Key Conditions in Capillary Electrophoresis of Amino Acids with Indirect Ultraviolet Detection

Key factors for capillary electrophoresis of amino acids with indirect ultraviolet detection were illustrated. Buffer compositions and additives were found to be influential as expected, while buffer pH was shown to be particularly critical to the separation and detection. The effect of pH also depended on the electrophoretic mode used. Ways to obtain recurring and selective were suggested.

Determination of toluene diisocyanate in synthetic-rubber track by ion chromatography with ultraviolet detection after alkaline suppressor

In the present work, a novel analytical method was proposed for the determination of toluene diisocyanate （TDI） in syntheticrubber track by ion chromatography （IC） coupled with an ultraviolet detector setting at 212 nm. TDI can be hydrolyzed to toluene diamine （TDA） which can be separated by cation-exchange IC easily. The optimum IC separation was performed on an IonPac CS12A column （150 mm ×4.0 mm） using 20 mmol L^-1 sodium sulfate, 10 mmol L^-1 sulfuric acid and 10% acetonitrile as eluent. It was found that a higher signal response of TDA could be obtained under alkaline condition. A suppressor was used to change the acidic eluent into alkaline one. 0.8 mol L^-1 potassium hydroxide was chosen as the optimum regeneration eluent. With the added suppressor and regenerant, signal response was magnified by about 16 times and lower limit of detection （LOD, 0.13 μg L^-1） was obtained. Within-day relative standard deviation （R.S.D.） was less than 3.6%. The recoveries of TDI spiked in synthetic-rubber track samoles were 96.4-110.6%.

DNA Separation by Capillary Electrophoresis with Ultraviolet Detection using Mixed Synthetic Polymers

The mixtures of two polymers, poly (N,N-dimethylacrylamide) (PDMA) and polyvinylpyrrolidone (PVP) were synthesized and used as the separation medium for double-stranded and single-stranded DNA fragments by capillary electrophoresis with UV detector. On optimal conditions, 2%w/v PDMA + 2%w/v PVP can be used to separate the doublet 123/124bp in pBR322/Hae III Markers.

Determination of tetraethyl ammonium by ion-pair chromatography with indirect ultraviolet detection using 4-aminophenol hydrochloride as background ultraviolet absorbing reagent

A method was developed for the determination of tetraethyl ammonium （TEA） by reversed-phase ion- pair chromatography with indirect ultraviolet detection, Chromatographic separation was achieved on a reversed-phase C18 column using background ultraviolet absorbing reagent - ion-pair reagent - organic solvent as mobile phase. The effects of the background ultraviolet absorbing reagents, detection wavelength, ion-pair reagents, organic solvents and column temperature on the determination method were investigated and the retention rules discussed. Results found that TEA could be successfully analyzed by using 0.7 mmol/L 4-aminophenol hydrochloride and 0.15 mmol/L 1-heptanesulfonic acid sodium mixed with 20% （v/v） methanol as mobile phase at a UV detection wavelength of 230 nm. Under these conditions, the retention time of tetraethyl ammonium was 2.85 min. The detection limit （S/N = 3） for TEA was 0.06 mg/L. The relative standard deviations （n = 5） for peak area and retention time were 0.35% and 0.02%, respectively. The method has been successfully applied to the determination of synthesized tetraethyl ammonium bromide. Recovery of tetraethyl ammonium after spiking was 99.1%.

Separation and identification of moxifloxacin impurities in drug substance by high-performance liquid chromatography coupled with ultraviolet detection and Fourier transform ion cyclotron resonance mass spectrometry

In this paper, a high-performance liquid chromatography coupled with ultraviolet detection and Fourier transform-ion cyclotron resonance mass spectrometry （HPLC-UV/FrICRMS） method was described for the investigation of impurity profile in moxifloxacin （MOX） drug substance and chemical reference substance. Ten impurities were detected by HPLC-UV, while eight impurities were identified by using the high accurate molecular mass combined with multiple-stage mass spectrometric data and fragmentation rules. In addition, to our knowledge, five impurities were founded for the first time in MOX drug substance.

