Characteristics of key intermediates generated in uncatalyzed bis(2,4-dinitrophenyl) oxalate (DNPO) chemiluminescence reactions

Article abstract of DOI:10.1039/b206367k

The characteristics of two distinct perylene chemiluminescence (CL) decay curves generated by the reaction between bis(2,4-dinitrophenyl) oxalate (DNPO) and H₂O₂ in the absence of base catalysts were investigated. When the intensity of peroxyoxalate chemiluminescence (PO-CL) vs. time was measured under relatively low H₂O₂ and high DNPO concentrations in ethyl acetate, a slowly decaying curve appeared. However, upon increasing the H₂O₂ concentration under the same DNPO-CL reaction conditions, two distinct emission maxima were observed: a fast decaying CL curve and a slowly decaying CL curve. The fast decaying CL curve appeared alone when the H₂O₂ concentration greatly exceeded the DNPO concentration in ethyl acetate. To learn more about the properties of both CL decay curves, we further investigated the effects of adding H₂O or phenols having different nucleophilicity [2,4-dinitrophenol (DNP), 2,4-dichlorophenol (DCP), pentachlorophenol (PCP), and 2,4,6-trichlorophenol (TCP)] and the stability of DNPO used in the CL reaction. The slowly decaying curve was predominant with the addition of H₂O and relatively strong nucleophile. Based on the observed results, we propose that the likely high-energy intermediates generated in DNPO-CL reactions without added base catalysts are hydroperoxyoxalate ester and a six-membered cyclic peroxide.

Full text of DOI:10.1039/b206367k

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Characteristics of key intermediates generated in uncatalyzed
bis(2,4-dinitrophenyl) oxalate (DNPO) chemiluminescence
reactions
a
a
b,c
c
2
Ji Hoon Lee,*† James C. Rock, Mark A. Schlautman and Elizabeth R. Carraway
a
Occupational Health & Safety Institute, Texas A&M University, College Station,
TX 77843-3133, USA. E-mail: lee@clemson.edu
Department of Agricultural & Biological Engineering, Clemson University, Clemson,
SC 29634-0357, USA
Department of Environmental Toxicology and the Clemson Institute of Environmental
Toxicology, Clemson University, Pendleton, SC 29670, USA
b
c
Received (in Cambridge, UK) 2nd July 2002, Accepted 30th July 2002
First published as an Advance Article on the web 22nd August 2002
The characteristics of two distinct perylene chemiluminescence (CL) decay curves generated by the reaction
between bis(2,4-dinitrophenyl) oxalate (DNPO) and H O in the absence of base catalysts were investigated. When
2
2
the intensity of peroxyoxalate chemiluminescence (PO-CL) vs. time was measured under relatively low H O and
2
2
high DNPO concentrations in ethyl acetate, a slowly decaying curve appeared. However, upon increasing the H O2
2
concentration under the same DNPO-CL reaction conditions, two distinct emission maxima were observed: a fast
decaying CL curve and a slowly decaying CL curve. The fast decaying CL curve appeared alone when the H O2
2
concentration greatly exceeded the DNPO concentration in ethyl acetate. To learn more about the properties of
both CL decay curves, we further investigated the effects of adding H O or phenols having different nucleophilicity
2
[2,4-dinitrophenol (DNP), 2,4-dichlorophenol (DCP), pentachlorophenol (PCP), and 2,4,6-trichlorophenol (TCP)]
and the stability of DNPO used in the CL reaction. The slowly decaying curve was predominant with the addition
of H O and relatively strong nucleophile. Based on the observed results, we propose that the likely high-energy
2
intermediates generated in DNPO-CL reactions without added base catalysts are hydroperoxyoxalate ester and a
six-membered cyclic peroxide.
1
1
Introduction
amine or sodium salicylate, and the solvent property. In par-
ticular, Lee et al. obtained two different decay curves when they
measured CL intensities generated by the reaction of DNPO
Although various high pressure liquid chromatography
(
(
HPLC) systems with a peroxyoxalate chemiluminescence
PO-CL) detector have been successfully used for quantifying
and excess H O2 in the presence of imidazole (ImH) and
-aminoanthracene ([H O ] > [DNPO] > [ImH]). Lee et al.
2
11
1
1
–3
2
2
fluorescent compounds at trace levels, the identity of the
high-energy intermediate(s) generated during PO-CL reactions
continues to be debated by several research groups.
