Resolution Mass Spectrometer Research Articles

Computational simulation of mass spectral peak shape

On the base of a statistical modelling method the computational algorithm of an ion current density distribution, a shape of a mass spectral peak obtained due to an ion beam movement relative to a receiver slit, a mass spectrometer transmission and resolution is described. The state of an ion beam at a source output slit is defined by the volume in a beam parameter six-dimensional space. Ion trajectories in electric and magnetic sector fields are computed analytically considering fringing effects. Resolution is determined by an equal intensity peak converging method.

Gas chromatographic mass spectrometric identification of O-demethylated and mono-hydroxylated metabolites of levomepromazine in blood from psychiatric patients by selected ion recording with high resolution.

An O-demethylated and two mono-hydroxylated metabolites of levomepromazine have previously been identified as conjugates in the urine from psychiatric patients. The three metabolites were identified in hydrolysed and nonhydrolysed plasma and erythrocytes from three patients by selected ion monitoring of the trimethylsilyl derivatives, with a mass spectrometric resolution of 5000. The three metabolites were mainly found as conjugates in the plasma, and smaller amounts were found unconjugated in the plasma and the erythrocytes.

Analysis of testosterone and dehydroepiandrosterone in saliva by gas chromatography-mass spectrometry

Testosterone and 3β-hydroxyandrost-5-en-17-one (dehydroepiandrosterone) have been identified in human parotid fluid and saliva by gas chromatography-mass spectrometry/ selected ion monitoring analyses of the t-butyldimethylsilyl ether and methyl oxime, t-butyldimethylsilyl ether derivatives. High specificity of analysis has been achieved by the use of high mass spectrometric resolution or by the monitoring of metastable peaks. Quantitative analyses indicate concentrations of both unconjugated testosterone and unconjugated dehydroepiandrosterone in the range 200–800 pmol/l in the saliva and parotid fluid of the normal males examined. These represent 1.5–7.5% of the concentrations of the steroids in blood plasma taken from the same subjects.

A simple, direct radioimmunoassay for plasma cortisol, featuring a 125I radioligand and a solid-phase separation technique.

A simple, direct radioimmunoassay for cortisol in human serum and plasma is described. An antiserum, raised in sheep to a cortisol-3-(O-carboxymethyl)oxime/bovine serum albumin conjugate, is coupled to microcellulose. No extraction is required because plasma samples and standards are incubated with the antiserum and an 125I radioligand in a low-pH buffer, which denatures cortisol-binding globulins. The assay satisfies accepted validation criteria. In addition, results from the radioimmunoassay compare well with those obtained by a gas chromatographic-mass spectrometric technique (r = 0.968; FRIA = 0.97 FGCMS + 2.0 nmol/L). The latter procedure features the very high intrinsic specificity obtained by selected ion monitoring at high mass-spectrometric resolution (M/deltaM = 8500) with a Varian MAT-731 instrument. The simplicity of the radioimmunoassay procedure, with use of reagents prepared "in house," makes this a very practical and economical assay for use in the medium or large endocrine laboratory.

The development of a computer-assisted search for anomalous compounds (casac)

An automated system for the recognition of anomalies in multi-compound mixtures is described. The mixtures to be investigated are injected into a combined gas chromatograph—mass spectrometer and low resolution spectra are acquired by repetitive scanning. Using an on-line computer, all of these spectra are compared with a pre-recorded file of spectra obtained by identical analyses of a “normal” mixture. The matching procedure has been designed to allow for differences in retention times. The CASAC program calculates and plots the degree of coincidence and in this way determines whether the sample spectrum contains fewer or more fragments than the corresponding library spectrum. The system has been applied to studies on pathological urine samples.

High resolution ion cyclotron resonance spectroscopy

Methods are described for greatly improving the mass resolution of an ion cyclotron resonance mass spectrometer. The factors affecting mass resolution are examined in detail, and the conditions for maximum resolution are discussed. Only three parameters — magnetic field strength, cyclotron frequency, and analyzer cell trapping voltage — are needed to make accurate, absolute mass measurements. Ions are detected with a solid-state marginal oscillator circuit which has been designed to be stable at very low r.f. levels.

Resolution of a solid state fission fragment mass spectrometer

The resolution of a fission fragment mass spectrometer using two, heavy ion, surface barrier, silicon detectors is investigated. The mass assignment is made on the basis of the detector pulse heights. The average initial fragment mass and the initial mass resolution are calculated as a function of the measured (apparent) mass for three different thickness of the fissile material deposit. This treatment gives a clear indication of those factors most important for good mass resolution work.

Investigation of Energy Gain, Resolution, and Harmonics of an Aperiodic Radio-Frequency Mass Spectrometer with 5- and 7-Grid Energy Modulators

In this work the possibilities of three- and four-stage Bennett-type aperiodic rf mass spectrometers with energy modulators of 5 and 7 grids have been explored. The expressions for the energy gain, resolving power, harmonics, and their relative peak heights have been obtained. The oscillatory behavior of the energy-modulating functions has been analyzed using an IBM 1620 Computer, and graphical representations are given which permit the determination of the energy interval over which the analyzer can be operated. Resolution for the most favored combinations of stage separations has been calculated at Vr1 and 90% values of the retarding voltage level, A grid with improved microoptics and relatively higher ionic transmission coefficient has been developed for use in rf mass analyzers.

Mass spectrometers - Part two

Examines mass-analyzer systems and detectors as well as the resolution and performance of mass spectrometers.

Method for Improving Sensitivity and Resolution of Mass Spectrometer

First Page

Mass Spectrometer Resolution of Ion Pairs of Similar m/e

Mass Spectrometer Resolution of Ion Pairs of Similar <i>m/e</i>