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SEMI C54-1103 © SEMI 2003 4 9.4.1 Detection Limit — 0.6 ppm (vol/ vol) at − 79°C ( − 110°F). 9.4.2 Flow Requi rements 9.4.2.1 Set sample flow rate and pres sure in accordance with the instrument manufacturer’s instructio…
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9.2 Nitrogen — This procedure is for the determination
of nitrogen in oxygen using a gas chromatograph with a
thermal conductivity detector.
9.2.1 Detection Limit — 10 ppm.
9.2.2 Instrument Parameters
9.2.2.1 Column: 5A molecular sieve, 4.6 m (15 ft) by
3.2 mm (1/8 in) stainless steel or equivalent.
9.2.2.2 Carrier Flow: 30 mL/min helium.
9.2.2.3 Sample Volume: 2.0 mL.
9.2.2.4 Temperatures:
Detector 200°C
Column Oven 21°C
9.2.3 Calibration Standard — 100 ppm nitrogen in
oxygen.
9.2.4 Operating Procedure
9.2.4.1 Inject the calibration standard into the column
using a gas-sampling valve. Record the retention time
and peak area. (See Note 1.)
NOTE 1: Introduce the calibration standard as many times as
necessary to achieve the desired precision.
9.2.4.2 Inject the sample to be tested in same manner
as the calibration standard. Record the retention time
and peak area.
9.2.4.3 Repeat Section 9.2.4.2.
9.2.4.4 Compare the average peak area of the
calibration standard to that of the oxygen sample being
tested. Calculate the concentration of nitrogen, using
the formula below. The result may not exceed the
specification in Section 7 of this standard.
Sample Peak Area
Standard Peak Area
×
Concentration
of Standard
=
Concentration
of Sample
9.3 Total Hydrocarbons — This procedure is for the
determination of total hydrocarbons (THC) in oxygen
using a continuous flow flame ionization detector
equipped total hydrocarbon analyzer. (See Notes 2, 3,
4.)
NOTE 2: The 0-1 range can be used provided that zero and
span gas standards in oxygen with known levels of
hydrocarbons between 0-1 ppm are used in the calibration of
the analyzer.
NOTE 3: As the flow rate and heat capacity of the matrix gas
affect the instrument output, the zero and span gas matrices
must coincide with that of the sample gas.
NOTE 4: 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
oxygen can be accurately totaled and compared to methane.
9.3.1 Detection Limit — 0.1 ppm.
9.3.2 Flow Requirements
9.3.2.1 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.
9.3.2.2 Dry, hydrocarbon-free (less than 1.0 ppm) air:
350–400 mL/min.
9.3.2.3 Set sample flow rates in accordance with the
instrument manufacturer’s instructions.
9.3.3 Calibration Standards
9.3.3.1 Zero oxygen with known quantity of
hydrocarbons at less than 0.5 ppm level.
9.3.3.2 The upper level span gas must be in oxygen and
the CH
4
level must not exceed 4 times the concentration
of the specification.
9.3.4 Operating Procedure
9.3.4.1 Do not change the flow settings for hydrogen,
air, and sample once established.
9.3.4.2 Introduce the zero oxygen 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.
9.3.4.3 Introduce the span gas standard in oxygen and,
using the span adjust knob, set the needle (or output
reading) to match the level of hydrocarbons in the span
gas.
9.3.4.4 Introduce oxygen sample into the analyzer and
read the quantity of hydrocarbons on the analyzer
meter. The result may not exceed the specification in
Section 7 of this standard.
9.4 Water — This procedure is for the determination of
trace moisture (water) in oxygen using a continuous
flowing, cooled-surface condensation, dewpoint/frost-
point hygrometer. (See Notes 5, 6, 7.)
NOTE 5: 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 6: The National Institute of Standards and Technology
(NIST) provides calibration services for the thermometers
used in dewpoint/frostpoint hygrometers.
NOTE 7: This method is not applicable if other constituents
in the gas will condense before water vapor, e.g., carbon
dioxide and/or oil contamination.
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9.4.1 Detection Limit — 0.6 ppm (vol/vol) at −79°C
(−110°F).
9.4.2 Flow Requirements
9.4.2.1 Set sample flow rate and pressure in accordance
with the instrument manufacturer’s instructions.
