A Chemiluminescence Sensor for the Detection of α-Fetoprotein and Carcinoembryonic Antigen Based on Dual-Aptamer Functionalized Magnetic Silicon Composite.

In this work, a dual-aptamer functionalized magnetic silicon composite was prepared and used to construct a chemiluminescence (CL) sensor for the detection of α-fetoprotein (AFP) and carcinoembryonic antigen (CEA). First, SiO2@Fe3O4 was prepared, and polydiallyl dimethylammonium chloride (PDDA) and AuNPs were sequentially loaded on SiO2@Fe3O4. Subsequently, the complementary strand of CEA aptamer (cDNA2) and the aptamer of AFP (Apt1) were attached to AuNPs/PDDA-SiO2@Fe3O4. Then, the aptamer of CEA (Apt2) and G quadruplex peroxide-mimicking enzyme (G-DNAzyme) were sequentially connected to cDNA2, leading to the final composite. Then, the composite was used to construct a CL sensor. When AFP is present, it will combine with Apt1 on the composite to hinder the catalytic ability of AuNPs to luminol-H2O2, achieving AFP detection. When CEA is present, it will recognize and bind with Apt2, so G-DNAzyme is released to solution and catalyzes the reaction of luminol-H2O2 to achieve CEA determination. After the application of the prepared composite, AFP and CEA were detected in the magnetic medium and supernatant, respectively, after simple magnetic separation. Therefore, the detection of multiple liver cancer markers is realized through the CL technology without additional instruments or technology, which broadens the application range of CL technology. The sensor for detecting AFP and CEA shows wide linear ranges of 1.0 × 10-4 to 1.0 ng·mL-1 and 0.0001-0.5 ng·mL-1 and low detection limits of 6.7 × 10-5 ng·mL-1 and 3.2 × 10-5 ng·mL-1, respectively. Finally, the sensor was successfully used to detect CEA and AFP in serum samples and provides great potential for detection of multiple liver cancer markers in early clinical diagnosis.

Ultrasensitive Electrochemiluminescence Biosensor with Silver Nanoclusters as a Novel Signal Probe and α-Fe2O3-Pt as an Efficient Co-reaction Accelerator for Procalcitonin Immunoassay.

Herein, a high-efficiency biosensor based on ternary electrochemiluminescence (ECL) system was constructed for procalcitonin (PCT) detection. Specifically, silver nanoclusters (Ag NCs) with stable luminescence properties were prepared with small-molecule lipoic acid (LA) as the ligand, and its ECL emission in persulfate (S2O82-) was first reported. Meanwhile, the prepared Ag NCs possessed ligand-to-metal charge-transfer characteristics, thus transferring energy from LA to Ag+ for luminescence. Based on the small particle size, good biocompatibility, and molecular binding ability, Ag NCs-LA was used as an ideal luminescent probe. In addition, α-Fe2O3-Pt was introduced to facilitate the activation of S2O82-, thereby generating more sulfate radicals to react with the free radicals of Ag NCs to enhance ECL emission. The synergistic effect of the variable valence state of transition metals and high catalytic activity of noble metals endows α-Fe2O3-Pt with excellent catalytic ability for S2O82-. Importantly, the sensing mechanism was systematically demonstrated by UV-vis, fluorescence, and ECL analysis, as well as density functional theory calculations. At last, NKFRGKYKC was designed for specific immobilization of antibodies, thus releasing the antigen binding sites to improve the antigen recognition efficiency. Based on this, the developed biosensor showed high sensitivity for PCT detection, with a wide linear range (10 fg/mL-100 ng/mL) and a low detection limit (3.56 fg/mL), which could be extended to clinical detection of multiple biomarkers.

A Portable Microfluidic-Based Electrochemiluminescence Sensor for Trace Detection of Trenbolone in Natural Water.

