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排序方式: 共有672条查询结果,搜索用时 11 毫秒
51.
Libuse Trnkova Ladislav Novotny Nuria Serrano Katerina Klosova Petra Polaskova 《Electroanalysis》2010,22(16):1873-1880
Elimination voltammetry with linear scan (EVLS) in connection with renewed mini‐ drop mercury electrodes provides valuable information about the character and kinetics of processes at electrode/electrolyte interfaces. Based on the experiment related to the hydrogen evolution, it is presented that the EVLS is more sensitive than other voltammetric methods. Using miniaturized mercury electrodes, the EVLS is capable of detecting the effect of spherical diffusion associated with both the scan rates and the size of an electrode drop. 相似文献
52.
Analyzing highly charged protein ions by ion trap instruments has been hindered by the low resolving power and the space charge effect. To improve mass resolution, the resonant ejection scan rate was often decreased, causing long cycle time that was not compatible with a chromatographic time scale. We described a new method that allowed the acquisition of high-resolution protein mass spectra on a chromatography time scale. The method was based on the data-dependant enhanced resolution scan (DDER) function of the triple quadrupole linear ion trap (Q Trap). We demonstrated the effectiveness of the method by analyzing liquid chromatography-resolved polypeptide components of a monoclonal antibody. The results showed that DDER-derived spectra significantly improved the resolution and accuracy for deconvoluted mass. Our approach would extend the utilities of ion trap instruments in protein analysis. 相似文献
53.
建立了直接进样电喷雾串联质谱测定草鱼肌肉组织中磷脂的方法.以Bligh Dyer法提取总脂质,采用流动注射泵直接进样的方式将样品导人电喷雾离子源,利用串联三重四级杆质谱的母离子扫描和中性丢失扫描功能,通过扫描磷脂的特征性子离子或中性质量丢失实现对磷脂酰胆碱、磷脂酰乙醇胺、磷脂酰肌醇、磷脂酰丝氨酸、磷脂酰甘油和磷脂酸六类磷脂的源内分离和鉴定.结果显示,在-定的浓度范围内,磷脂的浓度与磷脂直接进样电喷雾电离后形成准分子离子的响应值呈现良好的线性关系,回收率(67.1%~96.6%)和精密度可以满足生物样品分析的要求.采用本方法测定了草鱼肌肉组织中磷脂酰胆碱、磷脂酰乙醇胺、磷脂酰肌醇和磷脂酰丝氨酸4类磷脂的分子种及含量.本方法前处理简单,定性和定量分析快速准确,可以应用于其它生物样本脂质组学中磷脂的分析. 相似文献
54.
Dobson G Murrell J Despeyroux D Wind F Tabet JC 《Journal of mass spectrometry : JMS》2004,39(11):1295-1304
Electrospray ionization mass spectra obtained from different scan directions are observed to be dependent on the axial modulation potential amplitudes used for resonant ejection and on the positive deviation caused by higher even-multipole fields present in most commercial ion traps. The axial modulation voltage influences the dissociation of ions during resonant ejection and the observed mass shifts. The higher even-multipole fields in commercial ion traps are known to influence resonant ejection from the ion trap and can cause a loss in mass resolution for peaks in reverse scan mass spectra compared with that obtained by the forward scan. However, along with the dissociation of ions during resonant ejection causing a loss in resolution, the possibility of resolving an isotopic distribution is also shown to be influenced by the mass shifts caused by the space charge. These mass shifts differ depending on the scan direction employed. A significant loss in resolution can also result from resonant ejection using non-optimal axial modulation voltages. We also present results showing the ejection of ions at betaz = 1/2 using the reverse scan mode without the axial modulation voltage. Ion ejection at betaz = 1/2 is uncommon in commercial (stretched ion traps) with the conventional analytical scan without the use of a frequency of the axial modulation voltage corresponding to this non-linear resonance. 相似文献
55.
《Electroanalysis》2004,16(12):1051-1058
The voltammetric behavior of α‐ketoglutarate (α‐KG) at the hanging mercury drop electrode (HMDE) has been investigated in acetate buffer solution. Under the optimum experimental conditions (pH 4.5, 0.2 M NaAc‐HAc buffer solution), a sensitive reductive wave of α‐KG was obtained by linear scan voltammetry (LSV) and the peak potential was ?1.18 V (vs. SCE), which was an irreversible adsorption wave. The kinetic parameters of the electrode process were α=0.3 and ks=0.72 1/s. There was a linear relationship between peak current ip, α‐KG and α‐KG concentration in the range of 2×10?6–8×10?4 M α‐KG. The detection limit was 8×10?7 M and the relative standard deviation was 2.0% (Cα‐KG=8×10?4 M, n=10). Applications of the reductive wave of α‐KG for practical analysis were addressed as follows: (1) It can be used for the quantitative analysis of α‐KG in biological samples and the results agree well with those obtained from the established ultraviolet spectrophotometric method. (2) Utilizing the complexing effect between α‐KG and aluminum, a linear relationship holds between the decrease of peak current of α‐KG Δip and the added Al concentration Cequation/tex2gif-inf-5.gif in the range of 5.0×10?6–2.5×10?4 M. The detection limit was 2.2×10?6 M and the relative standard deviation was 3.1% (Cequation/tex2gif-inf-6.gif=4×10?5 M, n=10). It was successfully applied to the detection of aluminum in water and synthetic biological samples with satisfactory results, which were consistent with those of ICP‐AES. (3) It was also applied to study the effect of AlIII on the glutamate dehydrogenase (GDH) activity in the catalytically reaction of α‐KG+NH +NADH?L ‐glutamate+NAD++H2O by differential pulse polarography (DPP) technique. By monitoring DPP reductive currents of NAD+ and α‐KG, an elementary important result was found that Al could greatly affect the activity of GDH. This study could be attributed to intrinsic understanding of the aluminum's toxicity in enzyme reaction processes. 相似文献
56.
