[Solid phase microextraction of benzenes in river water by pomelo peel biochar].

Pomelo peel, as a by-product of pomelo consumption, is rich in various fiber and functional compounds. The utilization of the valuable components found in pomelo peel may mitigate environmental concerns. In this study, pomelo peel rich in lignin and oxygen-containing functional groups was used to prepare pomelo peel biochar (PPB) via temperature-programmed pyrolysis at different temperatures (800 ℃ and 1000 ℃). Their structures were investigated by N2 adsorption-desorption isotherms and BJH pore size distribution. The results showed that PPB1000 (pomelo peel biochar prepared at 1000 ℃) had a higher specific surface area (749.9 m2/g), larger pore volume (0.42 cm3/g), more concentrated pore size distribution (2-3 nm), and better adsorption performance than commercial activated carbon. PPB1000 exhibited excellent capability to capture benzenes (BTEX, including benzene (B), toluene (T), ethylbenzene (E), and xylene (X)) through hydrogen bonds, π-π, and electrostatic interactions. Additionally, their honeycomb porous structure could provide additional adsorption sites and material transport paths. PPB1000 was coated on iron wire using the sol-gel method to prepare chemically and mechanically stable solid phase microextraction (SPME) fibers. By combining PPB1000-based SPME analysis with gas chromatography-flame ionization detection (GC-FID), an effective method was developed for the extraction and determination of BTEX. The optimized method had low LODs (0.004-0.032 µg/L), wide linear range (1-100 µg/L), and good linear relationship (determination coefficients, r2≥0.9919). The RSDs of the intra-batch (n=6) and inter-batch (n=5) precisions were 1.04%-6.56% and 1.03%-12.42%, respectively. The method validation results showed that PPB1000 had good stability. Compared with the commercial reagent polydimethylsiloxane (7 µm), PPB1000 had a higher extraction efficiency. When applied to the analysis of BTEX in natural water samples, trace levels of ethylbenzene (4.80 µg/L), o-xylene (3. 00 µg/L), and m-xylene and p-xylene (2.46 µg/L) were detected. Recovery tests were performed to validate the reliability of the method, and recoveries were between 75.7% and 117.6%. This effective pretreatment process combined with GC-FID could realize the rapid detection of BTEX and is promising for the analysis of BTEX in complex matrixes in the future.

Electro-enhanced solid-phase microextraction of bisphenol A from thermal papers using a three-dimensional graphene coated fiber.

Three-dimensional (3-D) graphene was synthesized by the assembly of graphene oxide with phenolic resin, followed by carbonization in argon. The as-synthesized 3-D graphene has excellent conductivity, good thermal stability, large specific surface area (1511 m² g-1) and pore volume (0.90 cm3 g-1). By immobilizing the 3-D graphene onto the stainless steel wire (SSW), we obtained a 3-D graphene coated fiber that was then used as a working electrode for electro-enhanced SPME, which shows a 3.2-fold improvement of extraction efficiency for bisphenol A (BPA) over that of traditional SPME. Coupled to gas chromatography, the method was developed to the determination of BPA with good linearity (R2 = 0.9935) in the range of 0.1-10 µg mL-1. The limit of detection was calculated to be 0.006 µg mL-1 based on the signal-to-noise of 3. The proposed method was applied for the analysis of three kinds of thermal papers with BPA being detected in all samples (0.696-3.78 mg g-1). Recovery tests were performed to validate the reliability of the method, and the recoveries were found between 81.9% and 119% with relative standard deviations lower than 4.8%.

Determination of amphetamines in biological samples using electro enhanced solid-phase microextraction-gas chromatography.

In this work, an ordered mesoporous carbon (OMC)/Nafion coated fiber for solid-phase microextraction (SPME) was prepared and used as the working electrode for electro-enhanced SPME (EE-SPME) of amphetamines. The EE-SPME strategy is primarily based on the electro-migration and complementary charge interaction between fiber coating and ionic compounds. Compared with traditional SPME, EE-SPME exhibited excellent extraction efficiency for amphetamine (AP) and methamphetamine (MA) with an enhancement factor of 7.8 and 12.1, respectively. The present strategy exhibited good linearity for the determination of AP and MA in urine samples in the range of 10-1000ngmL(-1) and 20-1000ngmL(-1), respectively. The detection limits were found to be 1.2ngmL(-1) for AP and 4.8ngmL(-1) for MA. The relative standard deviations were calculated to be 6.2% and 8.5% for AP and MA, respectively. Moreover, the practical application of the proposed method was demonstrated by analyzing the amphetamines in urine and serum samples with satisfactory results.

A simple, rapid and eco-friendly approach for the analysis of aromatic amines in environmental water using single-drop microextraction-gas chromatography.

Single-drop microextraction (SDME) coupled with gas chromatography-flame ionization detector (GC-FID) was developed for the extraction and determination of aromatic amines (AAs) in environmental water samples. A silicon tube was introduced for the SDME procedure by inserting it into the needle of the micro-injector. In this manner, a large volume of extractant is allowed to be suspended for the extraction, leading to the enhancement of method sensitivity and reproducibility. Extraction parameters which control the performance of SDME such as the type of microextraction solvent and volume, sample pH, ionic strength and extraction time were investigated and optimized. Under the optimized conditions, the SDME-GC method exhibited good linearity from 0.5 to 50 µg mL(-1) for aniline and 4-methylaniline and 0.1 to 50 µg mL(-1) for N-methylaniline and N, N-diethylaniline. The enrichment factors were calculated to be 42-509. The SDME-GC method was performed for the determination of AAs in environmental water samples including drinking, lake and sea water, and excellent recoveries and relative standard deviations (RSD values) ranging from 79.5 to 122.7% and 3.2 to 13.3%, respectively, were obtained. The results demonstrated that SDME-GC is a rapid, simple and effective sample preparation method and could be successfully applied for the determination of AAs in environmental water samples.

Ordered mesoporous carbon/Nafion as a versatile and selective solid-phase microextraction coating.

In this study, ordered mesoporous carbon (OMC) with large surface area (1019m(2)g(-1)), uniform mesoporous structure (pore size distribution centering at 4.2nm) and large pore volume (1.46cm(3)g(-1)) was synthesized using 2D hexagonally mesoporous silica MSU-H as the hard template and sucrose as the carbon precursor. The as-synthesized OMC was immobilized onto a stainless steel wire using Nafion as a binder to prepare an OMC/Nafion solid-phase microextraction (SPME) coating. The extraction characteristics of the OMC/Nafion coating were extensively investigated using a wide range of analytes including non-polar (light petroleum and benzene homologues) and polar compounds (amines and phenols). The OMC/Nafion coating exhibited much better extraction efficiency towards all selected analytes than that of a multi-walled carbon nanotubes/Nafion coating with similar length and thickness, which is ascribed to its high surface area, well-ordered mesoporous structure and large pore volume. When the OMC/Nafion coating was used to extract a mixture containing various kinds of analytes, it possessed excellent extraction selectivity towards aromatic non-polar compounds. In addition, the feasibility of the OMC/Nafion coating for application in electrochemically enhanced SPME was demonstrated using protonated amines as model analytes.