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SEMI C3.20-92 © SE MI 1982, 1999 2 4.2.1 D etection Limit — 500 ppb. 4.2.2 In strument Parameters 4.2.2.1 Colu mn: 5A molecular sieve, 1 . 9 m (6 ft) by 3.2 mm (1/8 in) ss, or equi valent. 4.2.2.2 C arrie r Flow : 30 mL …
SEMI C3.20-92 © SEMI 1982, 19991
SEMI C3.20-92 (Reapproved 0999)
STANDARD FOR HELIUM (He), IN CYLINDERS, 99.9995% QUALITY
This standard was technically reapproved by the Global Gases Committee and is the direct responsibility of
the North American Gases Committee. Current edition approved by the North American Regional Standards
Committee on April 15, 1999. Initially available at www.semi.org August 1999; to be published September
1999. Originally published in 1982; previously published in 1992.
1 Description
1.1 Helium is a rare gas or cryogenic liquid that is
inert, colorless, odorless, and tasteless.
2 Specifications
QUALITY: 99.9995%
Impurities Maximum Acceptable
Level (ppm)*
Carbon monoxide and carbon
dioxide (CO + CO
2
)
1
Nitrogen (N
2
)
2
Oxygen (O
2
)0.5
Total Hydrocarbons expressed as
Methane (THC)
0.5
Water (H
2
O) (v/v) 0.5
TOTAL SPECIFIED IMPURITIES 4.5
* An analysis of significant figures has not been considered. The
number of significant figures will be based on analytical accuracy and
the precision of the provided procedure.
3 Physical Constants (for in formation only)
Metric Units US Units
Molecular weight 4.003 4.003
Boiling point at 1 atm
-268.9°C -452.0°F
Density of gas at
21.1°C (70°F) and 1
atm
0.1656 kg/m3 0.01034 lb/ft3
Specific gravity of
gas at 21.1°C and 1
atm
(air = 1)
0.138 0.138
Density of liquid at
boiling point
124.9 kg/m3 7.798 lb/ft3
4 Analytical Procedures (Se e Notes 1, 2)
4.1 Carbon Monoxide and Carbon Dioxide — This
procedure is for the determination of carbon monoxide
and carbon dioxide in helium using a gas
chromatograph with a flame ionization detector and
methanizer.
4.1.1 Detection Limit — 100 ppb (mole/mole).
4.1.2 Instrument Parameters
4.1.2.1 Column:
Porapak T or Q, 3 m (9.8 ft) by 3 mm (1/8 in) ss;
or
Chromosorb 102, 2 m (6.6 ft) by 3 mm ss;
or equivalent.
4.1.2.2 Carrier Flow: 30 mL/min helium.
4.1.2.3 Sample Volume: 0.5 to 2.0 mL.
4.1.2.4 Temperatures:
Detector 280°C
Column Oven 60°C
Methanizer 350°C
4.1.3 Calibration Standards — 1-10 ppm (mole/mole)
carbon monoxide, 1-10 ppm (mole/mole) carbon
dioxide, balance helium.
4.1.4 Operating Procedure
4.1.4.1 Inject the calibration standard into the column
using a gas sampling valve. Record the retention times
and peak areas. Order of elution is carbon monoxide,
carbon dioxide.
4.1.4.2 Inject the sample to be tested in same manner
as the calibration standard. Record the retention times
and peak areas.
4.1.4.3 Repeat 4.1.4.1.
4.1.4.4 Compare the average peak areas of the
calibration standard to that of the helium sample being
tested. Calculate the concentrations of carbon monoxide
and carbon dioxide, using the formula below. The result
may not exceed the specification in Section 2 of this
Standard.
Sample Peak Are
a
Standard Peak Area
×
C
oncentrat
i
on
of Standard
=
C
oncentrat
i
on
of Sample
4.2 Nitrogen — This procedure is for the
determination of nitrogen in helium using a gas
chromatograph with a helium ionization detector.
SEMI C3.20-92 © SEMI 1982, 1999 2
4.2.1 Detection Limit — 500 ppb.
4.2.2 Instrument Parameters
4.2.2.1 Column: 5A molecular sieve, 1.9 m (6 ft) by
3.2 mm (1/8 in) ss, or equivalent.
4.2.2.2 Carrier Flow: 30 mL/min helium.
4.2.2.3 Sample Volume: 3.0 mL.
4.2.2.4 Temperatures:
Detector
125°C
Column Temperature
65°C
4.2.3 Calibration Standard — 5-15 ppm nitrogen in
helium.
4.2.4 Operating Procedure
4.2.4.1 Inject the calibration standard into the column
using a gas sampling valve. Record the retention time
and peak area.
4.2.4.2 Inject the sample to be tested in same manner
as the calibration standard. Record the retention time
and peak area.