In this study, a portable electrochemiluminescence sensor chip was designed for trenbolone (TBE) trace detection in environmental water. First, a stable ECL signal was obtained with low-toxicity 3,4,9,10-perylenetetracarboxylic acid (PTCA) as a luminophore and persulfate (S2O82-) as a coreactant. Second, hollow-structured Cu2MoS4 was introduced as a coreaction accelerator to catalyze S2O82- reduction. The reversible conversion of the mixed-valence transition metal ions in Cu2MoS4 (Cu+/Cu2+ and Mo4+/Mo6+) greatly promoted the generation of the sulfate radical (SO4•-). Meanwhile, the special porous structure of Cu2MoS4 possessed a large specific surface area, thus enhancing its catalytic performance. Based on these enhancement mechanisms, a strong ECL signal was acquired, which improved the detection sensitivity of the constructed sensor. Importantly, a microfluidic chip was introduced for sensing detection, thereby improving the practicality of the sensor. The developed sensor chip was miniature and portable, exhibiting high sensitivity for TBE detection with a wide linear range (10 fg/mL-100 ng/mL) and lower detection limit (3.32 fg/mL). This was of great significance for timely and rapid analysis of steroid pollutants in natural water.

Efficient ABEI-Dissolved O2-Ce(III, IV)-MOF Ternary Electrochemiluminescent System Combined with Self-Assembled Microfluidic Chips for Bioanalysis.

A signal-amplified electrochemiluminescent (ECL) sensor chip was developed for sensitive analysis of procalcitonin (PCT). Herein, we first prepared a self-enhanced luminophore, which enhanced ECL responses through intramolecular reactions. Second, Au-Pd bimetallic nanocrystals and mixed-valence Ce-based metal-organic frameworks (MOFs) were introduced as co-reaction promoters to facilitate the reduction of dissolved O2. Based on the synergistic catalysis of Au and Pd, the spontaneous cyclic reaction of Ce(III)/Ce(IV), and the high electrochemical active surface area of Ce(III, IV) MOF, a large number of superoxide anion radicals (O2•-) and hydroxyl radicals (OH•) were produced. Therefore, the luminescence efficiency of N-(aminobutyl)-N-(ethylisoluminol)-dissolved O2 (ABEI-O2) systems were greatly improved, providing a new prospect for the application of dissolved O2 in ECL analysis. In addition, the affinity peptide ligands were used for the directional connection of antibodies to provide protection for the bioactivity of the proposed sensor. Finally, the microfluidic technology was applied to ECL analysis to integrate the three-electrode detection system into the self-assembled microfluidic chip, which realized the automation and portability of the detection process. The developed sensor showed high sensitivity for PCT detection with a detection limit of 3.46 fg/mL, which possessed positive significance for the clinical diagnosis of sepsis.

Zinc-Based Metal-Organic Framework with MLCT Properties as an Efficient Electrochemiluminescence Probe for Trace Detection of Trenbolone.

In this work, we utilized polycyclic aromatic hydrocarbon (PAH) derivatives as ligands to develop a zinc-based metal-organic framework (Zn-MOF) as an effective detection probe to construct an electrochemiluminescence (ECL) sensor for trenbolone detection. As traditional ECL emitters, PAHs and their derivatives have limited luminescence efficiency because of the aggregation-induced quenching (ACQ) effect. Therefore, Zn-PTC was designed by the coordination of 3,4,9,10-perylenetetracarboxylic (PTC) in the MOF to eliminate the ACQ effect. Meanwhile, Zn-PTC formed based on an aromatic ligand possessed the metal-to-ligand charge-transfer (MLCT) effect, which could transfer the energy of Zn2+ to the aromatic ligand for strong luminescence. The ECL efficiency of Zn-PTC was calculated to be approximately 2.2 times that of the ligand (K4PTC). Second, the Ag@Fe core-shell bimetallic nanocrystal was prepared for efficient activation of persulfate (S2O82-), thereby generating more sulfate radicals (SO4•-) to further promote ECL emission. According to ECL characterizations, UV-vis and fluorescence spectra, and density functional theory calculations, the luminescence and signal amplification mechanisms were investigated. In addition, NKFRGKYKC (NKF) was introduced as an affinity ligand to directionally immobilize the target antibodies, thus releasing specific sites in their Fab fragment to enhance binding activity. Based on the above strategies, the constructed biosensor exhibited high sensitivity, realizing trace detection of TBE with a wide detection range (10 fg/mL-100 ng/mL) and a low detection limit (3.28 fg/mL). This study provided an important reference for sensitive monitoring of steroid pollutants in the environment.

A chemiluminescence aptasensor for sensitive detection of alpha-fetoprotein based on hemin@ZIF-67.

