FARMACIA, 2008, Vol.LVI, 5
541
QUALITATIVE ANALYSIS OF CONFISCATED
ILLEGAL DRUGS BY THIN-LAYER
CHROMATOGRAPHY
MIHAELA GHEORGHE1*, DAN BĂLĂLĂU2, MIHAELA ILIE2,
DANIELA LUIZA BACONI2, ANNE-MARIE CIOBANU3
1
Criminalistics Research Institute of the Romanian Police General
Inspectorate, 13-15 Ştefan cel Mare str., Bucharest, Romania
2
”Carol Davila” University of Medicine and Pharmacy, Faculty of
Pharmacy, Toxicology Department, 6 Traian Vuia Str., Bucharest,
Romania
3
”Carol Davila” University of Medicine and Pharmacy, Faculty of
Pharmacy, Medicines Control Department, 6 Traian Vuia Str.,
Bucharest, Romania
*
corresponding author: mihag72@yahoo.com
Abstract
Criminalistic investigation often has as a task the identification of the
compounds from confiscated materials (powders, tablets, etc.). Sometimes the speed and
flexibility of the method choosed for the purpose are crucial.
A simple, yet robust analytical method for the identification of organic
compounds from mixtures is the thin-layer chromatography (TLC).
The paper presents a TLC method for the separation and identification of
caffeine, codeine and phenobarbital from mixtures, using silicagel F 254 precoated glass
plates as a stationary phase. Best results for the separation were obtained using the solvent
mixture ethyl acetate:methanol:ammonia (85:10:5).
Two components out of three unknown confiscated drug samples could be
identified in these conditions.
Rezumat
Investigaţia în domeniul criminalistic are adesea ca obiectiv identificarea
componentelor unor materiale confiscate în cursul unor activităţi specifice (pulberi,
comprimate, etc.). Uneori, durata şi flexibilitatea metodei alese în acest scop sunt cruciale.
O metodă simplă şi totuşi robustă de identificare a compuşilor organici din
amestecuri o constituie cromatografia în strat subţire (CSS).
Lucrarea prezintă o metodă CSS de separare şi identificare a unor substanţe de
abuz (cafeină, codeină, fenobarbital) din amestecuri, folosind plăci de sticlă 20 x 20 cm
acoperite cu silicagel F254 ca fază staţionară. Cele mai bune rezultate în ceea ce priveşte
separarea compuşilor de interes au fost obţinute folosind drept fază mobilă amestecul acetat
de etil: metanol: amoniac concentrat (85:10:5).
Prin această metodă au putut fi identificate componentele a două din trei probe,
sub formă de pulbere, confiscate în urma unor activităţi de investigare criminalistică
specifice.
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


illegal drugs
codeine
caffeine



phenobarbital
heroin
thin-layer chromatography
INTRODUCTION
Delict body analysis represents an important field of research in
criminalistics. A specific direction in this regard is the qualitative analysis
of confiscated drug samples, which frequently contain mixtures of different
psychoactive compounds, including substances that are under legal control
[1].
Often, samples of illegal drugs are adulterated (e.g. heroin contains
caffein and phenobarbital as most used adulterants, codeine contains also
acetylcodeine and noscapine, which are impurities of the production
process, etc.), and identification of the components can give information on
the drug origin.
A simple, rather inexpensive and still robust separation and
identification method for the components of such mixtures is the thin-layer
chromatography (TLC). Even less precise than other instrumental methods,
such as immunoanalysis, high performance liquid chromatography (HPLC)
or gas-chromatography – mass spectrometry (GC-MS), TLC finds its place
among the criminalistic investigation methods [2, 3].
TLC methods have been sucessfully applied to identify caffeine,
codeine and phenobarbital from a mixture [3], opium, morphine, codeine,
thebaine, papaverine, noscapine, ethylmorphyne, heroine, buprenorphine,
dextromethorphan and methadone from a sinthetic mixture [4], codeine,
dihidrocodeine, hydrocodeone and hydromorphone [5], and also as a
screening test for morphine, codeine, quinine, methadone and
norpropoxiphene from the urine samples of addicted subjects [6].
The paper presents the results obtained for the identification of
three confiscated drug samples in an attempt to establish a method for the
best separation of the compounds that can be found in illegal drugs.
MATERIALS AND METHODS
-
Substances:
caffeine (CF), from Janssen Chemica, 1 mg/mL in chloroform;
codeine phosphate (C), from Janssen Chemica, 1 mg/mL in
methanol HPLC grade (Sigma);
natrium phenobarbital (F), from Fluka, 1 mg/mL in methanol HPLC
grade (Sigma);
FARMACIA, 2008, Vol.LVI, 5
543
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three confiscated illicit drug samples, noted as X, Y, Z,
solubilised in methanol HPLC grade (Sigma)
Stationary phase:
- precoated silicagel glass plates, 60 F254, 20 x 20 cm, from Merck
Solvents and substances for mobile phases:
- methanol (HPLC, Sigma);
- ethyl acetate (p.a., Chimopar S.A.);
- ammonia 25% (Chimactiv S.A.);
- chloroform (Chimopar S.A.);
- n-buthanol (Merck);
- NaBr (Chimopar S.A.).
