Harry J. Svec

THE ABSOLUTE ABUNDANCE OF THE NITROGEN ISOTOPES IN THE ATMOSPHERE AND COMPRESSED GAS FROM VARIOUS SOURCES

The absolute abundance of the isotopes in atmospheric and commercial compressed N2 from various sources has been determined. Nitrogen gas standards, prepared by mixing separated nitrogen isotopes in the form of (NH4)2SO4 solutions, were employed to calibrate two 60° sector mass spectrometers. As a result, the absolute ratio of N14/N15 in atmospheric nitrogen was found to be 272.0 ± 0.3 Small variations from this value were found for commercial compressed gas. The mass spectrometric procedure used in determining the N229+N228+ ratio allowed for detection of differences to 1 part in 3500. However, the absolute accuracy of the abundance measurements was limited to 1 part in 1000 because of the semi-micro Kjedahl distillation employed to determine the amount of (NH4)2SO4 present in the solutions of the separated isotopes. In these measurements, instrumental background played a very significant role. A reliable method of correcting the observed N229N228+ ratio for the contribution of the background at these mass position was developed.

Mass spectrometric evidence for suprathermal ionization in an inductively coupled argon plasma

Mass spectra have been obtained of species in the axial channel of an inductively coupled argon plasma by extracting ions from the inductively coupled plasma into a vacuum system housing a quadrupole mass spectrometer. Ionization temperatures (Tion) are obtained from relative count rates of m/z-resolved ions according to two general types of ionization equilibrium considerations: (a) the ratio of doubly/singly charged ions of the same element, and (b) the ratio of singly charged ions from two elements of different ionization energy. The Tion values derived from measurement of Ar+2/Ar+, Ba+2/Ba+, Sr+2/Sr+, and Cd+/I+ are all greater than those expected from excitation temperatures measured by other workers. The latter three values for Tion are in reasonable agreement with values obtained by optical spectrometry for a variety of argon inductively coupled plasmas.

Elemental partitioning in ash depositories and material balance for a coal burning facility by spark source mass spectrometry

Spark source mass spectrometry is shown to be an excellent analytical tool for determining enrichment factors and a useful tool for measuring material balances for a coal-burning facility. Measurements of enrichment and material balance are reported for 62 elements in two US coals obtained by using SSMS as the sole analytical technique. Copper was used as an internal reference. The halogens, Hg, S and Se were found to be lost to the stack. Systematic errors are noted in relative sensitivity coefficients for some of the elements, and between coal and ash samples.

The absolute abundance of the lithium isotopes in natural sources

The absolute abundance of the lithium isotopes in natural sources from North America and Africa has been determined. The absolute 6Li/7Li ratio from thirteen spodumene samples was found to be 0.08182 ± 0.00033. This ratio for a batch of reagent Li2CO3 was found to be 0.d07926 and for Li2NaPO4 from Searles Lake was found to be 0.07957. Considering the thirteen spodumene samples to represent the principal commercial sources of lithium, an atomic weight of 6.9403 ± 0.0005 is calculated for the element on the basis of these absolute abundances and values for the nuclidic masses.

Energetics of the Ionization and Dissociation of Ni(CO)4, Fe(CO)5, Cr(CO)6, Mo(CO)6 and W(CO)6

The mass spectra of the metal carbonyls of Ni, Fe, Cr, Mo and W have been established. The ionization potentials and the energy necessary to form the various fragment ions have been measured. These data are used to calculate heats of formation for the various ions. The following dissociation energies were also calculated from the appearance potential data and ancillary thermochemical data and the valence state excitation energies: 1) specific bond dissociation energies for singly charged metal carbonyl ions, 2) average dissociation energies for singly charged parent ions, 3) average dissociation energies of neutral metal carbonyls to ground state products in which case comparison to calorimetric measurements are given, and 4) average dissociation energies of the metal carbonyls to valence state excited products. The unimolecular decomposition of metal carbonyls is discussed and the appearance potentials of the metal ions are used to calculate valence state excitation energies for the metal atoms. These values, W* = 3.18 eV, Mo* =4.92 eV, Cr* = 8.04 eV or 7.41 eV and Fe* = 6.57 eV are in excellent agreement with the observed spectroscopic values for Mo and with the values calculated from spectroscopic measurements of Cr and Fe. The value for the valence state excitation energy of W is the first reported in the literature.

Applications of resins for extracting organic components from water

ZusammenfassungDie verwendeten Harze, die Extraktionsvorrichtungen, einige Leistungstests sowie die allgemeine Methodik werden kurz beschrieben. Neue Entwicklungen von einfachen und wirtschaftlichen Verfahren zur Überwachung interessierender Verschmutzungsstoffe werden besonders erwähnt. Als Beispiele werden Wasserverunreinigungen durch PVC-Röhren, durch Pesticide, Amine, halogenierte Kohlenwasserstoffe sowie Modellverbindungen diskutiert. Das Verfahren der Sorption an Harz wird mit der Sorption an Aktivkohle sowie mit der Lösungsmittelextraktion verglichen. Ein neu entwickeltes Kleingerät zur Probenahme wird beschrieben.SummaryThe discussion of the applications is prefaced by very brief descriptions of: 1) the resin characteristics, 2) the extraction device, 3) some efficiency tests, and 4) the general methodology. Recent developments of simple and inexpensive procedures for the monitoring of selected contaminants of concern are stressed. Examples are given of the contamination of water by PVC tubes and of the measurements of pesticides, amines, halocarbons, and model compounds in water. Practical comparisons of the resin sorption method to carbon sorption and solvent extraction procedures are presented and recently developed mini-samplers are discussed.

A mass spectrometer for the characterization of neutral species produced in the electron bombardment of gases

Abstract A mass spectrometer which permits the direct study of neutral species produced by the electron bombardment of gases is described. Functionally, it consists of an ion source with two independent electron beams, a quadrupole mass filter, and a phase-sensitive ion detector. The instrument provides for automatic scanning and recording of mass spectra and ionization efficiency data for the neutral species produced in one electron beam (pulsed at 260 Hz) and subsequently ionized in the other electron beam. The mass spectrum of the neutral species obtained from the electron bombardment of benzene, along with the ionization efficiency data for the neutral species, are presented to demonstrate the quality of the data obtained.

The determination of trace elements in aqueous media without preconcentration using a cryogenic hollow-cathode ion source

The glow discharge in a hollow cathode containing 20–50 μl of an aqueous sample held at liquid-nitrogen temperature is used as a source of ions in a double-focussing mass spectrometer. The device was tested with nine solutions containing an aggregate of seventy elements. Seven elements (F, P, S, Sc, Mn, Ni, and Ta) could not be determined because of interferences. The remainder of the elements could be determined at various detection limits ranging from sub-ng ml−1 to μg ml−1. Mercury (32 pg) could be detected in 20 μl of water in the presence of Tl, Pb, Bi, Th, U, and Al.

Effect of laser focus on ion production in the laser ion source for elemental analysis

Abstract Optimization of the laser ion source is best done via ion beam diagnostics rather than by visual focusing to the specimen surface or to a minimum diameter brightest plasma. Doubly charged ions signals are especially useful for the optimization of both the laser focus and the local laser power density level.

A 15-cm radius mass spectrometer which simultaneously collects positive and negative ions

Abstract A mass spectrometer which simultaneously extracts positive and negative ions from a single electron beam is described. Its features include: ready accessibility to the ion source and collectors, convenient attainment of alignment, simultaneous display of positive and negative ion spectra, and direct plotting of ionization efficiency data.