In this work, hemin@ZIF-67 composites were prepared and were used to construct a chemiluminescence (CL) aptasensor for alpha-fetoprotein (AFP) detection. Hemin is a catalytic porphyrin with two carboxylate groups that can covalently bond to metal ions. A hemin/ZIF-67 composite was prepared via covalent bonding between the carboxyl groups of hemin and the cobalt ion of ZIF-67, and these materials were characterized by scanning electron microscopy (SEM), infrared spectroscopy (IR), and X-ray diffraction (XRD). Hemin@ZIF-67 was used as the peroxidase material, and the aptamer of alpha-fetoprotein was modified on its surface by electrostatic adsorption. Then a simple CL aptasensor was constructed based on the CL system of luminol-H2O2-NaOH. Under the optimal conditions, the CL intensity value was linearly proportional to the concentration of AFP in the range of 4 × 10-10 to 200 × 10-10 mg/mL. The detection limit was 1.3 × 10-10 mg/mL. Thus the aptasensor enables highly sensitive and selective detection of AFP.

Peptide-Based Biosensor with a Luminescent Copper-Based Metal-Organic Framework as an Electrochemiluminescence Emitter for Trypsin Assay.

A copper-based metal-organic framework (JUC-1000) has emerged as a promising electrochemiluminescence (ECL) emitter in the domains of bioanalysis and immunoassay. Herein, a highly efficient signal "on-off" peptide-based biosensor was constructed for trypsin (TPN) assay. JUC-1000 synthesized using an organic ligand of H4BDPO was functionalized as the ECL emitter, whose cathodic ECL behavior in aqueous media was first investigated using potassium persulfate (K2S2O8) as the coreactant. To further amplify the ECL signal, highly catalytic Ag@CeO2 nanoparticles were fabricated as both a substrate and an coreaction accelerator, which can efficiently catalyze the reduction of S2O82- to generate more sulfate anion radicals (SO4•-) for ECL enhancement, thereby generating strong and stable ECL signals in a "signal on" state. The functionalized JUC-1000 emitter was connected to the Ag@CeO2 sensing layer though a heptapeptide (HWRGWVC, HGC), and TPN as the target can specifically cleave the carboxyl side of arginine residues in HGC, leading to the release of emitters in a "signal off" state. Based on the efficient signal-switching, the biosensor exhibited linear ECL responses to the added TPN concentration, realizing sensitive detection of TPN in 10 fg/mL to 100 ng/mL with a limit of detection of 3.46 fg/mL. This work proposed an attractive orientation for the fundamental research of applying transition metal-organic frameworks as ECL emitters in bioanalysis and immunoassay.

Peptide-Based Electrochemiluminescence Biosensors Using Silver Nanoclusters as Signal Probes and Pd-Cu2O Hybrid Nanoconcaves as Coreactant Promoters for Immunoassays.

Metal nanoclusters (NCs) possess high light stability and biocompatibility because of their unique quantum size effect, which has gradually become a new type of electrochemiluminescence (ECL) nanomaterial for immunoassays. However, the luminescence efficiency of metal NCs is too low to meet the needs of trace analysis, which limits its application. Herein, Ag NCs served as signal probes and Pd-Cu2O hybrid nanoconcaves served as coreaction promoters, developing a highly efficient peptide-based biosensor for neuron-specific enolase (NSE) detection. Utilizing the reversible cycle of Cu+/Cu2+ and the reduction characteristics of Pd NPs, Pd-Cu2O greatly accelerates the reduction of S2O82-. Meanwhile, Pd-Cu2O has good hydrogen evolution activity, which promotes the generation of oxygen by improving the redox efficiency of the overall reaction, thus increasing the yield of active intermediates (OH•) to promote the reduction of S2O82-. Specially, this is an effective attempt to use the hydrogen evolution reaction (HER) to accelerate the ECL emission of the S2O82- system. In addition, a short peptide ligand (NARKFYKGC, NFC) was developed to implement the targeted immobilization of antibodies, which can specifically bind to the Fc fragment of antibodies, thereby avoiding the occupation of the antigen binding site (Fab fragment). The introduction of NFC not only improves the binding efficiency of antibodies but also protects its bioactivity, thus significantly improving the sensitivity of the biosensor. Based on these strategies, the proposed biosensor provides a new perspective for the applications of metal NCs in ECL systems.

