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Simultaneous measurement of positive and negative ions enables the analysis of 19 explosives in about 5 minutes.
Thermally labile explosives can be detected with high sensitivity under optimized MS conditions.
Regioisomers of nitrobenzenes can be separated under optimal LC conditions.
Rapid LC-MS/MS Analysis of 19 Explosives in Soil
Triple Quadrupole Liquid Chromatograph Mass Spectrometer
Introduction
Explosives are defined as chemical substances that decompose
rapidly and release high-temperature, high-pressure gases.
There are many types of explosives, including nitramines,
nitrobenzenes, nitrates, and peroxides. While these are widely
used for military and industrial purposes, they may remain in
the environment due to accidental leakage or illegal use. In
particular, soil tends to retain explosives and their residues. The
analysis of these substances is useful for evidence collection in
criminal investigations and for assessing environmental impacts.
Traditionally, GC-MS has been widely used for the analysis of
explosives. However, some compounds are prone to thermal
decomposition during vaporization. Therefore, LC-MS/MS
methods are increasingly being applied to such analyses.
In this study, 19 explosives listed in Table 1, including nitramine,
nitrobenzene, nitrate ester, and peroxide, were analyzed in soil
using LCMS-8060RX (Fig. 1).
Calibration standards were prepared by diluting a mixed
solution of each standard with methanol to obtain
concentrations equivalent to 1.0, 5.0, 10, 50, 100, 500, and 1,000
ng/mL in soil samples. The extraction method for soil samples
was based on EPA 8330B
1)
(Fig. 2). First, the dried soil samples
were passed through a 10-mesh sieve to remove coarse
particles. The samples were weighed in 10-g portions, and 10
mL of methanol was added to each. As an internal standard
(I.S.), 10 µL of a 1,2-DNB solution (50 µg/mL) was added to each
sample, and a mixed solution of 19 explosives (10 µg/mL) was
also added for validation. The samples were then mixed with a
vortex mixer for 1 minute, shaken for 10 minutes at room
temperature using a shaker, and centrifuged. The resulting
supernatant was collected and filtered through a 0.45 µm filter.
The filtrate was concentrated under a nitrogen stream and
dissolved in 1 mL of methanol to prepare the analytical samples.
Sample Preparation & Extraction
Abbreviation Compound name Group Formula M.W.（monoisotopic mass）
RDX Hexahydro-1,3,5-trinitro-1,3,5-triazine Nitramine C3H6N6O6 222.03
HMX Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine Nitramine C4H8N8O8 296.05
NQ Nitroguanidine Nitramine CH4N4O2 104.03
TNT 2,4,6-Trinitrotoluene Nitrobenzene C7H5N3O6 227.02
4A-2,6-DNT 4-Amino-2,6-Dinitrotoluene Nitrobenzene C7H7N3O4 197.04
2A-4,6-DNT 2-Amino-4,6-Dinitrotoluene Nitrobenzene C7H7N3O4 197.04
2,4-DNT 2,4-Dinitrotoluene Nitrobenzene C7H6N2O4 182.03
2,6-DNT 2,6-Dinitrotoluene Nitrobenzene C7H6N2O4 182.03
TNB 1,3,5-Trinitrobenzene Nitrobenzene C6H3N3O6 213.00
1,3-DNB 1,3-Dinitrobenzene Nitrobenzene C6H4N2O4 168.02
3,5-DNA 3,5-Dinitroaniline Nitrobenzene C6H5N3O4 183.03
Tetryl 2,4,6-N-tetranitro-N-methylaniline Nitrobenzene C7H5N5O8 287.01
PA 2,4,6-Trinitrophenol (Picric acid) Nitrobenzene C6H3N3O7 229.00
PETN Pentaerythritol tetranitrate Nitrate ester C5H8N4O12 316.01
NG Nitroglycerin Nitrate ester C3H5N3O9 227.00
1,2-DNG 1,2-Dinitroglycerin Nitrate ester C3H6N2O7 182.02
1-MNG 1-Mononitroglycerin Nitrate ester C3H7NO5 137.03
TATP Triacetone triperoxide Peroxide C9H18O6 222.11
HMTD Hexamethylene triperoxide diamine Peroxide C6H12N2O6 208.07
1,2-DNB 1,2-Dinitrobenzene I.S. (Nitrobenzene) C6H4N2O4 168.02
Dried Soil Samples
Weigh 10 g
Collect Supernatant
Analyze samples
Filter through 10-mesh sieve
Add 10 µL mixed std solution (10 µg/mL)
Add 10 µL of I.S., 1,2-DNB (50 µg/mL)
Extract (10 mL MeOH)
Vortex 1 min
Shake 10 min
Centrifuge
Filter 0.45 µm
Concentrate under N
2
stream
Dissolve（1 mL MeOH）
Table 1 List of Target Compounds
Fig. 1 Nexera X3 + LCMS-8060RX
Fig. 2 Workflow for Soil Sample Pretreatment
Toshinari Ishii
1
, Yuki Sakamoto
1
, Maiko Kusano
2
, Masaya Fujishiro
2
, Taka-aki Matsuyama
2
1 Shimadzu Corporation, 2 Department of Legal Medicine, SHOWA Medical University
