Mass Spectral Detector Research Articles

PAENIBACILLUS POLYMYXA КВ — PRODUCER OF BIOLOGICALLY ACTIVE SUBSTANCES

Objective. To investigate the ability of Paenibacillus polymyxa KB to produce biologically active substances that stimulate the growth and development of plants. Methods. Qualitative and quantitative determination of auxins, abscisic acid (ABA) and cytokinins in the culture fluid (CF) of P. polymyxa KB was carried out by high-performance liquid chromatography (HPLC) using Agilent 1200 liquid chromatograph; gibberellins were measured by high-performance liquid chromatography (HPLC/MS) using Agilent 1200 liquid chromatograph (Agilent Technologies, USA) and Agilent G1956B mass spectral detector. The content of vitamins in P. polymyxa KB was determined using Waters liquid chromatograph with a tqs-micro mass-selective detector. The content of amino acids in CF was studied by ion exchange chromatography on a Sycam amino acid analyser. The ability of P. polymyxa KB to synthesize exopolysaccharides and enzymes was determined using classical microbiological and biochemical research methods. Antifungal properties of the bacterium were studied by the dual culture method. Statistical calculations were carried out using analysis-of-variance method. Results. P. polymyxa KB synthesises phytohormonal compounds: auxins — up to 81.15 μg/g of dry biomass, abscisic acid — up to 9.84 μg/g; gibberellic acids (GA3 — within 2.48 μg/g and GA4 — 1.96 μg/g of dry biomass); cytokinins (zeatin — up to 16.42 μg/g, kinetin — up to 6.78 μg/g, isopentenyl-adenine — up to 9.03 μg/g of dry biomass), as well as vitamins: thiamine (B1) — within 0.93 mg/dm3 CF, riboflavin (B2) — 0.48 mg/dm3, pyridoxine (B6) — 0.27 mg/dm3, folic acid (B9) — 0.18 mg/dm3 CF. P. polymyxa KB shows phosphatase, amylolytic, proteolytic, pectolytic activity, produces amino acids: histidine — within 300.4 mg/dm3, alanine — 236.3 mg/dm3, proline — 164.2 mg/dm3, valine — 157.8 mg/dm3, isoleucine — 148.4 mg/dm3, threonine — 126.2 mg/dm3, cystine — 124.0 mg/dm3 CF and others. The bacterium synthesizes exopolysaccharides amylopectin and levan. P. polymyxa KB shows antagonistic activity against phytopathogenic micromycetes from the genera Fusarium, Alternaria, Nigrospora — pathogens of agricultural crops. Conclusion. P. polymyxa KB synthesizes a significant amount of physiologically active substances that can play an important role in the processes of plant organogenesis.

Study on pyrolysis behavior of long-chain n-alkanes with photoionization molecular-beam mass spectrometer

To understand the pyrolysis behavior of long linear alkanes, six n-alkanes (n-CnH2n+2, n = 10, 12, 13, 14, 15, 16) were conducted by pyrolysis coupled with photoionization molecular-beam mass spectrometer at pressure below 10 Pa and temperature between 200 °C and 1000 °C. Lots of important alkyl and alkenyl radicals (CH3, C4H9, C8H15, C9H19, C3H5, C5H9, etc.), which are the direct evidence to understand the pyrolysis reaction pathway, were real-time detected by mass spectral detector. The results suggested that the predominant pyrolysis mechanism of n-alkanes is a free-radical chain mechanism, beginning with the CC bond homolysis of n-CnH2n+2 to produce primary alkyl radicals (CmH2m+1, m < n) and termination by βC-H homolysis and mutual combination of radicals. The chain is propagated by the βC-C homolysis and H-abstraction of primary alkyl radicals to produce secondary alkyl radicals (ChH2h+1), and then the βC-C homolysis and H-abstraction of the secondary alkyl radicals to form alkyl/alkenyl radicals (ChH2h+1/CkH2k-1, h ≤ n, k < n-3) and alkenes (CkH2k/CkH2k-2) and the hydrogen-shift to form free-radical isomers. During the process, H-abstrction, and hydrogen-shift reactions exist as a synergistic reaction. In addition, the position of free radical in alkyl isomers is closer to the central carbon at low temperature. With the increase of temperature, 2-CmH2m+1 radical are gradually dominated.

