Forensic and toxicological applications of atomic analysis

Abstract

Toxicological and forensic applications of analytical chemistry provide both interesting and unique opportunities for analytical chemists to hone their skills and push their abilities. Modern analytical chemistry has afforded researchers the ability to probe into the intricate pathways of biochemical processes by systematic identification and characterization of biologically relevant compounds. Unfortunately, often due to the restrictive specifications of the instrumentation used, it is necessary to remove those compounds from their natural environments such that their structure and at the very least the significance of those compounds may not be fully recognized. The work described herein identifies and characterizes two biologically relevant arsenic and selenium containing species. These species were synthesized and identified in environments that are very similar to those found in vivo. The use of chemical information contained within a small arms cartridge has seen extremely limited use by forensic laboratories despite the wealth of chemical information that may be useful in differentiating between cartridges of various manufacturers. The study herein uses the elemental composition of small arms rifle primers to develop a multivariate model against which unknown primers were compared and ultimately classified. The FBI's practice of elemental analysis of small arms projectiles has recently come under fire as the result of an ex-FBI metallurgist's research study which concluded that the trace elements analyzed were too rigidly controlled by Pb smelters and therefore not useful in distinguishing between batches of ammunition. The scientific community is now scrutinizing the practice with a National Academy of Science review of the FBI's practices. Unlike the trace elements utilized by the FBI for distinguishing between projectiles of various "origins" Pb isotopic signature is not controlled by smelters and should, even in the case of recycled Pb, vary when Pb from differing origins is utilized for the manufacture of small arms projectiles. The study described herein shows that Pb isotopic analysis of small arms projectiles from various regions of the world is useful for differentiating between small arms projectiles and in limited cases may even be useful in determining the geographic origin of projectile manufacture.