ISO/CD 15338

DRAFT INTERNATIONAL STANDARD ISO/DIS 15338
ISO/TC 201/SC 8 Secretariat: JISC
Voting begins on: Voting terminates on:
2005-04-11 2005-09-12
INTERNATIONAL ORGANIZATION FOR STANDARDIZATION • МЕЖДУНАРОДНАЯ ОРГАНИЗАЦИЯ ПО СТАНДАРТИЗАЦИИ • ORGANISATION INTERNATIONALE DE NORMALISATION
Surface chemical analysis — Glow-discharge mass
spectrometry (GD-MS) — Introduction to use
Analyse chimique des surfaces — Spectromètrie de masse à décharge luminescente (GD-MS) — Introduction
à l'utilisation
ICS 71.040.40
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© International Organization for Standardization, 2005

ISO/DIS 15338
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ii ISO 2005 – All rights reserved

Contents Page
Foreword.v
Introduction.vi
1 Scope .1
2 Normative references.1
3 Safety .1
3.1 General.1
3.2 Use of high voltage power supply and connection of the instrument.1
3.3 Use and storage of compressed gas cylinders.2
4 Principle.2
5 Terms and definitions .2
6 Materials (Reagents).4
7 Apparatus .5
7.1 General.5
7.2 Ion source.5
7.2.1 General.5
7.2.2 Source parameters .6
7.2.3 Operational modes .6
7.3 Ion source.7
7.4 Detector system.9
7.5 Vacuum system .9
7.6 Data acquisition and control.9
8 Samples and sample preparation .10
8.1 General.10
8.2 Sample type.10
8.3 Sample geometry.10
8.4 Sample preparation .10
8.4.1 General.10
8.4.2 Metals, alloys and semi-conductors.11
8.4.3 Powders.11
8.4.4 Non-conducting samples.11
8.4.5 Depth profiling samples.11
9 Procedures of measurements .11
9.1 System precautions.11
9.1.1 General.11
9.1.2 Interferences .12
9.2 Obtaining a discharge.12
9.2.1 Uncharacterized samples .12
9.2.2 Characterized samples.12
9.3 Presputtering .12
9.4 Optimizing the ion current.13
9.5 Analysis set-up .13
9.6 Data analysis.13
9.7 Depth profile analysis .14
9.8 Instrument performance .14
9.9 Calibration and analysis-General.14
9.9.1 General.15

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9.9.2 Measurement using relative sensitive factor.15
9.9.3 Measurement using a matrix corrected relative sensitivity factors.18
9.10 Calibration and analysis criteria .19
9.10.1 Number of determinations.19
9.10.2 Calibration standard samples .19
9.10.3 Calibration verification.21
9.10.4 Acceptance of results .21
10 Test report.21

iv © ISO 2004 – All rights reserved

DRAFT 2005
Foreword
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(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
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rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 15338 was prepared by Technical Committee ISO/TC 201, Surface Chemical analysis, Subcommittee
SC 8, Glow discharge spectroscopy.