Rational design of the Z-scheme hollow-structure Co9S8/g-C3N4 as an efficient visible-light photocatalyst for tetracycline degradation.

The development of photocatalysts with high catalytic activity that are capable of full utilization of solar energy is a challenge in the field of photocatalysis. Accordingly, in the present study, an efficient Z-scheme cage-structured Co9S8/g-C3N4 (c-CSCN) photocatalyst was constructed for the degradation of tetracycline antibiotics under visible-light irradiation. The Z-scheme charge-transfer mechanism accelerates the separation of photogenerated charge carriers and effectively improves photocatalytic activity. Moreover, c-CSCN has a hollow structure, allowing light to be reflected multiple times inside the cavity, thereby effectively improving the utilisation efficiency of solar energy. As a result, the photocatalytic activity of c-CSCN is 1.5-, 2.5-, and 5.8-times higher than those of sheet-type Co9S8/g-C3N4 (s-CSCN), c-Co9S8, and g-C3N4, respectively, for the degradation of tetracycline. c-CSCN maintains favourable photocatalytic activity over five consecutive degradation cycles, demonstrating its excellent stability. In addition, c-CSCN performs efficient tetracycline removal in different water substrates. Moreover, c-CSCN exhibits excellent ability to remove tetracycline under direct natural sunlight. This work fully demonstrates that c-CSCN has high catalytic activity and the potential for practical application as a wastewater treatment material.

A chemiluminescence assay for determination of lysozyme based on the use of magnetic alginate-aptamer composition and hemin@HKUST-1.

Lysozyme aptamer-functionalized magnetic alginate hydrogel was prepared for separation and enrichment of lysozyme. Luminol-labeled aptamer was used as a signal tag, and the signal tag was adsorbed on magnetic carboxylated carbon nanotubes based on the π-interaction. When lysozyme was added, the aptamer specifically binds to the lysozyme, causing the signal tag to detach from the magnetic carboxylated carbon nanotubes. When the aptamer/lysozyme complex bound to the complementary single strand of aptamer on the hemin@HKUST-1, lysozyme was released. The released lysozyme can be recombined with the signal tag adsorbed on the magnetic carboxylated carbon nanotube, allowing more signal tag to be dispersed into the solution. Determination of lysozyme was achieved by releasing the luminol-labeled aptamer to generate a chemiluminescence signal at a wavelength of 425 nm. It was proved by experiments that the synthesized hemin@HKUST-1 had a strong catalytic effect on the luminol-NaOH-H2O2 system. The chemiluminescence signal was increased nearly 100 times. The complementary pairing allowed the luminol to be immobilized on the surface of hemin@HKUST-1. The generation and consumption of short-lived reactive oxygen species were concentrated on the surface of the MOFs, which improves the chemiluminescence efficiency. The introduction of hemin@HKUST-1 and DNA solved the defects of chemiluminescence analysis. The chemiluminescence assay was able to detect lysozyme with linear range of 1.05 × 10-6 U∙mg-1 (6.00 × 10-13 mol∙L-1)-1.25 × 10-2 U∙mg-1 (7.14 × 10-9 mol∙L-1); the detection limit was 3.50 × 10-7 U∙mg-1 (2.00 × 10-13 mol∙L-1) (R2 = 0.99). The recovery of lysozyme in spiked saliva samples was 97.4-102.8%. Graphical abstract Schematic presentation of chemiluminescence assay. Lysozyme (Lys) was captured by aptamer-modified magnetic sodium alginate (M-Alg-Apt); Glycine (pH = 2) as eluent for Lys. Luminol-modified Apt (Apt-luminol) as signal tag; magnetic carbon nanotubes (MCNTs) as adsorption matrix; cDNA was complementary to Apt; hemin@HKUST-1 as catalyst.

Electrochemical assays for determination of H2O2 and prostate-specific antigen based on a nanocomposite consisting of CeO2 nanoparticle-decorated MnO2 nanospheres.