4.2.4.3 Repeat 4.2.4.1.
4.2.4.4 Compare the average peak area of the
calibration standard to that of the helium sample being
tested. Calculate the concentration of nitrogen, using
the formula below. The result may not exceed the
specification in Section 2 of this Standard.
Sample Peak Are
a
Standard Peak Area
×
C
oncentrat
i
on
of Standard
=
C
oncentrat
i
on
of Sample
4.3 Oxygen — This procedure is for the determination
of oxygen in helium using a continuous flow analyzer
using an electrochemical method.
4.3.1 Detection Limit — 100 ppb (mole/mole).
4.3.2 Flow Rate — Set sample flow rates in
accordance with the instrument manufacturer's
instructions.
4.3.3 Calibration Standard — 1-10 ppm (mole/mole)
oxygen in helium or in accordance with the instrument
manufacturer's instructions.
4.3.4 Operating Procedure
4.3.4.1 Do not change the initial sample flow setting
once established.
4.3.4.2 Introduce helium sample and record oxygen
reading. The result may not exceed the specification in
Section 2 of this Standard.
4.4 Water — This procedure is for the determination
of trace moisture (water) in helium using a continuous
flowing piezoelectric hygrometer. (See Note 3.)
4.4.1 Detection Limit — 0.1 ppm (vol / vol) or -90°C
(-130°F).
4.4.2 Flow Requirements — Set the sample pressure
and flow rate in accordance with the instrument
manufacturer's instructions.
4.4.3 Calibration Standards — Construct a calibration
curve which contains at least three points covering the
range of interest. Verify the standards employed
independently by another analytical method.
4.4.4 Operating Procedure
4.4.4.1 Obtain a continuous flow of sample gas from
the source using a clean and passivated 316 stainless
steel line which has been purged dry after exposure to
ambient moisture.
4.4.4.2 After prepurging with a dry gas, allow the
sample gas to flow through the sampling system and the
piezoelectric hygrometer until a stable reading is
obtained. Determine the concentration of moisture by
comparing the reading to the calibration curve obtained
in 4.4.3. The result may not exceed the specification in
Section 2 of this Standard.
4.5 Total Hydrocarbons — This procedure is for the
determination of total hydrocarbons in helium using a
continuous flow flame ionization detector-equipped
total hydrocarbon analyzer. (See Notes 4, 5, 6.)
4.5.1 Detection Limit — 0.1 ppm (mole/mole).
4.5.2 Flow Requirements
4.5.2.1 High purity, hydrocarbon-free (less than 1.0
ppm) hydrogen: 35-40 mL/min or 40% hydrogen in
either helium or nitrogen matrix at 75-80 mL/min.
4.5.2.2 Dry, hydrocarbon-free (less than 1.0 ppm) air:
350-400 mL/min.
4.5.2.3 Set sample flow rates in accordance with
instrument manufacturer's instructions.
4.5.3 Calibration Standards
4.5.3.1 Helium with known quantity of hydrocarbons
at 0.5 ppm level.
4.5.3.2 The span gas not exceeding 5 times the
concentration of the specification.
4.5.4 Operating Procedure
4.5.4.1 Do not change the initial flow settings for
hydrogen, air and sample once established.
SEMI C3.20-92 © SEMI 1982, 19993
4.5.4.2 Introduce the zero helium with known quantity
of hydrocarbons and, using the 0-10 ppm range, set the
needle (or output) to read the correct level using the
zero adjust knob.
4.5.4.3 Introduce the span gas standard in helium and,
using the span adjust knob, set the needle (or output
reading) to match the level of hydrocarbons in the span
gas.
4.5.4.4 Introduce helium sample into the analyzer and
read the quantity of hydrocarbons on the analyzer. The
result may not exceed the specification in Section 2 of
this Standard.
4.6 Notes
NOTE 1: Introduce the calibration standard as many times as
necessary to achieve the desired precision.
NOTE 2: All gases used in the analysis of the sample should
contain not more than 10% of the specified value of the
component of interest unless otherwise specified.
NOTE 3: The sampling system and hygrometer must be
designed to operate under the sample pressure, or the sample
pressure must be reduced (by a regulator with a diaphragm of
stainless steel or other suitable material) to accommodate the
pressure restrictions of the analytical hygrometer.
NOTE 4: The 0-1 range may be used provided that zero and
span gas standards in helium with known levels of
hydrocarbons between 0-1 ppm are used in the calibration of
the analyzer.
NOTE 5: As the flow rate and heat capacity of the matrix gas
affect the instrument output, the zero gas matrices must
coincide with that of the sample gas.
NOTE 6: The effective response of a flame ionization
detector-equipped total hydrocarbon analyzer to different
hydrocarbons can vary and must be approximated. However,
the response of the most common hydrocarbon impurities in
helium can be accurately totaled and compared to methane.
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