Abstract
The first comprehensive assessment of 34 solid phase extraction sorbents is presented for organic explosive residues in wastewater prior to analysis with liquid chromatography-high resolution accurate mass spectrometry (LC-HRMS). A total of 18 explosives were selected including nitramines, nitrate esters, nitroaromatics and organic peroxides. Three polymeric divinylbenzene-based sorbents were found to be most suitable and one co-polymerised with n-vinyl pyrrolidone offered satisfactory recoveries for 14 compounds in fortified wastewater (77–124%). Limits of detection in matrix ranged from 0.026–23μgL−1 with R2≥0.98 for most compounds. The method was applied to eight 24-h composite wastewater samples from a London wastewater works and one compound, 2,4-dinitrotoluene, was determined over five days between 332 and 468g day−1 (225–303ngL−1). To further exploit the suspect screening capability, 17 additional explosives, precursors and transformation products were screened in spiked wastewater samples. Of these, 14 were detected with recoveries from 62 to 92%, highlighting the broad applicability of the method. To our knowledge, this represents the first screen of explosives-related compounds in wastewater from a major European city. This method also allows post-analysis detection of new or emerging compounds using full-scan HRMS datasets to potentially identify and locate illegal manufacture of explosives via wastewater analysis.
Highlights
In recent years, sewage epidemiology has been successfully applied to estimations of community pharmaceuticals and illicit drugs usage across several cities [1]
Other explosives detected in surface waters include octahydro-1,3,5,7-tetranitro-1,3,5,7-triazine (HMX) and cyclotrimethylene-trinitramine (RDX) at low g L−1 concentrations in groundwater from a military base and HMX, RDX and pentaerythritol tetranitrate (PETN) at sub ng L−1 concentrations in lake and river water used for military activities [2,4,5]
For optimisation of the analytical method for a set of n = 18 prioritised explosives, standard solutions of hexahydro-1,3,5-trinitroso-1,3,5-triazine (Rsalt, 99.8%), HMX (99.1%), RDX (98.6%), nitrobenzene (NB, 99.8%), nitroglycerine (NG, 99.4%), 3,4-dinitrotoluene (3,4-DNT, 100%), 2,4dinitrotoluene (2,4-DNT, 100%), 2,6-DNT (100%), 2-nitrotoluene (2-NT, 99%), 3-nitrotoluene (3-NT, 98.7%), 4-nitrotoluene (4-NT, 99.2%), erythritol tetranitrate (ETN, 99.9%), tetryl (98.6%), TNT (100%) and PETN (99.4%) at 1000 mg L−1, and triacetone triperoxide (TATP, 99.1%), hexamethylene triperoxide diamine (HMTD, 89.1%) and ethylene glycol dinitrate (EGDN, 96.2%) at 100 mg L−1 were sourced from Accustandard (New Haven, CT, USA)
Summary
Sewage epidemiology has been successfully applied to estimations of community pharmaceuticals and illicit drugs usage across several cities [1]. Several extraction and pre-concentration techniques have been applied to wastewater effluent, seawater, surface waters, groundwater and drinking water and include salting-out solvent extraction [9], solid phase extraction (SPE) [4,10,11,12,13,14] solid phase micro-extraction [5,15] dispersive liquid–liquid micro-extraction [16,17] and direct ultra-sound assisted dispersive liquid–liquid micro-extraction [18]. The main objectives were to develop a broadly applicable SPE method based on the extraction of 18 high-order organic explosives, including nitramines, nitrate esters, nitroaromatics and peroxides (Table 1) at the ng L−1 concentration range; and to exploit the capability of HRMS further via application to suspect screening of several additional explosives in wastewater influent sampled from one of the largest wastewater treatment plants (WWTP) in the EU, based in London, UK. With continual monitoring of explosive components in influent wastewater, deviations from any measured background concentration could produce intelligence on the catchment area in which explosives may be illegally manufactured
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