Table 2. Development times.
Separation of nitramines and nitrate esters
using laboratory-grade and commercial-grade
Solvent system
Time (min.)
solvents
The solvent system of petroleum ether and ac-
Stoddard solution : isopropanol (2 : 1) and (1 : 1)
50
etone (1 : 1) was found to be very effective in sepa-
Chloroform
10
rating the nitramines, such as RDX and HMX, and
Petroleum ether : acetone (3 : 1) and (2 : 1)
16
to produce a fair separation of the nitrate esters,
Petroleum ether : isopropanol (4 : 1)
17
PETN and NG (Table 4). RDX, PETN, and NG were
Xylene
25
3M adhesive cleaner : isopropanol (4 : 1)
24
also effectively separated with petroleum ether :
Duracryl : isopropanol (4 : 1)
26
isopropanol (4 : 1), but HMX failed to move from
Deglosser : isopropanol (4 : 1)
44
the line of origin.
Recorder paint thinner : isopropanol (4 : 1)
46
Mobile-phase solvents consisting of commercial-
Parks VM & P naphtha : isopropanol (4 : 1)
30
brand acetone and some paint thinners (1 : 1) were
Sterling VM & P naphtha : isopropanol (4 : 1)
23
Sterling Thin-X paint thinner : isopropanol (4 : 1)
50
also effective in producing a good separation of
Ace paint thinner : isopropanol (4 : 1)
45
RDX and HMX (Table 5). However, the separation
of PETN and NG was not as clear, thus resulting
in very similar Rf values.
phases prepared with these alcohols resulted in
very little or no movement of the nitroaromatic
Evaluation of TLC plates
TLC plates used in this study were all glass
compounds. However, when commercially avail-
plates precoated with silica gel. The differing fea-
able paint thinners were mixed with laboratory-
tures of these plates included different commer-
grade isopropanol (4 : 1), compounds such as TNT,
cial brands, fluorescence vs. nonfluorescence, and
DNT, TNB, and tetryl could be distinguished from
preconcentration zone vs. no preconcentration
each other (Table 3). Commercial brands such as
zone. The preconcentration area, located on the
Recorder paint thinner, Sterling VM & P naphtha,
bottom of the plate, is made up of inert material
Sterling Thin-X paint thinner, and Ace paint thin-
that is meant to absorb sample solvent. The two
ner were among the tested brands that have re-
brands of TLC plates, EM and Adsorbosil, did not
sulted in good-to-fair separation of TNT, DNT,
show any significant differences regarding sepa-
TNB, and tetryl. However, in most cases, the de-
ration of analytes. When using the same solvent
velopment time took longer than when the mo-
system and visualizing procedures, both plates
bile phase was composed solely of laboratory-
were nearly identical in results with slight color
grade solvents (Table 2).
Table 3. Separation of nitroaromatic compounds with commercial-brand paint thinners and
laboratory-grade isopropanol (4 : 1).
Solvent
TNT
TNB
2,4-DNT
Tetryl
2-A-DNT
4-A-DNT
Rf S.D.
Rf S.D.
Rf S.D.
Rf S.D.
Rf S.D.
Rf S.D.
systems
0.78 0.04
0.76 0.04
0.68 0.05
0.54 0.01
0.56 0.01
1
0.65
0.88 0.02
0.88 0.01
0.86 0.01
0.85 0
0.83 0.01
0.84 0.01
2
0.74 0.01
0.69 0.02
0.65 0.04
0.59 0.04
0.61 0.04
3
0.71
0.70 0.07
0.67 0.05
0.61 0.04
0.52 0.04
0.39 0.01
0.43 0.04
4
0.72 0.02
0.68 0
0.63 0.01
0.57 0.02
0.40 0.01
0.43 0
5
0.65 0.00
0.60 0
0.55 0
6
0.48
0.35
0.40
0.74 0.01
0.68 0
0.64 0.01
0.53 0
0.42 0.02
0.44 0
7
0.79 0.01
0.76 0.02
0.66 0.01
0.62 0.02
0.45 0.01
0.49 0.02
8
Solvent system key:
1--3M adhesive cleaner : isopropanol, n = 2
2--Duracryl : isopropanol, n = 2
3--Deglosser : isopropanol, n = 2
4--Recorder paint thinner : isopropanol, n = 2
5--Parks VM & P naphtha : isopropanol, n = 2
6--Sterling VM & P naphtha : isopropanol, n = 2
7--Sterling Thin-X paint thinner : isopropanol, n = 2
8--Ace paint thinner : isopropanol, n = 3
6
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