共查询到20条相似文献,搜索用时 15 毫秒
1.
Ferrocene-mediated carbon paste electrode modified with d-fructose dehydrogenase for batch mode measurement of d-fructose 总被引:1,自引:0,他引:1
A mediated modified carbon paste and renewable surface electrode for fructose amperometric measurement based on d-fructose dehydrogenase (FDH) was prepared and optimized. Commercially available ferrocene (FcH) and hydroxymethyl ferrocene
(FcCH2OH) were used as mediators. The substituted FcH showed better linearity and higher sensitivity. The influence of different
experimental parameters was studied for optimum analytical performance. The final FDH-modified electrode showed good analytical
performance for batch mode measurements of fructose. 相似文献
2.
Yu. S. Nekrasov R. S. Skazov A. A. Simenel L. V. Snegur I. V. Kachala 《Russian Chemical Bulletin》2006,55(8):1368-1371
The electrospray ionization behavior of some ferrocenylalkylazoles CpFeC5H4CH(R)Az (AzH are derivatives of imidazole, pyrazole, triazole and their benzo analogs; R = H, Me, Et, Ph), ferrocenylalkanols
CpFeC5H4CH(R)OH (R = H, Me), and mixtures of the latter with azoles was studied. The electrospray ionization mass spectra of these
compounds, in addition to the molecular ion [M]+·, the protonated molecule [M + H]+, and ferrocenylalkyl cation [FcCHR]+ peaks, exhibit also intensive peaks for the binuclear ions [(FcCHR)2X]+ (X = Az or O), resulting from ferrocenylalkylation of the initial compounds with the ferrocenylalkyl cations. Electrospray
ionization of an equimolar mixture of ferrocenylmethanol FcCH2OH and imidazole gives the protonated ferrocenylmethylimidazole molecule [FcCH2Im + H]+ and the [FcCH2(Im)2 + H]+ dimer, apart from the ions typical of each component, i.e., ferrocenylalkylation of azoles with the ferrocenylalkylcarbinols, known in the chemistry of solutions, takes place under
electrospray conditions.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1318–1321, August, 2006. 相似文献
3.
Desorption electrospray ionization-mass spectrometry (DESI-MS) was evaluated for the direct analysis of liquid samples. Several
interesting results were found. First, in contrast to the previous DESI analysis of dried solid samples that was limited to
proteins with MW ≤25 kDa (Anal. Chem. 2007, 79, 3514), bovine serum albumin (BSA, 66 kDa) was successfully ionized from solutions by DESI with observation of corresponding
multiply charged ions. Second, direct DESI analysis of protein tryptic digest solutions without chromatographic separation,
sample clean-up, and the sample drying step was demonstrated, providing reasonably good sequence coverage of 52% to 97%. Third,
direct analysis of biofluids such as an undiluted urine sample without sample pretreatment is possible, emphasizing the high
tolerance of DESI with salt. These results suggest that a charged droplet pick-up mechanism is responsible for desorption
and ionization of liquid samples by DESI. Also, unlike in electrospray ionization (ESI), inhibition of electrochemical reduction
in the negative ion mode was observed for liquid sample DESI. In addition, reactive DESI can be performed with ion/ion reactions
of Zn(II) complexes for the selective binding of phosphoserine in the presence of serine. DESI experiment can also be carried
out directly to liquid samples flowing out of a pumped syringe needle tip, allowing rapid analysis. Furthermore, on-line coupling
of electrochemical cell with DESI-MS was demonstrated, in which perylene radical cations generated in the cell were successfully
transferred to the gas-phase for MS detection by DESI. This study extended the scope of DESI-MS applications, which could
have potentials in bioanalytical and forensic analysis. 相似文献
4.
Joanna E. Barbara John R. Eyler David H. Powell 《Rapid communications in mass spectrometry : RCM》2008,22(24):4121-4128
Reactive desorption electrospray ionization (DESI), an ambient technique, has been explored as a tool for the development of a fast screening approach for supramolecular complexes capitalizing on the specificity of mass spectrometric detection. A library of twelve potential guests for inclusion by a β‐cyclodextrin host was initially screened via DESI using a spray solution incorporating the host directed toward an array of deposited guests. The steroid nortestosterone was used to verify the applicability of reactive DESI for complexation experiments with β‐cyclodextrin. Results from the DESI experiment and results from an analogous electrospray ionization (ESI) mass spectral screen were compared with solution‐phase data obtained by nuclear magnetic resonance (NMR) spectroscopy. The complexes detected using DESI were identical to those determined using NMR, validating the applicability of the technique to supramolecular applications, but the ESI data exhibited significant disparities, predominantly due to the interference of nonspecific artifacts. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
5.