Alvarez et al. first proposed the existence of multiple inter-
mediates capable of generating light during PO-CL reactions,
including two high-energy intermediates (1,2-dioxetanedione
proposed that the relatively rapidly decaying curve might be
generated by the interaction between fluorescent molecules
having low oxidative half-wave potentials and an intermediate
e.g., hydroxyperoxyoxalate ester) formed from the reaction
e.g., direct CL reaction) between DNPO and H O with a base
in low viscosity solvents (e.g., acetonitrile, ethyl acetate). For
example, they were not able to obtain the fast decaying curve in
DNPO-CL reactions with fluorescent compounds having
relatively high oxidative half-wave potentials (e.g., anthracene,
perylene).
Based on their results, Lee et al. proposed that the high-
energy intermediate producing the fast decaying curve was the
hydroperoxyoxalate ester. Also, they proposed that the slowly
decaying curve generated in the base-catalyzed CL reaction is
always predominant in DNPO-CL reactions in non-aqueous
solvents because the intermediate is more reactive with fluor-
escent molecules than the hydroperoxyoxalate ester.
In general, trace levels of fluorescent compounds can be
detected by the reaction of DNPO and H O without a catalyst,
4
–15
8
(
(
2
2
9
and 1,2-dioxetanone). Chokshi et al. proposed the hydro-
peroxyoxalate ester as a possible high-energy intermediate
capable of interacting with fluorescent compounds by studying
the bis(2,6-difluorophenyl) oxalate (DFPO) CL reaction using
19
F-NMR. Based on the kinetics of photoinitiated CL reac-
1
0
tions, Milofsky and Birks proposed a six-membered cyclic
peroxide as an intermediate capable of generating singlet-
11
1
1
excited states of fluorescent molecules. Lee et al. proposed
that bis(2,4-dinitrophenyl) oxalate (DNPO) CL reactions
exhibit complex pathways (e.g., direct CL reaction, base-
catalyzed CL reaction, and acid–base CL reaction) that involve
many of the highly energetic intermediates previously suggested
by other research groups.
of various key intermediates in DNPO-CL reactions is strongly
dependent on the concentrations of DNPO and H O , and is
4
–10
According to Lee et al., formation
2
2
which is the most fundamental PO-CL reaction. This is because
DNPO is more sensitive and selective than bis(2,4,6-trichloro-
phenyl) oxalate (TCPO) and bis(pentachlorophenyl) oxalate
2
2
influenced by the nature of bases such as imidazole, triethyl-
(
PCPO). To date, however, key intermediate(s) formed under
the simplest PO-CL reaction conditions have never been pro-
posed. In the present paper, we investigate the properties of two
†
Present address: Department of Environmental Toxicology and the
Clemson Institute of Environmental Toxicology, Clemson University,
PO Box 709, 509 Westinghouse Road, Pendleton, SC 29670, USA.
decay curves generated by the reaction of DNPO and H O
2 2
DOI: 10.1039/b206367k
J. Chem. Soc., Perkin Trans. 2, 2002, 1653–1657
This journal is © The Royal Society of Chemistry 2002
1653

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without added catalyst in the presence of perylene. Based on
results observed for this simplest PO-CL reaction condition, we
propose the identity of key intermediates capable of interacting
with perylene to produce light emission.
generating an excited singlet state of perylene in DNPO-CL
reactions without an added catalyst. The two decay profiles
shown in Fig. 1 are similar to the two peaks observed by Lee
et al. who measured 1-aminoanthracene CL intensity generated
by the reaction of DNPO and H O in ImH-catalyzed CL reac-
2
2
1
1
tions ([H O ] > [DNPO] > [ImH]). However, when the highest
2
2
Experimental
H O2 concentration reacted with DNPO in the presence of
2
perylene as shown in Fig. 1, the fast decaying curve dominated.
Chemicals
These results are contrary to the observations of Lee et al. that
DNPO, TCPO, PCPO, 2,4-dinitrophenol (DNP), 2,4-dichloro-
phenol (DCP), pentachlorophenol (PCP), 2,4,6-trichloro-
phenol (TCP), H O (50%), 1-aminoanthracene, anthracene,
and perylene were all purchased from Aldrich. H O was stored
in a refrigerator at Ϫ10 ЊC. It was titrated with KMnO solu-
tion (Aldrich) to determine the exact concentration before use.
