Abstract This study describes the process of parameter optimization of an XRF method for casework use. The work expands upon previous discrimination studies by broadening the total sample set of characterized tapes and evaluating the use of spectral overlay, spectral contrast angle, and Quadratic Discriminant Analysis (QDA) for the comparison of XRF spectra. The expanded sample set consisted of 114 samples, 94 from different sources, of which 90 were previously analyzed, and 20 from the same roll. XRF provided superior discrimination to SEM-EDS on the expanded dataset and a more comprehensive elemental characterization (15 elements by XRF vs. 8 by SEM-EDS). While previous SEM-EDS analysis of the 90 electrical tapes resulted in 15 distinct groups and a discrimination power of 87.3%, current XRF analysis resulted in 61 distinct groups with further subgroups providing a discrimination power of 96.7%. Duplicate controls and tape fragments from the same roll were also analyzed to assess inter-day, intra-day, and intra-roll variability (n = 20). Parameter optimization included comparison of atmospheric conditions, collection times, and instrumental filters. A study of the effects of adhesive and backing thickness on spectrum collection revealed key implications to the method that required modification to the sample support material. Figures of merit and the performance of different methods for comparing and contrasting spectra are reported. The optimization of this method was part of an assessment to incorporate XRF to a forensic laboratory protocol for rapid, highly informative elemental analysis of electrical tape backings and to expand examiners’ casework capabilities.

中文翻译：

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通过 X 射线荧光对电工胶带背衬的光谱比较进行优化和评估

摘要 本研究描述了用于案例工作的 XRF 方法的参数优化过程。这项工作通过扩大特征带的总样本集并评估使用光谱叠加、光谱对比角和二次判别分析 (QDA) 来比较 XRF 光谱，从而扩展了先前的鉴别研究。扩展的样本集由 114 个样本组成，其中 94 个来自不同来源，其中 90 个先前已分析过，20 个来自同一卷。XRF 在扩展数据集上提供了优于 SEM-EDS 的辨别力和更全面的元素表征（XRF 为 15 个元素，SEM-EDS 为 8 个元素）。虽然之前对 90 个电工胶带的 SEM-EDS 分析导致了 15 个不同的组和 87.3% 的区分能力，目前的 XRF 分析产生了 61 个不同的组，进一步的亚组提供了 96.7% 的区分能力。还分析了来自同一卷的重复控件和磁带片段，以评估日间、日内和卷内可变性 (n = 20)。参数优化包括比较大气条件、收集时间和仪器过滤器。对粘合剂和背衬厚度对光谱收集的影响的研究揭示了需要修改样品支撑材料的方法的关键影响。报告了用于比较和对比光谱的不同方法的品质因数和性能。该方法的优化是将 XRF 纳入法医实验室协议的评估的一部分，以便快速、