Determination of thiophenols with a novel fluorescence labelling reagent: analysis of industrial wastewater samples with SPE extraction coupled with HPLC

β-cyclodextrin-modulated ratiometric supramolecular BODIPY fluoroprobe for highly selective and sensitive detection of thiophenol

Thiophenol (PhSH) is an important industrial intermediate but displays significant toxicity towards environmental and biological systems. Here, we introduce a supramolecular system based on β-cyclodextrin (β-CD) and boron dipyrromethene (BODIPY) as a ratiometric fluorescence probe to discriminate PhSH in environmental water samples, cells, and in vivo. In aqueous solutions, BODIPY shows extremely weak fluorescence intensity due to its aggregation into nanometer-sized clusters, which prevents its interaction with thiols. However, within a β-CD environment, it can selectively and sensitively detect PhSH. Also, the stability of the probe was significantly improved. The mechanism studies based on stoichiometry, NMR spectroscopy, and theoretical calculation revealed distinct intermolecular interactions between β-CD and BODIPY, including host-guest interactions and hydrogen bonds. Low limit of detection (10.7 nM) and rapid response time (5 min) have been achieved, and the practicality of the supramolecular system (BODIPY@β-CD) has been verified by actual sample analysis. Furthermore, the first hydrogel-based sensing system for portable PhSH detection has been developed, facilitating rapid and on-site colorimetric visualization across both liquid and gas phases. Most importantly, using a low amount of the probe, early stages of low-dose exposure to PhSH can be visualized in living cells and zebrafish. Therefore, BODIPY@β-CD is a robust new monitoring tool for the detection of PhSH in various scenarios, indicating the promising application value of the host-guest supramolecular probe in detecting highly toxic substances.

Trimetallic FeCoNi Metal-Organic Framework with Enhanced Peroxidase-like Activity for the Construction of a Colorimetric Sensor for Rapid Detection of Thiophenol in Water Samples

In recent years, nanozymes have attracted particular interest and attention as catalysts because of their high catalytic efficiency and stability compared with natural enzymes, whereas how to use simple methods to further improve the catalytic activity of nanozymes is still challenging. In this work, we report a trimetallic metal-organic framework (MOF) based on Fe, Co and Ni, which was prepared by replacing partial original Fe nodes of the Fe-MOF with Co and Ni nodes. The obtained FeCoNi-MOF shows both oxidase-like activity and peroxidase-like activity. FeCoNi-MOF can not only oxidize the chromogenic substrate 3,3,5,5-tetramethylbenzidine (TMB) to its blue oxidation product oxTMB directly, but also catalyze the activation of H2O2 to oxidize the TMB. Compared with corresponding monometallic/bimetallic MOFs, the FeCoNi-MOF with equimolar metals hereby prepared exhibited higher peroxidase-like activity, faster colorimetric reaction speed (1.26-2.57 folds), shorter reaction time (20 min) and stronger affinity with TMB (2.50-5.89 folds) and H2O2 (1.73-3.94 folds), owing to the splendid synergistic electron transfer effect between Fe, Co and Ni. Considering its outstanding advantages, a promising FeCoNi-MOF-based sensing platform has been designated for the colorimetric detection of the biomarker H2O2 and environmental pollutant TP, and lower limits of detection (LODs) (1.75 μM for H2O2 and 0.045 μM for TP) and wider linear ranges (6-800 μM for H2O2 and 0.5-80 μM for TP) were obtained. In addition, the newly constructed colorimetric platform for TP has been applied successfully for the determination of TP in real water samples with average recoveries ranging from 94.6% to 112.1%. Finally, the colorimetric sensing platform based on FeCoNi-MOF is converted to a cost-effective paper strip sensor, which renders the detection of TP more rapid and convenient.