A nanocomposite consisting of CeO2 nanoparticle-decorated MnO2 nanospheres (CeO2@MnO2) was synthesized for the first time via a hydrothermal method. CeO2@MnO2 was exploited to construct an electrochemical assays for detecting H2O2 and prostate-specific antigen (PSA) with square wave voltammetry (SWV). The electrochemical results proved that CeO2@MnO2 owned a better electrocatalytic effect towards H2O2 reduction than pure MnO2 NS and CeO2 NP due to the synergistic effect between MnO2 NS and CeO2 NP. Under optimized conditions, CeO2@MnO2-based assay can be applied to detect H2O2 in the range 1 to 3.0 × 103 µmol L-1. The label-free electrochemical immunoassay based on CeO2@MnO2 displayed linearly with concentrations of PSA from 0.005 to 50.0 ng mL-1. The electrochemical assays also possessed acceptable sensitivity, selectivity, and stability. The study showed that CeO2@MnO2 hold great potential as a biosensing platform and the clinical determination of tumor markers in human serum. Graphical abstract A nanocomposite consisting of CeO2 nanoparticles decorated MnO2 nanospheres (CeO2 @MnO2) was firstly synthesized via a hydrothermal method. CeO2@MnO2 was firstly exploited to construct electrochemical assays for detecting H2O2 and prostate-specific antigen (PSA) with square wave voltammetry (SWV), respectively. The electrochemical results proved that CeO2@MnO2 owned better electrocatalysis towards H2O2 reduction than pure MnO2 NS and CeO2 NP due to the synergistic effect between MnO2 NS and CeO2 NP. Under optimized conditions, CeO2@MnO2 based assay relative to the H2O2 system can be applied to detect H2O2 with range from 1 to 3.0 × 103 µmol L-1. The label-free electrochemical immunoassay based on CeO2@MnO2 relative to the H2O2 system displayed linearly with concentrations of PSA from 0.005 to 50.0 ng mL-1. The electrochemical assays also possessed acceptable sensitivity, selectivity and stability. The study showed that CeO2@MnO2 hold great potential for biosensing platform and the clinic determination of tumor markers in human serum.

A nanocomposite prepared from bifunctionalized ionic liquid, chitosan, graphene oxide and magnetic nanoparticles for aptamer-based assay of tetracycline by chemiluminescence.

A nanocomposite was prepared from a bifunctionalized ionic liquid, chitosan on magnetic nanoparticle-modified graphene oxide (IL/Chit@MGO). It was used in a chemiluminescencc (CL) assay for tetracycline. The materials were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray powder diffraction, nitrogen adsorption-desorption isotherm, vibrating sample magnetometry and zeta potentials. Subsequently, a tetracycline-binding aptamer (TC-Apt) acting as a recognition element, and G-quadruplex DNAzyme (G-DNAzyme) acting as a signal amplification component were modified on IL/Chit@MGO. So, the bifunctional G-DNAzyme/TC-Apt/IL/Chit@MGO was prepared. The IL/Chit@MGO is found to possess excellent loading capability for TC-Apt. This is attributed to the large specific surface and abundant charge on the surface of IL/Chit@MGO. The composite was used to construct a CL assay for tetracycline. Tetracycline binds to TC-Apt and causes the release of the G-DNAzyme. The latter catalyzes the CL of luminol-H2O2 CL system at pH 7.4. Under optimized conditions, the blue CL at the emission wavelength of 425 nm increases linearly in the 0.16 pM to 2.0 nM concentration range, and the detection limit is 21 fM (at 3σ). The assay is selective, reproducible and stable. The assay was applied to tetracycline detection in practical samples. The apparent recoveries are 98.0% to 101.3% for the milk sample and 97.0% to 102.2% for the water sample. Graphical abstractG-quadruplex DNAzyme (G-DNAzyme) and tetracycline aptamer (TC-Apt) bifunctionalized ionic liquid/chitosan@magnetic graphene oxide (IL/Chit@MGO) was prepared. The nanocomposite was used to construct a chemiluminescence (CL) assay for tetracycline.

An ionic-liquid-modified melamine-formaldehyde aerogel for in-tube solid-phase microextraction of estrogens followed by high performance liquid chromatography with diode array detection.

