Three-element doped carbon dots for the detection of p-nitrophenolEI北大核心CSCD

Based on the characteristics that heteroatom doping can improve the luminescence performance of carbon dotsa new type of three-element co-doped carbon dots NSSi-CDswas prepared. The synthesis conditions were optimizedand the morphologystructure and luminescence properties of NSSi-CDs were characterized. NSSi-CDs can emit 450 nm blue fluorescence under excitation at 370 nmand the fluorescence quantum yield reached 11%. The study found that p-nitrophenol PNPhas a strong fluorescence quenching effect on NSSi-CDsand thus a new method for the determination of PNP with NSSi-CDs fluorescent probe was constructed. When the concentration of PNP was in the range of 0.9-60 μµmol/Lit had a good linear relationship with the fluorescence quenching efficiencyF0 /Fand the detection limit was 0.36 μµmol/L. This method was used to determine PNP in actual water samples with good recoveries of 90.6%-95.2%. © 2022, Youke Publishing Co.,Ltd. All rights reserved.     

Effect of organic modifiers on the capacity factor in micellar electrokinetic chromatography

Organic modifiers were effective both to extend the migration time window and to improve the separation of very hydrophobic compounds in MEKC.An iteration method was used to determine the migration time of micelles.The quantitative relationship between the capacity factor k' and the concentration of organic modifiers was derived,which was investigated experimentally.The linear solvation energy relationships (LSER) methodology was applied to MEKC,and good linear relationships between Ink' and solvatochromic parameters of 15 solutes were obtained in the presence of organic modifier in different concentrations,which indicated a new access in MEKC to predict k' from the structural parameters of solutes.The effect of column temperature T on k' was also investigated.     

Triacontyl modified silica gel as a sorbent for the preconcentration of polycyclic aromatic hydrocarbons in aqueous samples prior to gas chromatographic-mass spectrometry determination

<正>Triacontyl modified silica gel as a sorbent coupled with gas chromatography-mass spectrometry(GC-MS) was developed to determine EPA prior 16 polycyclic aromatic hydrocarbons(PAHs) in water samples.Various parameters of solid-phase extraction such as organic modifier solvent,eluent,sample flow rate and volume were optimized.The developed method was found to yield a linear calibration curve in the concentration range of 0.05-8μg/L with respect to naphthalene,acenaphthylene,acenaphthene and 0.01-8μg/L for dibenz[a,h]anthracene and 0.05-14μg/L for fluorene,phenanthrene,anthracene and 0.01-14μg/L for the rest of analytes.Furthermore,the good accuracy and repeatability of the method made sure the requirements for achieving reliable analysis of PAHs in the environmental water samples,and the recoveries of optimal method were in the range of 80-120%except to higher volatility PAHs.C_(30)-bonded silica was proved to be an efficient sorbent for extraction of high molecular weight PAHs.     

Trace determination of hexabromocyclododecane diastereomers in water samples with temperature controlled ionic liquid dispersive liquid phase microextraction

A novel temperature controlled ionic liquid dispersive liquid phase microextraction(TCIL-DLPME) coupled with rapid resolution liquid chromatography-electrospray tandem mass spectrometry(RRLC-ESI-MS-MS) has been developed for the enrichment and determination of three hexabromocyclododecane diastereomers(HBCDs) in water samples.Green solvent ionic liquid(IL) was used as extraction solvent instead of toxic organic solvents.This technique also avoided the usage of dispersive solvent.Some important parameters that might affect the extraction efficiency were optimized.Under the optimum conditions,good linear relationship,sensitivity and reproducibility were obtained.All the limits of detection for the three diastereomers were 0.1 ng/ mL.The linear range was obtained in the range of 1-100 ng/mL for the total amount of three HBCD diastereomers.It was satisfactory to analyze real environmental water samples with the recoveries ranging from 77.2%to 99.3%.The main advantage of the method is toxic organic solvent-free.     

Iodide-selective polymeric membrane electrode based on copper(Ⅱ) bis(N-2-bromophenylsalicyldenaminato) complex

A PVC membrane electrode based on copper（Ⅱ） bis（N-2-bromophenylsalicyldenaminato） as ionophor was prepared.The ion selective electrode was tested by inorganic anions and showed a good selectivity for iodide ion.This sensor exhibited Nernstian behavior with a slope of—57.8 mV per decade at 25℃.The proposed electrode showed a linear range from 1.0×10⁵ to 1.0×10^-1 mol/L with a detection limit of 5.0×10^-6 mol/L.The electrode response was independent of pH in the range of 3.0- 10.0.The proposed sensor was applied to determine the iodide in water and antiseptic samples.     