Imidazolium ionic liquid as the background ultraviolet absorption reagent for determination of morpholinium cations by high performance liquid chromatography-indirect ultraviolet detection

A novel analytical method was developed for determining morpholinium cations lacking ultraviolet absorption groups.This determination was carried out by high performance liquid chromatographyindirect ultraviolet（HPLC-1UV） detection using imidazolium ionic liquid as background absorption reagents,and imidazolium ionic liquid aq.soln.-organic solvent as mobile phase by a reversed-phase C18 column.The background ultraviolet absorption reagents,imidazolium ionic liquids and organic solvents were investigated.The imidazolium ionic liquid in the mobile phase is not only the background ultraviolet absorption reagent for IUV,but also an active component to improve the separation of morpholinium cations.It was found that morpholinium cations could be adequately determined when0.5 mmol/L 1-ethyl-3-methylimidazolium tetrafluoroborate aq.soln./methanol（80：20,v/v） was used as mobile phase with an IUV detection wavelength of 210 nm.In this study,the baseline separation of Nmethyl,ethylmorpholinium cations（MEMo） and N-methyl.propylmorpholinium cations（MPMo） was successfully achieved in 8.5 min.The detection limits（S/N = 3） for MEMo and MPMo were 0.15 and0.29 mg/L,respectively.This simple and practical method has been successfully applied to the determination of two morpholinium ionic liquids synthesized by the chemistry laboratory.

Olefin-linked covalent organic frameworks with twisted tertiary amine knots for enhanced ultraviolet detection

Though Olefin-linked covalent organic frameworks(oCOFs)possess excellentπ-electron delocalization,the barely reversible olefin linkage brings challenges for oCOFs’synthesis and functionalization.Here,we synthesize new oCOFs with tertiary amine knots which have twisted configuration and electron-donating nature.Investigation into the structural variation and photoelectric performance shows that the twisted configuration of oCOF-TFPA could favor to the intramolecular charge transfer process and reduce the pos-sibility of aggregation-caused quenching.Photoelectrical measurements and electric band structure cal-culation both verify the superiority of this oCOFs’structure in photoelectric sensing.

Amplified ultraviolet detection of natural DNA based on Mo_6S_(9-x)I_x nanowires

We demonstrate that Mo6S9-xIx nanowires （MoSI NWs） can serve as an excellent signal-intensifying nanomaterial for highly sensitive and label-free detection of DNA by ultraviolet （UV） spectrophotometry. The DNA extinction at 260 nm was greatly enhanced after addition of MoSI NWs solute, and the extinction value was linear with DNA concentration in the range of 0.0289-11.68 μg/mL with the real determination limit of 28.9 ng/mL. The association of DNA with the nanowires was characterized by transmission electronmicroscopy and circular dichroic spectroscopy. The results illustrate that the UV response amplification of DNA in the presence of MoSI NWs is attributed to the greater DNA coverage on the MoSI NW surface and the conformational transformation of DNA due to interaction of DNA with MoSI NWs. MoSI NWs are a promising nano-structured material for developing ultrasensitive sensors for detection of DNA.

Organometallic perovskite single crystals grown on lattice-matched substrate for photodetection

In this work,we demonstrate that an organometallic perovskite(OP)single crystal for effective photodetection can be grown on a gold(Au)-decorated substrate using liquid phase epitaxy.The covered gold could both control the shape of the epitaxial layer and act as its electrodes.An MAPbCl3 single crystal and an MAPbBr1.5Cl1.5 single crystal were used as the substrate and the epitaxial layer,respectively.The device,with an Au-perovskite-Au structure,can be fully characterized.Due to the high-quality epitaxial layer,the maximum external quantum efficiency(EQE)value is over 60%under the voltage of
20 V.In addition,the response speed can reach 200 and 500 ns(ns)rise and fall,respectively.Our work provides an effective and promising method to fabricate efficient perovskite-based photodetectors.

Recent progress of SiC UV single photon counting avalanche photodiodes

4H-SiC single photon counting avalanche photodiodes(SPADs)are prior devices for weak ultraviolet(UV)signal detection with the advantages of small size,low leakage current,high avalanche multiplication gain,and high quantum efficiency,which benefit from the large bandgap energy,high carrier drift velocity and excellent physical stability of 4 H-SiC semiconductor material.UV detectors are widely used in many key applications,such as missile plume detection,corona discharge,UV astronomy,and biological and chemical agent detection.In this paper,we will describe basic concepts and review recent results on device design,process development,and basic characterizations of 4 H-SiC avalanche photodiodes.Several promising device structures and uniformity of avalanche multiplication are discussed,which are important for achieving high performance of 4 HSiC UV SPADs.

