用集成电路进行法医检查分析
AN-S-395
2020-10
zh
Determining low concentrations of chlorate, thiosulfate, thiocyanate, and perchlorate beside major anions in explosives and explosion residues
法医机构通过对使用过的爆炸物及其残留物进行痕量检测分析来检查恐怖袭击和战争制剂。特别重要的是为刑事调查部门和政府安全机构获取 "化学指纹"。使用抑制电导检测离子色谱法（IC）进行法医调查，可在广泛的浓度范围内灵敏、可靠地测定阴离子污染物，如氯酸盐、硫代硫酸盐、硫氰酸盐和高氯酸盐，以及常见的无机阴离子。
Forensic institutes examine terrorist attacks and warfare agents via trace detection analysis of the used explosives and their residuals. Main ingredients of explosives are fuels and oxidizers, such as oxyhalides (e.g., chlorate, perchlorate), as well as nitrates, sulfur, phosphorous containing compounds, metals, sugars, and hydrocarbons [1]. Typical inorganic post-blast residues include thiocyanate and thiosulfate. Of particular importance is the acquisition of «chemical fingerprints» for criminal investigation departments and governmental security agencies. Institutes for public health and environmental protection analyze such compounds that can contaminate the underlying soil and infiltrate ground water. Ion chromatography (IC) using suppressed conductivity detection allows a sensitive and robust determination of anionic contaminants such as chlorate, thiosulfate, thiocyanate, and perchlorate next to the common inorganic anions over a broad concentration range.
Artificial samples were dissolved in 10% methanol and automatically filtered using Inline Ultrafiltration. The Metrohm intelligent Partial Loop Injection Technique (MiPT) allows the injection of a precise variable volume depending on the sample load, and an automatic calibration.
The anions are separated on the analytical column Metrosep A Supp 4 - 250/4.0 using a sodium carbonate / sodium hydrogen carbonate eluent and a flow gradient (Figure 1).
Sequential suppression, including chemical and CO2-suppression, reduces the background conductivity to around 1 μS/cm and vastly improves the signal-to-noise ratio. All anions are determined with a conductivity detector and quantified with the MagIC Net software.
The developed IC method offers a straightforward, robust, and fast analysis of anionic additives and residuals related to explosives. Figure 2 displays the chromatogram of a 1 mg/L standard solution. The method covers the specifications shown in Table 1.
| Parameter | Specification |
|---|---|
| LOQ | ≤ 1mg/L for each anion, RSD ≤ 25% |
| Calibration | Anions = 1–100 mg/L Perchlorate = 1–50 mg/L |
| Resolution | ≥ 2 for each separation |
| Blank | < 0.1 mg/L |
| Run time | 32 min |
A flow gradient accelerates late-eluting components, which shortens analysis time to 32 minutes and improves peak shapes. The added methanol in the sample matrix did not interfere with the analysis in any way. For all components, the limit of quantification was below 1 mg/L and the resolution was above 2 for the full calibration range.
Using the Metrosep A Supp 4 column at ambient temperature enables the analysis with a compact IC system. For a comprehensive explosive characterization including the above specified anions as well as for cations, a two channel professional system provides a profitable solution.
Advanced studies of explosive residues are performed with IC-MS (ion chromatography coupled to mass spectrometry) to additionally confirm the analyte’s identification with a mass detector [2].
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