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Recovery and Detection of Urea Nitrate in Traces

NCJ Number
Journal of Forensic Sciences Volume: 52 Issue: 6 Dated: November 2007 Pages: 1284-1290
Joseph Almog Ph.D.; Gila Burda M.Sc.; Yael Shloosh B.A.; Sara Abramovich-Bar M.Sc.; Ehud Wolf M.Sc.; Tsippy Tamiri Ph.D.
Date Published
November 2007
7 pages
This paper describes a method for the recovery and detection in trace evidence of urea nitrate (UN), a powerful improvised explosive that has frequently been used by terrorists, notably in the first World Trade Center bombing in New York (February 1993) and in attacks on Israelis.
A technique for identifying UN in traces was demonstrated. It involves extraction with hot acetone, clean-up on chromosorb G-HP column, and analysis by HPLC/APCI/MS (high performance liquid chromatography/atmospheric pressure chemical ionization/mass spectrometry). Corroborative techniques are infrared spectroscopy and UN-1 color tests. UN can be formed, however, during the analytical process by reaction between urea, nitrate salts, and acids or acidic salts. Consequently, the detection of the characteristic adduct ion by mass spectrometry does not necessarily prove the presence of authentic urea nitrate in the sample. Further study is required in order to find ways to distinguish between authentic urea nitrate and an artifact formed during the analysis. A study for optimizing the analytical protocol is underway. These study findings are important, because it is difficult to identify UN in traces because of its instability under various conditions, including contact with carbonate, soils, and structural materials, and particularly in hydrolysis during hot aqueous extraction and clean-up. The paper describes the materials used and their sources, instrumentation, dissolution tests, the compatibility of UN with commonly encountered substances, LC/MS (liquid chromatography/mass spectrometry) measurement of potential interferences, column chromatography of UN, recovery and detection of UN and interferences, and recovery of UN from "natural" matrixes. 4 tables, 4 figures, and 19 references