ASMS 1984

ASMS Committee on Nomenclature

San Antonio, 1984

The meeting of the Nomenclature Committee was held on May 26, 1984, and it was attended by 10 people including the Chairman. The Chairman gave a brief history of the actions of the Committee since 1979. The history was deduced from reports of the Committee meetings published in the Bound Volumes from 1979 through 1983. It was particularly pointed out that 370 and expressions referring to mass spectrometry have been defined and given in these issues of the Bound Volume, and it may be concluded that the Committee has been very active. It was also deduced from the report of the 1983 meeting of the Committee that action was required at the 1984 meeting on the terms listed on p. 970 of the 1983 Bound Volume under the heading, "Definitions for Consideration" and on the 58 terms given on pp. 904-909 of the 1982 Bound Volume starting with the terms under the heading "Secondary Ion Mass Spectrometry."

The Committee voted to accept all of the terms under consideration on p. 970 of the 1983 Bound Volume with the exception of the definition of Preformed Ions, which was deleted as being obvious and unnecessary. A small editorial change was made on Lhe definition for Average Mass. The Chairman regrets that the maker and seconder of the motion on these matters was inadvertently not recorded.

It was moved by J. Yergey and seconded .by J. Hiller not to accept any of the terms referring to Secondary Ion Mass Spectrometry given on pp. 904-907 of the 1982 Bound Volume. The motion carried. However, in addition it moved by T. Lehman and seconded by K. Busch that these terms and their definitions be given to the organizers of the conference on secondary ion mass spectrometry going to be held this Fall. The motion carried, and the Chairman asked Dr. Lehman to undertake theaction called for by the motion. He agreed to do this.

In the material received by the Chairman from the previous Chairman was a list of 268 terms relating to computers and computer technology. The correspondence examined by the Chairman seemed to imply that these terms should be considered at the 1984 meeting of the Committee. Consequently they were examined with as much care as was possible given the very large number of terms and the relatively limited time of the meeting. It was moved by H. Fales and seconded by J. Yergey that these terms not be accepted by the Committee. The motion passed unanimously.

It was moved by J. Watson and seconded by J. Yergey that the Chairman bring together all of the terms which have appeared in the Bound Volumes through 1983 (and including those approved at this meeting) to make one . complete list for easy reference by members of ASMS and mass spectrometrists in general. The Chairman agreed to do this, and the resulting list is included as pa.t of this report.

The Committee discussed the question of what should be the future actions of the Committee. In view of the large number of terms already defined, the sense of the meeting was not to consider any new category of terms for the next year. However, the Committee agreed to meet at the next ASMS meeting to consider further activities.

F.H. Field Chairman 6 June 1984

Combined List of Defined Terms/big>

Analyzers

Electrostatic analyzer

A velocity focusing device composed of means for producing an electrostatic field perpendicular to the direction of ion travel. Effect is to bring to a common focus all ions of a given kinetic energy. Usually used in combination with a magnetic analyzer for mass analysis.

Magnetic analyzer

A direction focusing device composed of means for producing a magnetic field perpendicular to the direction of ion travel. Effect is to bring to a common focus all ions of a given momentum with the same mass to charge ratio.

Quadrupole analyzer

A mass filter consisting of means of creating a quadrupole fiel of a constant component and a varying component in such a manner as to allow transmission of only a selected mass-charge ratio,

Time of flight analyzer

A device consisting of a means to measure the flight time of particles with an equivalent kinetic energy over a fixed distance.

Wien analyzer

A velocity filter composed of means for creating crossed homogeneous electric and magnetic fields such that only ions of a fixed velocity are transmitted.

Mass resonant analyzer

A mass analyzer composed of means for mass dependent resonant energy transfer and measurement of the resonance frequency, power or ion current of the resonant ions. (The following are standard instrumental configurations utilizing one or more of the above techniques.)

Double focusing analyzer

The combination of a magnetic analyzer and electrostatic analyzer in either sequence to effect direction and velocity focusing.