Enantiomeric analysis of chiral compounds using phosphorus acid chlorides

New achiral separating bifunctional reagents, dichlorides of methylphosphonic and O-ethyl-thiophophoric acids, have been used for the quantitative determination of the enantiomeric composition of α-amino acids (alanine, valine, proline), secondary alcohols (2-octanol, 2-pentanol, 1-methoxy-2-propanol) and α-phenylethylamine. The determination of the enantiomeric composition of optically active α-amino acids, secondary alcohols, and amines is based on the transformation of compounds into symmetric diastereometers using organophosphorous achiral bifunctional reagents followed by the determination of the derivatives by gas chromatography with a mass spectral detector.

Improving Longevity of Fibrin Sealant in a Proteolytic Environment

Fibrin sealants are used in surgical procedures as an adjunct to sutures and staples to prevent fluid leakage and bleeding. These applications require extended longevity of fibrin sealant. It takes about 2 weeks for a typical surgical wound to heal, whereas fibrin sealant typically survives only 2 to 3 days in vivo due to its degradation by proteases such as plasmin present in the tissue micro-environment. Tranexamic acid (TA) is a well-known inhibitor of proteases including plasmin present in the blood. However, water soluble TA rapidly diffuses out of the sealant under in vivo conditions. Therefore, an investigation aimed to study the mechanism of sustained release of TA has been undertaken using microspheres of an absorbable PLGA (poly-lactic-glycolic-acid) polymer. TA particles of average dimension 3 micron are impregnated at a loading of 5% and 30% in average 40 micron PLGA microspheres. These are verified by Scanning Electron Microscopy / Energy Dispersive X-Ray spectroscopy. Confocal Raman spectroscopy shows that TA is distributed desirably more towards the core of the microsphere. Release study of TA by LC-MS using direct auto-sampler injection into Mass Spectral detector with ESI MS positive ion mode ionization shows that about 70% of TA from 5% TA Loaded / PLGA microspheres is released continuously over a period of 144 hours (or 6 days). Rate of TA release significantly slows down after the initial 72 hours. A gravimetric in vitro method has been developed to monitor the degradation of the sealant in a plasmin containing medium at pH 7.4 and 37 0C. The plasmin medium has been changed each day continuously up to 4 days. The proof-of-principle of improving longevity of fibrin sealant has been demonstrated with both 5% and 30% TA loaded / PLGA microspheres compared to the control.

Methyllycaconitine: A non-radiolabeled ligand for mapping α7 neuronal nicotinic acetylcholine receptors — In vivo target localization and biodistribution in rat brain

IntroductionReduction of cerebral cortical and hippocampal α7 neuronal nicotinic acetylcholine receptor (nAChR) density was observed in the Alzheimer's disease (AD) and other neurodegenerative diseases. Mapping the subtypes of nAChRs with selective ligand by viable, quick and consistent method in preclinical drug discovery may lead to rapid development of more effective therapeutic agents. The objective of this study was to evaluate the use of methyllycaconitine (MLA) in non-radiolabeled form for mapping α7 nAChRs in rat brain. MethodsMLA pharmacokinetic and brain penetration properties were assessed in male Wistar rats. The tracer properties of MLA were evaluated in rat brain by dose and time dependent differential regional distribution studies. Target specificity was validated after blocking with potent α7 nAChR agonists ABBF, PNU282987 and nicotine. High performance liquid chromatography combined with triple quad mass spectral detector (LC–MS/MS) was used to measure the plasma and brain tissue concentrations of MLA. ResultsMLA has shown rapid brain uptake followed by a 3–5 fold higher specific binding in regions containing the α7 nAChRs (hypothalamus — 1.60ng/g), when compared to non-specific regions (striatum — 0.53ng/g, hippocampus — 0.46ng/g, midbrain — 0.37ng/g, frontal cortex — 0.35ng/g and cerebellum — 0.30ng/g). Pretreatment with potent α7 nAChR agonists significantly blocked the MLA uptake in hypothalamus. The non-radiolabeled MLA binding to brain region was comparable with the α7 mRNA localization and receptor distribution reported for [3H] MLA in rat brain. DiscussionThe rat pharmacokinetic, brain penetration and differential brain regional distribution features favor that MLA is suitable to use in preclinical stage for mapping α7 nAChRs. Hence, this approach can be employed as an essential tool for quicker development of novel selective ligand to map variation in the α7 receptor densities, as well as to evaluate potential new chemical entities targeting neurodegenerative diseases.

