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1.
Summary A method has been developed for the determination of valproic acid, without derivatization, in human serum by isotope-dilution mass spectrometry using labelled 2-propyl[3,3,3-d3]valeric[5,5,5-d3] acid as internal standard for accurate quantification of the concentration of valproic acid in the sample. After acidification, the analyte and internal standard are extracted withn-hexane. The amounts of valproic acid in the serum are calculated from the isotope ratio of valproic acid to labelled valproic acid, which is measured by electron impact (EI) and chemical ionization (CI) selected ion monitoring (SIM). The concentrations of valproic acid in sera measured using isotope-dilution mass spectrometry are compared with results from gas-liquid chromatography (GLC) and fluorescence polarization immunoassay (FPIA). The accuracy, precision and recovery of the GC-MS methods are discussed. The coefficient of variation determined from duplicate samples was less than 1.5%. The detection limit was 10 ng mL−1 at a signal-to-noise ratio of 3∶1. Part of this work was presented at the Kongre? der Deutschen Gesellschaft für Laboratoriumsmedizin, Berlin, 1994.  相似文献   

2.
Butachlor is an aromatic amide compound that plays a role as a herbicide, a xenobiotic, and an environmental contaminant. The aim of this work was to develop a highly selective and sensitive ultra-performance liquid chromatography-tandem mass spectrometry method based on the tandem mass spectrometry cubed technique to determine butachlor in a biological matrix. Butachlor and internal standard acetochlor were separated on a Waters Acquity ultra-performance liquid chromatography BEH C18 column (2.1 × 50 mm, 1.7 μm) with gradient elution using 0.1% formic acid aqueous solution (A) and acetonitrile (B) as mobile phases. The transitions selected for tandem mass spectrometry cubed quantitative analysis in positive ion mode were: for butachlor, mass-to-charge ratio 312.2→238.1→162.1; for acetochlor, mass-to-charge ratio 270.1→224.0→148.1. The total running time for each sample was 5.5 min. The ultra-performance liquid chromatography-tandem mass spectrometry cubed method showed a linear relationship (R2 ≥ 0.995) in the concentration range of 0.5–100 ng/ml. The intra and interday accuracies are within the range of -10.6%–4.3% and precisions are between 4.48% and 13.14%. The novelty of the method is the use of tandem mass spectrometry cubed scanning mode, which improves selectivity and sensitivity. The results indicated that butachlor was cellular toxic. The safety of butachlor should be considered when it is used as a herbicide.  相似文献   

3.
Photodissociation of trimethylaluminum [Al(CH3)3] adsorbed on a silica (SiO2) substrate at 110 K has been studied by multiphoton ionization time-of-flight mass spectrometry. Translational energy distributions of aluminum and AlCH3 fragments can be fitted with a composition of two Maxwell–Boltzmann distributions. The two components are attributed to different environments of photodissociating parent molecules in the multilayer.  相似文献   

4.
5.
Summary A new method has been developed for qualitative and quantitative analysis of fumonisin FB1 and FB2 in corn and corn products. After extractive sample preparation followed by solid phase extraction using a strong anionexchanger, highest selectivity and sensitivity was achieved by high-performance liquid chromatography-electrospray-ionization, tandem mass spectrometry (HPLC-ESI-MS-MS) analysis combined with selected reaction monitoring (SRM). With deuterated fumonisin FB1-d6 as internal standard the routine quantitation limit for FB1 was set at 400 pg (0.8 ng g–1 sample) with a signal-to-noise ratio of 101. Almost all corn grit and corn meal samples under study were found to be contaminated with fumonisin FB1 and FB2 in concentrations ranging from 1 to 200 ng g–1. Lower fumonisin levels were found in cornflakes, popcorn and baby food, while no fumonisins were detected in canned sweet corn.  相似文献   

6.
The effect of the calcination procedure on the decomposition of the [Pt(NH3)4]2+ complex in a NaX zeolite was studied by mass spectrometry (MS-TPDE) and diffuse reflectance spectroscopy (DRS). The decomposition of the complex took place in two steps. In the first step, under oxygen, the [Pt(NH3)4]2+ complex was first converted to [Pt(NH3)2]2+ complex, accompanied by nitrogen release. In the second step, corresponding to the decomposition of the remaining two amine ligands, NO formation was also observed. Under He, the decomposition also occurred in two steps with H2 liberation. A reaction scheme was proposed for these results.  相似文献   