Yu.S. Nekrasov 《Journal of organometallic chemistry》2009,694(12):1807-1812
Under the conditions of electrospray ionization of ferrocenylalkyl azoles FcCH(R)X (Fc-η5-C5H5Fe-η5-C5H4, R - H, Me, XH - 2-methyl imidazole, pirazole) the processes of oxidation, protonation, fragmentation and ferrocenylalkylation to form, molecular ions [М]+, protonated molecules [М+Н]+, ferrocenylalkyl cations [FсCHR]+ and bisferrocenylalkyl azole cations [(FcCHR)2X]+, respectively, take place. Using special experimental techniques (deuterated solvents, saturation of ionic source of an ESI mass-spectrometer by the vapors of solvents, the experiments under the “inverse” ESI conditions when the solvent is subjected to electrospray in the presence of ferrocenylalkyl derivative vapours) and quantum-chemical calculations at the level of the B3LYP/LanL2DZ theory the scheme of the formation of these ions in a gas phase according to the mechanism of “activating protonation” was suggested. it was found that all these ions are formed through the protonation stage, which is taking place mainly in a gas phase. The key stage is the exothermic process of the protonation of the initial compounds by hydroxonium ions giving rise to protonated [M+H]+ molecules which further oxidize and alkylate ferrocenylalkylazoles to form molecular radical cations and bisferrocenylalkyl azole ions [FcCH(Me)-X-CH(Me)Fc]+. The decomposition of protonated ions with the elimination of the azole molecule gives rise to ferrocenylalkyl cations [FсCHR]+ capable in turn of oxidizing and alkylating the initial compounds. 相似文献
6.
Summary Three-component systems of ferrocene (FcH): carbon tetrachloride: tetranitromethane have been investigated spectrally in the 290–800 nm range. Quantitative relationships were investigated between electron-donor acceptor (EDA) complexes of ferrocene and CCl4 (FcH · CCl4) and C(NO2)4 [FcH · C(NO2)4] and the ferricenium cation (FcH+) which is formed as a result of dissociation of complexes and which depends upon the initial concentration of C(NO2)4 and duration the reaction. The results prove the destabilizing influence of C(NO2)4 on the EDA complex of ferrocene and CCl4. 相似文献
7.
Ferrocenylmethyldimethylamine, FcCH2NMe2, reacts with CH2Cl2 in either the presence or absence of non-coordinating counterions to give equimolar amounts of the bis(ferrocenylmethyl)dimethyl ammonium salts (FcCH2)2NMe2+X− (X−=PF6−, SbF6−, BPh4− or Cl−, 1a–d) and the corresponding protonated ammonium salts FcCH2NMe2H+ which have been isolated as the SbF6− and Cl− salts 2b,d. The reaction proceeds via fragmentation of an intermediate quaternary chloromethylated ammonium ion to chloromethylferrocene, FcCH2Cl, and dimethyliminium chloride NMe2CH2+Cl−. The parent amine acts as a nucleophile toward FcCH2Cl to give 1a–d and as a base toward NMe2CH2+ to give FcCH2NMe2H+, NMe2H and (Me2N)2CH2. The FcCH2Cl intermediate is intercepted by NEt3 while KCN or LiH do not successfully compete with FcCH2NMe2. A new, non-toxic, selective, high-yield route to 1d is also presented. Electrochemistry and UV–vis spectroelectrochemistry reveal, that the two identical redox centers in 1a–d are essentially non-interacting. Individual E1/2 values have been determined for different solvents by digital simulation. The corresponding ferrocenium salts were prepared by either chemical or electrochemical means and accordingly characterized. Our studies are augmented by X-ray structure analyses of 1b, 1d and 2d. 1d contains three different cation conformers and four molecules of water per unit cell. The latter are hydrogen bonded to the chloride counterions to form one-dimensional infinite chains parallel to the a axis. 相似文献
8.
