Determination of Inorganic Arsenic Species by Electrochemical Hydride Generation Atomic Absorption Spectrometry with Selective Electrochemical Reduction

A new direct procedure for the determination of inorganic arsenic species was developed by electrochemical hydride generation atomic absorption spectrometry （EcHG-AAS） with selective electrochemical reduction. The determination of inorganic arsenic species is based on the fact that As（Ⅲ） shows significantly higher absorbance at low electrolytic currents than As（Ⅴ） in 0.3 mol·L^-1 H2SO4. The electrolytic current used for the determination of As（Ⅲ） without considerable interferences of As（Ⅴ） was 0.4 A, whereas the current for the determination of As（Ⅲ） and As（Ⅴ） was 1.2 A. For equal concentrations of As（Ⅲ） and As（Ⅴ） in a sample, the interferences of As（Ⅴ） during the As（Ⅲ） determination were smaller than 5%. The absorbance for As（Ⅴ） could be calculated by subtracting that for As（Ⅲ） measured at 0.4 A from the total absorbance for As（Ⅲ） and As（Ⅴ） measured at 1.2 A, and then the concentration of As（Ⅴ） can be obtained by its calibration curve at 1.2 A. The methodology developed provided the detection limits of 0.3 and 0.6 ng·mL^-1 for As（Ⅲ） and As（Ⅴ）, respectively. The relative standard deviations were of 3.5% for 20 ng·mL^-1 As（Ⅲ） and 3.2% for 20 ng·mL^-1 As（Ⅴ）. The method was successfully applied to determination of soluble inorganic arsenic species in Chinese medicine.     

Arsenic Determination in Plant Samples by Hydride Generation and Axial View Inductively Coupled Plasma Atomic Emission Spectrometry

The present work describes a study on the determination of arsenic in plant samples with hydride generation coupled with an axial view inductively coupled plasma atomic emission spectrometer. The accuracy of the measurements was not affected by elements present in high concentrations in the plant matrix (K, Ca, Mg, and P). Interference from transition metals was not observed either. When using real samples (maize and oak leaves) with standard additions, a decrease in the recoveries was sometimes observed when using KI to reduce As(V) to As(III), which reached 13.5% in the most unfavourable case. The use of a mixture containing KI and ascorbic acid is recommended. The accuracy of the method was verified using three certified reference materials. No statistically significant differences were observed between the measured concentrations and the certified values. The optimized method was found to be sensitive (detection limit: 0.1 μg L⁻¹) and reliable. The results obtained under routine conditions over a period of several months also demonstrated its reproducibility.     

Determination of As(III) and total as in water by graphite furnace atomic absorption spectrometry after electrochemical preconcentration on a gold-plated porous glassy carbon electrode

Arsenic(III) was preconcentrated in a flow-through electrochemical cell on a gold coated porous carbon electrode. On stripping, arsenic was eluted with diluted nitric acid and determined off-line by GF AAS. The deposition and stripping steps were optimized. The limit of detection and limit of quantification were found to be 1.9 μg L⁻1 and 6.4 μg L⁻¹, respectively. The repeatability and reproducibility were found to be 5.3 % and 9.3 %, respectively. Total arsenic was determined after a microwave assisted chemical reduction of As(V) to As(III) making the procedure suitable for speciation analysis. The method was applied in analysis of water samples.     

Double Magnetic Separation-assisted Fluorescence Method for Sensitive Detection of Ochratoxin A

A double magnetic separation-assisted fluorescence method was developed to rapidly detect ochratoxin A(OTA). The OTA aptamer functionalized magnetic nanomaterial(Fe3O4-Aptanier) and complementary DNA conjugated nitrogen-doped graphene quantum dots(NGQDs-cDNA) were used in this assay. Aptamer could hybridize with cDNA, which induced tlie NGQDs-cDNA to bind onto Fe3O4-Aptamer, and resulted in the fluorescence quenching of NGQDs. After the addition of OTA, the NGQDs-cDNA could release into the solution, and resulted in the recovery of fluorescence signal of NGQDs consequently. By utilizing the magnetic separation, the unbonded NGQDs-cDNA and residual Fe3O4-Aptamer were removed, which significantly increased the fluorescence signal intensity. OTA could be detected in the linear range of 10 nmol/L to 2000 nmol/L, with a limit of detection as 0.66 mnol/L. The advantages of this method include simple operation, good selectivity and high sensitivity, and this method can be used for the rapid detection of ochratoxin A in wheat and com.     