7.
Structure and properties of even‐electron anionic species formed by bis(2‐ethylhexyl)sulfosuccinate (AOT) and divalent metal ions (MII) with stoichiometry [AOTMIICl2] have been investigated by using electrospray ionization and different mass spectrometry techniques, such as high resolution, accurate mass measurements, collision‐induced dissociation (CID) multiple‐stage mass spectrometry. Owing to CID, eliminations of neutrals, mainly consisting in hydrochloric acid, 2‐ethyl‐1‐hexene and 2‐ethylhexanol, and an unexpected loss of an alkyl radical have been observed. The radical anions [C4HO6SMIICl]–? so produced have been characterized by MS3 experiments. Density functional theory calculations have been carried out for investigating structure and stability of the ionic species formed in the decomposition pathways. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

8.
 A method for the determination of theophylline (TH), without derivatization, in serum by isotope dilution mass spectrometry using labelled [1, 3-15N2-2-13C]theophylline (LTH) as internal standard is described. After deproteinization, the analyte is directly injected into a high performance liquid chromatography – mass spectrometer operating with atmospheric-pressure chemical-ionization (APCI HPLC/MS). The concentrations of TH in sera measured by APCI HPLC/MS are compared with results from gas chromatography – isotope dilution mass spectrometry (GC-ID/MS), high performance liquid chromatography (HPLC) and fluorescence polarization immunoassay (FPIA). The accuracy, precision and recovery of the APCI HPLC/MS and GC-ID/MS methods are discussed. The coefficient of variation (CV) determined from duplicate samples was less than 2%. The detection limit was 10 ng/ml at a signal-to-noise ratio of 3:1. Received: 17 January 1996/Revised: 26 March 1996/Accepted: 5 April 1996  相似文献   

9.
A certified reference material (CRM) for the determination of perfluorooctane sulfonate (PFOS) in acrylonitrile-butadiene-styrene (ABS) resin (NMIJ CRM 8155-a) has been issued by the National Metrology Institute of Japan (NMIJ). The bulk material was prepared by mixing commercial ABS resin powder and potassium PFOS and cut into square plates (20 × 20 mm, 2 mm thick) as the CRM. Analytical processes combined with isotope-dilution mass spectrometry and liquid chromatography/mass spectrometry were optimised and applied for characterisation. One of the approaches adopted by NMIJ for certification is that results from two or more primary methods of measurement should be used; thus, two optimised isotope-dilution mass spectrometric methods (Methods 1 and 2 with reprecipitation and with reprecipitation/solid phase extraction, respectively, were validated mutually and employed) were used to determine the certified value. Homogeneity and stability of the square plates were evaluated and their uncertainty contributions (as relative standard uncertainties) were 1.43% for inhomogeneity and 6.96% for approximately two years’ instability. The certified mass fraction of linear PFOS (heptadecafluoro-1-octanesulfonic acid) in the CRM with expanded uncertainty (coverage factor k = 2, approximately 95% confidence interval) was (33.1 ± 5.0) mg kg?1 as free acid of PFOS.  相似文献   

10.
Laser desorption/ionisation of discrete molecular clusters combined with time-of-flight (TOF) or Fourier-transform ion cyclotron resonance (FTICR) mass spectrometry affords spectra in which extensive higher mass clusters are observed. The size of the largest cluster aggregates (or supraclusters) is of the same order of magnitude as nanoclusters. The spectra obtained using TOF mass spectrometry sometimes exhibit post-source decay fragmentation, depending upon the operational conditions employed during data acquisition, which, although providing useful data on the ligand dissociation dynamics, complicate spectral interpretation. Complementary FTICR mass spectra are free of such features. The identities of the supra/nanoclusters generated from the molecular cluster precursors have not been conclusively established but are mostly coordinatively unsaturated. Density functional molecular orbital calculations have identified the possible structures of the comparatively simple electronically unsaturated system, [Ru3(CO)6], that provides a clue to the aggregation mechanism.  相似文献   

11.
Summary An isotope dilution, GC-MS method for the quantitation of histamine in wines and grape juices was assayed. This method includes isolation of histamine and its, deuterated analogue [α,α,β,β-2H4]histamine, used as the labelled internal standard, by ion-pair extraction with bis-2-ethylhexylphosphate, conversion to the volatile derivative: tris-pentafluorobenzyl-histamine, capillary GC separation and measurement of the abundance ratio of the (M-181)+ ions from labelled and unlabelled derivatives. The method was successfully applied to the determination of histamine in several samples of Port wine, red and white table wine and grape juice. Data are given on detectability, linearity, repeatability and recovery.  相似文献   

