Firearm Residue Detection by Instrumental Neutron Activation Analysis

The neutron activation technique for firearm residue detection [1] is well known but not extensively applied. Additional work utilizing an optimized firearm residue detection technique by neutron activation analysis (NAA) [2] it made it clear that postirradiation radiochemical separations are the cause of several limitations which discourage a more general use of neutron activation analysis. The inherent time limitation due to 87-min half-life of 139Ba necessitates fast manipulations of radioactive solutions, which in turn requires an experienced radiochemist. In addition, there is an ever-present danger of overexposure and contamination. Besides, typically only a dozen samples can be irradiated per batch, which makes the method quite expensive. The developed statistical treatment bivariate-normal analysis [3] is inconvenient for routine applications. With this in mind, a method was developed which: (1) eliminates postirradiation radiochemistry and thus maximizes time for analysis, (2) accommodates over 100 samples per irradiation capsule (rabbit); (3) does not require a collection of occupational hand blanks, and (4) utilizes a simplified statistical concept based on natural antimony (Sb) and barium (Ba) levels on hands for the interpretation of data [4].