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Guide for Characterization of Sites Contaminated with Energetic Materials
47
Calibration Standards
Analytical standards containing all of the explosive analytes listed for
Method 8330 can be purchased as a mixed stock standard (each analyte 1.00
mg/mL) from AccuStandard, Inc. (New Haven, Connecticut). These commer-
cially prepared stock standards need to be specially prepared using acetone as the
solvent. Additional standards, e.g., PETN, NG, and 3,5-DNA, are also commer-
cially available from the same vendor.
Instrument Calibration
Initially a five-point calibration curve should be established. This number of
standards allows a nonlinear model (quadratic through the origin) to be used
when a linear regression through the origin fails to establish a correlation coeffi-
cient (r) of greater than 0.990. Continuing calibration checks should be made
after every five samples. If the calibration model fails to establish a concentration
within +20% of the expected value for a working standard, recalibration should
be performed.
Advantages and Limitations of GC-TID On-Site Analysis
This on-site method can be used to measure several explosives at concentra-
tions well above and below current action levels. Presently this task cannot be
achieved using current on-site colorimetric techniques because they lack ade-
quate selectivity, and the enzyme immunoassay methodologies measure exclu-
sively TNT and RDX. The cost of this instrument (less than K), a personal
computer (
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K) for controlling oven temperature and data processing, auxiliary
support (tank of nitrogen and electrical power), and initial training makes this
method less economical than the colorimetric or immunoassay methods for small
projects. However, the GC-TID is economical for larger projects, particularly
when knowledge of identity of the explosives is critical.
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