12.
Two [N???I+???N] halogen‐bonded dimeric capsules using tetrakis(3‐pyridyl)ethylene cavitands with different lower rim alkyl chains are synthesized and analyzed in solution and the gas phase. These first examples of symmetrical dimeric capsules making use of the iodonium ion (I+) as the main connecting module are characterized by 1H NMR spectroscopy, diffusion ordered NMR spectroscopy (DOSY), electrospray ionization mass spectrometry (ESI‐MS), and ion mobility‐mass spectrometry (TW‐IMS) experiments. The synthesis and effective halogen‐bonded dimerization proceeds through analogous dimeric capsules with [N???Ag+???N] binding motifs as the intermediates as evidenced by the X‐ray structures of (CH2Cl2)2@[ 3 a 2?Ag4?(H2O)2?OTs4] and (CH2Cl2)2@[ 3 a 2?Ag4?(H2O)4?OTs4], two structurally different capsules.  相似文献   

13.
Treatment of [Ru(COD)(MeAllyl)2] and [Ru(COD)(COT)] with GaCp* under hydrogenolytic conditions leads to reactive intermediates which activate Si−H or C−H bonds, respectively. The product complexes [Ru(GaCp*)3(SiEt3)H3] ( 1 ) and [Ru(GaCp*)3(C7H7)H3] ( 2 ) are formed with HSiEt3 or with toluene as the solvent, respectively. While 1 was isolated and fully characterized by NMR, MS, IR and SC-XRD, 2 was too labile to be isolated and was observed and characterized in situ by using mass spectrometry, including labelling experiments for the unambiguous assignment of the elemental composition. The structural assignment was confirmed by DFT calculations. The relative energies of the four isomers possible upon toluene activation at the ortho-, meta-, para- and CH3-positions have been determined and point to aromatic C−H activation. The Ru−Ga bond was analyzed by EDA and QTAIM and compared to the Ru−P bond in the analogue phosphine compound. Bonding analyses indicate that the Ru-GaCp* bond is weaker than the Ru-PR3 bond.  相似文献   

14.
Palladium ate complexes are frequently invoked as important intermediates in Heck and cross‐coupling reactions, but so far have largely eluded characterization at the molecular level. Here, we use electrospray‐ionization mass spectrometry, electrical conductivity measurements, and NMR spectroscopy to show that the electron‐poor catalyst [L3Pd] (L=tris[3,5‐bis(trifluoromethyl)phenyl]phosphine) readily reacts with Br ions to afford the anionic, zero‐valent ate complex [L3PdBr]. In contrast, more‐electron‐rich Pd catalysts display lower tendencies toward the formation of ate complexes. Combining [L3Pd] with LiI and an aryl iodide substrate (ArI) results in the observation of the PdII ate complex [L2Pd(Ar)I2].  相似文献   

15.
The reactions of [Fe3(CO)12] or [Ru3(CO)12] with RNC (R=Ph, C6H4OMe-p or CH2SO2C6H4Me-p) have been investigated using electrospray mass spectrometry. Species arising from substitution of up to six ligands were detected for [Fe3(CO)12], but the higher-substituted compounds were too unstable to be isolated. The crystal structure of [Fe3(CO)10(CNPh)2] was determined at 150 and 298 K to show that both isonitrile ligands were trans to each other on the same Fe atom. For [Ru3(CO)12] substitution of up to three COs was found, together with the formation of higher-nuclearity clusters. [Ru4(CO)11(CNPh)3] was structurally characterised and has a spiked-triangular Ru4 core with two of the CNPh ligands coordinated in an unusual μ32 mode.  相似文献   

16.
The reaction of [(3,5‐Me2–C5H3N)2Zn(SeSiMe3)2] with a solution of Cd(OAc)2, Se(Ph)SiMe3 and PPr3 at low temperature was used to prepare single crystals of ternary group 12–12′‐16 nanoclusters with the composition [Zn1.8Cd8.2Se4(SePh)12(PPr3)4]. A ligand exchange reaction using Na[SePh] was performed to displace the neutral PPr3 ligands. The resulting clusters were probed using electrospray ionization mass spectrometry to determine the number of zinc and cadmium atoms in the cluster and compared to the all cadmium cluster [Cd10Se4(SePh)12(PPr3)4]. The dianionic clusters [ZnxCd10–xSe4(SePh)14]2– where x = 0, 1, 2 were assigned in the mass spectra, revealing that the clusters exhibit elemental distributions that are quite narrow in these experiments.  相似文献   