Spectrophotometric grade ethyl acetate and acetonitrile pur-
chased from Baker were used as the solvents. Deionized water
of resistivity greater than 17.8 MΩ cm was obtained from a
Millipore Super Q system.
11
the slowly decaying curve always dominated.
The fast decay curve shown in Fig. 1 is generated from the
interaction between perylene (0.85 V) and a high-energy inter-
mediate formed from the reaction between H O and DNPO.
2
2
2
2
2
2
4
We also observed the fast decay curve using anthracene (1.09 V)
and 1-aminoanthracene (0.40 V) as the fluorescent compounds
under the same reaction conditions as curve 4 in Fig. 1 ([H O ]
2
2
=
84 mM, [DNPO] = 0.5 mM, and [fluorophor] = 0.5 mM) (data
Ϫ1
not shown). The intensity ratio of the fast decay CL curve to
the slow decay CL curve in the presence of each of the three
fluorescent compounds is dependent on the oxidative half-wave
potential of each fluorescent compound (1-aminoanthracene >
perylene > anthracene). These results are consistent with the
Procedures
A typical CL reaction was conducted at room temperature
11
results obtained by Lee et al. They suggested that the possible
high energy intermediate capable of generating the fast CL
decay curve is hydroperoxyoxalate ester. They called this
(
22.0 ± 1.0 ЊC) in a 1-cm fluorescence cell placed in the sample
compartment of a spectrofluorometer (PTI, Inc.). H O solu-
2
2
tion (0.5 ml) was added to the cell followed by 0.5 ml of the
perylene solution. The reaction was initiated by injecting 1.0 ml
of oxalate solution. Each experiment was repeated three times.
Fresh solutions were prepared daily and kept in the dark.
DNPO was used within 4 hours after being prepared. The CL
intensity vs. time was monitored by the spectrofluorometer at
the maximum emission wavelength (468 nm) of perylene. DNP
formed from the DNPO-CL reaction was observed by absorb-
ance at 420 nm using the kinetics function of an 8452A diode
array spectrophotometer (Hewlett Packard).
11
reaction a direct CL reaction.
10
Milofsky and Birks suggested that ImH acts as a base-
catalyst in PO-CL reactions, and that the decay curve observed
in the absence of an added base such as ImH may result
because TCP produced from the reaction between TCPO and
H O acts as a nucleophile in this reaction. Based on this refer-
2
2
ence, we propose that the slow decay curve obtained in Fig. 1
might be generated by the base-catalyzed DNPO-CL reactions
10
like the decay curves observed by Milofsky and Birks and Lee
11,15
et al.
In other words, DNP produced from the reaction
between DNPO and H O2 becomes the nucleophile in this
2
Results and discussion
reaction. They suggested that the possible high energy inter-
mediate capable of generating the slow CL decay curve is a
Decay curves in uncatalyzed DNPO-CL reactions
Fig. 1 shows typical perylene CL intensity vs. time profiles for
10,11,15
six-membered cyclic peroxide.
Fig. 1 shows that the appearance of the two decay curves
generated in the DNPO-CL reaction depends on the concen-
tration of reagents (DNPO vs. H O ) in the presence of peryl-
2
2
ene. Therefore, after isolating each CL curve by changing the
concentrations of DNPO and H O in the presence of perylene,
2
2
we were able to further investigate various properties of the
decay curves.
Effects of other oxalates
We conducted experiments using TCPO and PCPO instead of
DNPO for the same experimental conditions as Fig. 1 (data not
shown). When PCPO reacted with excess H O (540 mM), a
2
2
weak fast decay CL curve appeared even though the slow decay
CL curve predominated. However, even at H O concentrations
2
2
higher than 540 mM, the fast decay CL curve was not present
for TCPO. These results suggest that a high-energy inter-
mediate capable of interacting with fluorescent molecules to
generate a fast decay CL curve must have a strong electron
withdrawing group in its structure. This is consistent with our
belief that the CL efficiency of the fast decaying curve depends
on the strength of electron withdrawing group (DNP > PCP >
TCP) substituted in oxalate esters.
Fig. 1 Effect of H O concentration in the uncatalyzed DNPO-CL
2
2
reactions in ethyl acetate. [H O ] (mM) = 4.5 (1), 14.0 (2), 42.0 (3), 84.0
2
2
(
4), and 168.0 (5), [DNPO] = 0.5 mM, [perylene] = 0.05 mM.
Direct CL reaction
the reaction of H O and DNPO in the absence of catalysts.
