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 Fourie r-transform infrared spectroscopy (FT-IR). This analysis differentiates bet ween greases with different main constituents. When two samples can not be differentiated with IR, a more thorough analysis has to be performed. The b ase oil and the soap are separated. The soap is derivatized and the two com ponents are each analyzed with gas chromatography. The metal ions of the so ap are analyzed with scanning electron microscopy with an energy dispersive X-ray detector (SEM-EDX). By the method presented, grease from a weapon ma y be differentiated or proven to be identical to grease collected from a su spect. As thr results indicate that the grease does not change with respect to composition when the weapon is fired, the method may be used in many ca ses. The application of the method to an authentic case is reported.