Chromatographic Techniques and their
Applications in Characterization of Trace
Post Explosive Residues
SK Chakrabarti*, HK Pratihari and S Ghosh
Tripura State Forensic Science Laboratory, India
Submission:May 30, 2021;Published:June 16, 2021
*Corresponding author:SK Chakrabarti, Tripura State Forensic Science Laboratory, Narsingarh, Agartala-15, India
How to cite this article:Tahir J, Muhammad U, Zahid M, Imtiaz H, Abid N, et al. Detection of Chloroquine in Opium Using GC-MS: A Toxic Adulterant for
Opium Abusers. J Forensic Sci & Criminal Inves. 2021; 15(3): 555911 DOI:10.19080/JFSCI.2021.15.555911.
In most of the explosive cases, the post blast investigation of the scene is challenging to the scientists working in the field of forensic chemistry. The evidence analysis at the blast site is very complex and heterogeneous in nature. Moreover, the trace material available in the post blast site is contaminated with organic/inorganic substances with many other impurities. It requires proper separation to analyze the explosive components present in the post blast exhibits. In such situation, the chromatographic techniques are ideal for isolation and characterization of the post blast explosive residues. The Thin layer chromatography (TLC) and High-Performance Liquid Chromatography (HPLC) and Ion chromatography (IC) with different solvent system and visualization reagent are very much helpful to establish the identity both qualitatively & quantitatively to help the investigation. In addition to chromatographic studies, the spectrophotometric techniques are also further helpful to strengthen the results. The different post blast exhibits related to some cases, examined using state-of-the-art equipment for characterization of the trace quantity of post blast explosive residues, have been discussed in this paper.
Keywords: Post explosive residues; TLC; HPLC; TNT; Chromatography
The terrorists throughout the world use to widely rely on Improvised Explosive Device (IED)and sophisticated firearms in their activities to kill innocent people and achieve their goal. Their main activities are to attack armed forces to snatch firearms to strengthen their base and to spread terror among the people. As per available literature there are different terrorist groups working underground in different regions of the country. As per data from 2000 to 2010 a quite good number of civilians and security personnel have been killed and several firearms snatched.
The reason for use of IED are attributed for the following reasons.
1) Convenient to conceal and carry.
2) Ease of execution.
3) Cause more casualties in minimum time.
4) Create more fear psychosis.
5) Fog like condition produced creating poor visibility after explosion helping the terrorist to escape from the site.
Almost in all such explosive cases the forensic team use to visit the post blast site and different types of physical exhibits encountered during crime scene management are mentioned below:
a) Crater on the site, help to estimate the approx quantity of charge used.
b) Brick pebbles, loose soil, sand from inside/near the crater.
c) Scrapings of stains from immovable objects at the blast site
d) Iron and other different metallic pieces/stones used as sharpnels.
e) On/off switch/timer device chips and other trigger mechanism.
f) Molten and twisted metallic pieces.
g) Jute string, paper pieces.
h) Unidentified mass and debris mostly charred.
i) Burnt cloth from the site of explosion.
j) Pieces of single and multi-stranded wire.
k) Perforated and plain metallic sheets and wood pieces
with switch mechanism.
l) Different shapes of glass/porcelain/plastic pieces.
m) Diffused detonator with/without wire.
n) Wearing apparel of the victim/dead body.
o) Burnt vegetables.
p) Shattered/deformed containers.
q) Hand wash /barrel swab/swab collected from
immovable objects etc.
In addition to the above, other evidence are also observed
depending on the seat of explosion and place.
In one case an IED was planted but fortunately before
explosion it was detected and diffused by the bomb disposal
squad. All the diffused materials were received for examination
(Figure 1). The identification of the chemicals and to trigger the
mechanism of the IED was comparatively easier in this case.
In this case several IED’s were planted in different places
and successive explosions took place resulting in loss of life and
property. The post explosive sites are shown in the (Figure 2). The
relevant post explosive exhibits were collected for analysis to help
Residues of parent compound after explosion are often
trapped and fused into surrounding making the extraction task
complex. Extraction of residues from debris by aqueous/organic
solvent depend on their solubility factor.
The extraction from debris is done in different medium as
i. Extraction by hot water.
ii. Extraction by alkali.
iii. Extraction with acetone.
iv. Extraction after sodium fusion for detection of elemental
The extract made by different media are concentrated and
analyzed by different colorimetric reactions and instrumental
The extracts are first subjected to inorganic analysis for
detection of inorganic ions that constitute to form an explosive
mixture from extract no- 1, 2 & 3. Application of classical
chemistry on the extract no- 1 & 2, for detection of different
inorganic explosive ions and organic explosive residues e.g.,
RDX, TNT NG, etc. by colorimetric reactions [1-4]. Griess reagent,
Nesslers reagent are useful for preliminary identification of RDX,
PETN, TNT and ammonium ion, respectively. Further the chloride
reagent, sulphate reagent, perchlorate reagent, peroxide reagents
help in preliminary identification of respective ions. The inorganic
ions can be further subjected to analysis by Ion Chromatography.
Simultaneous detection of anions and cations in inorganic
explosive residues by ion chromatography helps in reduction of
analysis time and use of chemical [4,5]. The inorganic explosive
residues are examined with extract-1 & 2 .
The instrumental analyses of post explosive residues
require sample preparation to avoid any damage to instrument.
The sample without purification, should not be subjected
to spectroscopic study. But in a chromatographic technique
separation and identification can be carried out simultaneously.
Comparison with a known standard are helpful for confirmatory
b) Stationary phase-Pre coated Aluminum TLC plates.
c) Visualization reagent- 5% Diphenylamine in 95%
The TLC study can be further carried out with different solvent
system and visualization reagents.
The organic samples are then subjected to analysis by High
Performance Liquid Chromatography (HPLC), and Fourier
Transform-Infra Red Spectroscopy (FT-IR), Gas Chromatography
coupled with Mass Spectroscopy (GC-MS).
Detector – Waters 2487 Dual λ Absorbance, Column: Reverse
Phase C-18 column, particle size - 5μm, size -4.6×10mm, Mode
– Isocratic; Pump -Waters 1525Binary HPLC pump, Data Mode-
Absorbance; Run time- 12-20 minutes, Mobile Phase-Acetonitrile:
Water (70:30) . Detection limit for debris -10ng, wavelength of
UV- 210nm. Alternatively, separation from soil can also be achieved
with 25cm×4.6mm, C-18 column(5μm) with mobile phase MeOH:
H2O (50:50) at a flow rate of 1.5m/min, UV detector-254nm as
nitro aromatic explosives absorbed strongly at this wavelength,
whereas interferents like chlorinated organic compounds do
not . HPLC is preferred for debris analysis admixed with
polar/nonpolar compounds and biological fluids like blood etc.
Qualitative/quantitative analysis can also be done with a parallel
run with standard samples.
The post explosive cases always present the forensic scientists
a complex and difficult circumstances to investigate . In the
above-mentioned cases, the application of a combination of
techniques could help to extract, analyses and characterize the
explosive residues present in the exhibits to be Trinitrotoluene.
The extraction and analysis techniques has evolved and changed
a lot from conventional techniques to a safe green chemistry
technology. A combination of different chromatographic methods
was required in the post explosive cases for detection of residues
of explosives from post blast samples. The successful investigation
and detection of the explosive in the above case has helped the
court of law beyond doubt for effective prosecution resulting in
conviction of the prime accused persons.