目的：枪弹射击时间估算是法庭科学物证研究的重要方面，能够为涉枪案件侦破和法庭诉讼提供不可替代的物证。近年来国外对此研究报道逐渐深入，而国产枪弹的射击时间研究尚属起步阶段。现代枪支的射击往往伴随着含氮发射药燃烧产生多种气相和固相射击残留物的过程，射击后可挥发的射击残留物随时间从枪管中不断逸散，对这种逸散过程的测量是估计发射时间的基础。随着化学分析手段的发展，近年来发展起来的固相微萃取技术，在用于分析化学领域的同时，因为其精准和低检出限，也引发了法庭科学枪弹领域研究者的关注。使用固相微萃取进行弹壳空腔内非接触采样，通过气相色谱进样，并使用热能分析仪、质谱等检测器对样品进行定量/半定量分析，是目前推断枪弹射击时间的主要方法；国产枪支和枪弹的发射时间问题，尚无通过这一方法进行的研究报道。方法射击用枪选用54式7.62 mm手枪和国产12号唧筒式猎枪，实验枪弹选用国产51式7.62 mm手枪弹和嘉陵牌12号猎枪弹。射击实验后的射击弹壳在室温、通风条件下保存，保证射击弹壳内的挥发性有机射击残留物能正常挥发。在随后的分析测试中，以射击实验到取样测试的时间为射击时间。通过固相微萃取提取国产51式7.62 mm手枪弹和嘉陵牌12号猎枪弹射击弹壳空腔内的挥发性含氮有机残留物，使用气相色谱-热能分析仪进行分析，测量含氮有机物相对含量随时间的推移变化，并使用这一含量参数变化估测射击时间。结果在12号猎枪弹射击弹壳从射击后1 d到9 d的气相色谱-热能分析谱图中，1~2 min之间均能观察到一个显著的双峰，且这个双峰随着射击时间的增加而不断减弱。通过对谱图的运算处理，得到含氮有机物峰的峰面积和峰高，分别得到与射击时间的关系，不论是峰面积还是峰高，都随射击时间的增长表现出降低的趋势。在11 d所测得的谱图中，也能观察到有两个峰值，但已变得微弱且不明显，峰面积与峰高接近于0。结果说明12号猎枪弹射击弹壳中不仅存在挥发性含氮有机物，而且其含量会随时间不断减少。对于51式手枪弹弹壳，在相同的取样分析方法获取的谱图中，相同时间范围内没有出现类似的显著谱峰，说明51式手枪弹的发射过程没有形成可供分析测量的含氮有机物。对于不同种类枪弹，挥发性含氮物质存在并得以检出，是使用气相色谱-热能分析仪进行发射时间估算的前提。不论是枪支还是枪弹的射击时间研究，尽管能采用相同或类似有机物残留量的气相色谱分析方法，但其变化趋势不同，因此必须针对不同品种、规格和品牌的枪支、枪弹分别得出有机物残留量变化曲线。结论建立了通过固相微萃取手段，对射击弹壳中有机射击残留物取样，并使用气相色谱-热能分析仪进行含氮有机物总量测试的方法，首次实现对国产枪弹射击弹壳的含氮有机射击残留物随时间衰减变化的无损检测。得出嘉陵牌12号猎枪弹含氮物质峰的面积和峰高与射击时间的关系曲线，该曲线可用于估计该种枪弹的发射时间。从51式7.62 mm手枪弹中未检出含氮有机物残留，气相色谱-热能分析法不适用于51式7.62 mm手枪弹的射击时间估计。%ABSTRACT:Objective The time lapse of spent cartridge usually plays an important part in gunshot crime investigation. This study conducted quantiifcational analysis of volatile nitrate organics for estimation of the discharge time of Chinese-made cartridges.Methods Volatile nitrate organic products on the internal of ifred cartridge cases, shotgun shells and gun barrels diffused into air slowly with time. After shooting, 7.62 mm model 51 pistol cartridges and 12/70 JIALING shotgun shells were sampled with solid phase micro-extraction (SPME) since discharge from day 1 and day 9, and analyzed by gas chromatography-thermal energy analyzer GC-TEA in order to detect the volatile nitrate organic of gunshot residues.Results One notable double peak detected from ifred 12/70 JIALING shotgun shells was observed in GC-TEA chromatogram. The observed double peak became weaker along with the increasing time since discharge, and it became too weak to be identiifed on day 11. Not only the existence of volatile nitrate organic compounds but also the decrease of its amount was indicated in the analysis. However, the similar double peak of volatile nitrate organic compounds, observed in 12/70 JIALING shotgun shells, was not existent at all in 7.62 mm model 51 pistol cartridges. The content of volatile nitrate organics, generated during shooting, was not enough for GC-TEA test.Conclusions For the ifrst time, the variety curves of the volatile nitrate organic compound content and the time since discharge of cartridges made in China was obtained. The test method of GC-TEA could be used in the discharge time estimation of the 12/70 JIALING shotgun shells, but not in that of the 7.62 mm model 51 pistol cartridges. For different types of cartridge, the concentration of volatile nitrate organic compound extracted from the shell has to be detectable with SPME-GC-TEA, prior to estimating the time since cartridge discharge.
展开▼