DRAFT 2005
COMMITTEE DRAFT ISO/CD 15338
Surface chemical analysis — Glow-discharge mass
spectrometry (GD-MS) — Introduction to use
1 Scope
This Standard is a guide to the operation and recommendations for the use of glow discharge mass
spectrometry (GD-MS).
Note: This Standard should be read in conjunction with the instrument manufacturer’s manuals and recommendations.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 18115:2001/PDAM 1, Surface chemical analysis — Vocabulary — Supplement
ISO 5725-1:1994, Accuracy (trueness and precision) of measurement methods and results — Part 1: General
principles and definitions.
ISO 5725-2:1994, Accuracy (trueness and precision) of measurement methods and results — Part 2: Basic
method for the determination of repeatability and reproducibility of a standard measurement method.
ISO 5725-6:1994, Accuracy (trueness and precision) of measurement methods and results — Part 6: Use in
practice of accuracy values.
ISO/DIS 18115, Surface chemical analysis — Vocabulary
1 Safety
3.1 General
The following precautions should be taken to ensure the safety of operators and their environment, during
operation of glow discharge mass spectrometry:
(a) Use of high voltage power supply and connection of the instrument.
(b) Use and storage of compressed gas cylinders.
(c) Handling of cryogenic materials.
3.2 Use of high voltage power supply and connection of the instrument
Electrical connection should comply with the regulations in force. Particular care should be taken to ensure
that connection of the instrument to ground/earth is correct, and the efficiency of the ground/earth connection
should be checked.
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3.3 Use and storage of compressed gas cylinders
The compressed gas cylinders should be regularly tested by the appropriate authorities. Preferably, cylinders
should not be stored or used inside the laboratory. Rather, they should be located outside the laboratory in a
place that is well ventilated, away from direct heat, and accessible to service and safety personnel. The
cylinders should be provided with suitable pressure reducing valves. If more than one cylinder is to be used or
stored in close proximity, it is advisable to indicate in some way which cylinder or cylinders are currently in use.
3.4 Handling of cryogenic materials
The installation of vessels of cryogenic materials shall be located so as to minimize the risk to personnel. Area
where cryogenic liquids are stored and used shall be ventilated to prevent the accumulation of gas or vapour
which could evaporate from the liquid. It is good practice to keep areas where cryogenic liquids are used very
clean. All transfer operation shall be in accordance with statutory requirement. When a cryogenic liquids is
being transferred from one vessel to another, precautions shall be taken to minimize any spills and splashing.
The requirement of the relevant regulatory authority shall also be met.
4 Principle
In a glow discharge source electrical power is supplied between the sample (cathode) and the anode by a
power supply typically operated in direct current (dc) at 0.5 to 2 kV and 1 to 30 mA. Argon (or other inert gas
such as neon, krypton or helium) is introduced into the discharge cell. The pressure inside the discharge cell
is typically a few hundred Pascals (Pa). The potential difference between the cathode and the anode is
applied and a glow discharge (plasma) is established. Sample material (single atoms and/or clusters) which
are sputtered by ions and neutrals diffuse into the plasma.
Ions formed in the glow discharge are extracted from the cell and pass into a mass analyzer. The mass
analyzer is used to transmit ions of given mass to charge ratio to the detector(s). The ions reaching the
detector(s) are measured directly as ion current or counted by a counting system. Information is stored in a
computer system. Elemental mass fractions are typically calculated by the instrument software using the ion
currents of isotopes, by normalizing the signal to the signal of a matrix element and subsequently comparing
the normalized signals with those arising from the corresponding elements in calibration samples.
5 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
5.1
Abundance sensitivity
ratio of the maximum ion current recorded at a mass m to the ion current arising from the same species
recorded at an adjacent mass (m ± 1).
5.2
Accuracy of measurement
the closeness of the agreement between a test result and the accepted reference value.
5.3
Anode
more positively charged electrode in a glow discharge device.
5.4
Cathode
more negatively charged electrode in a glow discharge device.
2 © ISO 2004 – All rights reserved

DRAFT 2005
5.5
Chemical specie
atom, molecule, ion or functional group.
5.6
Detection limit (DL)
smallest amount of an element or compound that can be measured under specified analytical conditions.
5.7
Elemental intensity
the amount of ion current recorded for a particular element.
5.8
Flat cell
a sample cell used for the analysis of flat samples.
5.9
Glow discharge, abnormal
glow discharge operated in a current/voltage regime for which an increase in current is accompanied by an
increase in voltage.
5.10
Glow discharge, normal
glow discharge operated in a current/voltage regime for which an increase in current is accompanied by little
or no detectible change in voltage.
5.11
Ion beam ratio (IBR)
the signal intensity of the analyte ion divided by the intensity of the matrix ion(s), both corrected for isotopic
abundance.
5.12
Intensity, peak
measure of signal intensity for a constituent spectral peak.
5.13
Intensity, signal
strength of a measured signal at a spectrometer detector or after some defined processing.
5.14
Interference signal
signal measured at the position of mass of interest due to another, undesired, species.
5.15
Mass to charge ratio
mass of an ion divided by the number of electrons added to or removed from it to form an ion.
5.16
Pin cell
sample cell used for the analysis of wire and rod samples.
5.17
Plasma
gas consisting of ions, electrons, and neutral particles.
5.18
Preburn
period during which preburning occurs, i.e. period when plasma is on before analysis.
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5.19
Presputtering period
process of sputtering, prior to signal registration, employed to allow steady state sputtering to be established
and analytical signals to stabilise.

5.20
Precision of measurements
the closeness of the agreement between independent test results obtained under stipulated conditions,
normally reported as a standard deviation.
5.21
Reference material
material or substance one or more of whose property values are sufficiently homogeneous and well
established to be used for the calibration of an apparatus, the assessment of measured methods, or for
assigning value to materials.
5.22
Reference material, certified
reference material, accompanied by a certificate, one or more of whose property values are certified by a
procedure which establishes its traceability to an accurate realization of the unit in which the property values
are expressed, and for which each certified values is accompanied by an uncertainty at a stated level of
confidence.
5.23
Resolution of spectrometer
contribution of the spectrometer to the measured full width at half maximum (FWHM) or at 10% height of
maximum intensities of spectral peaks above their local backgrounds.
5.24
Resolving power of a spectrometer
ratio of the mass to the resolution of the spectrometer at that mass.
5.25
Pin, rod and wire sample
a sample with cylindrical or square cross section of nominal length typically 20 mm and not normally
exceeding 10 mm across.
5.26
Secondary cathode
electrically conductive mask, containing an aperture, used to enable sputtering of an electrically
nonconductive sample surface in a direct glow discharge device.
5.27
Sensitivity factor, relative (RSF)
coefficient for an element with which the measured intensity of a mass peak for that element, divided by the
measured intensity of a mass peak of a matrix element, is multiplied to yield the mass fraction of that element
in the sample divided by the mass fraction of the matrix element.
NOTE RSF values for some other techniques are sometimes calculated as the inverse of the definition used here for GD-
MS.
5.28
Transmission
a ratio of the number of ions reaching the detector relative to the number of ions entering the mass analyzer.
6 Materials (Reagents)
Water- deionized water, 18 M ohm or better.
4 © ISO 2004 – All rights reserved