An ethanol biosensor based on a bacterial cell-immobilized eggshell membrane

An ethanol biosensor was fabricated based on a Methylobacterium organophilium-immobilized eggshell membrane and an oxygen（O₂） electrode.A linear response for ethanol was obtained in the range of 0.050-7.5 mmol/L with a detection limit of 0.025 mmol/L（S/N= 3） and a R.S.D.of 2.1%.The response time was less than 100 s at room temperature and ambient pressure. The optimal loading of bacterial cells on the biosensor membrane is 40 mg（wet weight）.The optimal working conditions for the microbial biosensor are pH 7.0 phosphate buffer（50 mmol/L） at 20-25℃.The interference test,operational and storage stability of the biosensor are studied in detail.Finally,the biosensor is applied to determine the ethanol contents in various alcohol samples and the results are comparable to that obtained by gas chromatographic method and the results are satisfactory.Our proposed biosensor provides a convenient,simple and reliable method to determine ethanol content in alcoholic drinks.     

Chelatometric dispersive liquid-liquid microextraction followed by capillary electrophoresis for the analysis of total and water soluble copper in Rhizoma coptidis

A new method for the analysis of copper and its speciation in Rhizoma coptidis was proposed using chelatometric dispersive liquid-liquid microextraction(cDLLME) followed by capillary electrophoresis. Dithizone was used as a chelating agent for extraction and carbon tetrachloride and ethanol were used as extraction and dispersive solvent,respectively.The calibration curve was linear in the range of 0.5- 20.0μg/mL with a correlation coefficient of 0.9990(n = 6) and the average recovery was in the range of 88.26%-94.44%.The method was successfully used to determine the total and water soluble copper in Rhizoma coptidis herbal medicine.The results suggested that it would be reasonable to setting the criterion of heavy metals in an herbal medicine according to the dosage forms.     

Trace determination of cobalt ion by using malic acid-malonic acid double substrate oscillating chemical system

A novel kinetic method for determination of trace amounts of cobalt ion was proposed and validated. The method is based on adding malic acid into classical Belousov-Zhabotinskii （B-Z） oscillating chemical system to form a double substrate one. The results showed that when the concentration of cobalt ion was in the range of 5.27× 10^-8 to 5.37 × 10^-12 mol L^-1, the change of the oscillating period was directly proportional to the negative logarithm of cobalt ion concentration. The sensitivity and precision of the developed method were quite satisfactory. The limit of detection was down to 5.20 × 10^-13 mol L^-1 which was a highest sensitivity found for determination of metal ions using oscillating chemical reaction so far. Some factors influencing the determination were also examined. The method has been successfully used to determine cobalt ion in vitamin B12 injection.     

Determination of chloride ion by electrochemiluminescence and investigation of the mechanism

The electrochemiluminescence (ECL) of luminol in aqueous alkaline solution was studied.Trace amounts of chloride showed significant effect on the efficiency of light emission of luminol as a posi-tive trigonometrical wave pulse was exerted on the solution. The detection limit for the chloride is5.0 ×10~(-6) mol/L and the linear calibration range extends up to 1.0 ×10~(-2) mol/L; the relative standarddeviation for 1.0 ×10~(-5) mol / L chloride is 5%. The influencing factors for chloride determination arealso discussed. The possible mechanism for the electrochemiluminescence reaction may be due to theoxidation of chloride ion in the solution to ClO~-, and the latter acts on luminol and then gives outluminescence. The method has been applied to determine the total chloride in tap water with satisfactoryresults.     

Voltammetric studies on the interaction of amikacin with methyl blue and its analytical application

A new method to determine the concentration of amikacin(AMK)using methyl blue(MB)as electrochemical probe was developed in this paper.In pH 4.5 Britton-Robinson(B-R)buffer solution,the MB reacted with AMK to form ion association complexes,which led to the reductive peak current of MB at-0.275 V(versus SCE)to decrease,and the decreases were linear with the concentration of AMK in the range of 1.0-60.0 mg/L,the regression of equation isΔIp(nA)=-8.48 102.36c(mg/L), correlation coefficientγis 0.997.The conditions for determining the concentration of AMK using linear sweep voltammetry(SLV) were optimized.The method was used to determine the content of amikacin commercially available with satisfactory results.     