Determination of Pb（II） in environmental water by nano-ceria-graphene modified electrodeEI北大核心CSCD

Nafion solution as a binder,the Gr/CeO2 /Nafion/GCE modified electrode was prepared based on graphene （Gr）-nano cerium oxide （CeO2 ）composite materials. The electrochemical behavior of Pb（II）on the modified electrode was investigated using differential pulse anodic stripping voltammetry （DPASV）. Subsequently,a determination method for Pb（II）was established. The concentrations and ratio of composite materials,buffer solution pH,modification amount,enrichment potential and time were optimized. Under the optimal conditions ,the peak current of Gr/CeO2 /Nafion/GCE showed good linearity in the range of 0.24-48.31 μµmol/L of Pb（II）,and the detection limit was 4.3 nmol/L. Interference experiments showed that the other common anions and cations in water samples caused little interference to Pb（II）detection. Furthermore,the interference of Cu（II）within 10 times is acceptable. The modified electrode was used to the detection of Pb（II） in four complex water samples,and the recovery rates of the spiked assays were from 89.5% to 107.7%. © 2023, Youke Publishing Co.,Ltd. All rights reserved.     

Synthesis of a fluorescent probe based on naphthalimide derivative for simultaneous detecting of NO and pH in bioimagingEI北大核心CSCD

A new type of fluorescent probe Na-pHNO was synthesized for the simultaneous detection of NO and pH based on naphthalimide derivative. The probe had good fluorescence property in mixture solution of 99% phosphate buffer solution（PBS）and 1% dimethyl sulfoxide（DMSO）solution. It can produce a yellow-green emission peak at 544 nm,and the fluorescence intensity can be enhanced with the increase of NO concentration or the decrease of pH. The probe Na-pHNO displayed good selectivity,high sensitivity,and strong anti-interference towards NO,exhibiting good fluorescence reversibility at pH 5.5-8.5. The spectral studies showed that the probe Na-pHNO exhibited weak fluorescence due to a dual photoinduced electron transfer（PET）effect. After interacting with NO or pH,the dual PET inhibitory effect occurred,and the fluorescence intensity was significantly enhanced. The fluorescence imaging of probe Na-pHNO in HeLa cells showed that it could realize the visual monitoring of the changes of intracellular pH and NO concentration. The probe has been successfully applied to fluorescence imaging of Caenorhabditis elegans. © 2023, Youke Publishing Co.,Ltd. All rights reserved.     

A Study on the Interaction of the DAS-K with Bovine Serum Albumin by On-line Ultrafiltration and Chemiluminescence

Potassium dehydroandrographolide succinate （DAS-K） has antibacterial and antiviral effects. It has been used widely for the treatment of virus pneumonia, malaria and respiratory infections. In this work, a novel flow-injection chemiluminescence （CL） method for the determination of DAS-K was proposed. The method is based on the reaction between DAS-K and hexacyanoferrate（III） in alkaline solution to give weak CL signal, which is enhanced by rhodamine B. The experimental conditions for the CL reaction were optimized and the possible reaction mechanism was discussed. Under the optimum conditions, the concentration of DAS-K is proportional to the CL intensity in the range of 0.1-80 μmol·L^-1 with a detection limit of 0.05 μmol·L^-1. The interaction of the DAS-K with bovine serum albumin by on-line ultrafiltration and flow-injection chemiluminescence was studied. The concentrations of unbound DAS-K from ultra filter tube were determined by the flow-injection CL method. The binding parameters were estimated by the Scatchard plot and Klotz plot. The proposed system proved that FIA-CL coupled with on-line ultrafiltration sampling was a fast and simple technique for the study of drug-protein interaction.     

L-cysteine modified gold nanoparticles / paper chip system for rapid detection of chiral dopaEI北大核心CSCD

A new detection method for L-Dopa based on paper chips was established. The L-Cys-AuNPs were characterized by their size, zeta potential, and UV-visible absorption spectra. The system had the high selectivity for the colorimetric detection of L-Dopa with the color changing from red to blue. The results were recorded using a common cell phone and subsequently analyzed using Photoshop software. A ratiometric color intensity method was designed for the quantification analysis. The ratio of color intensity at red channel and blue channel (R / B) increases linearly with L-Dopa concentration in the range of 5 to 80 μmol / L (R = 0. 9944), with the limit of detection of 4 μmol / L. The spiked recoveries of samples were 98%-102%. The RSDs of inter-day and intraday were 3. 3% and 3. 8%, respectively. Real samples were detected, and the error between the determination and the labeled value was within 5%. The method can be used to detect L-Dopa in real samples. © 2022, Youke Publishing Co.,Ltd. All rights reserved.     

