Direct analysis of methcathinone from crude reaction mixture by flowing atmospheric-pressure afterglow mass spectrometry

Full text of DOI:10.1002/rcm.6262

Letter to the Editor
Received: 17 February 2012
Revised: 24 April 2012
Accepted: 24 April 2012
Published online in Wiley Online Library
Rapid Commun. Mass Spectrom. 2012, 26, 1577–1580
(wileyonlinelibrary.com) DOI: 10.1002/rcm.6262
Dear Editor,
compounds;[20] usually the sample is deposited on a surface,
but other ways of sample application are possible. In another
approach, discharge-based methods accomplished by the
use of dielectric barriers have also been used for analytical
applications.[21] Methods similar to APGD were also used
for identification of illicit drugs, such as direct analysis in real
time (DART)[22] or desorption electrospray ionization
(DESI).[23] DART, DESI and FAPA offer similar advantages.
They all operate at atmospheric pressure and can all be used
to ionize analytes on surfaces. DESI uses an electrospray
solvent, whereas DART and FAPA are “dry” methods
using ionization involving metastable atoms of helium or
nitrogen molecules. The most abundant positive reagent
ions produced by the FAPA are protonated water clusters,
(H2O)nH+.[20] DESI is very valuable for the analysis of
peptides and proteins, and also for imaging various surfaces
(e.g. tissue slices). DESI forms multiply charged ions, simi-
larly to ESI, whereas DART and FAPA do not. Neither DART
nor FAAPA has been effective in producing peptide ions.
In contrast to DART and FAPA, DESI may suffer from ion
suppression problems.
Direct analysis of methcathinone from crude reaction
mixture by flowing atmospheric-pressure afterglow mass
spectrometry
The direct analysis of methcathinone, produced by an illicit
synthesis found on the Internet, by a flowing atmospheric-
pressure afterglow (FAPA) source was demonstrated. This
method allows for fast product identification from crude
reaction mixtures without any sample preparation, although
the efficiency of product synthesis is low. The ability to carry
out fast and direct analysis of such mixtures can be a
useful supporting tool for an initial and rapid identification
of compounds of interest present in unpurified legal
psychoactive compounds.
Psychoactive compounds can be easily synthesized from
commonly available substrates that can be purchased over
the counter. The so-called ’legal highs’ are frequently used
by teenagers as a cheap alternative to the more expensive
and chemically advanced drugs. It is not a difficult task to
find procedures for the home synthesis of many drugs or
to buy such legal highs via the Internet. Some of these
procedures are extremely simple, such as the synthesis of
methcathinone from pseudoephedrine.[1,2] For this reaction,
any medicine containing pseudoephedrine (such as Sudafed
available without prescription), acetic acid and potassium
permanganate are sufficient to complete the synthesis (Fig. 1).
Fast analysis of such mixtures can be a time-consuming task,
as frequently the sample has to be purified before mass
spectrometric analysis. There are several methods available
for the analysis of illicit drugs: for example, amphetamine-
type stimulants (ATS) have been analyzed by thin-layer
chromatography (TLC),[3] gas chromatography/flame ionization
detection (GC/FID ),[4–6] gas chromatography/mass spectro-
metry (GC/MS),[7,8] high-performance liquid chromatography
(HPLC) with diode-array[5,9] or fluorescence detection,[10]
and Fourier transform infrared spectroscopy (FTIR),[11] or
Figure 1. Scheme of methcathinone synthesis from
pseudoephedrine.
A
rapid FAPA technique for the identification of
products in legal highs might be helpful for the fast screening
of illicit drugs seized on the street and for emergency
departments where patients are not aware of the composition
of a drug taken.
A prototype NOVA011 (ERTEC, Wrocław, Poland) flowing
atmospheric-pressure afterglow (FAPA) plasma source was
used for the desorption/ionization of all the compounds
studied. A schematic diagram of the source is shown in Fig. 2.
The quartz tube from the rear side is axially mounted along a
Teflon head, which also serves as a compartment for the cable
delivering high-voltage potential to the anode and as a
housing for the helium gas fitting. The discharge tube restricts
the flow of plasma stream and helium afterglow. It also
protects against electric breakdown in the radial direction.
The plasma cavity is connected to the high-voltage generator.
