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1.
We provide a highly sensitive and selective assay to detect Hg2+ in aqueous solutions using a novel β-functionalised porphyrin-based chemosensor 5 at room temperature. The binding properties of the chemosensor 5 for cations were examined by UV–vis spectroscopy and 1H NMR. The results indicate that a 1:1 stoichiometric complex is formed between chemosensor 5 and mercury (II) ion. The recognition mechanism between chemosensor 5 and metal ion was discussed based on their absorbance changes and the chemical shift changes when they interact with each other. Control experiments revealed that chemosensor 5 has a selective response to mercury (II) ion compared with other metal ions.  相似文献   

2.
Matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) and electrospray ionization mass spectrometry (ESI-MS) are used to evaluate the alkali metal ion binding selectivities of a series of calixarenes. Each calixarene of interest is mixed with one or more alkali metal salts (1:100 ratio of calixarene to metal), either in the ESI solution or on the MALDI probe surface, and the relative binding selectivities are directly determined from the intensities of the calixarene/metal complexes in the mass spectra. For t-butylcalix[4]arene-tetraacetic acid tetraethyl ester (calixarene 1), complexation of Na+ is favored over complexation of K+, in agreement with prior solution results obtained by conventional methods. For the three calixarenes that do not have t-butyl groups on the upper rims, the calixarenes preferentially bind K+ over Na+, thus demonstrating that size selective complexation can be probed with both the ESI and MALDI methods. Collision-activated dissociation results indicate that the phenyl oxygens, but not necessarily the ethoxy ethyl oxygens of the lower rims, are the primary binding sites for the alkali metal ions.  相似文献   

3.
The luminescence and absorption spectra of some metal complexes of new tetraphenylporphyrin derivatives containing a chelating group with a heavy atom in the ligand structure were studied and compared with the properties of the zinc complex of unsubstituted tetraphenylporphyrin. The quantum yields of fluorescence and phosphorescence of liquid and frozen solutions of these compounds were measured. The life-times of delayed emission have been estimated, and the nature of bands in the absorption and luminescence spectra of the complexes and their relation with the structure are discussed.  相似文献   

4.
Negative chemical ionization mass spectrometry is used as a probe to examine reactions between hydrocarbon radicals and metal complexes in the gas phase. The methane negative chemical ionization mass spectra of 27 complexes of cobalt(II ), nickel(II ) and copper(II ) in the presence of O4, O2N2 and N4 donor atom sets are characterized by two dominant series of adduct ions of the form [M + CnH2n]? and [M + CnH2n+1]? at m/z values above the molecular ion, [M]?. Insertion of the CH radical into the ligand followed by radical/radical recombination and electron capture is proposed as the major mechanism leading to the formation of [M + CnH2n]? adduct ions. A second pathway involves ligand substitution by CnH2n+1 radicals concomitant with H elimination and electron capture. Oxidative addition at the metal followed by ionization is suggested as the principal pathway for the formation of [M + CnH2n+1]? adduct ions.  相似文献   

5.
To clarify the ionization mechanism of large molecules under multi-photon ionization conditions, photo-electron spectroscopic studies on anthracene have been performed with electron imaging technique. Electron kinetic energy distributions below a few eV reveal that three kinds of ionization channels coexist, viz., vertical ionization, ionization from Rydberg states, and thermionic hot electron emission. Their relative yield is determined by the characteristic of the laser pulse. The duration in particular influences the ratio between the first two processes, while for higher intensities the last process dominates. Our results provide strong evidence that internal conversion plays an important role for the ionization of the molecule.  相似文献   

