NCJ Number
198078
Journal
Journal of Forensic Sciences Volume: 47 Issue: 6 Dated: November 2002 Pages: 1283-1287
Editor(s)
Michael A. Peat Ph.D.
Date Published
November 2002
Length
5 pages
Annotation
This paper presents quantitative results from the interlaboratory study assessing the state-of-the-practice of smokeless powder measurements, used by forensic scientists and military laboratories, through an international measurement comparison exercise.
Abstract
The accurate determination of additive ingredients in smokeless gunpowder is important to both forensic scientists investigating the source of explosives and military laboratories assuring the safety and efficacy of munitions. Accurate measurements are imperative to offering useful gunpowder compositional measurements for forensic and military application. However, the accuracy of quantitative determination of gunpowder or propellant composition can suffer as a result of a number of factors. Gunpowder is a blend of nitrocellulose (NC) and several possible additives, such as an additional propellant, nitroglycerin (NG), and stabilizers diphenylamine (DPA) and ethyl centralite (EC). To evaluate powder additive measurement practice, the National Institute of Standards and Technology (NIST) conducted a measurement comparison in the Spring of 2000. Test materials utilized included two samples of commercial smokeless reloading powders used for handgun ammunition. In addition to qualitative results, the five laboratories involved quantitatively evaluated the concentrations of the NG propellant and stabilizer additives. All five laboratories reported values for nitroglycern (NG), ethyl centralite (EC), diphenylamine (DPA), and N-nitrosodiphenylamine (NnDPA). The unstable NG propellant additive seemed to be more susceptible to method-specific calibration biases then the stabilizer additives. All results from one participant laboratory were strongly biased relative to those of the other four. Within the scope of this study, it was impossible to quantitatively assess the contribution of the analytical methods to bias and long-term precision. In addition, calibration and operator skill contributed to measurement differences found in this comparison. It is recommended that a reference material be developed to facilitate a more complete accounting of the relative contributions of the analytical method, calibration, and operator skill to the bias and precision of smokeless powder additive measurements. References