Christian Berchtold Vivian Müller Lukas Meier Stefan Schmid Renato Zenobi 《Journal of mass spectrometry : JMS》2013,48(5):587-593
Most pesticides, herbicides and other plant treatment agents are applied to the crop surface. Direct mass spectrometric methods, such as desorption electrospray ionization (DESI), offer new ways to analyze plant samples directly and rapidly. A strategy for the development and optimization of a DESI method for the direct determination of chemicals on complex surfaces is described. Chlorpropham (CP) was applied to potato surfaces as an example for a crop protection agent and analyzed using a self‐made DESI source. Aspects such as instrument selectivity, sensitivity and reproducibility were investigated. The MS4 fragmentation pattern of CP was analyzed to achieve the necessary detection selectivity, and is discussed in detail. Similar fragmentation was found in the ESI and DESI mass spectra, indicating that the mechanisms of ESI and DESI are closely related. A DESI method for semi‐quantification of CP on potatoes was developed. Detection limits of 6.5 µg/kg were found using MS/MS. The reproducibility, in the range of 12% (signal variation), appears to be sufficient for semi‐quantitative measurements. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
9.
Gabriela Petroselli Mridul Kanti Mandal Lee Chuin Chen Gustavo T. Ruiz Ezequiel Wolcan Kenzo Hiraoka Hiroshi Nonami Rosa Erra‐Balsells 《Journal of mass spectrometry : JMS》2012,47(3):313-321
A group of rhenium (I) complexes including in their structure ligands such as CF3SO3‐, CH3CO2‐, CO, 2,2′‐bipyridine, dipyridil[3,2‐a:2′3′‐c]phenazine, naphthalene‐2‐carboxylate, anthracene‐9‐carboxylate, pyrene‐1‐carboxylate and 1,10‐phenanthroline have been studied for the first time by mass spectrometry. The probe electrospray ionization (PESI) is a technique based on electrospray ionization (ESI) that generates electrospray from the tip of a solid metal needle. In this work, mass spectra for organometallic complexes obtained by PESI were compared with those obtained by classical ESI and high flow rate electrospray ionization assisted by corona discharge (HF‐ESI‐CD), an ideal method to avoid decomposition of the complexes and to induce their oxidation to yield intact molecular cation radicals in gas state [M]+. and to produce their reduction yielding the gas species [M]–.. It was found that both techniques showed in general the intact molecular ions of the organometallics studied and provided additional structure characteristic diagnostic fragments. As the rhenium complexes studied in the present work showed strong absorption in the UV–visible region, particularly at 355 nm, laser desorption ionization (LDI) mass spectrometry experiments could be conducted. Although intact molecular ions could be detected in a few cases, LDI mass spectra showed diagnostic fragments for characterization of the complexes structure. Furthermore, matrix‐assisted laser desorption ionization (MALDI) mass spectra were obtained. Nor‐harmane, a compound with basic character, was used as matrix, and the intact molecular ions were detected in two examples, in negative ion mode as the [M]–. species. Results obtained with 2‐[(2E)‐3‐(4‐tert‐buthylphenyl)‐2‐methylprop‐2‐enylidene] malononitrile (DCTB) as matrix are also described. LDI experiments provided more information about the rhenium complex structures than did the MALDI ones. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
10.
Brent N. Jewett Louis Ramaley Jan C. T. Kwak 《Journal of the American Society for Mass Spectrometry》1999,10(6):529-536
This paper compares two liquid introduction atmospheric pressure ionization techniques for the analysis of alkyl ethoxysulfate (AES) anionic surfactant mixtures by mass spectrometry, i. e., electrospray ionization (ESI) in both positive and negative ion modes and atmospheric pressure chemical ionization (APCI) in positive ion mode, using a triple quadrupole mass spectrometer. Two ions are observed in ESI(+) for each individual AES component, [M + Na]+ and a “desulfated” ion [M − SO3 + H]+, whereas only one ion, [M − Na]− is observed for each AES component in ESI(−). APCI(+) produces a protonated, “desulfated” ion of the form [M − NaSO3 + 2H]+ for each AES species in the mixture under low cone voltage (10 V) conditions. The mass spectral ion intensities of the individual AES components in either the series from ESI(+) or APCI(+) can be used to obtain an estimate of their relative concentrations in the mixture and of the average ethoxylate (EO) number of the sample. The precursor ions produced by either ESI(+) or ESI(−), when subjected to low-energy (50 eV) collision-induced dissociation, do not fragment to give ions that provide much structural information. The protonated, desulfated ions produced by APCI(+) form fragment ions which reveal structural information about the precursor ions, including alkyl chain length and EO number, under similar conditions. APCI(+) is less susceptible to matrix effects for quantitative work than ESI(+). Thus APCI(+) provides an additional tool for the analysis of anionic surfactants such as AES, especially in complex mixtures where tandem mass spectrometry is required for the identification of the individual components. 相似文献
11.