6.
Plasmatic chlorophacinone is commonly measured with liquid chromatographic assay, which convenient but lacks sensitivity and selectivity and usually requires ion pair reagents to reduce the chromatographic tailed peak. In this paper, a novel method using eluent generator reagent‐free ion chromatography coupled with electrospray ionization ion trap mass spectrometric detection for the determination of chlorophacinone in plasma has been developed. After samples were extracted with 10% (v/v) methanol in acetonitrile and cleaned by solid‐phase extraction, chromatographic separation was performed on an IonPac® AS11 analytical column (250 × 4.0 mm) using 40.0 mmol/L KOH containing 10% (v/v) methanol as organic modifier. Quantification was performed by negative electrospray ionization in multiple reaction monitoring mode. The transition m/z 373 → 201 was for the quantification ion; the transitions m/z 373 → 172 and m/z 373 → 145, as well as the isotope ions m/z 375 and m/z 203, were for the qualitative ions. All the method parameters were validated. It was confirmed that this method can be used in clinical diagnosis and forensic toxicology. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

7.
A simple ion source was constructed for in-beam ionization by alkali ion attachment. A wire probe covered with sample was placed near an alkali ion emitter prepared from a mixture of silica gel and alkali halides. The ionization of various thermally labile compounds and of mixtures was investigated. Na+ proved to be the most suitable alkali ion for cationization. For monosaccharides experiments revealed the elimination of water upon ionization by Li+ attachment. The experimental set-up was also examined for measuring the heat of sublimation of organic solids.  相似文献   

8.
A variety of N-confused tetraphenylporphyrin rhodium complexes were synthesized, and their structures and physical properties were investigated. Depending on the reaction conditions, the rhodium(I), -(III), and -(IV) complexes were produced, which exemplified the versatile coordination mode of N-confused porphyrin ligands.  相似文献   

9.
A recently developed atmospheric pressure ionization source, a distributed plasma ionization source (DPIS), was characterized and compared to commonly used atmospheric pressure ionization sources with both mass spectrometry (MS) and ion mobility spectrometry (IMS). The source consisted of two electrodes of different sizes separated by a thin dielectric. Application of a high RF voltage across the electrodes generated plasma in air yielding both positive and negative ions. These reactant ions subsequently ionized the analyte vapors. The reactant ions generated were similar to those created in a conventional point-to-plane corona discharge ion source. The positive reactant ions generated by the source were mass identified as being solvated protons of general formula (H2O)nH+ with (H2O)2H+ as the most abundant reactant ion. The negative reactant ions produced were mass identified primarily as CO3, NO3, NO2, O3 and O2 of various relative intensities. The predominant ion and relative ion ratios varied depending upon source construction and supporting gas flow rates. A few compounds including drugs, explosives and amines were selected to evaluate the new ionization source. The source was operated continuously for 3 months and although surface deterioration was observed visually, the source continued to produce ions at a rate similar that of the initial conditions.  相似文献   

10.
The application of ion mobility to separate the electronic states of first-, second-, and third-row transition metal cations generated by the laser vaporization/ionization (LVI) technique is presented. The mobility measurements for most of the laser-generated transition metal cations reveal the presence of two or three mobility peaks that correspond to ground and excited states of different electronic configurations. The similarity of the measured reduced mobilities for the metal cations generated by LVI, electron impact, and glow discharge ion sources indicates that the same electronic configurations are produced regardless of the ion source. However, in comparison with electron impact of volatile organometallic compounds, the LVI populates fewer excited states due to the thermal nature of the process. Significant contributions to the production and populations of excited states of Ni+, Nb+, and Pt+ cations have been observed in the presence of argon during the LVI process and attributed to the Penning ionization mechanism. The origin of the mobility difference between the ground and the excited states is mainly due to the different interaction with helium. The ratio of the reduced mobilities of the excited and ground states decreases as one goes from the first- to the second- to the third-row transition metal cations. This trend is attributed to the ion size, which increases in the order 6sd(n-1) > 5sd(n-1) > 4sd(n-1). This work helps to understand the mechanisms by which transition metal cations react in the gas phase by identifying the ground and excited states that can be responsible for their reactivity.  相似文献   

11.
Unsaturated carboxylic acids have been found to undergo hydrogenation in the presence of methanol prior to ionization. Z-Isomers are found to undergo more facile reduction than the E-isomers in the case of two pairs of dicarboxylic acids studied.  相似文献   

