Experimental Assessment of Analytical Holding Times for Nitroaromatic andNitramine Explosives in Soil

摘要

A study was conducted to experimentally evaluate the maximum acceptable pre-extraction analytical holding, times (MHTs) for three nitroaromatic compounds and two nitramines in soil. Three spiked soils and a field-contaminated soil were utilized in the study.Analytes investigated were HMX, RDX, TNB, TNT and 2,4-DNT, all at the low microgram/gram level. Subsamples of each soil were extracted with acetonitrile in an ultrasonic bath after being held for periods of 0, 3, 7, 14, 28 and 56 days at either room temperature (22 deg C), under refrigeration (2 deg C) or frozen (-15 deg C). Extracts were analyzed by RP-HPLC. The two nitramines, HMX and RDX, were stable over the entire period for all soils under all storage temperatures. For the three nitroaromatics (TNB, TNT and 2,4-DNT) the results were very different, in that all three analytes rapidly degraded in spiked soils at room temperature, more slowly degraded under refrigerator temperature and remained quite stable when frozen. Of the three, TNB degraded most rapidly, followed by TNT and 2,4-DNT. The degradation at room temperature and in the refrigerator was much faster for one soil than for the others. Even when frozen there was a small loss of 2,4-DNT in the soil showing the most rapid degradation. For the field-contaminated soil, the nitroaromatics were much more stable, even at room temperature, although some degradation occurred. Because of the large stability difference between fortified and field-contaminated soils, the efficacy of using fortified soils to estimate -MHTs is discussed. When frozen, an MHT of eight weeks is recommended. Analyte holding time, Nitramine explosives, Nitroaromatic explosives, Soil contamination.