A combination between an ionic liquid and melamine-formaldehyde aerogel on the carbon fibers was developed for in-tube solid-phase microextraction of estrogens with high efficiency. The sorbent has a high enrichment capability for several estrogens. Scanning electron microscopy showed that the aerogel on the carbon fibers has a porous three-dimensional network structure. Several important parameters such as sampling volume, sampling rate, the concentration of organic solvent in sample, pH value of sample as well as desorption time were optimized towards estrogen targets. Comparing with melamine-formaldehyde aerogel coating, the coating gave higher extraction efficiency. Comparing with melamine-formaldehyde aerogel coating, the new coating displays higher extraction efficiency. An online analytical method of estrogens was established, by the combination between in-tube solid-phase microextraction and high performance liquid chromatography with diode array detector. Analytical figures of merit include low limits of detection (<0.20 µg L-1), wide linearity (0.15-20 µg L-1), high enrichment factors (1028-1256), good extraction repeatability (RSDs<2.5%) and satisfactory preparation repeatability (RSDs<10.5%). The method was applied to the determination of trace estrogen targets in plastic bottle, tap water and surface water. Graphical abstractSchematic representation of online combination between in-tube solid-phase microextraction and high performance liquid chromatography, based on an ionic liquid (IL)-modified melamine-formaldehyde (MF) aerogel coating on carbon fibers (CFs) in a polyether-etherketone (PEEK) tube.

Silicon carbide nanomaterial as a coating for solid-phase microextraction.

Silicon carbide has excellent properties, such as corrosion resistance, high strength, oxidation resistance, high temperature, and so on. Based on these properties, silicon carbide was coated on stainless-steel wire and used as a solid-phase microextraction coating, and polycyclic aromatic hydrocarbons were employed as model analytes. Using gas chromatography, some important factors that affect the extraction efficiency were optimized one by one, and an analytical method was established. The analytical method showed wide linear ranges (0.1-30, 0.03-30, and 0.01-30 µg/L) with satisfactory correlation coefficients (0.9922-0.9966) and low detection limits (0.003-0.03 µg/L). To investigate the practical application of the method, rainwater and cigarette ash aqueous solution were collected as real samples for extraction and detection. The results indicate that silicon carbide has excellent application in the field of solid-phase microextraction.

Basalt fibers functionalized with gold nanoparticles for in-tube solid-phase microextraction.

Basalt fibers were functionalized with gold nanoparticles and characterized by scanning electron microscopy and energy-dispersive X-ray spectroscopy. An in-tube solid-phase microextraction device was developed by packing the functionalized basalt fibers in a polyether ether ketone tube. The device was connected into high performance liquid chromatography equipment with a diode array detector to build online enrichment and analysis system. Eight polycyclic aromatic hydrocarbons were used as model analytes, important factors including sampling rate, sampling volume, organic solvent content in sample, and desorption time were investigated. Linear range (0.01-20 µg/L), detection limits (0.003-0.015 µg/L), and enrichment factors (130-1628) were given by the online analysis method. Relative standard deviations (n = 5) of extraction repeatability on one tube and tube-to-tube repeatability were less than 5.2 and 14.7%, respectively. The analysis method was applied to detect polycyclic aromatic hydrocarbons in environmental water samples, and relative recoveries ranged from 87 to 128%.

Basalt fibers grafted with a poly(ionic liquids) coating for in-tube solid-phase microextraction.

To improve the durability and extraction efficiency of an ionic liquid coating, 1-dodecyl-3-vinylimidazolium bromide was polymerized and grafted onto basalt fibers for in-tube solid-phase microextraction. To develop an extraction tube, basalt fibers grafted with the poly(ionic liquids) coating were filled into a polyether ether ketone tube with a 0.75 mm inner diameter. The extraction tube was connected to high-performance liquid chromatography system equipped with a sampling pump to build an online enrichment and analysis system. Using four common phthalates as model analytes, the extraction tube was investigated by the online analysis system. Good enrichment performance was exhibited by high enrichment factors ranging from 851 to 1858. Under the optimum conditions, an online analysis method was established, and good linearity (0.03-12 and 0.15-12 µg/L) and low limits of detection (0.01-0.05 µg/L) were achieved. This analysis method was applied to real samples including water in a disposable plastic box and the bottled water, some targets were detected but not quantified, and the relative recoveries spiked at 2, 5 and 10 µg/L were in the range of 86.4-119.5%.

Diamond nanoparticles coating for in-tube solid-phase microextraction to detect polycyclic aromatic hydrocarbons.

