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SEMI C54-1103 © SEMI 2003 3 9.2 Nitrogen — This procedur e is for the determination of nitrogen in oxygen using a gas chrom atograph with a thermal conductivity detector. 9.2.1 Detection Limit — 10 ppm. 9.2.2 Instrum ent…

SEMI C54-1103 © SEMI 2003 2

Table 1 Impurity and Other Requirements for Various Grades of Oxygen

Previous SEMI Reference #

C3.22-1000

(Specification)

C3.23-1000

(Specification)

C3.41-0697

(Specification)

Grade 2.5 3.8 5.8

Purity 99.5% 99.98% 99.9998% (See Note

1.)

Impurities Maximum Acceptable Level (ppm) (See Note 2.)

Carbon Dioxide and Carbon Monoxide (CO

+ CO) 5 N/A N/A

Carbon Dioxide (CO

) N/A 1 0.1

Carbon Monoxide (CO) N/A 1 0.1

Hydrogen (H

) N/A N/A 0.1

Nitrogen (N

) 100 30 0.5

Nitrous Oxide (N

O) 2 1 N/A

Argon (Ar) N/A 100 1.0

Krypton (Kr) N/A 10 N/A

Water (H

O) (ppmv) 1 1 0.1

Total Hydrocarbons expressed as Methane (THC) 25 1 0.1

TOTAL IMPURITIES INCLUDING RARE GASES 5000 N/A N/A

TOTAL IMPURITIES N/A 145 2.0

Particles (See Note 3) (See Note 3) (See Note 3)

Note 1: A purifier is allowed to be used to meet this specification.

Note 2: An analysis of significant figures has not been considered. The number of significant figures is based on analytical accuracy and the

precision of the provided procedure.

Note 3: To be determined between supplier and user.

8 Physical Constants

8.1 The physical constants of oxygen are given in

Table 2 (for information only).

Table 2 Physical Constants of Oxygen (for

information only)

Metric Units US Units

Molecular weight 31.999 31.999

Boiling point at 1 atm −183°C −297.4°F

Density of gas at 21.1°C

(70°F) and 1 atm

1.309 kg/m

0.082 lb/ft

Specific gravity of gas at

21.1°C and 1 atm (air = 1)

1.1049 1.1049

Density of liquid at boiling

point

1142 kg/m

71.27 lb/ft

9 Analytical Procedures for Grade 2.5 Oxygen

9.1 Carbon Monoxide, Carbon Dioxide, and Nitrous

Oxide — This procedure is for the determination of

carbon monoxide, carbon dioxide and nitrous oxide

concentration in oxygen using infrared

spectrophotometry.

9.1.1 Detection Limits — 0.5 ppm carbon monoxide,

0.1 ppm carbon dioxide, and 0.2 ppm nitrous oxide.

9.1.2 Instrument Parameters

9.1.2.1 10 meter variable path infrared gas cell.

9.1.2.2 Grating infrared spectrophotometer.

9.1.2.3 Bourdon Vacuum Gauge.

9.1.3 Calibration Standards — 10 ppm carbon

monoxide, 10 ppm carbon dioxide and 10 ppm nitrous

oxide, balance oxygen.

9.1.4 Operating Procedure

9.1.4.1 Pressurize the evacuated gas cell to 50 psia

with the calibration standard. Scan the following wave

numbers for absorbance: carbon monoxide 2172 cm

-1

nitrous oxide 2235 cm

-1

, and carbon dioxide 2360 cm

-1

9.1.4.2 Evacuate the cell and pressurize to 50 psia with

the oxygen sample. Scan the appropriate wave numbers

as in Section 9.1.4.1.

9.1.4.3 Compare the absorbance of the calibration

standard to that of the oxygen sample being tested.

Calculate the concentrations of carbon monoxide,

carbon dioxide and nitrous oxide, using the formula

below. The results may not exceed the specifications in

Section 7 of this standard.

Sample Absorbance

Standard Absorbance

Concentration

of Standard

Concentration

of Sample

SEMI C54-1103 © SEMI 2003 3

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

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.

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 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