Mesoporous nickel hydroxyapatite nanocomposite for microwave-assisted Henry reaction

The utility of nickel hydroxyapatite nanocomposite (Ni-HAp) as a green catalyst for solvent free, microwave-assisted Henry reaction using nitromethane and a series of aromatic aldehydes as substrates is presented. The selected catalyst performed well to afford the respective nitrostyrenes which were quantified by gas chromatography equipped with a mass spectral detector (GC–MS). A few of the products were identified from the respective nuclear magnetic resonance (NMR) spectral data.

Gas chromatography determination of trace of biomarkers of mustard agent and some organophosphoric toxic agents in urine

A procedure has been developed for the determination of thioglycol, 1,1′-sulfonyl-bis[2-(methylsulfonyl)-ethane], 1-methylsulfonyl-2-[2-(methylthio)ethylsulfonyl]ethane (biomarkers of mustard agent) and methylphosphonic acid, O-ethylmethylphosphonic acid, O-isopropylmethylphosphonic acid, and O-pinacolyl methylphosphonic acid (biomarkers of organophosphoric toxic agents) in urine. The procedure includes the recovery of components by liquid extraction, derivatization, separation by gas-liquid chromatography, and detection by flame-photometric and mass spectral detectors. The procedure has been applied to the analysis of samples of artificial urine by the standard addition method.

In vivo receptor occupancy method that simultaneously quantifies four tracers: raclopride, pirenzepine, MDL‐100907, and SB‐221284

The atypical antipsychotics share the common attributes of working on serotonin and dopamine receptors. However, a comprehensive mechanism of action of these agents is unknown. In order to better elucidate the mechanism by which these drugs produce their therapeutic and the undesired effects, a robust method for measuring in vivo receptor binding is needed. The authors developed a liquid chromatography/triple quad mass spectral detectors (LC/MS/MS) method to measure the brain distribution of receptor occupancy using tracers targeting dopamine D2, serotonin 5‐HT2A, 5‐HT2C and muscarinic M1 receptors. The tracers are raclopride, MDL‐100907, SB‐221284 and pirenzepine, respectively. All four non‐radiolabeled tracers were detectable in discrete rat brain areas after intravenous administration. These tracers demonstrated a differential brain distribution corresponding to the regional differences in their respective receptor densities. Oral pretreatment of various antipsychotic agents that occupy these receptors decreased this differential distribution in a dose‐dependent manner. Our results demonstrate the utility of LC/MS/MS to quantify the in vivo receptor occupancy of antipsychotic and other agents acting in the CNS.

Use of LC/MS to assess brain tracer distribution in preclinical, in vivo receptor occupancy studies: Dopamine D2, serotonin 2A and NK-1 receptors as examples

High performance liquid chromatography combined with either single quad or triple quad mass spectral detectors (LC/MS) was used to measure the brain distribution of receptor occupancy tracers targeting dopamine D2, serotonin 5-HT2A and neurokinin NK-1 receptors using the ligands raclopride, MDL-100907 and GR205171, respectively. All three non-radiolabeled tracer molecules were easily detectable in discrete rat brain areas after intravenous doses of 3, 3 and 30 μg/kg, respectively. These levels showed a differential brain distribution caused by differences in receptor density, as demonstrated by the observation that pretreatment with compounds that occupy these receptors reduced this differential distribution in a dose-dependent manner. Intravenous, subcutaneous and oral dose–occupancy curves were generated for haloperidol at the dopamine D2 receptor as were oral curves for the antipsychotic drugs olanzapine and clozapine. In vivo dose–occupancy curves were also generated for orally administered clozapine, olanzapine and haloperidol at the cortical 5-HT2A binding site. In vivo occupancy at the striatal neurokinin NK-1 binding site by various doses of orally administered MK-869 was also measured. Our results demonstrate the utility of LC/MS to quantify tracer distribution in preclinical brain receptor occupancy studies.

