ASMS 1983

ASMS Nomenclature Committee Workshops

Boston, 1983

Two workshops were held this year. The first was on Monday, May 9, and the second on Thursday, May 12. The attendance was low for both workshops, no more than 30 people at any one time, but this was a sufficient number to make some progress and still have a wide cross section of ideas and opinions. There was a general consensus that this committee should be focusing its attention to the more current areas in the field of mass spectrometry in an effort to avoid unnecessary confusion where possible. A significant portion of the second workshop was devoted to this ideal.

The attached list is divided into two parts. The first section consists of terms that were agreed upon at the workshops and are being sent to the ASMS Board for approval. The second section is a list of terms for consideration at next year's meeting. In addition to this section there are the definitions on secondary ion mass spectrometry and ion mass that were listed in the 1982 Bound Volume that are to be considered next year.

All comments on this year's list of definitions or suggestions for future consideration should be sent to:

Doug Cameron

Science and Technology Division

Union Oil Company

P.O. Box 76

Brea, CA 92 621

(714)528-7201

Definitions for Approval

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.

Ionization

Desorption ionization (DI)

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 condensed phase sample by energy input.

Note: Intent is to establish a broad term analogous to chemical ionization which also encompasses a group of related ionization processes.

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.

Ion/molecule reactions

Collision-induced dissociation (CID)

The fragmentation of a polyatomic ion due to a collision of the ion with a target, usually a neutral gas molecule. This is brought about by conversion of part of the ion's translational energy to internal energy during the collision. (Collision activated dissociation (CAD) is a synonymous term, but collisional activation is not recommended.)

Collisional activation (CA)

This refers to the increase in internal energy of an ion as the result of a collision between the ion and a target, usually a neutral gas molecule or atom. (The ion may decompose subsequently.)

Note: The definitions for the terms collision-induced dissociation and collisional activation are modifications of the definitions printed in the 1981 "Bound Volume."

Definitions for Consideration:

Nominal ion mass

The mass of an ion for a given empirical formula calculated using the integer masses of the most abundant isotope of each element, e.g. C=l2, H=l, 0=16.

Monoisotopic ion mass

The mass of an ion for a given empirical formula calculate using the exact mass of the most abundant isotope of each element, e.g. C=12.00000, H=1.007825, 0=15.9949.

Average mass

The mass of an ion for a given empirical formula calculated using the atomic mass of each element, e.g., C=12.011, H=1.00797, O=15.999.

Preformed ions

Vapor phase ions that existed as ionic species in the condensed state.

Thermal desorption

The removal of ionic or neutral from the condensed state by the input of thermal energy into condensed state. The mechanism of energy input should be specified.

Dynamic headspace gas chromatography/mass spectrometry

The distillation of volatile and semivolatile compounds into a continuously flowing stream of carrier gas and onto a gas chromatographic column. This is followed by mass spectrometric analysis of compounds eluting from the gas chromatograph.