Ion cyclotron resonance analyzer

A device to determine the mass of an ion by measuring its resonant frequency.

Ion trap analyzer

A mass resonance analyzer co'mposed of means for creating a three dimensional rotationally symmetric quadrupole field capable of storing ions at selected masses,

Mass spectrometer configurations

Multianalyzer instruments should be named or the analyzers in the sequence in which they are traversed by the ion beam, where B is for a magnetic analyzer, E for an electrostatic analyzer, Q for a quadrupole analyzer, TOF for time of flight analyzer, and ICR for an ion cyclotron resonance analyzer. For example, we have a BE mass spectrometer ("reversed" geometry double focusing instrument), BQ mass spectrometer (hybrid sector and quadrupole instrument), EB Q (high resolution followed by a quadrupole). Note that a triple quadrupole which has il'.!2, mass analyzers is a QQ mass spectrometer. Problem: Time of flight, simultaneously or sequentially with other mass analyzers.

Data System

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Ionization Nomenclature

Electron ionization

This is the term used to describe ionization of any species by electrons. The process may, for example, be written

Photo-Ionization by photons.

and

M + e- + M+ + 2eM

0 + e- + M+ + 2e

for atoms or molecules, for radicals.

This is the term generally used to describe ionization of any species The process may, for example, be written

[Note: Electrons and photons do not "impact" ,oolecules or atoms. They interact with them in ways that result in various electronic excitations including ionization. For this reason it is recommended that the terms 'Electron impact' and 'Photon impact' be not used].

Field Ionization This tern relates to the removal of electrons from any species by interaction with a high electrical field.

Field Desorotion This tern is used to describe the fornation of ions in the gas phase from a material deposited on a solid surface (known as an 'emitter') in the presence of a high electrical field. 'Field desorption' is an ambiguous term because it implies that the electric field desorbs a material as an ion from some kind of emitter on which the material is deposited. There is growing evidence that some of the ions formed are due to thermal ionization, some to field ionization of vapor evaporated from material on the emitter. Because there is little or no ionization unless the emitter is heated by an electric current, 'field desorption' is a misnomer. The term is however firmly implanted in the literature and most users (by no means all) understand what is going on regardless of the implications of the term. In addition, no better simple term has been suggested to take its place and so, reluctantly, it is recommended that it be retained.

Chemi-ionization and chemical ionization are two terns which should not be used inter-changeably.

Chemi-ionization refers to a process whereby gaseous molecules are ionized when they interact with other internally excited gaseous molecules or molecular moieties.

Chemical ionization concerns the process whereby new ionized species are formed when gaseous molecules interact with ions. The process may involve transfer of an electron, proton or other charged species to or between the reactants. When a positive ion results from chemical ionization, the tern may be used without qualification. When a negative ion results, the term neBative ion chemical ionization should be used.

Surface Ionization takes place when an atom or molecule is ionized when it interacts with a solid surface. Ionization only occurs when the work function of the surface, the temperature of the surface, and the ionization energy of the atom or molecule have an appropriate relationship.

Thernal Ionization takes place when an atom or ,oolecule interacts with a heated surface or is in a gaseous environment at high temperatures. [Examples of the latter may be a capillary arc plasma, a microwave plasma, or an inductively coupled plasma].

Atmospheric Pressure Ionization is an ambiguous term. In essence, it is used to describe chemical ionization at atmospheric pressure. It is recommended that use of the tern should be discouraged.

Spark (Source) Ionization occurs when a solid sample is vaporized and partially ionized by an internittent electric discharge. Further ionization occurs in the discharge when gaseous atoms and small molecular ,ooieties interact with energetic electrons in the internittent discharge. It is recommended that the word 'source' be dropped from this term.

Auto-ionization occurs when an internally supra excited atom or molecular moiety loses an electron spontaneously without further interaction with an energy source. (The state of the atom or molecular moiety is known as a pre-ionization state).

Associative Ionization occurs when two excited gaseous atoms or molecular moieties interact and the sum of their internal energies is sufficient to produce a single, additive ionic product.