DRAFT 2005
Argon gas (Ar) - Of purity at least 99.9995% argon (or other gases of high purity)
Liquid nitrogen (LN2) - For cryogenic cooling of discharge cell.
Compressed air - To operate pneumatic valves.
7 Apparatus
7.1 General
A glow discharge mass spectrometer typically consists of the following parts:
(a) Ion source
(b) Mass analyzer
(c) Detector system
(d) Data acquisition and control
7.2 Ion source
7.2.1 General
A glow discharge ion source consists of a glow discharge cell and a power supply. The ion source also may
contain a series of focusing plates, external to the cell, whose function is to extract ions from the cell and
focus these ions into the mass spectrometer.
Typically the body of the discharge cell is connected to the anode output of the power supply. The sample
serves in the glow discharge cell as a cathode and is connected to the cathode output of the power supply.
The discharge cells have been designed to accommodate samples in the geometries recommended in 8.3
and examples of the discharge cells are illustrated with the appropriate sample holders in Figures 1a and 1b.
IInnsulsulaatotorr
IoIonn
ExExitit
SlSlitit
SampleSample
AnodAnodee
PlatPlatee
SampleSample Holder Holder
CatCathhodeode
PlatePlate
Figure 1a — Example of a cell used for the analysis of pin samples

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InInsusullaattoorr
CeCellll B Booddyy
SprinSpringg
IoIonn
ExExitit
SlitSlit
AnAnodode e
PlatPlatee
SampleSample
(Ca(Catthodhode)e)
Figure 1b — Example of a cell used for the analysis of flat samples

7.2.2 Source parameters
The source parameters are as follows:
(a) Electrical
a. Potential difference
b. Current
c. Power
(b) Geometrical
a. Dimension of sample exposed to plasma
b. Anode to sample distance
c. Cathode dimension
d. Mask dimension, where appropriate
(c) Gas type and pressure
(d) Cell temperature
(e) Type of sample
1.1.1 Operational modes
The direct current source may be operated in different modes, including:
6 © ISO 2004 – All rights reserved

DRAFT 2005
(a) Constant current with potential difference selected by adjusting the plasma gas pressure.
(b) Constant potential difference with current selected by adjusting the plasma gas pressure.
The discharge pressure may be regulated using a mass flow controller or a needle valve. For some types of
GD-MS instruments, the high accelerating voltages encountered require a capillary in the gas line to prevent
electrical breakdown through the gas line. Radio frequency powered GD sources are also being developed for
GD-MS.
7.3 Ion source
There are two types of mass analyzers commonly used for glow discharge mass spectrometry: magnetic
sector and quadrupole instruments. Other types like time-of-flight instruments are also becoming more
common.
(a) Magnetic sector - This type of instrument (see Figure 2a) typically utilizes an electro-magnet and an
electrostatic analyzer (ESA). The magnet achieves mass separation, and as the magnetic field is
increased, ions with a greater mass to charge ratio are transmitted. The ESA acts as an energy filter and
transmits only those ions with the appropriate energies.
This arrangement permits high transmission and high resolution operation, giving accurate mass
information advantageous in complex sample matrices where there is an increased possibility of
interferences. A resolving power of 4000 is sufficient to overcome most common interferences.

Figure 2a—Schematic diagram of a magnetic sector mass analyzer

(b) Quadrupole - Ions of increasing mass are transmitted as an increasing direct current bias is imposed
using a radio frequency (rf) potential applied to four parallel rods (see Figure 2b). The mass to charge
ratio is used to filter the elements such that only those selected emerge.
DRAFT 2005
Whilst a quadrupole does not have the high resolution of a magnetic sector instrument, typically it has a
resolving power of less than 200, it has a much faster scanning speed, is compact and is able to achieve
low detection limits if interferences are kept low.

Figure 2b—Schematic diagram of a quadrupole mass analyzer
(c) TOF (time-of-flight mass spectrometers) – An ensemble of ions are accelerated simultaneously by an
electric field and then allowed to drift a certain distance before impinging onto an ion detector(see Figure
2c). In the accelerating field all ions receive a similar E/z (energy per charge). Therefore, ions with low m/z
will arrive at the detector earlier than ions with higher m/z. By measuring the arrival time of ions the, m/z of
those ions can be determined.
Whilst quadrupoles and sector instruments are m/z filters, TOFs do not have to scan in order to record a
mass spectrum and therefore have the potential for higher duty cycle. TOFs intrinsically have a large
mass range and good mass accuracy. They also have reasonably good resolvin
...