Volume 46, Issue 3 (May 2001)
Comparative Analysis of Lubricants Used for Weapons
A method for analysis and comparison of mineral oil-based greases thickened with a metal soap is presented. The greases are first analyzed with Fourier-transform infrared spectroscopy (FT-IR). This analysis differentiates between greases with different main constitutents. When two samples can not be differentiated with IR, a more thorough analysis has to be performed. The base oil and the soap are separated. The soap is derivatized and the two components are each analyzed with gas chromatography. The metal ions of the soap are analyzed with scanning electron microscopy with an energy dispersive X-ray detector (SEM-EDX). By the method presented, grease from a weapon may be differentiated or proven to be identifical to grease collected from a suspect. As the results indicate that the grease does not change with respect to composition when the weapon is fired, the method may be used in many cases. The application of the method to an authentic case is reported.