Multi-photon Ionization occurs when an atom or molecule and their concomitant ions have energy states whereby the energy in two or more photons can be absorbed.

Penning Ionization occurs through the interaction of two or more neutral gaseous species at least one of which is internally excited.

CharBe Exchange (Olarge Transfer) Ionization occurs when an ion/atom or ion/molecule reaction takes place in which the charge on the ion is transferred to the neutral species without any dissociation of either.

Ion-Pair Formation involves an ionization process in which a positive fragment ion and a negative fragment ion are the only products.

Ionization Cross Section This is a measure of the probability that a given ionization process will occur when an atom or molecule interacts with an electron or a photon.

Electron Attachment A resonance process whereby an external electron is incorporated into an atomic or molecular orbital of an atom or molecule.

Ionization Energy This is the minimum energy of excitation of an atom, molecule or molecular moiety required to remove an electron in order to produce a positive ion.

Vertical Ionization This is a process whereby an electron is removed from a molecule in its ground or an excited state so rapidly tha.. a positive ion is produced without change in the positions or momenta of the atoms. The resultant ion is often in an excited state.

Adiabatic Ionization A process whereby an electron is removed from the ground state of an atom or molecule producing an ion in its ground state.

Ionization A process which produces an ion from a neutral atom or molecule. Dissociative Ionization An ionization process in which a gaseous molecule decomposes to form products, one of which is an ion.

Ionic Dissociation A decomposition of an ion into another ion of lower formula weight and one or more neutral species.

Ionization Efficiency is the ratio of the number of ions formed to the number of electrons or photons used..

An Ionization Efficiency Curve shows the number of ions produced as a function of the energy of the electrons or photons used to produce ionization.

Laser Ionization occurs when a sample is irradiated with a laser beam. In the irradiation of gaseous samples, ionization occurs via a single- or multi-photon process. In the c,se of ..olid samples, ionization occurs via a thermal process.

Desorption Ionization (DJ). General term to encompass the various procedures (secondary ion mass spectrometry, fast atom bombardment, californium fission fragment desorption, thermal desorption) in which ions are generated directly from a solid sample by energy input.

Types of Ions

Positive ion

This is an atom, radical, molecule or molecular moiety which has lost one or more electrons thereby retaining an electrically positive charge. The use of the term cation as an alternative is not recommended. The use of mass ion is not recommended.

Negative ion

An atom, radical, molecule or molecular moiety in the vapor phase which has gained one or more electrons thereby acquiring an electrically negative charge. The use of the term anion as an alternative is not recommended.

Ion/molecule reactions

Sample Introduction

Sample introduction system

This is a system used to introduce sample to a mass spectrometer ion source before and/or during analysis. (sample introduction system, introduction system, sample inlet system, inlet system, and inlet are synonymous terms.)

Reservoir inlet

This is an inlet system having an enclosed volume (the reservoir), with provision to evacuate the reservoir, to admit sample to the reservoir, and to allow gas or vapor from the reservoir to flow through a leak to the mass spectrometer ion source. A complete description of a reservoir inlet should include a description of the method by which the sample is introduced into the reservoir (e.g. with gas-metering, septum, fritted-disc, or teflon-cup introduction), an indication as to whether the leak provides viscous or molecular flow, and an indication whether the reservoir is heated.

Batch inlet

This is the historic term for a reservoir inlet. Reservoir inlet is preferred because a direct inlet probe is also a form of batch inlet. Batch gas inlet or batch vapor inlet is, however, a completely descriptive term.

Dual viscous-flow reservoir inlet

This is an inlet having two reservoirs, used alternately, each having a leak that provides viscous flow. This inlet is used for making precise comparisons of isotope ratios in two samples.

Continuous inlet

This is an inlet in which gas or vapor passes continuously into a mass spectrometer ion source, as distinguished from a reservoir inlet or a direct inlet probe.

Non-fractionating continuous inlet

This is a continuous inlet in which gas flows from a gas stream being analyzed to the mass spectrometer ion source without any change in the conditions of flow through the inlet or by the conditions of flow through the ion source.

