Forensic discrimination of bottle glass by refractive index measurement and analysis of trace elements with ICP-MS

Measurement of refractive index and trace element analysis by ICP-MS were a pplied to the forensic discrimination of bottle glass samples from differen t origins. Refractive index was calculated from the matching temperature at which glass fragments became invisible in the silicone oil. Sample solutio n for ICP-MS was prepared by dissolving approximately 10 mg of glass fragme nts into a mixture of 0.5 mi of KF and 0.5 mi of HClO4 and heating for 2 h using a microwave oven, followed by dilution to 25 mi after 2 mi of HNO3 wa s added. Thirteen elements (Co, Cu, Zn, Rb, Sr, Zr, Ag, Sn, Sb, Ba, La, Ce and Pb) were found to be useful for the discrimination of bottle glasses. T hese elements in NIST SRM 612 (Trace Elements in Glass) could be determined with an RSD less than 3.2%, except for Sn and Pb. The proposed method was applied to 16 bottle glass samples. Of 120 pairs among 16 bottle samples, 1 3 pairs were indistinguishable by RI only. Combination of trace element ana lysis by ICP-MS and refractive index measurement made it possible to distin guish all the pairs.