Rational construction of reliable fluorescent probes for rapid detection and imaging evaluation of hazardous thiophenol in real-food and biosystems

Thiophenol (PhSH), a highly reactive aromatic thiol, plays an essential role as a common industrial raw material in food, pesticides, pharmaceuticals, and cosmetics. In this work, we designed and constructed two fluorescent probes CM-PhSH and CM-Ratio-PhSH by a rational strategy. Specifically, coumarin fluorophores with excellent optical properties were modified, and olefinic unsaturated bonds served as reaction sites for the detection of PhSH. Based on this, the introduction of the nitro group at specific positions of the CM-PhSH changed the fluorescence emission of the CM-Ratio-PhSH, eventually obtaining a novel ratiometric fluorescent probe CM-Ratio-PhSH for PhSH detection. Surprisingly, these two probes exhibited advantages such as high specificity and low limit of detection (LOD) for CM-PhSH 32.3 nM and CM-Ratio-PhSH 40.2 nM, respectively. Furthermore, subsequent experiments demonstrated CM-PhSH and CM-Ratio-PhSH could be successfully used for highly selective and rapid detection of PhSH in aqueous solutions, live cells, and complex food samples.

Reduction of Odor-causing Compounds in Wastewater using Biochar: A Review

Wastewater contains chemical compounds that cause malodors, such as ammonium cation, dimethyl sulfide, and volatile organic compounds. Biochar-based reduction in the odorants has been proposed as an effective approach along with maintaining environmental neutrality as biochar is a sustainable material made from biomass and biowaste. Biochar can have high specific surface area and microporous structure with proper activation, appropriate for sorption purposes. Recently, various research directions have been proposed to determine the removal efficiency of biochar for different odorants contained in wastewater. This article is aimed at providing the most updated review of biochar-based removal of odor-causing compounds in wastewater while highlighting the current advances. It was distinguished that the odorant removal performance of biochar is highly associated with the raw material and modification method of biochar, and the kind of odorants. Further research should be required for more practical use of biochar for the reduction of odorants in wastewater.

Cascade reaction-based highly sensitive fluorescent sensing systems applicable for dual-pattern fluorescence visualizing of thiophenol flavors in meat products and condiments

Thiophenols (ArSHs) are widely used as popular flavoring ingredients for making daily dishes. Dissecting the ArSHs contents in common foodstuffs is meaningful in the field of food safety science. Herein, a novel small-molecule sensor 2-(1H-benzo[d]imidazol-2-yl)-3-(2-(2,4-dinitrophenoxy)-4-morpholinophenyl)acrylonitrile (NOSA) has been tailored. The NOSA is able to respond to ArSHs, spontaneously yielding highly green-emissive fluorescent iminocoumarin (I₅₀₀). This cascade reaction-based strategy is sensitive (limit-of-detection = 2.8 nM), rapid (within 5 min), and selective toward ArSH flavors. Probe NOSA has been applied to the determination of ArSHs in real-life meat products and condiments. Moreover, a far-red fluorescent compound, 2-(7-(diethylamino)-4-(4-(methylthio)styryl)-2H-chromen-2-ylidene)malononitrile (CMMT), has been first combined with NOSA to construct a composite probe NOSA@CMMT for the ratiometric detection of ArSHs (I₅₀₀/I₆₃₀). System NOSA@CMMT exhibits a conspicuous fluorescence change from deep-red to light-green. Benefitted from the gorgeous chromatic fluctuation, a smartphone-integrated analysis platform is established for the real-time evaluation of ArSHs level.

Surface Filtration in Mesoporous Au Films Decorated by Ag Nanoparticles for Solving SERS Sensing Small Molecules in Living Cells