12.
The formation and dissociation of dimer complexes consisting of a transition metal ion and two polyether ligands is examined in a quadrupole ion trap mass spectrometer. Reactions of three transition metals (Ni, Cu, Co) with three crown ethers and four acyclic ethers (glymes) are studied. Singly charged species are created from ion-molecule reactions between laser-desorbed monopositive metal ions and the neutral polyethers. Doubly charged complexes are generated from electrospray ionization of solutions containing metal salts and polyethers. For the singly charged complexes, the capability for dimer formation by the ethers is dependent on the number of available coordination sites on the ligand and its ability to fully coordinate the metal ion. For example, 18-crown-6 never forms dimer complexes, but 12-crown-4 readily forms dimers. For the more flexible acyclic ethers, the ligands that have four or more oxygen atoms do not form dimer complexes because the acyclic ligands have sufficient flexibility to wrap around the metal ion and prevent attachment of a second ligand. For the doubly charged complexes, dimers are observed for all of the crown ethers and glymes, thus showing no dependence on the flexibility or number of coordination sites of the polyether. The nonselectivity of dimer formation is attributed to the higher charge density of the doubly charged metal center, resulting in stronger coordination abilities. Collisionally activated dissociation is used to evaluate the structures of the metal-polyether dimer complexes. Radical fragmentation processes are observed for some of the singly charged dimer complexes because these pathways allow the monopositive metal ion to attain a more favorable 2 + oxidation state. These radical losses are observed for the dimer complexes but not for the monomer complexes because the dimer structures have two independent ligands, a feature that enhances the coordination geometry of the complex and allows more flexibility for the rearrangements necessary for loss of radical species. Dissociation of the doubly charged complexes generated by electrospray ionization does not result in losses of radical neutrals because the metal ions already exist in favorable 2+ oxidation states.  相似文献   

13.
Recent developments in the use of negative ion detection in GC-MS have indicated the potential for highly sensitive analyses for certain compounds. This paper describes the application of the techniques to the assay of Nitroglycerin and its metabolites yielding sensitivity to two femtograms. Because of the low levels of nitroglycerin in biological media such sensitivity is highly desirable if not essential for meaningful measurements. In addition to sensitivity the method is shown to yield extremely good selectivity contributing further to the credibility of quantitative results.  相似文献   

14.
K-shell vacancy production cross sections are measured using X-ray technique, in collisions of highly charged fluorine ions with various solid targets such as, Cl, K, Fe and Cu, at energies from 50 to 110 MeV. The experimental data is compared with an ab initio model based on local plasma approximation (LPA) and the usually employed ECPSSR. A detailed comparison with the LPA model is presented as a function of generalized perturbation strength.  相似文献   

15.
16.
A procedure is described for the analysis of the estrogens equilin and estrone in human plasma following oral administration of conjugated estrogen preparations. After enzymatic hydrolysis of the sulfate conjugates, plasma proteins are precipitated with methanol and the estrogens extracted into ethyl acetate. Derivatization with the reagent flophemesylamine converts equilin and estrone into volatile pentafluorophenyldimethylsilyl ethers ideally suited to capillary gas chromatography-negative ion chemical ionization mass spectrometry. Using a 15 meter dimethyl silicone bonded phase fused silica capillary column separation of the estrone and equilin derivatives is achieved within 9 minutes. Selected ion monitoring of the intense negative molecular ions enables levels of 1 ng.ml?1 to be measured with coefficients of variation of 9.3 % and 14.2 % for estrone and equilin respectively. Plasma levels of the compounds are reported in two male volunteers up to 24 hours after dosing with 5 milligrams of Premarin?. (? Ayerst Laboratories Inc., New York, USA.).  相似文献   

