yielded light blue spots while PETN and NG had
with Griess reagents yielded colors that charac-
lime green spots.
terize these compounds, but in most cases we
found nitroaromatic compounds to be more vis-
ible with the exception of 2,4-DNT and 4-A-DNT.
Estimation of detection capability
A preliminary estimation of the minimum de-
Griess reagent formulation by Peak and Higgs re-
tectable level for each explosive was determined
sulted in a pinkish color for NG. The Hach
NitriVer3, when used in conjunction with acidi-
by spotting different volumes (ranging from 0.5
to 30 L) of each standard solution. The concen-
fied zinc, detects RDX from soil and groundwater
extracts (Walsh and Jenkins 1991, Jenkins et al.
tration of the various standard solutions ranged
1994), but Hach NitriVer3 used in conjunction with
from 5 to 2000 mg/L. Depending on the analyte
5% KOH did not yield any color formation for ni-
of interest, UV viewing and visualizing agents
trate esters (PETN and NG) nor for nitramines
were employed to visualize (or detect) the in-
(RDX and HMX). The absence of color(s) may have
tended compound. Table 8 lists the lowest detect-
been due to the omission of an acidic environment.
able quantity that could be visualized for each ex-
plosive. All analytes were visible at 1-g quantity
When using the visualizing agents in this category
the best viewing of colors was after the plates had
either by UV viewing or by spraying with a visu-
completely dried.
alizing agent. In samples containing high concen-
tration of analyte (>1000 mg/L), a spotting vol-
ume of 1 L was sufficient to allow visualization
NaIO4/KMnO4
According to Carlson and Thompson (1986),
of the analyte, but in samples containing lower
sodium metaperiodate (0.1%) and potassium per-
levels (<100 mg/L), the spotting volumes could
be as high as 30 L (on a preconcentration zone)
manganate (0.5%) in a 4% sodium hydroxide so-
lution yields yellow spots for NG on a dry plate
without causing streaking or too much spreading
and green spots for PETN on a wet plate, all
of the analyte. TNT and TNB were the only
against a violet background. DiCarlo et al. (1964)
analytes that were consistently visualized at 0.1-
g quantity, which was equivalent to a spotting
also observed similar results for PETN when
volume of 10 L of standard solution of 10 mg/L
sprayed with a solution containing 4 : 1 : 1 of so-
or 1 L of 100 mg/L. The remaining nitroaromatics
dium metaperiodate (2%) : potassium permanga-
were also visible at 0.1-g quantity when sprayed
nate (1%) : sodium bicarbonate (2%). However, our
results yielded no color formation for nitrate es-
with TiCl3 and DMACA; however, more tests are
ters. Some nitroaromatics developed yellow spots
needed to fully assess the reliability of detection
after the plate had been dried in a 100C oven for
at this level. RDX was also visualized at 0.1-g
five minutes (Table 7). The failure to observe the
quantity under UV viewing, but the observations
nitrate esters may partly be due to spotting of
were more consistent with HPTLC plates than
lower levels of NG and PETN (1 to 2 g) compared
with conventional plates. While the HPTLC plates
to the literature values of 2 to 25 g.
did not play a role in significantly enhancing the
separation of analytes, with regard to detection
1% or 5% DPA and UV exposure
capabilities, the properties of HPTLC plates
DiCarlo et al. (1964), Parker et al. (1975), and
seemed to enhance the detectability of nitramines
Bagnato and Grasso (1986) all report color visual-
and nitrate esters.
ization of PETN with either 1% or 5% DPA fol-
lowed by UV light exposure. Parker et al. (1975)
Testing of soil samples collected from the field
also included NG and RDX while Bagnato and
Soil samples collected from the field (ranging
Grasso (1986) were able to also observe HMX. The
from ammunition plants to firing ranges) were
results we obtained were similar. PETN and NG
analyzed using the conventional TLC methods to
appeared greengray and RDX was light pinkish
determine or confirm the accuracy of its separa-
purple.
tion procedures. The concentration of the analytes
from these soil samples was previously deter-
Griess reagent and UV exposure
mined by standard HPLC methods. In most cases,
Spraying with Griess reagent followed by UV
soil samples were extracted with acetone (1 to 5
light exposure for approximately 30 minutes re-
ratio) and the filtered extracts were spotted on TLC
sulted in pink-colored spots for RDX, HMX, PETN,
plates. Soil from Umatilla Army Depot, which con-
tained 716 g of TNT per gram of soil, was ex-
and NG. However, when the plates were dried in
tracted and spotted (10 1 L). This yielded a vis-
a 110oC oven for 20 minutes, RDX and HMX
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