2.2 Samples Preparation
Calibration samples did not require complicated preparation steps. Neat samples consisted of 0.20 g of neat HEs or neat soils. Samples of mixes also consisted of approximately 0.20 g of HE/soil with concentrations of 0% to 20% w/w for each HE. The test samples were prepared by grinding the explosive into a fine powder using a mortar and pestle, followed by mixing in a mini vortex mixer for approximately 10 s at 3000 rpm. The mixed samples were ground again and mixed in the mini vortex mixer for a second time. The test samples, were classified into three concentrations ranges; high concentration test (Test_H> 10% w/w), medium concentration test (10% w/w > Test_M > 3% w/w) and low concentration test (Test_L < 3% w/w).