传统的泥土颜色分析方法是依靠人眼观察的蒙赛尔比色法,基于仪器的更加客观的颜色分析方法仍有待建立。显微分光光度计（MSP）兼具显微镜与分光光度计的功能,可分析微量物质的光学性质,具有无损、操作简单、分析快速等优势,是泥土物证颜色分析的理想工具。本文优化了MSP分析泥土颜色的条件,考察了泥土粒径及湿度对MSP分析结果的影响。结果表明,泥土粒径越小,明度越大,湿度会显著影响泥土颜色。因此在进行泥土颜色分析时,需将泥土完全干燥并研磨至相同粒径。本文所建立的方法重现性良好,日内、日间测量值RSD均小于3%;所需样品量少,可用于5mg泥土样品的颜色分析;结果客观可靠,可实现人眼无法分辨、颜色相近的泥土的进一步区分。
Abstract
Soil, a kind of trace evidence, is frequently encountered in forensic cases. Soil evidence plays an important role in linking crime scene with criminal tools or suspected people involved or both. Color is one of the important characteristics of soil. Thus, soil determination is often taking color analysis as its first step. The traditional soil color analysis method —Munsell colorimetric assay relies on the human-eye observation which is very subjective. A more objective and instrument-based color analysis method is still awaited. Microspectrophotometer (MSP) has the functions of both microscope and spectrophotometer, capable of analyzing the optical properties of trace samples (e.g. soil). MSP demonstrate the advantages of non-destructiveness, simple operation and rapid analysis, hence making it an ideal tool for the analysis of soil color. In this paper, the instrument conditions of MSP for the color analysis were optimized, with the influence of soil particle size and humidity on MSP analysis being investigated. The results showed that the smaller the soil particle size, the greater the soil brightness. Besides, humidity can significantly affect soil color. Therefore, in the comparison of soil color, the sampling soil is necessary to completely dry and grind to same particle size. Good reproducibility was obtained for the established method. The RSD of the intra- and intra-day measurements is less than 3% under a small required soil amount about 5 mg. Further discrimination of soils with similar color was realized successfully using the here-developed method. In conclusion, the MSP-based soil color determination has been established, revealing good reproducibility, low sample size, objective and reliable results. The method is able to distinguish the soils of similar color which cannot be discerned through human eyes. However, it should be mentioned that color determination is only a preliminary screening approach, therefore other analytical techniques ought to be combined so as to obtain more accurate and comprehensive identification about soil.
关键词
微量物证 /
泥土 /
颜色 /
色度差 /
显微分光光度法
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Key words
trace evidence /
soil /
color /
chromaticity difference /
microspectrophotometry
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参考文献
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脚注
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基金
国家重点研发计划（2017YFC0803803）; 中央级公益性科研院所基本科研业务费专项资金项目（2018JB015）
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