Solvent effects on the electron donor acceptor complex properties of ferrocene and tetranitromethane
Summary Spectral investigations in the 350–800 nm range of ferrocene (FcH) and tetranitromethane [C(NO2)4] solutions in cyclohexane and carbon tetrachloride at concentration-constant (FcH) and variable (tetranitromethane) were
made. The electron donor acceptor (EDA) complex of ferrocene and tetranitromethane and its dissociation to the ferricenium
cation (FcH+) were studied as a function of the solvent, the initial C(NO2)4 concentration and reaction time. 相似文献
12.
Desorption electrospray ionization (DESI) mass spectrometry is applied to the in situ detection of alkaloids in the tissue of poison hemlock (Conium maculatum), jimsonweed (Datura stramonium) and deadly nightshade (Atropa belladonna). The experiment is carried out by electrospraying micro-droplets of solvent onto native or freshly-cut plant tissue surfaces. No sample preparation is required and the mass spectra are recorded under ambient conditions, in times of a few seconds. The impact of the sprayed droplets on the surface produces gaseous ions from organic compounds originally present in the plant tissue. The effects of operating parameters, including the electrospray high voltage, heated capillary temperature, the solvent infusion rate and the carrier gas pressure on analytical performance are evaluated and optimized. Different types of plant material are analyzed including seeds, stems, leaves, roots and flowers. All the previously reported alkaloids have been detected in C. maculatum, while fifteen out of nineteen known alkaloids for D. stramonium and the principal alkaloids of A. belladonna were also identified. All identifications were confirmed by tandem mass spectrometry. Results obtained show similar mass spectra, number of alkaloids, and signal intensities to those obtained when extraction and separation processes are performed prior to mass spectrometric analysis. Evidence is provided that DESI ionization occurs by both a gas-phase ionization process and by a droplet pick-up mechanism. Quantitative precision of DESI is compared with conventional electrospray ionization mass spectrometry (after sample workup) and the RSD values for the same set of 25 dicotyledonous C. maculatum seeds (one half of each seed analyzed by ESI and the other by DESI) are 9.8% and 5.2%, respectively. 相似文献
13.
Pablo Martínez-Lozano Juan Fernández de la Mora 《Journal of the American Society for Mass Spectrometry》2009,20(6):1060-1063
Vapors released by the skin in the hand of one human subject are detected in real time by sampling them directly from the
ambient gas surrounding the hand, ionizing them by secondary electrospray ionization (SESI, via contact with the charged cloud
from an electrospray source), and analyzing them in a mass spectrometer with an atmospheric pressure source (API-MS). This
gas-phase approach is complementary to alternative on-line surface ionization methods such as DESI and DART. A dominating
peak of lactic acid and a complete series of saturated and singly unsaturated fatty acids (C12 to C18) are observed, in accordance with previous off-line studies by gas chromatography-mass spectrometry. Several other metabolites
have been identified, including ketomonocarboxylic and hydroxymonocarboxylic acids. 相似文献
14.
Myung S Wiseman JM Valentine SJ Takats Z Cooks RG Clemmer DE 《The journal of physical chemistry. B》2006,110(10):5045-5051
A desorption electrospray ionization (DESI) source has been coupled to an ion mobility time-of-flight mass spectrometer for the analysis of proteins. Analysis of solid-phase horse heart cytochrome c and chicken egg white lysozyme proteins with different DESI solvents and conditions shows similar mass spectra and charge state distributions to those formed when using electrospray to analyze these proteins in solution. The ion mobility data show evidence for compact ion structures [when the surface is exposed to a spray that favors retention of "nativelike" structures (50:50 water:methanol)] or elongated structures [when the surface is exposed to a spray that favors "denatured" structures (49:49:2 water:methanol:acetic acid)]. The results suggest that the DESI experiment is somewhat gentler than ESI and under appropriate conditions, it is possible to preserve structural information throughout the DESI process. Mechanisms that are consistent with these results are discussed. 相似文献
15.