The generator is a classic flyback converter (such as used in
old TV sets) operating in a current mode. The discharge
power is adjustable within the range of 3–30 W. The open
circuit voltage (OCV) is in excess of 20 kV, which always
assures self-ignition of the helium discharge; thus, due to
the presence of the high-voltage supply, gas breakdown
occurs without any other means of ionization. The end of a
occasionally by H-NMR,[12] capillary electrophoresis (CE),[13]
1
solid-phase-microextraction-gas chromatography (SPME-GC),[14]
and gas chromatography/Fourier transform infrared spectro-
scopy (GC/FTIR).[15] GC/MS is still the most frequently used
approach for analysis of drugs as it provides efficient separation
and highly specific spectral data on individual compounds in a
complex mixture. The drawback of this method is the need
for sample derivatization prior to analysis. For analysis using
electrospray ionization (ESI)-MS, chromatographic separation
or at least a SPE purification step has to be implemented
before sample introduction into the mass spectrometer
source.[16,17] In contrast to the above-mentioned techniques,
atmospheric-pressure glow discharge (APGD) and its
modified version, flowing atmospheric-pressure afterglow
(FAPA), allow fast sample identification without or with
little sample preparation.[18,19] An APGD source was
recently introduced for the chemical ionization of organic
Rapid Commun. Mass Spectrom. 2012, 26, 1577–1580
Copyright © 2012 John Wiley & Sons, Ltd.

Letter to the Editor
column (10 cm long, 2.1 mm i.d., 2.6 mm; Phenomenex,
Torrance, CA, USA). A fast gradient from 0% of B to 50%
of B in 15 min was applied, where mobile phase A was 2%
acetonitrile with 0.1% formic acid, and mobile phase B
consisted of 98% acetonitrile supplemented with 0.1%
formic acid. A flow rate of 500 mL/min was maintained.
For LC/MS experiments, an Amazon ETD ion trap mass
spectrometer (Bruker Daltonics) was used with standard
ESI settings.
In order to verify the stability of the FAPA source, the mass
spectrometer baseline measurement was performed for 60 min.
The result of the experiment (data not shown) proves that the
deviation of the total ion chromatogram (not smoothed) does
not exceed 10%. Sensitivity optimization of the FAPA source
was not a main task in this study, but the limit of detection
(LOD) for methcathinone in the crude reaction mixture was
approximately 10 ng of the compound consumed, although
all experiments were performed from undiluted reaction
mixtures. The LOD for caffeine standard solution was also
tested and it was 5 ng of the compound consumed.
A volume of 5 mL of the crude reaction mixture was
deposited on a glass slide and directly analyzed. For both
syntheses product formation was detected together with
unreacted substrate. Figures 3 and 4 clearly show that
the second reaction (all reagents in solution) provided a
much higher yield. The ratios between the peaks at
m/z 164 and 166 corresponding to protonated methcathinone
and pseudoephedrine, respectively, were used to estimate
the efficiency of the reaction, although this was confirmed
by a separate LC/MS experiment (see Fig. 5). For both
pseudoephedrine and methcathinone an in-source fragmen-
tation could be observed. Both [M + H]+ ions lose water,
leading to the formation of ions at m/z 146.3 and 148.3,
respectively. This observation was confirmed by an addi-
tional MS/MS experiment for both compounds (data for
methcathinone shown in Fig. 3).
We have successfully used the novel flowing atmospheric-
pressure afterglow source for the fast identification of
methcathinone in a crude reaction mixture. No sample pre-
paration and the possibility for fast and direct analysis with-
out any clean-up step are the main advantages of the
method. The technique could be useful for any applications
where speed and simplicity in sample preparation are required,
such as illicit drug identification (e.g. amphetamine and its
derivatives, heroin, cocaine, legal highs), monitoring of drug
decomposition or the progress of organic synthesis. The FAPA
source also accepts samples in solid and gaseous forms, as will
be reported elsewhere. The capabilities of the FAPA source
were reported previously.[24] Not all types of compounds can
be analyzed by FAPA and there is a particular problem
when analyzing larger compounds with molecular weight
higher than 400 Da and also for most amino acids. For such
compounds the sensitivity of the source markedly decreases.
In positive ion mode the analytes yielded [M + H]+ ions,
consistent with other reports for polar compounds.[20]
Polar compounds, such as pseudoephedrine and meth-
cathinone, usually elute close to the void volume of the
chromatographic reversed-phase column as an unsepa-
rated mixture. This is not an obstacle unless quantitation
is necessary. Here we also found that a novel Kinetex
stationary phase is suitable for such separations, and
possible ion suppression can be avoided.
Figure 2. Diagram of the flowing atmospheric-pressure after-
glow source.
hollow cathode tube (2mm o.d., 1.5 mm i.d, length 11 mm) is
fitted to the stainless steel body of the cavity. This stainless
steel body is equipped with a few holes of 8 mm diameter
for observation of the discharge. The dimensions of the
capillary were optimized. The position of the FAPA source
in relation to the mass spectrometer inlet can be adjusted with
an x-y-z manipulator and it is usually placed approx. 1 cm from
the mass spectrometer inlet, and at approx. 30ꢀ from the hori-
zontal. The helium discharge gas was continuously delivered
at a flow rate of 1.0 L/min. The cavity and power supply
were permanently connected with a mechanically strong
but flexible coaxial cable with the high-voltage wire pro-
tected inside. This guaranteed a high level of safety, as the
operator has no exposure to harmful potentials.