Diamond nanoparticles were coated onto stainless steel wires as a extraction material, then it was filled into a poly(ether ether ketone) tube for in-tube solid-phase microextraction. Coupled with high-performance liquid chromatography, the extraction tube was evaluated with different types of analytes including polycyclic aromatic hydrocarbons, estrogens and plasticizers. As the coating, diamond nanoparticles exhibited greater extraction capacity for hydrophobic analytes. Several polycyclic aromatic hydrocarbons were used as model analytes, four main extraction and desorption factors were optimized, including sampling volume, sampling rate, methanol content in sample and desorption time. A sensitive analysis method was established with wide linear range (0.016-20 µg/L), good correlation coefficients (0.9991-0.9997), low limits of detection (0.005-0.020 µg/L), low limits of quantitation (0.016-0.070 µg/L) and high enrichment factors (305-2396). Relative standard deviations for intra- and interday were less than 2.4% (n = 3) and 8.4% (n = 3), respectively. Durability and chemical stability were satisfactory with relative standard deviations less than 7.9% (n = 3). Finally, the method has been successfully applied to the detection of polycyclic aromatic hydrocarbons in real samples.

Ionic liquid chemically bonded basalt fibers for in-tube solid-phase microextraction.

Ionic liquids have been widely used in different fields by advantage of their specific properties. In this work, 1-methyl-3-(3-trimethoxysilyl propyl)imidazolium chloride was prepared and chemically bonded onto basalt fibers for in-tube solid-phase microextraction. Through combining in-tube extraction device with high-performance liquid chromatography equipped with a diode array detector, an online enrichment and analysis method for eight polycyclic aromatic hydrocarbons was established under the optimum conditions. A good enrichment factor (52-814), good linearity (0.10-15 and 0.20-15 µg/L), low limits of detection (0.03-0.05 µg/L), and low limits of quantitation (0.10-0.20 µg/L) were achieved using a sample volume of 50 mL. Analysis method was applied to the real samples including the groundwater and wastewater from a chemical industry park, some target analytes were detected and the relative recoveries were in the range of 80.4-116.8%.

In-situ hydrothermal synthesis of titanium dioxide nanorods on titanium wire for solid-phase microextraction of polycyclic aromatic hydrocarbons.

Titanium dioxide nanorods were prepared on the surface of titanium wire by hydrothermal synthesis for use as a solid-phase microextraction (SPME) fiber. The morphology of the SPME coating was observed by scanning electron microscopy (SEM). Employed in conjunction with gas chromatography (GC), the fiber was investigated with five polycyclic aromatic hydrocarbons (PAHs) and three terphenyls in direct-immersion extraction mode. Various parameters were optimized, such as the extraction time, the stirring rate, the extraction temperature, the ionic strength of the sample solution, and the desorption time. Under the optimized conditions, the SPME-GC analytical method achieved a low detection limit (0.003 µg L-1) and wide linear ranges (0.01-100 µg L-1 and 0.01-200 µg L-1) along with good correlation coefficients (0.9892-0.9962). The established method was also used to analyze rainwater and an aqueous solution of coal ash. The results indicated that this fiber could be applied in real-world environmental monitoring. The proposed fiber also exhibited excellent durability. Graphical Abstract The schematic diagram of experimental process.

Poly(ionic liquids)-coated stainless-steel wires packed into a polyether ether ketone tube for in-tube solid-phase microextraction.

An in-tube solid-phase microextraction device was developed by packing poly(ionic liquids)-coated stainless-steel wires into a polyether ether ketone tube. An anion-exchange process was performed to enhance the extraction performance. Surface properties of poly(ionic liquids)-coated stainless-steel wires were characterized by scanning electron microscopy and energy dispersive X-ray spectrometry. The extraction device was connected to high-performance liquid chromatography equipment to build an online enrichment and analysis system. Ten polycyclic aromatic hydrocarbons were used as model analytes, and important conditions including extraction time and desorption time were optimized. The enrichment factors from 268 to 2497, linear range of 0.03-20 µg/L, detection limits of 0.010-0.020 µg/L, extraction and preparation repeatability with relative standard deviation less than 1.8 and 19%, respectively were given by the established online analysis method. It has been used to detect polycyclic aromatic hydrocarbons in environmental samples, with the relative recovery (5, 10 µg/L) in the range of 85.1-118.9%.