Determination of nitroaromatic, nitramine, and nitrate ester explosives in water using solid-phase extraction and gas chromatography electron capture detection: Comparison with high-performance liquid chromatography

An analytical method for nitroaromatic, nitramine, and nitrate-ester explosives and co-contaminants in water based on solid-phase extraction (SPE) and gas chromatograph-electron capture detector (GC-ECD) is described. Samples are preconcentrated using cartridge or membrane SPE followed by elution with acetonitrile. The extract is compatible with GC and liquid chromatography, allowing direct comparison of concentration estimates obtained by different methods of determination and confirmation based on different physical properties. Quantitative GC analyses are obtained with deactivated direct-injection port liners, short widebore capillary columns, and high linear carrier gas velocities. Recoveries are 90% or greater for each of the nitroaromatics and nitrate esters and greater than 70% for nitramines and amino-nitrotoluenes. Concentration estimates for well water extracts from military sites analyzed by GC-ECD and high-performance liquid chromatography (HPLC) methods show good agreement for the analytes most frequently detected (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine, hexahydro-1,3,5-trinitro-1,3,5-triazine, 2,4,6-trinitrotoluene, and 1,3,5-trinitrobenzene). The GC provides lower method detection limits than HPLC for most analytes, but accurate calibration is more difficult. The ultraviolet detector used for HPLC has a much greater linear range than the ECD. The GC requires more care than the HPLC. Specifically, the injection port liner must be changed frequently for accurate determinations.