ELECTROCHEMICAL POLYMERIZATION OF ANILINE IN PHOSPHORIC ACID AND THE PROPERTIES OF POLYANILINE 总被引:1,自引:0,他引:1
The behavior of the electrochemical polymerization of aniline in a weak acid, phosphoric acid, is very similar to that in strong acids, i.e. its polymerization rate increases quickly with the electrolysis time. The FTIR spectra of polyaniline samples synthesized in phosphoric acid indicate that the counter ion H2PO4^- is present in both the oxidized form and the reduced form of polyaniline. The counter ion plays an important role in adjusting the pH value at the electrode surface of polyaniline during the oxidation and reduction processes. As a result, a pair of redox peaks still appear in cyclic voltammograms of polyaniline in a solution of sodium sulfate of pH 5.5 and in a solution of NaH2PO4 of pH 7.0,respectively, at low potential scan rate; and the color of polyaniline film also changes with applied potential at pH 7.0. Thus,the pH region for the electrochemical activity and the electrochromism of polyaniline is extended to pH 5.5 for a solution of sodium sulfate and to pH 7.0 for a solution of NaH2PO4. The conductivity of polyaniline is 3.3 S cm^-1, depending on the concentration of phosphoric acid used in the stage of polymerization of aniline. The result of elemental analysis of polyaniline is presented here. 相似文献
57.
《Analytical letters》2012,45(9):1523-1531
Abstract A new TLC-fluorescence spectrodensitometry method is described for the simultaneous determination of trace ofloxacin and enoxacin, using a optimized mobile phase of chloroformmethanolethyl acetatetetrahydrofuranaqueous ammonia (6:4.6:1.5:0.8:1.5, V/V). The influence of the silica gel plates previously treated with various concentrations of sodium edetate solution in various pH's are studied. Their R, values are 0.54 and 0.29 respectively. The excitation, wavelength is 335nm. The linear ranges are 0~75ng. The relative standard deviations are <6.9%. The mean recovery of the two antibiotics in body fluid ranged from 95.4% to 105.2%. 相似文献
58.
59.
Interfacial bonding mechanism and bonding strength of AlTiCrN coating by cathodic arc ion plating 下载免费PDF全文
AlTiCrN coating was prepared on the surface of YT14 tungsten carbide cutting tools by cathodic arc ion plating with Ti, Al and Cr as targets. The surface morphologies, interface energy spectrum, phase and elements' binding energy of the coatings were observed with SEM, EDS, XRD and XPS, respectively, and bonding strength of the coating interface was measured with scratch tester. The results show that the phases of AlTiCrN coating are mainly composed of AlN, CrN and TiN, the crystal plane of (111) has a strong preferred orientation. The concentrations of Al, Ti, Cr, N in the coating are higher than those in the substrate, showing the gradient diffusion distribution at the bonding interface, while C atoms of the substrate have diffused into the lattices of TiN, AlN and CrN to form an obvious interdiffusion layer, and the average bonding strength of coating interface is 57.65 N. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
60.
Anneli Kruve Riin Rebane Karin Kipper Maarja-Liisa Oldekop Hanno Evard Koit Herodes Pekka Ravio Ivo Leito 《Analytica chimica acta》2015
This is the part I of a tutorial review intending to give an overview of the state of the art of method validation in liquid chromatography mass spectrometry (LC–MS) and discuss specific issues that arise with MS (and MS/MS) detection in LC (as opposed to the “conventional” detectors). The Part I briefly introduces the principles of operation of LC–MS (emphasizing the aspects important from the validation point of view, in particular the ionization process and ionization suppression/enhancement); reviews the main validation guideline documents and discusses in detail the following performance parameters: selectivity/specificity/identity, ruggedness/robustness, limit of detection, limit of quantification, decision limit and detection capability. With every method performance characteristic its essence and terminology are addressed, the current status of treating it is reviewed and recommendations are given, how to determine it, specifically in the case of LC–MS methods. 相似文献