Spectrophotometric Determination of Water Content in Alcohol Organic Solvents

In this work, the absorption spectral characteristics and color‐change reaction mechanism of cobalt(II) chloride(CoCl₂) in alcohol organic solvents has been investigated in the presence of water, and then the optimum conditions for determining the water content in the solvents were selected. Results indicated that the absorption spectra of CoCl₂ in alcohols decreased with the increment of water content. At the maximum absorption wavelength of 656 nm, there were good linear relationships between the logarithm of the absorbance and the water content in organic solvents such as ethanol, n‐propanol, iso‐propanol and n‐butanol with related coefficients in the range of 0.9996?0.9998. For determining water content in organic solvents, this method is simple, rapid, sensitive, reproducible and environmentally friendly. Furthermore, the linear range cannot restrict determination of the water content in organic solvents. This method had been applied to determine the water content in ethanol and n‐butanol with satisfactory recovery of water in n‐butanol between 98.41%?101.29%.     

Selective Spectrophotometric Determination of Oxyphenbutazone Using a Chelate Forming Reaction

Abstract

A selective spectrophotometric method for the determination of oxyphenbutazone is described. The method is based on nitrosation reaction and simultaneous formation of copper(II) or cobalt (II) chelate of the nitrosoderivative. The formed chelates are extractable with organic solvents giving yellow solutions whose absorbance are proportional to the concentration of oxyphenbutazone. In addition, the chelate extracts, upon treatment with diethyldithiocarbomate develop an additional indirect method of high selectivity for determining oxyphenbutazone. The developed methods are highly accurate and comparable with an official method.     

A Mercury-Free Thick-Film Graphite Electrode for Determining Cobalt in Natural and Potable Waters by Stripping Voltammetry

A mercury-free thick-film graphite electrode is proposed for determining cobalt(II) by stripping voltammetry. It was found that nitroso-R-salt ensures the highest efficiency of the preconcentration and determination of cobalt(II), as compared to the other organic reagents. The effects of different parameters (the pH of the solution, the concentration of organic reagents, the potential and duration of preconcentration, potential sweep rate, and interfering elements) were studied to select the optimum conditions for determining cobalt(II) at a mercury-free thick-film graphite electrode. The detection limit for cobalt(II) was 7.3 × 10^–12 M (or 0.4 ng/L) for a preconcentration time of 30 s. A procedure for determining cobalt(II) in potable and natural waters was developed and certified (certificate no. 224.01.10.002/2004, Ural Scientific Research Institute of Metrology).     

Cathodic Stripping Determination of Water in Organic Solvents

A cathodic stripping voltammetry (CSV) method has been developed to determine water content in organic solvents based on electrooxidation of a gold electrode in the presence of water to form gold oxides upon anodic polarizations. Following cathodic potential scan, a sharp reductive stripping peak of gold oxides is generated and the magnitude of the peak current is related to the water content in the organic solvents. The method has been applied for determination of water in four commonly used water miscible organic solvents, acetonitrile, tetrahydrofuran, acetone and glacial acetic acid, with limits of detection of 60, 10, 40 and 10 ppm, respectively.     

Catalytic decomposition of H<Subscript>2</Subscript>O<Subscript>2</Subscript> in hydrophilic solvents: The kinetic aspect

Decomposition of hydrogen peroxide in organic hydrophilic solvents, catalyzed by cobalt(II) palmitate [Co(palm)₂], was studied by the method of inhibitors.     

Study and evaluation of a fluorimetric method for the determination of inorganic mercury in water

Summary A procedure for determining Hg(II) in water has been worked out. The cation reacts with bromine and fluorescein to form an ionic pair (ionic association) which is extracted with n-butyl acetate, and has an emission peak at 476 nm and an excitation peak at 452 nm. On optimum determination conditions, the detection limit was 0.4 ng ml^–1 and the linear range 1–20 ng ml^–1. The influence of different chemical species present in water samples was studied and the method was applied to determine Hg(II) in synthetic samples of water and in natural water with good recovery rates. In order to determine Hg(II) in samples of urban waste water, a simple pretreatment with HNO₃ is required. The method can be used to monitor Hg(II) contamination in water.     