The synthesis of methcathinone was performed according to
one of the procedures found on the Internet. Two versions of
the reaction were followed, resulting in different reaction
efficiencies. In procedure 1 one tablet of Sudafed was used for
one synthesis. First, the red coating from the tablet was removed,
the tablet was fine crushed, and ca. 200 mg of powder was placed
in a 1.5 mL tube; 200 mg of the tablet contain approximately
48 mg of pseudoephedrine. Next, 80 mg KMnO4 (in crystal form)
was added to the pseudoephedrine and the two substrates were
dissolved in 1 mL of 10% acetic acid, and mixed for 30 min at
60ꢀC. The overpressure was released by gentle opening of the
tube every 10 min. Procedure 2 was similar to the previous
protocol, except that a solution of 80 mg of KMnO4 in 1 mL of
10% acetic acid was first prepared. Next, the substrates were
mixed for 30 min at 60ꢀC. After being cooled to ambient tempera-
ture, the mixtures were directly applied to the plasma source for
analysis. The final reaction mixtures consisted of all products and
substrates of the reaction in 10% acetic acid.
Handling and synthesis of the material were performed under
permission from national authorities (Main Pharmaceutical
Inspectorate, Warszawa, Poland), and in the restricted area
of the laboratory with all safety precautions.
A Bruker Esquire 3000 quadrupole ion trap mass spectro-
meter (Bruker Daltonics, Bremen, Germany) was used for all
measurements. The standard ESI source settings were also
found to be optimal for the FAPA source, with the exception
of the capillary voltage where a much lower potential (1 kV)
than in the standard ESI settings (4.5 kV) was used.
A Prominence LC-20AD liquid chromatography system
(Shimadzu, Kyoto, Japan), with a SPD-M20A diode-array
detector, was used for separation using a XB-C18 Kinetex
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Rapid Commun. Mass Spectrom. 2012, 26, 1577–1580

Letter to the Editor
Figure 3. Crude reaction mixture applied from the glass slide. m/z 164.3 –
protonated methcathinone, m/z 166.3 – protonated pseudoephedrine, m/z 146.3 –
fragment ion from protonated methcathinone, 148.3 – fragmention from
protonated pseudoephedrine. The insert represents the MS/MS spectrum of
protonated methcathinone confirming in-source dehydration of this ion.
Figure 4. Crude reaction mixture applied from the glass slide – modified synthesis.
m/z 164.2 – protonated methcathinone, m/z 166.3 – protonated pseudoephedrine,
m/z 146.3 – fragment ion from protonated methcathinone, 148.3 – fragment ion
from protonated pseudoephedrine. Source contamination by phthalic anhydride
(plasticizer) at m/z 149.2 was also present in a blank run.
Figure 5. Reaction mixture separation after ZipTip clean-up on the XB-C18
Kinetex column (10 cm  100 mm i.d., 2.6 mm). Extracted ion chromatograms of
m/z 166.3 (pseudoephedrine) and 164.2 (methcathinone) are shown.
Rapid Commun. Mass Spectrom. 2012, 26, 1577–1580
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Letter to the Editor
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Acknowledgements
This work was partially supported by the Grant No. N N204
304837 from the Ministry of Science and Higher Education.
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Marek Smoluch1*, Edward Reszke2, Andrzej Ramsza3, Krzysztof
Labuz 4 and Jerzy Silberring1,5
0
,
1Department of Biochemistry and Neurobiology, Faculty of
Materials Science and Ceramics, AGH-University of Science
and Technology, Mickiewicza 30, 30-059 Krakow, Poland
2ERTEC-Poland, Rogowska 146/5, 54-440 Wrocław, Poland
3Institute of Applied Optics, Kamionkowska 18, 03-805
Warszawa, Poland
4The Rydygier Hospital in Krakow, Addiction Outpatient
Clinic, os. Zlotej Jesieni 1, 31-869 Krakow, Poland
5Centre of Polymer and Carbon Materials, Polish Academy of
Sciences, Sowinskiego St. 5, 44-121 Gliwice, Poland
*
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Correspondence to: M. Smoluch, Department of Biochemistry and
Neurobiology, Faculty of Materials Science and Ceramics, AGH-
University of Science and Technology, Mickiewicza 30, 30–059
Krakow, Poland.
E-mail: smoluch@agh.edu.pl
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Rapid Commun. Mass Spectrom. 2012, 26, 1577–1580