9.4.2.2 Gas must flow past the chilled mirror where
optic means are provided to detect the deposit (or frost)
and to read the thermometer measuring the temperature
of the mirror.
9.4.3 Calibration Standard — A calibration
thermometer designed to indicate temperatures around
the −79°C (−110°F) is required.
9.4.4 Operating Procedure
9.4.4.1 Obtain a continuous flow of sample gas from
the source using a clean stainless steel sampling line
which has been purged dry after exposure to ambient
moisture.
9.4.4.2 After prepurging with a dry gas, allow the
sample gas to flow through the sampling system and the
dewpoint/frostpoint hygrometer for one hour to 24
hours to allow the entire system to reach equilibrium
with regard to moisture content.
9.4.4.3 After equilibrium has been reached, cool down
the mirror to determine the actual dewpoint/frostpoint
of the sample gas. Follow the manufacturer’s
recommendations to create the temperatures needed.
9.4.4.4 Continue to verify the dewpoint/frostpoint for
at least 30 minutes after a stable reading has been
confirmed.
9.4.4.5 Correct the dewpoint reading from the
measured pressure to 1 atm of pressure. The result may
not exceed the specification in Section 7 of this
standard.
9.5 Assay of Oxygen — This procedure describes the
assay of oxygen using an “Orsat” device. This is a
volumetric determination of nonabsorbable/reactable
gas.
9.5.1 Method Capability — 99.9% Oxygen.
9.5.2 Instrument Parameters — See Figure 1.
9.5.2.1 Equipment:
• 1-100 mL calibrated certified burette, calibrated
every 0.1 mL for the top 5 mL equipped with a 3-
way stopcock on the top.
• 3-250 mL aspirator bottles.
• 1 one-hole rubber stop.
• 1-1/16 in OD soft copper wire made into hollow
coils 3/8 in OD by 3/4 in long.
• Sufficient 3/8 in OD tygon tubing.
• Sufficient surgical rubber tubing.
• 1 gallon distilled water.
• 2 lbs technical grade ammonium chloride.
• 1 gallon 27% ammonium hydroxide.
9.5.2.2 Test Solution Preparation
9.5.2.2.1 Two pounds of technical grade ammonium
chloride are dissolved in one gallon of distilled water
and stored in a glass jar. One-half gallon of this solution
shall be combined with one-half gallon of 27%
ammonium hydroxide.
9.5.3 Equipment Assembly — The equipment is to be
assembled, as per Figure 1, in a suitable wood or metal
frame so arranged that the aspirator bottle connected to
the burette can be raised and lowered, as required, to
transfer the gas being analyzed to and from the center
aspirator bottle which is filled with copper coils. The
two leveling bottles should be filled half full of testing
solution and the buret and aspirator bottle, which
contains the copper coils, should be completely filled.
9.5.4 Operating Procedure
9.5.4.1 Before analyzing the sample, perform a series
of analyses using a source of oxygen of which the
purity has been previously determined. This procedure
is necessary to age the test solution properly and
eliminate any air bubbles which may become trapped in
the apparatus. Only after three consecutive analyses
have been run, indicating the known purity, should you
proceed with testing. (See Note 8)
NOTE 8: This procedure will be required only immediately
after changing the test solution or contaminating the apparatus
with air.
9.5.4.2 Attach rubber tubing from the regulator of the
cylinder being tested to the stopcock of the burette.
Rotate the stopcock so as to draw the sample into the
gas measuring burette. Collect a little more than 100
mL (i.e., below the zero mark) in the burette, and then
rotate the stopcock so as to shut off the oxygen flow
and remove the rubber tubing attached to the intake of
the burette. If the gas sample in the burette is below the
zero mark raise the leveling bottle #1 so that the
“water” level in the burette is exactly zero (see Figure
2a).
9.5.4.3 Rotate the stopcock to connect the aspirator
bottle #3 containing the copper coils, and transfer the
oxygen into this aspirator bottle by raising the leveling
bottle #1 (see Figure 2b). Invert bottle #3 containing the
SEMI C54-1103 © SEMI 2003 5
copper coils so that both the inlet stopper and the sided
outlet are in a downward position and shake gently for
1 to 2 minutes. Stand test bottle #3 on its base and
lower the leveling bottle so as to withdraw any residual
gases into the gas measuring burette (see Figure 2c).
