Analysis of explosives and byproducts
Dr. Rainer Haas
Office of environmental investigation, Stadtwaldstrasse 45a, D-35037 Marburg
1 Sample preparation
Water samples are extracted with toluene (gas chromatographic investigation) or with solid phase extraction with LichroLut EN (produced by Macherey-Nagel) for HPLC investigations. Soil samples are extracted with methanol in an ultrasonic bath.
2 Gas chromatographic detection of nitroaromatic compounds
Nitroaromatic explosives and their byproducts can be detected by gas chromatography with electron capture detector (GC/ECD).
All compounds are separated with gas chromatography under the following chromatographic conditions:
Column: DB5 capillary column, length 30 m, diameter: 0.25 mm
Column temperature: 100°C (10°C/min) 230°C, 230°C (7 min)
Detector temperature: 300°C
Injector temperature: 250°C
Injection volume: 1 µl
Detector: electron capture detector (ECD).
The LOD are 0,2 mg/kg for soil samples and 0,1 µg/l for water samples or less.
The following nitroaromatic compounds can be detected and determined: mononitrotoluenes, dinitrotoluenes, 2,4,6-trinitrotoluene, amino-dinitrotoluenes, diamino-nitrotoluenes, 3,5-dinitroaniline, 1,3,5-trinitrobenzene, 1,3-dinitrobenzene and other dinitrobenzene-isomeres, mononitronaphthalenes, some isomeres of dinitronaphthalenes, aminonitrotoluenes and nitrobenzene.
3 HPLC analysis of other explosives
Other explosives can not be detected with gas chromatographic methods, either because they are not stable under GC conditions like RDX and HMX or they react with the column material like picric acid or hexanitrodiphenylamine. This explosives are separated and detected with HPLC analysis under the following conditions:
Column: reversed phase RP 18 Nucleosil 120, length 25 cm, diameter 3 mm
flow: 0.3 ml/min
gradient methanol/water 20/80 to methanol/water 100/00 within 40 min
Detector: diode array detector (DAD)
Injection volume: 50 µl.
The LOD of all compounds are 0,2 mg/kg for soil samples and 0,2 µg/l for water samples or less. The following explosives can be detected and determined: picric acid, nitroguanidine, tetranitromethylaniline, hexanitrodiphenylamine, pentaerythrite tetranitrate, nitroglycerine, ethylene glycol dinitrate, diethylene glycol dinitrate, RDX, HMX.
Calibration is done with standard solutions of reference materials. During the last years we investigated a lot of soil and water samples from more than 30 german old munition plants with this methods. More information about analysis of explosives you get at our homepage or from the author by email: haasr@gmx.net.
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