97/00705 Studies on the method of determination of Kovats retention indexes of alkylbenzene with high reproducibility

The positive identification of higher alkylbenzene isomers is a difficult task even with a mass spectral detector. A preliminary calculative identification could serve for a better orientation in the obtained mass spectra as well as acting as a complementary and independent identification tool. An accurate equation for the prediction of retention indices of C9C12 alkylbenzenes and their temperature coefficients, dI/dT, on OV-101 is given. The basic parameter is the molecular mass, while tuning parameters include the kind of substitution and the carbon chain of the substituents. The correlation coefficient obtained for 94 alkylbenzenes is 0.9995 and the mean standard deviation is 2.7 units. The predictive possibilities of the equation are demonstrated by inter- and extrapolative calculations of the retention indices of certain isomers with experimentally measured retention data, but without the mass spectral assignment of the positions of substituents.

97/00707 Study on the reaction mechanism of CO and H 2 in the corona discharge

The positive identification of higher alkylbenzene isomers is a difficult task even with a mass spectral detector. A preliminary calculative identification could serve for a better orientation in the obtained mass spectra as well as acting as a complementary and independent identification tool. An accurate equation for the prediction of retention indices of C9C12 alkylbenzenes and their temperature coefficients, dI/dT, on OV-101 is given. The basic parameter is the molecular mass, while tuning parameters include the kind of substitution and the carbon chain of the substituents. The correlation coefficient obtained for 94 alkylbenzenes is 0.9995 and the mean standard deviation is 2.7 units. The predictive possibilities of the equation are demonstrated by inter- and extrapolative calculations of the retention indices of certain isomers with experimentally measured retention data, but without the mass spectral assignment of the positions of substituents.

97/00713 Energy 1997 Projections—Australian energy consumption and production: Historical trends and projections to 2009-10

The positive identification of higher alkylbenzene isomers is a difficult task even with a mass spectral detector. A preliminary calculative identification could serve for a better orientation in the obtained mass spectra as well as acting as a complementary and independent identification tool. An accurate equation for the prediction of retention indices of C9C12 alkylbenzenes and their temperature coefficients, dI/dT, on OV-101 is given. The basic parameter is the molecular mass, while tuning parameters include the kind of substitution and the carbon chain of the substituents. The correlation coefficient obtained for 94 alkylbenzenes is 0.9995 and the mean standard deviation is 2.7 units. The predictive possibilities of the equation are demonstrated by inter- and extrapolative calculations of the retention indices of certain isomers with experimentally measured retention data, but without the mass spectral assignment of the positions of substituents.

97/00706 Study on association behavior of coal extracts in organic solvents by surface tension measurement

The positive identification of higher alkylbenzene isomers is a difficult task even with a mass spectral detector. A preliminary calculative identification could serve for a better orientation in the obtained mass spectra as well as acting as a complementary and independent identification tool. An accurate equation for the prediction of retention indices of C9C12 alkylbenzenes and their temperature coefficients, dI/dT, on OV-101 is given. The basic parameter is the molecular mass, while tuning parameters include the kind of substitution and the carbon chain of the substituents. The correlation coefficient obtained for 94 alkylbenzenes is 0.9995 and the mean standard deviation is 2.7 units. The predictive possibilities of the equation are demonstrated by inter- and extrapolative calculations of the retention indices of certain isomers with experimentally measured retention data, but without the mass spectral assignment of the positions of substituents.

Parallel column gas chromatography

AbstractA parallel column gas chromatography (PCGC) methodology that simultaneously collects retention information on multiple stationary phases is presented. The multidimensional PCGC configuration links a precolumn in series with a set of parallel analytical columns (having different stationary phases) all connected to a single detector. GC peaks heartcut from the precolumn are detected as a series of peaks due to retention differences on parallel columns. This provides a GC retention pattern that is characteristic of the analyte, the stationary phase array, and the conditions of the analysis. PCGC peak patterns observed for groups of C8, C9, and C10 compounds are presented. The use of PCGC with infrared and mass spectral detectors is reported. A methodology to account for changes in GC operating parameters using relative retentions of analytes to internal standards is presented. The first use of thermodynamic retention parameters to model retention behavior on parallel analytical columns under different temperature profiles is presented. Retention predictions within 0.3‐0.6% of experimental values are reported. These results indicate that PCGC has potential as a general qualitative analysis tool. Future efforts to calibrate retention predictions, to transport PCGC results between instruments, and to optimize the number of parallel columns are proposed. © 1995 John Wiley &amp; Sons, Inc.This article is a US Government work and, as such, is in the public domain in the United States of America.