Spectrophotometric determination of water in organic solvents with solvatochromic dyes

The correlation between the absorbance at a fixed wave-length of a betaine dye in an organic solvent and the water content of the same solvent has been investigated. The betaine dyes investigated are 2,4,6-triphenyl-N-(3,5-diphenyl-4-hydroxyphenyl)pyiidinium betaine (I), 1-methyl-8-hydroxyquinolinium betaine (II), 1-methyl-6-hydroxyquinolinium betaine (III) and 2-methyl-5-isoquinolinium betaine (IV), and the organic solvents are ethanol, isopropanol, acetone, dioxan, acetonitrile and pyridine. The possibility of determining a trace amount of water in an organic solvent is demonstrated. The sensitivity of the method depends on solvent and dye but for example, 0.06 mg of water in 1 ml of acetonitrile can be detected with III with an ordinary spectrophotometer. The limitations of practical applications are discussed.     

Residual solvents determination in drug products by static headspace-gas chromatography

Summary Two static headspace selective methods for residual solvents belonging to Class I, II and III have been developed, optimized and validated for drug products, which are insoluble in water. The methods give very good sensitivities (detection limits under 10 ppm) and precision (under 5.5% RSD) for all solvents. The detection limit for benzene was 0.1 ppm, in concordance with Pharmacopoeia requirements. During method optimization we found that sample volume and water content have a critical influence on the sensitivity. From our data, it is beneficial to choose low sample volume. If sample solubility in the organic solvent allows it, the optimum sample volume is between 0.1 and 0.3 mL. For drug products with water content greater than 7%, the increase in sensitivity produced by water presence should be taken into consideration, otherwise inconsistent recovery data and underestimation of residual solvent content will happen. The headspace vial volume has a critical influence on system precision. Presented at Balaton Symposium '01 on High-Performance Separation Methods, Siófok, Hungary, September 2–4, 2001     

Competitive transport of seven metal cations through bulk liquid membrane using 5,12-di(phenoxymethyl)-1,4-dioxa-7, 10-dithiacyclododecane-2,3-dione as carrier

The competitive metal ion transport of copper(II), cobalt(II), zinc(II), cadmium(II), silver(I), chromium(III) and lead(II) with a S-O donor compound was examined. Competitive transport experiments involving the metal cations from an aqueous source phase through an organic membrane into an aqueous receiving phase have been carried out using 5,12-di(phenoxymethyl)-1,4-dioxa-7,10-dithiacyclododecane-2,3-dione as the ionophore present in the organic phase. Fluxes and selectivities for competitive metal cations transport across bulk liquid membranes have been determined in a variety of chlorinated hydrocarbon and aromatic hydrocarbon solvents. The membrane solvents include: dichloromethane (DCM), chloroform (CHCl₃), 1,2-dichloroethane (1,2-DCE), and nitrobenzene (NB) and also in chloroform-dichloromethane (CHCl₃-DCM) and chloroform-nitrobenzene (CHCl₃-NB) binary mixtures. Although the selectivity for silver(I) cation in all of these organic solvents is fundamentally similar, but the most transport rate for Ag(I) was obtained in dichloromethane. The sequence of transport rate for silver ion in organic solvents was: DCM > CHCl₃ > 1,2-DCE > NB. A linear relationship was observed between the transport rate of silver ion and the composition of CHCl₃-DCM, but a non-linear behavior was observed in the case of CHCl₃-NB binary solution. The influence of the stearic, palmetic and oleic acids as surfactant in the membrane phase on the transport of the metal cations was also investigated.     

Stability of coordination compounds of Ni<Superscript>2+</Superscript> and Co<Superscript>2+</Superscript> ions with succinic acid anion in water–ethanol solvents

Stability constants of the coordination compounds of nickel(II) and cobalt(II) ions with succinic acid anion in water–ethanol solvents are determined via potentiometric titration at ionic strength of 0.1 and at T = 298.15 K. It is found that logβ values of monoligand complexes of these ions and succinic acid anions rise along with the content of ethanol in solution (X _EtOH = 0–0.7 mole fractions). Based on an analysis of the thermodynamic characteristics of the solvation of the reagents involved in complex formation, it is found that the increased stability of succinate complexes of nickel(II) and cobalt(II) ions in water–ethanol solvents is mainly determined by the weakening of the solvation of succinic acid anion (Y^2?).