DUGi

La Micro-fluorescència de raigs X en estudis forènsics : anàlisi d’aliatges de metalls nobles d’acord amb la norma ISO/DIS 23345/(2020)

http://dugi.udg.edu/item/http:@@@@hdl.handle.net@@10256@@24347

The objective of this final degree project is to develop a new methodology for the analysis of the elemental composition of noble metal alloys, according to the recently approved ISO DIS 23345 regulation. This new methodology is intended to be put into practice in common forensic analyses to intervene in expert trials of crimes of counterfeiting or theft of jewellery or gold objects. The motivation to develop this new method has been the multiple advantages that it allegedly presented over cupellation, the current official method of gold analysis according to the laws established by Spanish legislation. The official method presents significant drawbacks: high analysis time, destruction of the sample, generation of waste, high energy cost and consumption of reagents, among others. Since the X-ray spectroscopy technique could overcome these drawbacks, it was proposed to develop the new methodology. The analysis is carried out thanks to the energy dispersive X-ray microfluorescence technique (ED-XRF). Likewise, first of all, a general calibration was developed, which included the elements commonly found in jewellery. For this, appropriate reference materials were used, a total of 33 standards of different composition. Subsequently, a specific calibration for the Au-Ag-Cu alloy was carried out and all of this was subjected to a study to confirm that the methodology complied with the ISO DIS 23345 regulation. The results of these calibrations were satisfactory, so the study continued Forward. Thus, the next step was the quantitative analysis of different privately owned jewels to determine if they were legal gold, plated or counterfeit, also being able to determine their composition precisely, fulfilling the proposed objective. It was possible to determine that, of the seven jewels analysed, only four were legal gold, so the remaining three did not present the minimum amount of gold required by the BOE, 18K

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