Hydrocyanic acid (HCN) is a well-known defensive allomone in the chemical arsenal of millipedes in the order Polydesmida. The presence of HCN in the headspace vapor of adult Xystocheir dissecta (Wood, 1867), a common millipede from the San Francisco Bay Area, was traced by laser desorption/ionization-mass spectrometry (LDI-MS). To accomplish this, the headspace vapor surrounding caged, live millipedes was allowed to diffuse passively over gold-nanoparticle (AuNP) deposits placed at various distances from the emitting source. The stainless steel plates with AuNP deposits were removed and irradiated by a 355-nm laser. The gaseous ions generated in this way were detected by time-of-flight mass spectrometry. The intensity of the mass spectrometric peak detected at m/z 249 for the Au(CN)₂⁻ complex anion was compared to that of the residual Au⁻ signal (m/z 197). Using this procedure, HCN vapors produced by the live millipedes could be detected up to 50 cm away from the source. Furthermore, the addition of H₂O₂, as an internal oxygen source for the gold cyanidation reaction that takes place in the AuNP deposits, significantly increased the detection sensitivity. Using the modified H₂O₂ addition procedure, HCN could now be detected at 80 cm from the source. Moreover, we found a decreasing intensity ratio of the Au(CN)₂⁻/Au⁻ signals as the distance from the emitting source increased, following an exponential-decay distribution as predicted by Fick’s law of diffusion.

Graphical abstract

中文翻译：

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通过金纳米粒子上的反应吸附和激光解吸/电离质谱（LDI-MS）进行远程吸附，可远程检测到的聚丙烯酰胺的HCN发射。

氢氰酸（HCN）是千足虫的化学武器库中众所周知的防御性异源激素，顺序为Polydesmida。激光解吸/电离质谱（LDI-MS）可以追溯到成年的Xystocheir dissecta（Wood，1867）（一种来自旧金山湾地区的常见千足虫）的顶空蒸气中的HCN的存在。为实现此目的，允许笼状活的千足虫周围的顶部空间蒸气在与发射源不同距离放置的金纳米粒子（AuNP）沉积物上被动扩散。除去具有AuNP沉积物的不锈钢板，并用355 nm激光照射。通过飞行时间质谱检测以这种方式产生的气态离子。Au（CN）在m / z 249处检测到的质谱峰强度₂ ^-配阴离子是相比于余量的Au的^-信号（M / Z 197）。使用此程序，可以检测到距离生命源50 cm处的由活的千足虫产生的HCN蒸气。此外，添加H ₂ O ₂作为在AuNP沉积物中发生的金氰化反应的内部氧源，显着提高了检测灵敏度。使用改进的H ₂ O ₂添加程序，现在可以在距源80厘米处检测到HCN。此外，我们发现在Au（CN）的递减强度比₂ ^- /金^- 信号随着离发射源的距离增加而增加，遵循菲克扩散定律预测的指数衰减分布。

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