17.
Tigecycline, a novel intravenously administered glycylcycline antibiotic, currently plays a key role in the management of complicated multiorganism infections. However, current liquid chromatography with tandem mass spectrometry methods briefly describe parameters and the only reported internal standard was sometimes difficult to obtain. In our study, an updated liquid chromatography with tandem mass spectrometry method for the quantitative analysis of tigecycline in human serum was developed. Sample preparation involved precipitation with 20% trichloroacetic acid. Chromatographic separation of tigecycline and tetracycline (internal standard) was achieved on a Hypersil GOLD C18 column using gradient elution. The selected reaction monitoring transitions were performed at m/z 586.1→513.2 for tigecycline and m/z 445.1→410.2 for tetracycline. The assay was linear over the concentration range of 5–2000 ng/mL. The intra‐ and interday precisions at three concentration levels (10, 100, and 1600 ng/mL) were <15% and their accuracies were within the range of 95.1–106.1%. The mean recovery ranged from 94.3 to 105.6% and the matrix effect from 92.1 to 97.6%. Tigecycline was stable under all tested conditions. This validated method was successfully applied to a pharmacokinetic study in critically ill patients. The data demonstrated that our method allows quantification of tigecycline in serum in a quick and reliable manner for widespread application.  相似文献   

18.
Three new thiacalix[4]arene derivatives, 5,11,17,23-tetra-tert-butyl-25,27-di(2-hydroxyethoxy)-26,28-dihydroxythiacalix-{}[4]arene (2), 5,11,17,23-tetra-tert-25, 26,27,28-tetrakis[(methylcarboxyl)methoxy]thiacalix[4]arene (3),5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis(2-hydroxy-1-propanoxy)thiacalix[4]arene (4), were synthesized for the first time. The coordination properties of thiacalix[4]arene(1) and its derivatives (2 and 4) were investigated by detecting the interactions betweenthese compounds and two palladium complexes, cis-[Pd(en)(H2O)2]2+ and cis-[Pd(dtco-3-OH)(H2O)2]2+, by means of electrospray ionization mass spectrometry (ESI-MS) technique.  相似文献   

19.
The gas‐phase reactivity of [V2O5]+ and [Nb2O5]+ towards ethane has been investigated by means of mass spectrometry and density functional theory (DFT) calculations. The two metal oxides give rise to the formation of quite different reaction products; for example, the direct room‐temperature conversions C2H6→C2H5OH or C2H6→CH3CHO are brought about solely by [V2O5]+. In distinct contrast, for the couple [Nb2O5]+/C2H6, one observes only single and double hydrogen‐atom abstraction from the hydrocarbon. DFT calculations reveal that different modes of attack in the initial phase of C?H bond activation together with quite different bond‐dissociation energies of the M?O bonds cause the rather varying reactivities of [V2O5]+ and [Nb2O5]+ towards ethane. The gas‐phase generation of acetaldehyde from ethane by bare [V2O5]+ may provide mechanistic insight in the related vanadium‐catalyzed large‐scale process.  相似文献   

20.
The kinetic method was applied to differentiate and quantify mixtures of regioisomeric triacylglycerols (TAGs) by generating and mass selecting alkali ion bound metal dimeric clusters with a TAG chosen as reference (ref) and examining their competitive dissociations in a quadrupole ion trap mass spectrometer. This methodology readily distinguished pairs of regioisomers (AAB/ABA) such as LLO/LOL, OOP/OPO and SSP/SPS and consequently distinguished sn-1/sn-3, sn-2 substituents on the glycerol backbone. The dimeric complex ions [ref, Li, TAG(AAB and/or ABA)]+ generated by electrospray ionization mass spectrometry were subjected to collision induced dissociation causing competitive loss of either the neutral TAG reference (ref) leading to [Li(AAB and/or ABA)]+ or the neutral TAG molecule (TAG(AAB and/or ABA)) leading to [ref, Li]+. The ratio of the two competitive dissociation rates, defined by the product ion branching ratio (Riso), was related via the kinetic method to the regioisomeric composition of the investigated TAG mixture. In this work, a linear correlation was established between composition of the mixture of each TAG regioisomer and the logarithm of the branching ratio for competitive fragmentation. Depending on the availability of at least one TAG regioisomer as standard, the kinetic method and the standard additions method led to the quantitative analysis of natural TAG mixtures.  相似文献   

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