Forensic and Data Centres, Australian Federal Police, P.O. Box 401, Canberra, ACT 2601, Australia; Centre for Forensic Science, University of Technology, Sydney, P.O. Box 123, Broadway, NSW 2007, Australia.
Forensic Sci Int. 2013 Dec 10;233(1-3):355-64. doi: 10.1016/j.forsciint.2013.10.011. Epub 2013 Oct 19.
When undertaking any study of the isotope abundance values of a bulk material, consideration should be given to the source materials and how they are combined to reach the final product being measured. While it is demonstrative to measure and record the values of clean papers, such as the results published as part one of this series, the majority of forensic casework samples would have undergone some form of writing or printing process prior to examination. Understanding the effects of these processes on the δ(13)C values of paper is essential for interpretation and comparison with clean samples, for example in cases where printed documents need to be compared to paper from an unprinted suspect ream. This study was undertaken so that the source materials, the effects of the production process and the effects of printing and forensic testing could be observed with respect to 80 gsm white office papers. Samples were taken sequentially from the paper production facility at the Australian Paper Mill (Maryvale, VIC). These samples ranged from raw wood chips through the pulping, whitening and refinement steps to the final formed and packed paper. Cellulose was extracted from each sample to observe both fractionation and mixing steps and their effect on the δ(13)C values. Overall, the mixing steps were observed to have a larger effect on the isotopic values of the bulk materials than any potential fractionation. Printing of papers using toner and inkjet printing processes and forensic testing were observed to have little effect on δ(13)C. These experiments highlighted considerations for sampling and confirmed the need for a holistic understanding of sample history to inform the interpretation of results.
在对大量材料的同位素丰度值进行研究时，应考虑到源材料以及它们是如何组合成最终被测量的产品的。虽然测量和记录清洁纸张（如本系列第一部分发布的结果）的值是很有说明性的，但大多数法医案件样本在检查之前都已经经过某种形式的书写或打印过程。了解这些过程对纸张 δ(13)C 值的影响对于解释和与清洁样品进行比较是必不可少的，例如在需要将打印文件与来自未打印嫌疑纸卷的纸张进行比较的情况下。进行这项研究是为了观察 80 克/平方米白色办公用纸的源材料、生产过程的影响以及打印和法医测试的影响。样品从澳大利亚造纸厂（维多利亚州马里维尔）的造纸厂生产设施中按顺序采集。这些样品范围从原木木片到制浆、增白和精炼步骤，再到最终成型和包装的纸张。从每个样品中提取纤维素，以观察分馏和混合步骤及其对 δ(13)C 值的影响。总的来说，混合步骤对大量材料的同位素值的影响大于任何潜在的分馏。使用碳粉和喷墨打印过程打印纸张以及法医测试观察到对 δ(13)C 的影响很小。这些实验强调了采样的考虑因素，并证实了需要全面了解样本历史，以告知结果的解释。