Determination of Trace Amounts of Vanadium by Kinetic-Catalytic Spectrophotometric Methods

Kinetic-catalytic spectrophotometric methods were proposed for the determination of trace amounts of vanadium element as vanadium（Ⅳ） and/or V（Ⅴ） ions. The vanadium（Ⅳ） as VO^2＋ ion and/or vanadium（Ⅴ） as VO3^- ion showed a catalytic effect on the kinetic reactions between a color reagent such as methylthymol blue （MTB） or SPADNS and bromate in acidic media. The rate of decrease in the absorbance of the reagent MTB at 440 nm or SPADNS at 510 nm was proportional to concentration of V（Ⅳ） and/or V（Ⅴ） ions in the solution. The linear ranges for determination of vanadium were obtained in the range of 1.0-150 and 5.0-100.0 μg/L by the fixed-time and slope methods, respectively, with using MTB as reagent. In the presence of SPADNS as reagent, the calibration curves were made in the amplitude 1.0-200.0 and 5.0-150 μg/L of vanadium ion by the fixed-time and slope methods, respectively. Using fixed-time method, the limits of detection were obtained to be 0.5 and 0.7 μg/L of vanadium in the presence of MTB and SPADNS as reagents, respectively. Detection limits of vanadium by slope method and reagents of SPADNS and MTB were obtained to be 3.5 and 3.8 μg/L of vanadium, respectively. The proposed methods were applied successfully to determination of vanadium in synthetic and real samples.     

Organic-inorganic hybrid fluorescent sensor thin films of rhodamine B embedded Ag-SBA 15 for selective recognition of Hg (Ⅱ) ions in water

Nowadays, the rapid and effective detection of low doses of heavy metal pollutants in contaminated water is a timely challenge in environmental pollution research. In this study, a rapid and highly sensitive assay for the detection of Hg~(2+)based on quenching of metal-enhanced fluorescence of rhodamine B(RB)has been fabricated. RB and silver nanoparticle were incorporated into the mesoporous siliceous framework spin cast on a quartz glass through post-synthetic incorporation method. The morphology and crystallinity of mesoporous structure and Ag nanoparticle were characterized by transmission electron microscopy and X-ray diffraction analyses. Photoluminescence assays on the hybrid thin film of RB-Ag-SBA15 showed a high enhancement when compared to the intensity of silver free SBA15-RB in the wavelength of 575 nm. The fluorescence of RB-Ag-SBA15 thin film decreased gradually with the increase in the concentration of Hg~(2+)and the detection limits were 10.54 nmol/L. Furthermore, the fluorescence intensity increased linearly with the concentration of Hg~(2+)in the range from 1.0 ? 10à8mol/L to10 ? 10à8mol/L, with a response time of a few seconds. In addition, this system offers a high selectivity over interfering cations such as Cd~(2+) and Pb~(2+). Overall, we have developed an optical assay having a wellordered mesoporous SBA15 containing Ag-RBfor selective detection of Hg~(2+)in aqueous solution. The scheme combines the advantages of specific binding interactions between Hg~(2+)and RB molecule and optical emission properties of RB. The method is suitable for a single-shot and irreversible analytical assay in a quartz glass/microtiter plate.     

Detection of arsenic and lead in chromite by alkali fusion-acid dissolvingatomic fluorescence spectrometryEI北大核心CSCD

A hydride generation-atomic fluorescence spectrometry （AFS） method was developed for the detection of arsenic （As） and lead （Pb） in chromite by alkali fusing and acid dissolving. The sample was fused by Na2O2 and acidification dissolved by HCl. As was quantified by AFS with 10% （V/V） HCl as the carrier flow agent, and KBH4（15 g/L） as reducing agent. Pb was quantified by AFS with 1% （V/V） HCl as the carrier flow agent, and KBH4（20 g/L）-KOH（10 g/L）-K3［Fe（CN）6］ （15 g/L） as reducing agent. Under the optimum conditions, the correlation coefficient （R2） was 1.0000 in the range of 0.5-10 μg/L, the limit of detection （LOD） was 0.05 μg/g with the relative standard deviations （RSDs） of 1.4%-6.0% and the recoveries of 96.2%-116.7% for As. And the R2 was 0.9998 in the range of 1.25-25 μg/L, the LOD was 0.2 μg/g with the RSDs of 1.5%-3.7% and the recoveries of 95.9%-112.2% for Pb. In addition, the method was validated by certified reference sample analysis and multi-laboratory test, which meets the requirements for the standardized quantitative analysis of trace As and Pb in chromite. © 2023, Youke Publishing Co.,Ltd. All rights reserved.     