For surface-enhanced Raman spectroscopy (SERS) sensing of small molecules in the presence of living cells, biofouling and blocking of plasmonic centers are key challenges. Here, we have developed a mesoporous Au (AuM) film coated with a Ag nanoparticles (NPs) as a plasmonic sensor (AuM@Ag) to analyze aromatic thiols, which is an example of a small molecule, in the presence of a living cell strain (e.g., MDA-MB-231) as a model living system. The resulting AuM@Ag provides 0.1 nM sensitivity and high reproducibility for thiols sensing. Simultaneously, the AuM@Ag film filters large biomolecules, preventing Raman signals from overlapping produced by large biomolecules. After analysis, the AuM@Ag film undergoes recycling by the full dissolution of the Ag-thiol layer and removal of thiols from AuM. Furthermore, fresh AgNPs are formed for further SERS analysis, which circumvents the Ag oxidation issue. The ease of the AgNPs deposition allows up to 12 cycles of on-demand recycling and sensing even after utilization as a sensor in multicomponent media without enhancement and sensitivity loss. The reported mesoporous film with surface filtering ability and prominent recycling procedure promises to offer a new strategy for the detection of various small molecules in the presence of living cells.

A novel dibenzo[a,c]phenazine-based fluorescent probe for fast and selective detection of thiophenols in environmental water

A new dibenzo[a,c]phenazine-based fluorescent probe exhibits high selectivity and sensitivity towards thiophenols in environmental water.

A novel fluorescent labeling reagent, 2-(9-acridone)-ethyl chloroformate, and its application to the analysis of free amino acids in honey samples by HPLC with fluorescence detection and identification with online ESI-MS

In this study, a novel fluorescent labeling reagent 2-(9-acridone)-ethyl chloroformate (AEC-Cl) was designed, synthesized and applied for the determination of free amino acids by high-performance liquid chromatography with a fluorescence detector (HPLC-FLD). The free amino acids were rapidly and efficiently labeled by AEC-Cl in the presence of basic catalyst (pH 9.0) within 5 min at room temperature (25 °C). The derivatives exhibited excellent stability and fluorescence properties, with maximum excitation and emission wavelengths at 268 nm and 438 nm, respectively. Derivatives of 22 kinds of natural amino acids were completely separated by gradient elution on a Hypersil ODS C18 column. Under the optimal conditions, the calibration curves exhibited excellent linear responses, with correlation coefficients of R² > 0.9994. The detection and quantification limits were in the range of 0.61-2.67 μg kg^-1 and 2.07-8.35 μg kg^-1, respectively. Therefore, AEC-Cl was successfully applied for the detection of trace levels of free amino acids in honey samples. Graphical abstract A novel fluorescent labeling reagent was applied for the determination of free amino acids in honey by high-performance liquid chromatography with a fluorescence detector.

Dual-Function Fluorescent Probe for Detection of Hydrogen Sulfide and Water Content in Dimethyl Sulfoxide

To detect hydrogen sulfide (H2S) and water content in dimethyl sulfoxide, the fluorescent probe (Probe 1) was used, as it not only detects H2S but also detects the water content. After H2S was added into Probe 1, the intensity of fluorescence increased and was up to 1300 times. In case the H2S concentration was in the range 0-20 μM, it was able to be detected by Probe 1, and the limit of detection was 0.851 nM. When Probe 1 and H2S underwent a reaction, the solution color had some changes. These colors changed in terms of the concentration changes of H2S, ranging from colorless to yellow. The Probe 1 test paper only needed to be exposed to hydrogen sulfide gas for 20 s for the color change to occur. Besides, Probe 1-H2S was used to detect water content in dimethyl sulfoxide which ranged from 0 to 100%. The color change of the solution was opposite to that of H2S, ranging from yellow to colorless.

Development of a nitrogen-rich hyperbranched polymer as adsorbent for enrichment and determination of auxins in plants

In this study, a novel nitrogen-rich hyperbranched polymer was designed and synthesized via one-step precipitation copolymerization strategy. As possessing the lone-pair-electron-containing nitrogen atoms and positive-charged amine groups, as well as π electron-conjugated system, the prepared polymer displayed a strong tendency to adsorb protons acid, and negative-charged and conjugated compounds according to acid-base interaction, electrostatic interaction, and π-π stacking interaction. Based on these properties, a novel approach for assembling the proposed polymer coupled with high-performance liquid chromatography was successfully employed for selective enrichment and determination of auxins in plants. The extraction and desorption conditions were evaluated and the limits of detection and the limits of quantification of the proposed method were in the range of 0.15-0.29 μg L^-1 and 0.49-0.98 μg L^-1 for the four auxins based on the signal-to-noise ratio of 3:1 and 10:1, respectively. The recoveries of the target auxins from spiked plant samples were in the range from 85.0 to 116.3% with relative standard deviations lower than 9.6%. This study presented an inspiring thought for the construction of the versatile polymer adsorbent with highly efficient capturing of analytes from complex samples. Graphical abstract.

