The Utilization of MS-MS Method in Detection of GSRs

Abstract This paper describes a novel method to detect gunshot residues (GSRs). The components contained in the double-based smokeless powder were separated by using a HPLC system with UV detection at 223 nm. The result indicated that there are mainly two kinds of organic ingredients in the double-base smokeless powder used. These two organics do not include nitrocellulose because it has no evidential value in the HPLC-UV trace of the smokeless powder sample. By matching retention times of these two compounds with that of the five standards occurring in smokeless powder, the compounds are tentatively identified as methyl centralite (MC) and nitroglycerin (NG). These two compounds were finally identified by using MS spectrum. This MS-MS method was developed to detect MC since MC is less commonly found in the environment than NG. In Chinese ammunition, MC is widely used as a stabilizer instead of EC. Sixteen samples were used to evaluate the reliability of the method. The mean (±SD) MC level in the eight samples is 520.1 ± 271.9 pg/µL and that in the blanks is 31.0 ± 20.8 pg/µL. The result (P = 0.0007) shows that there is a significant difference between the two serial data. Sampling hands over a 24 h period showed that GSR could be detected even after 8 h with a 75% decrease in the level of MC. The result of the washing test shows that it is still possible to apply the proposed method to detect GSRs on a shooter's hands even if their hands have been washed three times. Another test shows that if the shooters wear gloves while firing, MC on the gloves can be easily detected using the proposed method.