MIL-PRF-87896A
4.5.3.1 Instrument parameters. The analyst may vary the column dimensions, carrier gas flow
rate, and temperatures to optimize the analysis.
Detector:
Thermal conductivity detector, discharge ionization detector, or a pulsed
discharged helium ionization detector.
Column:
Packing:
Molecular sieve 13X, 80/100 (or equivalent)
Length:
6.1 m (20 ft)
ID:
1.75 mm (1/16 in.)
OD:
3.2 mm (1/8 in.)
Column material:
stainless steel
Carrier Gas / Flow Rate:
Helium (MIL-PRF-27407) / 17 mL/min
Temperatures:
Detector:
140°C
Filament:
240°C
Oven:
100°C
Gas sampling valve:
60°C
4.5.3.2 Calibration. Prepare a gaseous standard of helium containing at least 0.1% NF3 and the
components being analyzed in a concentration between one tenth and 10 times the specification limit or
of the predicted measurement in the propellant sample. Analysis of the calibration standard must show a
clear separation of each specified component from all other components and from NF3.
4.5.3.3 Procedure. Inject the calibration standard into the column using a gas-sampling valve.
Record the retention times and peak areas for each component. The order of elution is oxygen+argon,
nitrogen, carbon monoxide, and nitrogen trifluoride. Inject the propellant sample to be tested into the
column in the same manner as the calibration standard. Record the retention times and the peak areas.
Repeat two times.
4.5.3.4 Calculation. Compare the average peak area of the calibration standard to that of the
nitrogen trifluoride sample being tested. Calculate the concentration of each component using the
formula in 4.5.2.4.
4.5.4 Total reactive fluoride as HF. The concentration of total reactive fluoride as HF in nitrogen
trifluoride is determined by one of the following procedures. In the event of dispute the procedure
outlined in 4.5.4.1 shall be the referee method.
4.5.4.1 Fluoride ion selective electrode.
4.5.4.1.1 Buffer solution. Place 500 mL of distilled or de-ionized water in a 1000 mL volumetric
flask. Add 57 mL glacial acetic acid and 58 g of sodium chloride. Adjust the pH to between 5.0 - 5.5 with
5 M sodium hydroxide. Cool to room temperature. Dilute to the mark with distilled or de-ionized water.
-3
ˉ
4.5.4.1.2 Calibration standard. Sodium fluoride (10 M F in water, freshly prepared).
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