Biological Mass Spectrometry

The gas-phase reactions of F − , OH −· , OH − , EtO − , NH and EtNH − with Si(OEt) 4 were investigated by Fourier transform ion cyclotron resonance in order to probe the intrinsic reactivity of substrates used in plasma chemical vapour deposition. Isotopic data and the nature of the product ...

Since the introduction of isotope ratio mass spectro-meters (IRMS), on-line coupled to a gas chromatograph (GC) via a combustion interface (C), there has been increasing interest in its various analytical applica-tions.'-' The merits of this system, however, are some-what ...

This study presents the atmospheric pressure photoionization (APPI) of high-chlorinated (five or more chlorine atoms) polychlorinated biphenyls (PCBs) using toluene as dopant, after liquid chromatographic separation. Mass spectra of PCB 101, 118, 138, 153, 180, 199, 206 and 209 were recorded by using liquid chromatography-APPI-tandem mass spectrometry (LC-APPI-MS/MS) in negative ion full scan mode. Intense peaks appeared at m/z that correspond to [M - Cl + O](-) ions, where M is the analyte molecule. Furthermore, a detailed strategy, which includes designs of experiments, for the development and optimization of LC-APPI-MS/MS methods is described. Following this strategy, a sensitive and accurate method with low instrumental limits of detection, ranging from 0.29 pg for PCB 209 to 8.3 pg for PCB 101 on column, was developed. For the separation of the analytes, a Waters XSELECT HSS T3 (100 mm × 2.1 mm, 2.5 µm) column was used with methanol/water as elution system. This method was applied for the determination of the above PCBs in water samples (surface water, tap water and treated wastewater). For the extraction of PCBs from water samples, a simple liquid-liquid extraction with dichloromethane was used. Method limits of quantification, ranged from 4.8 ng l(-1), for PCB 199, to 9.4 ng l(-1), for PCB 180, and the recoveries ranged from 73%, for PCB 101, to 96%, for PCB 199. The estimated analytical figures were appropriate for trace analysis of high-chlorinated PCBs in real samples.

Diphenylborinic acid is shown to react with a variety of polyfunctional molecules of biological interest to give products which are easily identifiable by mass spectrometry. The diphenylborinate adducts of amino acids possess extraordinary stability and are separable by reverse phase chromatography. The stability of products is discussed with regard to the nature and stereochemical arrangement of the functional groups involved in complex formation.

Three metoprolol metabolites containing an α-hydroxy group were identified in human urine by capillary column gas chromatography/mass spectrometry. After aqueous phase cyclization with phosgene the neutral or acidic derivatives formed were isolated by solvent extraction at pH 10 or 3, respectively. Following silylation the electron impact mass spectra of the metabolites exhibited a characteristic ion at m/z 336 of high abundance which originated from cleavage of the bond adjacent to the a-OTMS group. Most probably the identified compounds were formed by further biotransformations of α-hydroxy metoprolol, which is a primary metabolite. The analytical method is applicable to detect the metoprolol metabolites reported so far. A quantitative assay for one of the metabolites (H 119/72) with nitrogen selective detection is described. The total amount of this metabolite excreted by one subject within 24 h after dosing was about 0.25% of the given dose.

Gas chromatography mass spectrometry (GC-MS) was employed to determine the chemical composition of essential oil obtained from Eucalyptus globulus and Trachyspermum ammi. The essential oil obtained from leaves of Eucalyptus globulus and from seeds of Trachyspermum ammi by Clevenger apparatus. Chemical composition of the essential oils of E. globulus and T. ammi was analyzed by Gas chromatography – Mass spectrometry. Four main compounds in E. globulus were identified as Eucalyptol, Methyl –salicylate, Thymol, Para- cymene. 1, 8-cineole was found to be the main compound of E. globulus essential oil. Thymol, gamma- terpinene, para- cymene, beta- pinene were the main compounds of T. ammi oil and traces amount of beta myrcene, alpha- thujne, alpha- pinene, alpha- terpinene, carvacrol compounds of T. ammi were identified by GC-MS. Thymol was the main compound of T. ammi oil. The antifungal activity of E. globulus and T. ammi oils were screened against Trichophyton mentagrophytes and Epidermatophyton floccosum by using disc diffusion and modified micro dilution method. T. ammi oil shows highest inhibition zone in comparison to E. globulus oils and references antibiotics i.e. Clotrimazole and Ketoconazole.

The structure and mass spectrometric behaviour of molecular species of two benzo[ij]quinolizin-5-ones and one pyrrol [3,2,1-ij] quinolin-4-one were studied in detail with the aid of mass-analysed ion kinetic energy spectrometry and ion trapping experiments. Whereas in the usual electron impact spectra obtained with a double-focusing instrument clear differences are present among the three isomeric com ponds, the unimolecular fragmentation processes of the related M+· indicate the occurrence of isomerization processes to give a common structure. Significantly, under ion trap conditions nearly identical electron impact spectra are obtained; such unexpected behaviour was explained by either the presence of the buffer gas or the occurrence of different ionizing phenomena, leading to lower energy deposition in the molecular species. Under fast atom bombardment conditions, an acid-catalysed isomerization process occurs.

Ketobemidone (see below) is a narcotic analgesic drug which is rapidly eliminated from plasma with an elimina-tion half-life of about 2.3 h' after administration to man. The oral bioavailability of ketobemidone was 34 f 16% (n = 6). Ketobemidone is extensively metabolized in man ...

The development of an analytical method for the determination of brain tryptamine using capillary gas chromatography mass spectrometry (selected ion monitoring) is presented. The method involves solvent extraction of brain homogenates and further derivatization (pentafluoropropionyl derivatives) of the dried extracts. Gas chrmatographic analysis is performed using a bonded phase silica fused capillary column. Selected monitoring of M/z 289 and 292 (isotope dilution technique) allows the determination of tryptamine in adult rat brain (450 ± 73 pg g−1) (X ± SEM), n = 6.