Author: Marianne E. Walsh

Publisher:

Published: 1998

Total Pages: 74

ISBN-13:

An analytical method for the determination of nitroaromatic, nitramine, and nitrate ester explosives and Co-contaminants in water was developed based on SPE (solid-phase extraction) and GC-ECD (gas chromatograph-electron capture detector). Water samples are preconcentrated using either cartridge or membrane SPE followed by elution with acetonitrile. The acetonitrile extract is compatible with both liquid and gas chromatography, thereby allowing direct comparison of concentration estimates obtained by different methods of determination. Quantitative GC analyses were obtained by using deactivated direct-injection-port liners, short wide-bore capillary columns. and high linear carrier gas velocities. Recoveries from spiked samples were 90% or greater for each of the nitroaromatics and nitrate esters, and greater than 70% for nitramines and amino-nitrotoluenes. Estimates of analyte concentrations in well-water extracts from military sites in the United States and Canada analyzed by GC-ECD and the standard HPLC (high performance liquid chromatography) method showed good agreement for the analytes most frequently detected (HMX octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine, RDX hexahydro-1,3,5-trinitro-1,3,5-triazine, TNT 2,4,6-trinitrotoluene, and TNB 1,3,5-trinitrobenzene). The GC method provides lower method detection limits for most analytes than HPLC, but accurate calibration is more difficult. The ultraviolet (UV) detector used for the HPLC analysis has much greater linear range than the ECD used for GC analysis. In addition. the GC instrumentation requires more care than the LC. Specifically the injection port liner must be changed frequently to maintain accurate determination of the nitramines. Because the sample preparation technique yields extracts that are compatible with both GC and HPLC analysis, confirmation of analyte presence can be obtained based on different physical properties.