Preparation and Investigation of Arsenic Trioxide-loaded Polylactic Acid/Magnetic Hybrid Nanoparticles

In order to improve the therapeutic index and reduce the side effects of As2O3 so as to expand its clinical utility to solid tumors,As2O3-loaded polylactic acid（PLA）/magnetic nanoparticles（PAMNs） were prepared and the preparation conditions were optimized by the improved double emulsion solvent-evaporation method to obtain as a drug delivery system with a high As2O3 encapsulation efficiency and homogeneous nanosized particles.Successful loading of magnetic nanoparticles into the nanoparticles was confirmed by Fourier transform infrared（FTIR） spectroscopy.The drug loading,encapsulation efficiency and releasing properties of As2O3 in PAMNs were investigated by atomic fluorescence spectrometer analysis.Subsequently,the in vitro antitumor efficacy of free As2O3 and As2O3-PAMNs against SMMC-7721 cell line was investigated.Finally,confocal fluorescence microscopy was conducted to reveal the celluar uptake of As2O3-loaded PAMNs by SMMC-7721 cell line.     

Simultaneous Determination of Magnolol and Honokiol rby Synchronous Fluorescence Spectroscopy

A simple sensitive and quick assay for simultaneously determining magnolol （MOL） and honokiol （HOL） has been described based on their natural fluorescence. This method is based on the fact that synchronous fluorometry could resolve the overlapping of fluorescence spectra, which was aroused by their similar molecular structures. In this work, the synchronous spectrum, maintaining a constant difference of Aλ =10 nm between the emission and excitation wavelengths, has been selected for the determination of HOL and MOL. Under the optimum conditions, the fluorescence intensity is proportional to the concentration of MOL and HOL in solution over the range 0.075-0.7 μg/mL and 0.05-0.9 μg/mL with the detection limit of 0.029 μg/mL and 0.019 μg/mL, respectively. The method was applied to the simultaneous determination of MOL and HOL in pharmaceutical dosage with satisfactory results.     

Dual-modal Colorimetric and Fluorometric Method for Glucose Detection Using MnO2 Sheets and Carbon Quantum Dots

A novel dual-modal fluorometric and colorimetric method was developed for glucose detection using MnO2 sheets and carbon quantum dots(CQDs). The glucose could be oxidized by glucose oxidase, in accompanied witli the fbnnation of H2O2 intennediate, which resulted in the decomposition of MnO2 sheets, as well as tlie MnO2 sheets(brown) changed to Mn^2+ ions(colorless), which induced the absorption of MnO2 sheet decreased and the fluorescence of CQDs increased, consequently. The linear detection ranges of glucose are 5-1000 μmol/L by fluorescent method and 5-60 μmol/L by colorimetric method. The limits of detection of these two measurements are 2.11 and 2.18 μmol/L, respectively. This method is easy to conduct, has reasonable sensitive and selectivity, and could be applied for the glucose detection in real human senim.     

Determination of Arsenic in Dolomites with a Simple Field Spectrometric Device

A simple and an inexpensive procedure for the determination of total arsenic in dolomites is proposed. The method applies the spectrometric field device Supralab SD which was initially designed for the determination of arsenic in drinking water. The method relies on the formation of the volatile AsH₃ and its reaction with mercuric bromide, immobilized in a membrane, to yield a yellowish-brown reaction product, which is spectrophotometrically detected. The dolomite samples were rapidly dissolved in hot hydrochloric acid in an open vessel and then were analyzed with the portable instrument. The 3 s detection limit of the developed method was 0.1 μg L⁻¹ as in the solution containing dissolved dolomites. The time of As determination in the solution did not exceed 5 min. To validate the results obtained with the field device, hydrogen generation inductively coupled plasma optical emission spectrometry (HG-ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS) were used as reference methods using microwave-assisted mineralization. Excellent agreement between the methods was obtained.     

A New Tetrasubstituted Imidazole Based Difunctional Probe for UV-spectrophotometric and Fluorometric Detecting of Fe3+ Ion in Aqueous Solution

Two new compounds,4-(2-bromophenxl-4,5-diphenyl-imidazol-1-yl)ani 1 ine(probe 1)and 4-[2,4,5-tris(4-bromopheny1)-1H-imidazol-1-y1]aniline(probe 2),were synthesized via a soft and high-efficiency one-pot microwave-assisted method under solvent-free conditions.Their sensing to different metal ions was detected by UV spectrophotometry and fluorescence spectrometry.Probe 2 revealed highly selective and sensitive UV and fluorescence response to Fe^3+ion.Upon the addition of Fe^3+ion,probe 2 showed obvious color change of the solution,conspicuous absorbance enhancement and relatively quick fluorescence quenching.The detection limit for Fe^3+ion was respectively calculated to be 0.72μmol/L(fluorescent detection)and 0.48μmol/L(UV-spectnim detection).Also,probe 2 was bound by Fe^3+ion to tonn a 1:1 complex.Moreover,preliminary application of probe 2 tor detecting Fe^3+ion in aqueous solution was attempted,and satisfying results were obtained.     