Zhixin Miao Shiyong Wu Hao Chen 《Journal of the American Society for Mass Spectrometry》2010,21(10):1730-1736
The direct sampling feature of liquid sample desorption electrospray ionization (DESI) allows the ionization of liquid samples
without adding acids/organic solvents (i.e., without sample pretreatment). As a result, it provides a new approach for probing
protein conformation in solution. In this study, it has been observed that native protein ions are generated from proteins
in water by DESI. Interestingly, the intensities of the resulting protein ions appear to be higher than those generated by
ESI of the proteins in water or in ammonium acetate. For protein solutions that already contain acids/organic solvents, DESI
can be used to investigate the influences of these denaturants on protein conformations and the obtained results are in good
agreement with spectroscopic data. In addition, online monitoring of protein conformational changes by DESI is feasible; for
instance, heat-induced unfolding of ubiquitin can be traced with DESI in water without influences of organic solvents/acids.
This DESI method provides a new alternative tool for the study of protein conformation in solution. 相似文献
16.
Nefliu M Smith JN Venter A Cooks RG 《Journal of the American Society for Mass Spectrometry》2008,19(3):420-427
The internal energy distributions of typical ions generated by desorption electrospray ionization (DESI) were measured using the "survival yield" method, and compared with corresponding data for electrospray ionization (ESI) and electrosonic spray ionization (ESSI). The results show that the three ionization methods produce populations of ions having internal energy distributions of similar shapes and mean values (1.7-1.9 eV) suggesting similar phenomena, at least in the later stages of the process leading from solvated droplets to gas-phase ions. These data on energetics are consistent with the view that DESI involves "droplet pick-up" (liquid-liquid extraction) followed by ESI-like desolvation and gas-phase ion formation. The effects of various experimental parameters on the degree of fragmentation of p-methoxy-benzylpyridinium ions were compared between DESI and ESSI. The results show similar trends in the survival yields as a function of the nebulizing gas pressure, solvent flow rate, and distance from the sprayer tip to the MS inlet. These observations are consistent with the mechanism noted above and they also enable the user to exercise control over the energetics of the DESI ionization process, through manipulation of external and internal ion source parameters. 相似文献
17.
18.
Glenn A. Harris Dana M. Hostetler Christina Y. Hampton Facundo M. Fernández 《Journal of the American Society for Mass Spectrometry》2010,21(5):855-863
The internal energy (Eint) distributions of a series of p-substituted benzylpyridinium ions generated by both direct analysis in real time (DART) and electrospray ionization (ESI)
were compared using the “survival yield” method. DART mean Eint values at gas flow rates of 2, 4, and 6 L min−1, and at set temperatures of 175, 250, and 325 °C were in the 1.92–2.21 eV range. ESI mean Eint at identical temperatures in aqueous and 50% methanol solutions ranged between 1.71 and 1.96 eV, and 1.53 and 1.63 eV, respectively.
Although the results indicated that ESI is a “softer” ionization technique than DART, there was overlap between the two techniques
for the particular time-of-flight mass spectrometer used. As a whole, there was an increase in Eint with increasing reactive and drying gas temperatures for DART and ESI, respectively, indicating thermal ion activation. Three
dimensional computational fluid dynamic simulations in combination with direct temperature measurements within the DART ionization
region revealed complex inversely coupled fluid-thermal phenomena affecting ion Eint values during atmospheric transport. Primarily, that DART gas temperature in the ionization region was appreciably less than
the set gas temperature of DART due to the set gas flow rates. There was no evidence of Eint deposition pathways from metastable-stimulated desorption, but fragmentation induced by high-energy helium metastables was
observed at the highest gas flow rates and temperatures. 相似文献
19.
Rafał Frański 《Journal of mass spectrometry : JMS》2004,39(3):272-276
The complexes of 2,5-disubstituted-1,3,4-oxadiazoles, namely 2,5-diphenyl-1,3,4-oxadiazole (1), 2,5-bis(2-pyridyl)-1,3,4-oxadiazole (2) and 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (3), with copper cation were studied by electrospray ionization mass spectrometry (ESI-MS). The ability of the compounds studied to form complexes with copper (under the ESI conditions) can be ordered as 2 > 1 > 3. The compounds studied tend to form both 1 : 1 and 2 : 1 chelate complexes with both copper(II) and copper(I). The complexes with copper(I) are formed in the ESI process. The influence of solvent polarity, solution flow-rate, counter ions (Cl−, NO3−, CH3COO−, SO42−, acetylacetonates) on the type of the ions observed was studied. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献