Devices
- varipette, 2 – 20 µL;
- developing tank;
- computer assisted aquisition and image processing system
(Vilber Lourmat), consisting in dark chamber, UV lamps, monochrom video
camera, BioCapt software.
Procedure
We spotted aliquots of 2 to 15 μL of known stock solutions in
parallel with the samples (X, Y, Z). The plates were developped with the
mobile phase in a developping vertical tank. When the mobile phase front
reached about 1 cm the plate edge, the plates were extracted from the tank
and let still at dark for the evaporation of the residual mobile phase. The
examination of the plates was further performed using UV irradiation at
λ=254 nm, the image of the plate was captured with the video camera and
interpreted with the BioProfil ver. 2.0 software.
Analysis
The separation results were expressed as Rf values, according to the
equation (1):
l compound
(1)
Rf 
l solvent
where Icompound represents the migration distance of the compound from the
origin, and Isolvent represents the migration distance of the front solvent from
the origin [3].
RESULTS AND DISCUSSION
For the identification of caffeine, codeine and phenobarbital from a
mixture we tested six solvent systems (Table I). The results suggest that best
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FARMACIA, 2008, Vol.LVI, 5
separation results are obtained with systems 5 and 6 (figures 1 and 2), the Rf
values being definitely different.
Table I
Results obtained for the TLC separation of caffeine,
codeine and phenobarbital from mixtures
System
Mobile phase1
Rf values
CF
C
F
X
Y
Z
0.47 0.78
0
0.75
0.59
Methanol: 25% ammonia
S1
0.78 0.47 0.99
(100:1.5)
0.99
0.88
0.99
0.98
0.35 0.91
0
0.91
0.37
Chloroform: methanol
S2
0.90 0.30 0.87
(90:10)
1
0.64
1
1
0.22 0.58
0
0.58
0.22
Methanol: n-buthanol
S3
0.45 0.18 0.92
0.25
(15:10) + 0.1 M NaBr
0.95
0.95
0.81
0.91
0.03 0.25
0
0.26
0.10
0.11
S4
Ethyl acetate
0.29 0.03
1
1
0.52
1
0.72
1
0.25
0.32
0.71
0.71
0.83
S5
Methanol
0.71 0.21 0.96
0.14
0.96 0.96
0.96
0.28 0.59
0.15
0.56 0.70
0.53
Ethyl acetate:methanol:
S6
0.69 0.27 0.58
25% ammonia (85:10:5)
0.90
0.67 0.96
0.96
1
All mixtures of solvents are expressed as parts, v/v.
The identification of the compounds was possible only for samples
X (caffeine, codeine and phenobarbital) and Y (caffeine and
phenobarbital); in both samples a small spot which migrates with the
solvent front could not be identified with any of the standard substances
tested. Similarily, the composition of the Z sample remained unknown after
several tests performed with substances of abuse.
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A polar solvent (methanol – S5) results in greater Rf values for
weak acid substances (phenobarbital) and smaller Rf values for weak
alkaline substances (such as codeine). The increase of the pH of the mobile
phase with 25% ammonia results in an increase in the migration distance
(hence the Rf value) for codeine, but has no major influence on
phaenobarbital.
The decrease in the developant polarity (S1 compared to S6) by
adding ethyl acetate reduces the migration distance for phenobarbital. We
could conclude that a mixture between a polar solvent (methanol) and a mild
polar solvent (ethyl acetate) ensures the optimum separation between the
three tested drugs.
CF C
F
X Y Z
Figure 1
TLC chromatogram
obtained with system 5
(CF=5µg, C=5µg, F=10µg,
M1=4µgCF+8µgC+10µgF)
M1
CF C F
X Y
Z
M2
Figure 2
LC chromatogram
obtained with system 6
(CF=5µg, C=5µg, F=10µg,
M2=6µgCF+6µgC+12µgF)
CONCLUSIONS
Thin-layer chromatography is a simple and robust method that can
be used to identify the compounds from confiscated illegal drugs.
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Our results confirm the possibility of a rapid identification of three
substances of abuse (caffeine, codeine and phenobarbital) from mixtures,
using TLC method.
The stationary phase used was silicagel F254 precoated glass plates,
20 x 20 cm. From the mobile phases tested, best results were obtained with
a mixture of a mild polar and a polar solvent, alkalinised with 25%
ammonia (ethyl acetate:methanol: 25% ammonia, 85:10:5, v/v). The
examination of the plates was performed using 254 nm UV light. The
aquisition and the interpretation of the chromatograms was computer
assisted, using a video camera and a specialised image processsor.
The analysis of three confiscated drug samples resulted in the
identification of codeine, caffeine and phenobarbital in sample noted as X,
caffeine and phenobarbital in the sample noted as Y. The compounds of the
sample noted as Z could not be identified through this method, suggesting
that in certain cases another method should be used (e.g. GC-MS).
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