Determination of 12 additives in beverages by evaporation-assisted dispersive liquid-liquid microextraction based on the solidification of floating organic droplets combined with liquid chromatographyEI北大核心CSCD

An analytical method for the simultaneous determination of 12 additives in beverages was developed using evaporation-assisted dispersive liquid-liquid microextraction based on the solidification of floating organic droplets EVA-DLLME-SFOcombined with high performance liquid chromatography HPLC. The samples were extracted twice with 70%V/Vmethanol aqueous solution and extracted by EVA-DLLME-SFO method after the combination of the extractsand finally determined by HPLC. Extraction parameterssuch as types and amounts of extractantevaporant and heating agentthe concentration of saltand the extraction time were optimized. Under the optimized conditionsthere were good relationships in the ange of 0.25-50 μµg/mL with the limits of detection of 1.5 to 13.6 mg/kg and limits of quantification of 5.2 to 45.3 mg/kg. The recoveries at three spiked levels1025 and 50 mg/kgwere 76.8% to 101.2% with the relative standard deviations of 0.11% to 4.7%. The method can be used for rapid detection of 12 additives in beverages. © 2022, Youke Publishing Co.,Ltd. All rights reserved.     

Self-assembly of silica nanosheets on titanium fibers for solids-phase microex⁃traction of UV absorbers in environmental water samplesEI北大核心CSCD

Silica nanosheets （SiO2NSs）were successfully assembled on titanium （Ti）wires by sol-gel method. TiO2 nanosheets （TiO2NSs）were grown in situ on Ti wires using anodic oxidation in a fluoride-containing electrolyte to obtain Ti@TiO2NSs. The Ti@TiO2NSs@SiO2NSs fibers were obtained by coating Ti@TiO2NSs with SiO2NSs. It was characterized by scanning electron microscopy （SEM） and X-ray energy dispersive spectroscopy （EDS）. The fibers were used for solid-phase microextraction of ultraviolet absorbers （UVFs）. Under the optimized conditions, six UVFs presented good linearity with the correlation coefficients （R2） greater than 0.999, and the limits of detection （LODs）ranged from 9 to 59 ng/L. The intra-day and inter-day relative standard deviations （RSDs） were from 4.3% to 5.1% and 4.6% to 5.8% for a single fiber at the spiked level of 25 μg/L, respectively. The developed method was successfully applied to the selective enrichment and determination of target UVFs in environmental water samples with recoveries from 93.2% to 108.1% and RSDs from 4.5% to 7.1%. Moreover, the fiber can be fabricated in a precisely controllable manner and is stable for at least 200 extraction and desorption cycles. © 2023, Youke Publishing Co.,Ltd. All rights reserved.     

Hydrothermal Synthesis of PEG-capped ZnS：Mn2＋ Quantum Dots Nanocomposites

Water-soluble Mn2＋-doped ZnS nanocrystals surface capped with polyethylene glycol（expressed as PEG-ZnS：Mn2＋） were synthesized in aqueous solution with PEG as surface modifier without ligand exchange.The particles were obtained via chemical precipitation method at 100 ℃ with an average diameter of 3 nm and a zinc blende structure.The PEG modified on the surface of PEG-ZnS：Mn2＋ nanocrystals rendered the nanocrystals water soluble and biocompatible.And the PEG-ZnS：Mn2＋ nanocrystals have the potential application in molecular assembly and biological fluorescence analysis.The effects of the Mn2＋ concentration,stabilizer concentration,and synthesis time on the photoluminescence（PL） intensity of ZnS：Mn2＋ QDs were also investigated.     

Iodine Determination by Microwave Plasma Torch Atomic Emission Spectrometer Coupled with Online Preconcentration Vapor Generation Technique

This article focuses on iodine determination by microwave plasma torch atomic emission spectrometry （MPT-AES） coupled with online preconcentration vapor generation method. A new desolvation device, multistrand Nafion dryer, was used as the substitute for condenser desolvation system. Some experimental conditions, such as preconcentration time, acidity of sample solution, rinsing solution acidity and dynamic linear range were investigated and optimized. The new desolvation system eliminates the problem of decreasing emission intensity of I（I） 206.238 nm line with the increase of working time on a conventional condenser desolvation system, thus greatly improving the reproducibility.