Highly sensitive fluorescent probe based on a novel phenothiazine dye for detection of thiophenols in real water samples and living cells

Based on an excited-state intramolecular proton transfer (ESIPT) fluorophore, a novel fluorescent off-on probe for detection of thiophenols was designed and synthesized. This probe (λ_ex = 401 nm, λ_em = 527 nm) displayed high specificity for sensing thiophenols over other biologically related species. Besides, this probe possessed capabilities of monitoring thiophenols with rapid response rate (3 min), a large Stokes shift (126 nm), and high sensitivity (2.7 nM). The sensing mechanism was considered to be that thiophenols triggered thiolysis of the probe and the ESIPT fluorophore was released, as confirmed by means of HPLC and HRMS. Most notably, this probe was successfully applied to monitor levels of thiophenols in realistic samples and MDA-MB-231 cells. Graphical abstract A novel phenothiazine-based fluorescent probe was developed for sensitively sensing thiophenols in both aqueous medium and living cells.

Synchronous determination with double-wavelength by RP-HPLC-UV and optimization of ultrasound-assisted extraction of phenolic acids from Caragana species using response surface methodology

The utilization of Caragana korshinskii Kom. (CK) is currently concentrated on its ecological and fuel functions. Little attention has been devoted to the analysis of their phenolic acid (PA) components. To obtain more data for further utilization of CK, a new analysis protocol was tested to determine PAs synchronously by RP-HPLC-UV with double-wavelength (280nm and 320nm) detection. Specifically, separation of PA components was performed on a Hypersil Gold C₁₈ reverse phase column with gradient elution. A four-factor-three-level Box-Behnken design was implemented for optimization of PA extraction. The results demonstrated that CK were rich primarily in chlorogenic acid, vanillic acid, caffeic acid and rosmarinic acid. The total content of PAs in CK leaves was the highest compared with its other parts. The distribution of total flavonoid content of CK was leaves>flowers>bark, while that of the total phenolic content of CK was flowers>leaves>bark.

3-(2-Bromoacetamido)-N-(9-ethyl-9H)-carbazol fluorescent probe and its application for the determination of thiophenols in rubber products by HPLC with fluorescence detection and atmospheric chemical ionization mass spectrometry identification

A rapid, sensitive, and selective precolumn derivatization method for the simultaneous determination of eight thiophenols using 3-(2-bromoacetamido)-N-(9-ethyl-9H)-carbazol as a labeling reagent by high-performance liquid chromatography with fluorescence detection has been developed. The labeling reagent reacted with thiophenols at 50°C for 50 min in aqueous acetonitrile in the presence of borate buffer (0.10 mol/L, pH 11.2) to give high yields of thiophenol derivatives. The derivatives were identified by online postcolumn mass spectrometry. The collision-induced dissociation spectra for thiophenol derivatives gave the corresponding specific fragment ions at m/z 251.3, 223.3, 210.9, 195.8, and 181.9. At the same time, derivatives exhibited intense fluorescence with an excitation maximum at λ_ex = 276 nm and an emission maximum at λ_em = 385 nm. Excellent linear responses were observed for all analytes over the range of 0.033-6.66 μmol/L with correlation coefficients of more than 0.9997. Detection limits were in the range of 0.94-5.77 μg/L with relative standard deviations of less than 4.54%. The feasibility of derivatization allowed the development of a rapid and highly sensitive method for the quantitative analysis of trace levels of thiophenols from some rubber products. The average recoveries (n = 3) were in the range of 87.21-101.12%.