Direct-inlet probe

This is a rod having a sample holder at one end, which is inserted into the vacuum system of a mass spectrometer through a vacuum lock, placing the sample near to, at the entrance of, or within the ion source, so that the sample can be vaporized after introduction to the vacuum system by heat from the ion source or by heat applied to the probe from an external source. (direct inlet probe, direct-introduction probe or direct-insertion probe are synonymous terms. The use of DIP as an abbreviation for these terms is not recommended.)

Vacuum-lock inlet

This is an inlet in which a sample is placed in a chamber, the chamber is pumped out, and a valve is opened so that the sample can then be introduced to the mass spectrometer ion source. A vacuum-lock inlet commonly uses a direct- inlet probe which passes through one or more sliding seals, but other kinds of vacuum-lock inlets are possible.

Extended direct-inlet probe

This probe provides for insertion of a sample on an exposed surface (such as a flat surface or a wire) into (rather than up to the entrance of) the ion source of a mass spectrometer. (This term is synonymous with direct-exposure probe.)

Crucible direct-inlet probe

With this probe, the sample is held in a cup-shaped device (the crucible) rather than on an exposed surface. A direct-inlet probe is assumed to be a crucible type unless otherwise specified.

GC/MS interface

This is an interface between as gas chromatograph and a mass spectrometer which serves to provide continuous introduction to a mass spectrometer ion source of effluent gas from a gas chromatograph during the period for which the effluent gas is to be analyzed.

Direct GC/MS

This is an interface in which the entire effluent from the gas chromatograph passes to the mass spectrometer ion source during an analysis, without any splitting of this effluent.

Splitter GC/MS interface

This is an interface in which the effluent from the gas chromatograph is divided before admisssion to the mass spectrometer, without enrichment of sample with respect to carrier gas.

Separator GC/MS interface

This is an interface in which the effluent from the gas chromatograph is enriched in the ratio of sample to carrier gas. (Separator, molecular separator, and enricher are synonymous terms.) A separator should generally be defined as an effusion separator, a jet separator, or a membrane separator.

Effusion separator (or effusion enricher).

This is an interface in which carrier gas is preferentially removed from the gas entering the mass spectrometer by effusive flow (e.g. through a porous tube or through a slit).

Jet separator

This is an interface in which carrier gas is preferentially removed by diffusion out of a gas jet flowing from a nozzle. (jet separator, jet-orifice separator, jet enricher and jet-orifice enricher are synonymous terms.)

Membrane separator

With this separator, the gas or vapor passes to the mass spectrometer through a semi-permeable membrane (e.g. a silicone membrane) which selectively transmits organic compounds in preference to carrier gas. (Membrane Separator, Membrane Enricher, Semi-Permeable Membrane Separator, and Semi-Permeable Membrane EnrTcher are synonymous terms.)

Solvent-divert system

This system is used in conjunction with an interface which permits temporary interruption of the flow from a gas chromatograph to a mass spectrometer by opening a valve to a pumping line, so that an effluent present at a high concentration (usually solvent) does not enter the mass spectrometer ion source at a high concentration.

Liquid chromatograph/mass spectrometer (LC/MS) interface

This interface is between a liquid chromatograph and a mass spectrometer which serves to provide continuous introduction to a mass spectrometer ion source of the effluent from a liquid chromatograph during the period for which the effluent is to be analyzed.

Moving belt (ribbon or wire) interface

With this interface, all or a part of the effluent from a liquid chromatograph is continously applied to a belt (ribbon or wire), which passes through two or more orifices, with differential pumping, into the mass spectrometer vacuum system; after which heat is applied, to remove the solvent, and then to evaporate the solute into the ion source.

Direct chemical ionization interface

With this interface, all or a part of a liquid chromatograph effluent passes continuously to the mass spectrometer, in which the solvent is used as a chemical ionization agent for ionization of the solute.

Scanning of spectra

Vacuum

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