The Development of Analytical and Interpretational Protocols to Facilitate the Provenance Establishment of Polycarbonate Headlamp Lens Material*

Abstract

Despite the forensic significance of polycarbonate headlamp lenses, robust analytical protocols to facilitate their discrimination are scarce. In this study, laser ablation inductively coupled plasma mass spectrometry has been applied to the analysis of polycarbonate headlamp lenses with multivariate chemometrics techniques utilized to facilitate interpretation of the data. The analytical protocol involves the analysis of 46 analytes on material comprising the exterior surface of the lens. Using this data, it was found that although minor variation exists within a single headlamp lens, discrimination between lenses produced from a single manufacturing plant was still possible using iterative forward stepwise linear discriminant analysis processes. Discrimination between all headlamp lenses, with the exception of some lenses produced on the same day in a single plant, could be achieved using the analytical protocol. Furthermore, an interpretational protocol has been developed that has successfully classified all tested headlamp lens samples, within the discrimination limits of the analytical method.

Cassiterite fingerprinting by LA-ICP-MS

“…For instance the relative standard deviations analysed in oat glass samples range between 1.4% (Fe) and 7.3% (Hf) 10 and in exterior surfaces of polycarbonate headlamp lamps between 12% and 15%. 18 Replicate analyses of the same steel using LA-ICP-MS also give excellent reproducibility. 8 However, grains from the same cassiterite concentrate give relative standard deviations that are much higher (mean RSDs in the range of 100-200%) and the concentrations do not follow a normal distribution.…”

“…Distributions of element concentrations in cassiterite grains differ signicantly from those of man-made materials like glass, steel or polycarbonate headlamp lens materials for which ngerprinting applications based on LA-ICP-MS data are given in the literature. 8,10,18 Elements are signicantly more heterogeneously distributed in cassiterite than in those materials. For instance the relative standard deviations analysed in oat glass samples range between 1.4% (Fe) and 7.3% (Hf) 10 and in exterior surfaces of polycarbonate headlamp lamps between 12% and 15%.…”

“…LA-ICP-MS has been applied for discriminating and ngerprinting steel, 8 glass, 9,10 diamond, 11,12 gold, 13 columbite-tantalite (coltan), 14,15 cannabis crops, 16 cotton bre, 17 polycarbonate headlamp lenses 18 or bone and teeth samples. 19 A similar geochemical ngerprinting method for cassiterite based on LA-ICP-MS data shall be applied if doubt arises on the declared origin of a cassiterite concentrate.…”

Forensic comparison analysis of plastic vehicle headlamp lens by gel permeation chromatography and statistical methods

“…And there was a widespread adaption throughout the automotive industry all over the world. However, except a few papers [10,11], minimal available literature was reported about the analysis of plastic headlamp lenses.…”

“…Mw and PDI can provide a promising information to make further discrimination between PC headlight lens fragments. Although the data for the analysis of PC headlamp lenses have not appeared extensively in the literature before [11,24], gel permeation chromatography (GPC) used for polymer material analysis has been investigated for many years [25][26][27]. In this study, we explore the possibility and suitability to use Mw and PDI data to make further discrimination between polycarbonate headlamp lens fragments.…”