17.
We describe a method for the determination of memantine in plasma by use of the derivatization reagent o-(pentafluorobenzyloxycarbonyl)-benzoyl chloride. Memantine can be quantitatively analyzed down to 49?pg per mL of plasma using a 250?μL sample and negative ion chemical ionisation mass spectrometry (GC-NICI-MS). Plasma samples were made alkaline with carbonate buffer and extracted with n-hexane. The extracts were treated with reagent solution for 20?min, concentrated, and submitted to GC-NICI-MS. The method is rapid because extraction and derivatization occur in one single step. Amantadine is used as an internal standard. The utility and robustness of the assay is demonstrated by giving data on specificity, linearity, accuracy and precision, benchtop stability, freeze–thaw stability, autosampler stability, aliquot analysis, and prospective analytical batch size accuracy.
Figure
We describe a method for the determination of memantine in plasma by use of the derivatization reagent o-(pentafluorobenzyloxycarbonyl)-benzoyl chloride. Memantine can be quantitatively analyzed down to 49?pg per mL of plasma using a 250?μL sample and negative ion chemical ionisation mass spectrometry (GC-NICI-MS). Amantadine is used as an internal standard. The utility and robustness of the assay is demonstrated by giving data on specificity, linearity, accuracy and precision, benchtop stability, freeze–thaw stability, autosampler stability, aliquot analysis, and prospective analytical batch size accuracy.  相似文献   

18.
Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICRMS) was used to investigate metal ion interactions of the 18 amino acid peptide fragment B18 (LGLLLRHLRHHSNLLANI), derived from the membrane-associated protein bindin. The peptide sequence B18 represents the minimal membrane-binding motif of bindin and resembles a putative fusion peptide. The histidine-rich peptide has been shown to self-associate into distinct supramolecular structures, depending on the presence of Zn(2+) and Cu(2+). We examined the binding of B18 to the metal ions Cu(2+), Zn(2+), Mg(2+), Ca(2+), Mn(2+) and La(3+). For Cu(2+), we compared the metal binding affinities of the wild-type B18 peptide with those of its mutants in which one, two or three histidine residues have been replaced by serines. Upon titration of B18 with Cu(2+) ions, we found sequential binding of two Cu(2+) ions with dissociation constants of approximately 34 and approximately 725 micro M. Mutants of B18, in which one histidine residue is replaced by serine, still exhibit sequential binding of two copper ions with affinities for the first Cu(2+) ion comparable to that of wild-type B18 peptide, but with a greatly reduced affinity for the second Cu(2+) ion in mutants H112S and H113S. For mutants in which two histidines are replaced by serines, the affinity for the first Cu(2+) ion is reduced approximately 3-10 times in comparison with B18. The mutant in which all three histidine residues are replaced by serines exhibits an approximately 14-fold lower binding for the first Cu(2+) ion compared with B18. For the other metal ions under investigation (Zn(2+), Mg(2+), Ca(2+), Mn(2+) and La(3+)), a modest affinity to B18 was detected binding to the peptide in a 1 : 1 stoichiometry. Our results show a high affinity of the wild-type fusogenic peptide B18 for Cu(2+) ions whereas the Zn(2+) affinity was found to be comparable to that of other di- and trivalent metal ions.  相似文献   

19.
20.
Tetracycline antibiotics, tetracycline, chlortetracycline, demeclocycline, doxycycline, minocycline, methacycline, oxytetracycline, and anhydrotetracycline, are examined by electrospray ionization in a quadrupole ion trap. Studies were undertaken to evaluate the use of metal complexation as an alternative to conventional proton attachment. A variety of metal cationization processes, including attachment of Na+, Mg2+, Ca2+, Co2+, Ni2+, and Cu2+ were probed. Infrared multiphoton photodissociation and collisionally activated dissociation (CAD) were compared for generation of diagnostic fragmentation patterns of protonated and metal cationized tetracyclines. The photodissociation spectra provide a more informative signature, including more low mass ions that are not observed upon CAD. The metal complexes dissociate by pathways that are similar to those observed for the protonated molecules.  相似文献   

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