MIL-DTL-45444C
4.7.1.6 Alternate method for HMX purity and RDX content.
A high performance liquid chromatographic (HPLC) method shall be
used to determine HMX purity by quantifying the concentration of
RDX impurity in the HMX product.
4.7.1.6.1 HPLC method conditions. The HPLC system used in
the analysis of HMX product and appropriate method calibration
standards shall be comprised of a column, mobile phase, pumping
system, sample injection system, detector system and data capture
system. The column used in the testing shall be a microBondapak
CN (10 micron particle size, 3.9 mm x 150 mm Internal Dimensions;
see 6.6.1) or a direct column equivalent. The mobile phase shall
be a quaternary system consisting of the following components and
volumetric proportions: 70% by volume 2,2,4-trimethylpentane
(isooctane), 15% by volume of acetonitrile, 7.5% by volume
chloroform, and 7.5% by volume methanol. All solvents used in
the mobile phase shall be vendor certified as HPLC grade
chemicals. Prior to use in testing, the mobile phase should be
thoroughly degassed using either vacuum degassing techniques or
by purging with an inert gas. The injector component within the
HPLC system shall be equipped with a sample loop capable of
delivering a 20 microliter injection volume of sample to the HPLC
column. The detection system used in this HPLC testing shall
utilize a ultraviolet (UV) detector having a light wavelength of
254 nanometers.
4.7.1.6.2 Analysis of HMX samples and standards. Prior to
the analysis of either HMX samples or standards, the pumping of
mobile phase through the system shall be initiated at a flow rate
of 1.5 milliliters per minute. The HPLC system shall be allowed
to equilibrate at ambient conditions for approximately 10 minutes
or until the flow of mobile phase and the output reading on the
UV detector are stable. After the HPLC system has stabilized,
the sample loop on the HPLC injector system shall be filled with
an aliquot of the HMX sample or standard. Using either manual or
automated injection techniques, the aliquot of sample in the 20
microliter sample loop on the injector should be transferred to
the HPLC column. The peak area data from the HPLC chromatogram
for both the HMX and RDX components in the samples and standards
should be calculated and retained using the data collection
system (i.e. computer, computing integrator, etc.).
4.7.1.6.3 Preparation and analysis of HMX calibration
standards. Calibration standards having the approximate
concentrations provided in Table V shall be prepared. The RDX
and HMX used in the calibration standards shall have a minimum
purity of 99.9%. Prepare the calibration standards by weighing
the HMX and RDX components to the nearest 0.1 milligram in tared
250-ml glass volumetric flasks with ground glass stoppers. Add
approximately 100 milliliters of HPLC grade acetone to the
flasks. Cap the flasks and place the standards in an ultrasonic
bath for 10 minutes or until the RDX and HMX are completely
dissolved and uniformly mixed. Allow the standard mixtures to
cool to ambient temperature, and then fill to the mark of the
volumetric flasks using HPLC grade acetone.
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