aerogels, organic aerogels, triazinyl-functionalized materials, triazine-based polymers, molecularly imprinted polymers, covalent organic frameworks, metal-organic frameworks, and their derivatives. These materials have been applied to extract different types of pollutants, including metal ions, polycyclic aromatic hydrocarbons, plasticizers, alkanes, phenols, chlorophenols, chlorobenzenes, polybrominated diphenyl ethers, perfluorosulfonic acids, perfluorocarboxylic acids, estrogens, drug residues, and pesticide residues, from environmental samples (such as water and soil samples). These sample preparation materials possess high surface areas, numerous adsorption sites, and allow extraction via various mechanisms, such as π-π, electrostatic, hydrophobic, and hydrophilic interactions, as well as hydrogen and halogen bond formation. Various sample pretreatment techniques based on these extraction materials have been combined with various detection methods, including chromatography, mass spectrometry, atomic absorption spectroscopy, fluorescence spectroscopy, and ion mobility spectroscopy, and have been extensively used for the determination of environmental pollutants. The existing challenges associated with the development of sample preparation techniques are proposed, and prospects for such extraction materials in environmental analysis and monitoring are discussed. Major trends in the field, including the development of efficient extraction materials with high enrichment ability, good selectivity, excellent thermal stability, and chemical stability, are discussed. Green sample pretreatment materials, environmentally friendly synthesis methods, and green sample pretreatment methods are also explored. Rapid sample pretreatment methods that can be conducted within minutes or seconds are of significant interest. Further, online sample pretreatment and automatic analysis methods have attracted increasing attention. Besides, real-time analysis and in situ detection have been important development directions, and are expected to be widely applicable in environmental analysis, biological detection, and other fields. Modern synthesis technology should be introduced to synthesize specific extraction materials. Controllable preparation methods for extraction materials, such as the in situ growth or in situ preparation of extraction coatings, will acquire importance in coming years. It will also be important to adopt high-performance materials from other fields for sample pretreatment. Organic-inorganic hybrid extraction materials can combine the advantages both organic materials and inorganic materials, and mutually compensate for any disadvantages. Extraction materials doped with nanomaterials are also promising. Although existing sample pretreatment techniques are relatively efficient, it is still imperative to develop novel sample preparation methods.

Flower-like architecture magnesia-carbon composite material for highly sensitive solid-phase microextraction

The development of carbon sorbents with high specific surface areas remains a hot research field in analytical community. In the current study, a novel three-dimensional hierarchical flower-like magnesium glycollate sphere was synthesized. Then, the obtained magnesium glycollate sphere was carbonized to obtain magnesia-carbon composite material with enhanced performance. The flower-like carbon material exhibited good adsorption capacity towards polycyclic aromatic hydrocarbons due to the large surface area, the strong π-π interaction force and hydrophobic forces. The flower-like MgO&C material was used as a solid-phase microextraction fiber coating for the analysis of polycyclic aromatic hydrocarbons in real river water samples. Good linearity (5-1000 ng L^-1), satisfactory relatively recoveries (86.2-113.5%) and low limits of detections (0.01-0.20 ng L^-1) were obtained under the optimized conditions.

Supramolecular solvent-based microextraction method for cobalt traces in food samples with optimization Plackett–Burman and central composite experimental design

A new microextraction method based on formation of supramolecular solvent (Ss) was developed by using of chemometric optimization method for cobalt determination with microsampling flame atomic absorption spectrometry (MS-FAAS).

Development of a solid-phase microextraction fiber by the chemical binding of graphene oxide on a silver-coated stainless-steel wire with an ionic liquid as the crosslinking agent

Graphene oxide was bonded onto a silver-coated stainless-steel wire using an ionic liquid as the crosslinking agent by a layer-by-layer strategy. The novel solid-phase microextraction fiber was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy and Raman microscopy. A multilayer graphene oxide layer was closely coated onto the supporting substrate. The thickness of the coating was about 4 μm. Coupled with gas chromatography, the fiber was evaluated using five polycyclic aromatic hydrocarbons (fluorene, anthracene, fluoranthene, 1,2-benzophenanthrene, and benzo(a)pyrene) as model analytes in direct-immersion mode. The main conditions (extraction time, extraction temperature, ionic strength, and desorption time) were optimized by a factor-by-factor optimization. The as-established method exhibited a wide linearity range (0.5-200 μg/L) and low limits of determination (0.05-0.10 μg/L). It was applied to analyze environmental water samples of rain and river water. Three kinds of the model analytes were quantified and the recoveries of samples spiked at 10 μg/L were in the range of 92.3-120 and 93.8-115%, respectively. The obtained results indicated the fiber was efficient for solid-phase microextraction analysis.

Graphene coating bonded onto stainless steel wire as a solid-phase microextraction fiber

A graphene coating bonded onto stainless steel wire was fabricated and investigated as a solid-phase microextraction fiber. The coating was characterized by scanning electron microscopy and energy-dispersive X-ray spectrometer. The coating with rough and crinkled structure was about 1 μm. These characteristics were helpful for promoting extraction. Using five n-alkanes (n-undecane, n-dodecane, n-tridecane, n-tetradecane and n-hexadecane) as analytes, the fiber was evaluated in direct-immersion mode by coupling with gas chromatography (GC). Through optimizing extraction and desorption conditions, a sensitive SPME-GC analytical method was established. SPME-GC method provided wide linearity range (0.2-150 μg L(-1)) and low limits of determination (0.05-0.5 μg L(-1)). It was applied to analyze rain water and a soil sample, and analytes were quantified in the range of 0.85-1.96 μg L(-1) and 0.09-3.34 μg g(-1), respectively. The recoveries of samples spiked at 10 μg L(-1) were in the range of 90.1-120% and 80.6-94.2%, respectively. The fiber also exhibited high thermal and chemical stability, due to the covalent bonds between graphene coating and wire, and the natural resistance of graphene for thermal, acid and basic conditions.

Aqueous adsorption and removal of organic contaminants by carbon nanotubes

Organic contaminants have become one of the most serious environmental problems, and the removal of organic contaminants (e.g., dyes, pesticides, and pharmaceuticals/drugs) and common industrial organic wastes (e.g., phenols and aromatic amines) from aqueous solutions is of special concern because they are recalcitrant and persistent in the environment. In recent years, carbon nanotubes (CNTs) have been gradually applied to the removal of organic contaminants from wastewater through adsorption processes. This paper reviews recent progress (145 studies published from 2010 to 2013) in the application of CNTs and their composites for the removal of toxic organic pollutants from contaminated water. The paper discusses removal efficiencies and adsorption mechanisms as well as thermodynamics and reaction kinetics. CNTs are predicted to have considerable prospects for wider application to wastewater treatment in the future.