Benson Sarah J, Lennard Christopher J, Hill David M, Maynard Philip, Roux Claude
Forensic & Data Centres, Australian Federal Police, GPO Box 401, Canberra, ACT 2601, Australia.
J Forensic Sci. 2010 Jan;55(1):193-204. doi: 10.1111/j.1556-4029.2009.01241.x. Epub 2009 Dec 10.
A significant amount of research has been conducted into the use of stable isotopes to assist in determining the origin of various materials. The research conducted in the forensic field shows the potential of isotope ratio mass spectrometry (IRMS) to provide a level of discrimination not achievable utilizing traditional forensic techniques. Despite the research there have been few, if any, publications addressing the validation and measurement uncertainty of the technique for forensic applications. This study, the first in a planned series, presents validation data for the measurement of bulk nitrogen isotope ratios in ammonium nitrate (AN) using the DELTA(plus)XP (Thermo Finnigan) IRMS instrument equipped with a ConFlo III interface and FlashEA 1112 elemental analyzer (EA). Appropriate laboratory standards, analytical methods and correction calculations were developed and evaluated. A validation protocol was developed in line with the guidelines provided by the National Association of Testing Authorities, Australia (NATA). Performance characteristics including: accuracy, precision/repeatability, reproducibility/ruggedness, robustness, linear range, and measurement uncertainty were evaluated for the measurement of nitrogen isotope ratios in AN. AN (99.5%) and ammonium thiocyanate (99.99+%) were determined to be the most suitable laboratory standards and were calibrated against international standards (certified reference materials). All performance characteristics were within an acceptable range when potential uncertainties, including the manufacturer's uncertainty of the technique and standards, were taken into account. The experiments described in this article could be used as a model for validation of other instruments for similar purposes. Later studies in this series will address the more general issue of demonstrating that the IRMS technique is scientifically sound and fit-for-purpose in the forensic explosives analysis field.
已经开展了大量关于使用稳定同位素来协助确定各种材料来源的研究。在法医领域进行的研究表明，同位素比率质谱法（IRMS）有潜力提供传统法医技术无法实现的鉴别水平。尽管有这些研究，但针对该技术在法医应用中的验证和测量不确定度的出版物却很少，即便有也寥寥无几。本研究是计划系列中的第一项，它展示了使用配备ConFlo III接口和FlashEA 1112元素分析仪（EA）的DELTA(plus)XP（赛默飞世尔科技公司）IRMS仪器测量硝酸铵（AN）中总氮同位素比率的验证数据。开发并评估了合适的实验室标准、分析方法和校正计算。根据澳大利亚国家测试机构协会（NATA）提供的指南制定了验证方案。对AN中氮同位素比率测量的性能特征进行了评估，包括：准确性、精密度/重复性、再现性/耐用性、稳健性、线性范围和测量不确定度。确定AN（99.5%）和硫氰酸铵（99.99 +%）是最合适的实验室标准，并根据国际标准（有证参考物质）进行了校准。当考虑到潜在的不确定度，包括该技术和标准的制造商不确定度时，所有性能特征都在可接受范围内。本文所述的实验可作为类似目的其他仪器验证的模型。本系列后续研究将解决更普遍的问题，即证明IRMS技术在法医爆炸物分析领域在科学上是合理的且适用的。
