MIL-DTL-87173B(USAF)
APPENDIX A
A.4.9 Quantitative calibration mixture. Prepare several calibration mixtures by carefully weighing
quantities of MCH and C-10 into sample vials or other suitable closed containers. Handling and weighing
should be performed carefully so the weight of each component is accurately known to within one percent
(relative).
NOTE 6. The calibration mixtures shall be of varying compositions in order to confirm the linearity of the
detector and the validity of the calibration; response factors should be constant and independent of the
actual compositions. The compositions should approximate the range defined in the PF-1 specification
but it is helpful to prepare the samples so these limits are occasionally exceeded.
NOTE 7. Weighing may be done by difference into any convenient containers, provided care is taken to
introduce the materials quickly and thereby avoid loss by evaporation. Since MCH has appreciable vapor
pressure under ambient conditions, it should be weighed last. The containers should be leak-tight, and
stored in a cold box (preferably a freezer compartment). Properly prepared and stored samples are
stable for several months.
A.5 PREPARATION OF APPARATUS
A.5.1 Column. Any conventional method of conditioning and installing the column is satisfactory,
provided the system is free of gas leaks and the column resolution meets the minimum requirement
specified in A.5.2.
A.5.2 Column resolution. Run a sample of the qualitative calibration mixture and measure the
retention times and widths of the n-dodecane and n-tetradecane peaks as shown on figure A1.
Resolution is defined as the difference in retention times for n-C12 and n-C14 divided by their average
width:
2(RT14 RT12)
R=
W14 + W12
Resolution determined in this way must be at least 5.0 and can be optimized by varying the temperature
program and the carrier flow rate. If resolution cannot be increased to at least 5.0 by optimizing these
parameters, it is necessary to use a different column.
A.5.3 Chromatograph. Place in service according to the manufacturer's specifications; give particular
attention to flow rates through the detector.
A.6 PROCEDURE
A.6.1 Establish a suitable sample volume by making several trial runs with the qualitative calibration
mixture. For FID instruments, the volume may be between 0.5 and 1.0 microliter; for TCD instruments,
volumes from 1.0 to 5.0 microliters have been found satisfactory.
NOTE 8. To establish the optimum temperature program, it is necessary to begin the run at a low enough
temperature to allow complete elution of the solvent before the appearance of the MCH peak. If the area
is being monitored by an electronic integrator or computer, a time delay should be entered to inhibit
integration of the solvent peak(s).
A.6.2 Dilute an aliquot of each quantitative calibration mixture at least 1:10 (preferably 1:20) with either
pentane, hexane, or carbon disulfide. Mix thoroughly and inject a measured volume into the
chromatograph, simultaneously activating the temperature program, the integrator, and the recorder.
A.6.3 Integrate the area under the chromatogram continuously until the final peak has been eluted.
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