Dual-functional hydrogen-bonded organic frameworks for aniline and ultraviolet sensitive detection

A novel hydrogen-bonded organic frameworks(HOFs)FJU-200 has been constructed from N,N’-bis(5-isophthalic acid)naphthalimide(H_(4)L).FJU-200 has a good dual-function of aniline and ultraviolet detection.FJU-200 is the first case of HOF with dual sensing of visual color changes and photoluminescence quenching for aniline detection,and the detection limit of aniline can reach5.5 x 10^(-4)mol/L.Under ultraviolet FJU-200 will rapidly change from light yellow to rustic brown,which makes it possible to use FJU-200 to achieve minute-level ultraviolet detection.Moreover,for more convenient use,FJU-200 test papers are prepared.Using them,convenient and fast aniline or ultraviolet detection can be realized.The single-crystal X-ray structures show that compared with the original FJU-200,both PhNH_(2)@FJU-200 and UV-FJU-200 have larger pore sizes,and the dihedral angles of the H_(2)L^(2-)in framework has been changed.

离子排斥色谱用于厌氧消化处理的水中脂肪族羧酸的分析(英文)

The analysis of seven aliphatic carboxylic acids(formic,acetic,propionic,iso-butyric,n-butyric,iso-valeric and n-valeric acid) in anaerobic digestion process waters for biogas production was examined by ion-exclusion chromatography with dilute acidic eluents(benzoic acid,perfluorobutyric acid(PFBA) and sulfuric acid) and non-suppressed conductivity/ultraviolet(UV) detection.The columns used were a styrene/divinylbenzene-based strongly acidic cation-exchange resin column(TSKgel SCX) and a polymethacrylate-based weakly acidic cation-exchange resin column(TSKgel Super IC-A/C).Good separation was performed on the TSKgel SCX in shorter retention times.For the TSKgel Super IC-A/C,peak shape of the acids was sharp and symmetrical in spite of longer retention times.In addition,the mutual separation of the acids was good except for iso-and n-butyric acids.The better separation and good detection was achieved by using the two columns(TSKgel SCX and TSKgel Super IC-A/C connected in series),lower concentrations of PFBA and sulfuric acid as eluents,non-suppressed conductivity detection and UV detection at 210 nm.This analysis was applied to anaerobic digestion process waters.The chromatograms with conductivity detection were relatively simpler compared with those of UV detection.The use of two columns with different selectivities for the aliphatic carboxylic acids and the two detection modes was effective for the determination and identification of the analytes in anaerobic digestion process waters containing complex matrices.

Rapid and simultaneous determination of imidazolium and pyridinium ionic liquid cations by ion-pair chromatography using a monolithic column

A method for rapid and simultaneous determination of imidazolium and pyridinium ionic liquid cations by ion-pair chromatography with ultraviolet detection was developed. Chromatographic separations were performed on a reversed-phase silica-based monolithic column using 1-heptanesulfonic acid sodium-acetonitrile as mobile phase. The effects of ion-pair reagent and acetonitrile concentration on retention of the cations were investigated. The retention times of the cations accord with carbon number rule. The method has been successfully applied to the determination of four ionic liquids synthesized by organic chemistry laboratory.

High-performance liquid chromatography utilization of ionic liquids as mobile phase additives for separation and determination of the isomers of amino benzoic acids

For the isomers of amino benzoic acid, including o-, m-, p-amino benzoic acid, the beneficial effects of using the ionic liquid, l-butyl-3-methylimidazolium tetrafluoroborate （[BMIm][BF4]）, as mobile phase additives on retention behavior and separation were investigated. Chromatographic separation of the o-, m-, p-amino benzoic acid was performed on a reversed-phase C18 column by ultraviolet detection at 245 nm. The effects of several chromatographic parameters, concentrations and pH values of [BMIm][BF4] solutions, methanol concentration and length of alkyl chain on different ionic liquids, on the separation and determination of the isomers were evaluated. The optimized chromatographic conditions were established using an aqueous 0.5 mmol/L [BMIm][BF4] solution （pH 3.0）/methanol （40：60, v/v） as mobile phase without need of gradient eiution, with separation of three amino benzoic acids achieved within four min. The calibration curve showed good linearity over the tested range of 2 mg/L to 120 mg/L for the three isomers with a correlation coefficients of 0.9999. The recoveries of the three amino benzoic acids of spiked components were between 99.8% and 100%. The method has been successfully applied to the determination of p-amino benzoic acid in the pharmaceutical, Bromine Mitag Procaine Injection.