Quantitative aspects of a valve-based, multi-stage multidimensional gas chromatography-infrared spectroscopy-mass spectrometry system

Use of high-resolution capillary gas chromatography coupled with infrared and mass spectral detectors is a very powerful qualitative analytical technique. However, accurate qualitative analyses with spectroscopic detection requires that the separation system provide the detectors with pure components. Unfortunately, in very complex mixtures, this is virtually impossible when single-stage separations are employed. This paper describes the sample recycling capabilities of a valve-based multidimensional gas chromatography system equipped with both infrared and mass spectral detectors. Sample recycle efficiencies, valve adsorption effects and cycle-to-cycle reproducibility are considered. Mixtures including the Grob test mixture were analyzed and it was found that 35 out of the 40 total components examined could be recycled six times or more following injection of 500 ng or less of each component. Additionally, the first demonstration of a 23-stage recycling experiment with several components of a chlorinated hydrocarbon mixture is shown. This demonstrates the plausibility of performing GC n experiments, where n is the number of separation stages, with values of n up to 23 for these components. It is also shown that mechanical valves generally do not have deleterious effects on the majority of these components. The main limitations of the system appear to be the design of the heating system and the manual control of the pressure and flow switching systems. The applicability of the present results to qualitative analyses are discussed.

Improved method for prediction of gas chromatographic retention indices of C 9C 12 alkylbenzenes

The positive identification of higher alkylbenzene isomers is a difficult task even with a mass spectral detector. A preliminary calculative identification could serve for a better orientation in the obtained mass spectra as well as acting as a complementary and independent identification tool. An accurate equation for the prediction of retention indices of C 9C 12 alkylbenzenes and their temperature coefficients, d I/d T, on OV-101 is given. The basic parameter is the molecular mass, while tuning parameters include the kind of substitution and the carbon chain of the substituents. The correlation coefficient obtained for 94 alkylbenzenes is 0.9995 and the mean standard deviation is 2.7 units. The predictive possibilities of the equation are demonstrated by inter- and extrapolative calculations of the retention indices of certain isomers with experimentally measured retention data, but without the mass spectral assignment of the positions of substituents.

A fatty acid methyl ester (FAMES) analyzer

AbstractFatty acids, as their methyl esters (FAMES), are routinely analyzed from a wide variety of plant and animal tissues and fluids. Samples have mainly been analyzed to date using capillary GC with FID detection. However, FID detection is non‐specific, and open to misinterpretation. This is particularly important in the analysis of minor lipid components from, e.g. organ tissues, plasma and other body fluids, where non‐FAMES impurities or contaminants can be present in relatively high amounts. This suggests that even for routine work, a mass spectral detector is necessary for the unambiguous identification–or rather, recognition–of FAMES. The FAMES analyzer we propose consists of three components: an automatic injector; a medium polarity, high‐temperature stable capillary column; a mass spectrometric detector, in our case the Finnigan–MAT ion trap detector (ITD 800). Here, on‐column injection allowed controlled sample transfer even for low absolute concentrations of lipids, and a column effluent splitter gave simultaneous qualititative and quantitative analysis. For automatic routine analysis, a mass spectral library routine using a tailor‐made library of FAMES spectra of the most common naturally occurring fatty acids, plays an essential role. Library comparison parameters used in the standard ITD software usually give “first hit” recognition over a wide sample dynamic range (ca. 2 pg to &gt; 200 ng in the best cases). This gives an absolute recognition even of minor lipid components, especially when combined information from mass spectra and GC retention data is used. By analogy with the now well known concept of the Amino Acid Analyzer, we propose the system described as a FAMES Analyzer. Mass spectrometers like the Finnigan MAT ITD 800 are inexpensive, reliable, sensitive, and easy to operate. Unlike the Amino Acid Analyzer, the FAMES Analyzer needs the specific detection offered by mass spectrometry because the number of acids to be analyzed, including isomers, is much greater.