Walsh M E
US Army Cold Regions Research and Engineering Laboratory, 72 Lyme Road, Hanover, NH 03755-1290, USA.
Talanta. 2001 May 10;54(3):427-38. doi: 10.1016/s0039-9140(00)00541-5.
Hazardous waste site characterization, forensic investigations, and land mine detection are scenarios where soils may be collected and analyzed for traces of nitroaromatic, nitramine, and nitrate ester explosives. These thermally labile analytes are traditionally determined by high-performance liquid chromatography (HPLC); however, commercially available deactivated injection port liners and wide-bore capillary columns have made routine analysis by gas chromatography (GC) possible. The electron-withdrawing nitro group common to each of these explosives makes the electron capture detector (ECD) suitable for determination of low concentrations of explosives in soil, water, and air. GC-ECD and HPLC-UV concentration estimates of explosives residues in field-contaminated soils from hazardous waste sites were compared, and correlation (r>0.97) was excellent between the two methods of analysis for each of the compounds most frequently detected: 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), 2,4-dinitrotoluene (2,4-DNT), 1,3-dinitrobenzene (1,3-DNB), 1,3,5-trinitrobenzene (TNB), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX). The analytes were extracted from soils with acetonitrile by 18 h of sonication in a cooled ultrasonic bath. Two soil-to-solvent ratios were evaluated: 2.00 g:10.00 ml and 25.0 g:50.0 ml. GC-ECD method detection limits were similar for the two soil-to-solvent ratios and were about 1 mug kg(-1) for the di- and trinitroaromatics, about 10 mug kg(-1) for the mono-nitroaromatics, 3 mug kg(-1) for RDX, 25 mug kg(-1) for HMX, and between 10 and 40 mug kg(-1) for the nitrate esters (nitroglycerine [NG] and pentaerythritol tetranitrate [PETN]). Spike recovery studies revealed artifacts introduced by the spiking procedure. Recoveries were low in some soils if the amount of soil spiked was large (25.0 g) compared to the volume of spike solution added (1.00 ml). Recoveries were close to 100% when 2.00-g soil samples were spiked with 1.00 ml of solution. Analytes most frequently found in soils collected near buried land mines were the microbial transformation products of TNT (2-amino-4,6-dinitrotoluene [2-Am-DNT] and 4-amino-2,6-dinitrotoluene [4-Am-DNT]), manufacturing impurities of TNT (2,4-DNT, 2,6-DNT, and 1,3-DNB), and TNT. The microbial reduction products of the isomers of DNT and of 1,3-DNB were also detected, but the ECD response to these compounds is poor.
危险废物场地特征分析、法医调查和地雷探测等场景中，可能会采集土壤样本并分析其中硝基芳烃、硝胺和硝酸酯类炸药的痕迹。这些热不稳定分析物传统上通过高效液相色谱法（HPLC）测定；然而，市售的去活化进样口衬管和宽口径毛细管柱使气相色谱法（GC）的常规分析成为可能。这些炸药中常见的吸电子硝基使得电子捕获检测器（ECD）适用于测定土壤、水和空气中低浓度的炸药。比较了危险废物场地现场污染土壤中炸药残留的GC-ECD和HPLC-UV浓度估算值，对于每种最常检测到的化合物，两种分析方法之间的相关性（r>0.97）都非常好：2,4,6-三硝基甲苯（TNT）、六氢-1,3,5-三硝基-1,3,5-三嗪（RDX）、2,4-二硝基甲苯（2,4-DNT）、1,3-二硝基苯（1,3-DNB）、1,3,5-三硝基苯（TNB）和八氢-1,3,5,7-四硝基-1,3,5,7-四氮杂环辛烷（HMX）。通过在冷却的超声浴中超声处理18小时，用乙腈从土壤中提取分析物。评估了两种土壤与溶剂的比例：2.00 g:10.00 ml和25.0 g:50.0 ml。两种土壤与溶剂比例下GC-ECD方法的检测限相似，二硝基和三硝基芳烃约为1μg kg⁻¹，单硝基芳烃约为10μg kg⁻¹，RDX为3μg kg⁻¹，HMX为25μg kg⁻¹，硝酸酯类（硝化甘油[NG]和季戊四醇四硝酸酯[PETN]）为10至40μg kg⁻¹。加标回收研究揭示了加标过程引入的假象。如果加标的土壤量较大（25.0 g），与添加的加标溶液体积（1.00 ml）相比，某些土壤中的回收率较低。当向2.00 g土壤样品中加入1.00 ml溶液时，回收率接近100%。在靠近埋藏地雷处采集的土壤中最常发现的分析物是TNT的微生物转化产物（2-氨基-4,6-二硝基甲苯[2-Am-DNT]和4-氨基-2,6-二硝基甲苯[4-Am-DNT]）、TNT的制造杂质（2,4-DNT、2,6-DNT和1,3-DNB）以及TNT。还检测到了DNT异构体和1,3-DNB的微生物还原产物，但ECD对这些化合物的响应较差。
