The identification of explosive residues in crime scene forensic investigation, environmental site remediation and homeland security is an analysis of major significance to the public and regulatory authorities. The traditional and most commonly accepted method for the analysis of the nitro-aromatic class of explosives is USEPA Method 8330.  This method provides a moderately sensitive UV-based analysis, but lacks selectivity, placing a greater demand on chromatography.  Some laboratories have started to use LC/MS to provide better faster analyses and additional selectivity.  Although the quadrupole mass spectrometer demonstrates excellent sensitivity, the time-of-flight mass spectrometer is not only adequately sensitive, but it adds the additional feature of identification as a result of its high mass accuracy, useful for empirical formula determination.  In this report a comparison of the results in analyzing 22 known compounds found in explosives residues using three LC detection systems is presented, with particular emphasis on the usefulness of the time-of-flight mass spectrometer.  The results obtained are shown in Table 1.

 

TABLE 1	Limit of Quantitation
Compound	UV	Quad – Full Scan	Quad SIM	TOF – Full Scan
HMTD	10,000	200	10	30
HMX	1,000	50	3	10
RDX	100	20	3	0.5
TATB	1,000	50	3	5
EGDN	2,000	N.D.	N.D.	N.D.
1,3,5-TNB	3,000	25	2	3
1,3-DNB	500	20	3	2
Tetryl	500	50	4	5
4A-DNT	500	50	4	10
NB	800	5000	300	N.D.
NG	500	2000	600	N.D.
2A-DNT	500	20	1	5
TNT	200	30	0.5	4
2,6-DNT	400	80	10	8
2,4-DNT	400	20	1	4
HNS	500	20	0.5	1
2-NT	300	1000	100	100
4-NT	200	400	50	50
PETN	1,000	1000	500	250
3-NT	300	N.D.	N.D.	5000
TATP	10,000	500	50	1000
Carbamate	500	40	5	10