Transfer at least 25 to 30 mL of test solution from the
left-hand leveling bottle #2 into the right-hand leveling
bottle #l, through the copper coil bottle #3, and the gas
burette while, at the same time, gently rocking and
tapping the center bottle (see Figure 2d). This will
move any bubbles that might cling to the copper coil
into the gas measuring burette.
9.5.4.4 Turn the stopcock off and raise the leveling
bottle #l so that its liquid level is the same as the liquid
level inside the upper portion of the gas burette (see
Figure 2e). When the levels of the leveling bottle and
the gas burette are the same, read the gas purity
markings on the burette at the liquid level at this point.
9.5.5 Maintenance
9.5.5.1 Copper coils should be added to the test bottle
as required to keep the bottles completely full. The gas
burette should be kept clean with a strong detergent
solution to eliminate drops of liquid that might hang up
in the gas space and give incorrect purity readings. No
readings should be taken when the space above the
liquid level of the gas burette has any liquid drops
hanging in it, as this will give an erroneous purity
reading.
9.5.5.2 The solution must be replaced occasionally as it
becomes exhausted. The necessity of replacement may
be determined when the color begins to turn green, and
by the increased length of shaking time required to get a
minimum acceptable purity from the oxygen in a
cylinder of known purity. Suspect an exhausted solution
if analysis of a cylinder of known purity does not read
the correct purity.
9.5.6 Standardization
9.5.6.1 The method of analysis stated above can be
used as a primary standard, meaning cylinders analyzed
by this method can be used as standards of
measurement on electronic analyzers used to measure
oxygen.
9.5.6.2 This method is specific to oxygen when carbon
dioxide is not present in the sample gas. When carbon
dioxide is one of the components of the sample gas, the
carbon dioxide must first be scrubbed from the sample.
10 Analytical Procedures for Grade 3.8
Oxygen (See Notes 1 in 9.2.4.1 and 9)
NOTE 9: All gases used in the analysis of the sample should
contain not more than 10% of the sample value of the
component of interest unless otherwise specified
10.1 Argon — This procedure is for the determination
of argon using a gas chromatograph with a thermal
conductivity detector.
10.1.1 Detection Limit — 25 ppm.
10.1.2 Instrument Parameters
10.1.2.1 Column: 3.6 m (12 ft) by 3.2 mm (1/8 in)
stainless steel tubing packed with molecular sieve 5A,
60/80 mesh, washed to remove fines and activated at
300°C for 24 hours or equivalent.
10.1.2.2 Carrier Flow: 45 mL/min helium.
10.1.2.3 Sample Volume: 1–3 mL.
10.1.2.4 Temperatures:
Detector 40°C
Column −50°C
10.1.3 Calibration Standard — 50–150 ppm argon,
balance helium.
10.1.4 Operating Procedure (Refer to Figure 3.)
10.1.4.1 With the valve in Position A, purge the sample
loop with the calibration standard. Switch the valve to
Position B to inject the sample into the column. After
the argon has been detected, switch the valve back to
Position A to backflush the oxygen from the column.
Record the peak area and retention time.
10.1.4.2 Inject oxygen sample to be tested in the same
manner as in Section 10.1.4.1. Record the retention
times and peak areas.
10.1.4.3 Repeat Section 10.1.4.2.
10.1.4.4 Calculate the concentration of argon in the
sample, using the formula below. The result may not
exceed the specification Section 7 of this standard.
Sample of
ionConcentrat
Standard of
ionConcentrat
AreaPeak Standard
AreaPeak Sample
=×
10.2 Carbon Monoxide — This procedure is for the
determination of carbon monoxide using dual beam
optical non-dispersive infrared spectrophotometry.
10.2.1 Detection Limit — 0.2 ppm.
10.2.2 Instrument Parameters
10.2.2.1 Detector: “Luft” type or equivalent
10.2.2.2 10" Infrared Gas Cell or gas cell with
equivalent sensitivity
10.2.2.3 Sample Cell Pressure: 200 psig for full scale
range 0–20 ppm carbon monoxide or appropriate
pressure recommended by the cell manufacturer.