2
2
With a low H O concentration, only the slow decay curve was
Fast decay curves generated in DNPO-CL reactions with the
highest excesses of H O in ethyl acetate exhibited a character-
2
2
observed. Upon increasing the H O concentration, both a fast
2
2
2
2
decay curve and a slow decay curve appeared. With the highest
H O concentration, the fast decay curve was predominant.
We interpret the results shown in Fig. 1 as supporting our
hypothesis of at least two high-energy intermediates capable of
istic light intensity vs. time profile. For these conditions, the
reaction kinetics were well fit by the simple reaction scheme
shown in eqn. (1) where A and C are the initial reactant(s) and
final products respectively.
2
2
1
654
J. Chem. Soc., Perkin Trans. 2, 2002, 1653–1657

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Ϫ1
kf = 0.099 ± 0.004 s ) because perylene does not react with the
other reagents (DNPO and H O ) to generate high-energy
2
2
intermediates.
The CL intensity is presumed to be proportional to the con-
centration of intermediate species, B. Both reaction steps are
assumed to be irreversible pseudo-first-order reactions with rate
constants k and k corresponding to the rise and fall, respect-
DNP is one of the final products generated in the DNPO-CL
reaction, and Fig. 3 shows the effect of varying its concentration
r
f
ively in the CL intensity vs. time profiles. Based on these simpli-
fying assumptions, an integrated rate equation can then be
7,16
obtained for the CL intensity vs. time.
Using this simple model for the reaction kinetics, k and kf
r
were obtained from a nonlinear least-squares fit of eqn. (2) to
the experimental data using the optimization toolbox in Matlab
5
.2. The reported rate constant is an average of at least three
independent measurements.
To determine if a reactive intermediate leading to the fast
decay curve is consistent with the hydroperoxyoxalate ester
11
proposed by Lee et al., we calculated the rate constants of the
fast decay curves obtained in the DNPO-CL reactions having
H O in large excess over DNPO as shown in Fig. 2.
2
2
Fig. 3 Effect of DNP concentration in the direct CL reaction in ethyl
acetate. [DNP] (mM) = 0 (1), 0.006 (2), 0.032 (3), and 0.160 (4),
[
perylene] = 0.025 mM, [DNPO] = 0.005 mM, [H O ] = 34.0 mM.
2 2
when DNPO, H O , and perylene concentrations are constant
2
2
in ethyl acetate. Both the CL intensity and area under the fast
decay curves decreased upon increasing the DNP concen-
tration. DNP appears to interrupt the interaction between
perylene and the high-energy intermediate used to generate the
fast decay curve.
Based on the experimental results, the property of the high-
energy intermediate generating the fast decay curve in the reac-
tion is consistent with that of the intermediate generating the
fast decay curve observed from the direct CL reaction when a
11
low catalyst concentration is added. When ImH (0.01 mM)
was used as a base catalyst in the DNPO-CL reaction under
otherwise similar reactive conditions as Fig. 1, we observed
both a fast decay curve and a slow decay curve (data not
shown). From the results obtained here, we suggest that the
direct CL reaction to generate a fast decaying CL curve is pre-
dominant when a low concentration of DNPO reacts with
excess H O in the absence of a base catalyst. In addition, DNP
Fig. 2 Effect of H O concentration on the rise rate constants (k ) and
2
2
r
the fall rate constants (k ) for the direct CL reactions in ethyl acetate.
f
[DNPO] = 0.001 mM, [perylene] = 0.02 mM.
2
2
as a final product in the reaction acts as an inhibitor (quencher)
for the direct CL reaction.
Fig. 2 illustrates the dependence of k and k on H O concen-
r
f
2
2
tration. The rise rate constants (k ) were linearly dependent
r
on H O2 concentration, whereas the fall rate constants (kf)
2
DNP-catalyzed CL reaction
appeared to show a second-order dependence on H O concen-
2
2
10
tration. However, this latter observation most likely indicates
that the fall rate coefficients determined under these conditions
are also being affected slightly by the slow decay CL curve
generated from a different CL reaction pathway.
Milofsky and Birks first postulated that the possible reactive
intermediate in their photoinitiated CL reaction was a six-
membered cyclic peroxide. They also suggested that the decay
curve obtained in the absence of added bases might be due to
reactions with phenols, such as TCP, generated as a final prod-
The effect of varying the DNPO concentration (0.003 to
10
0
.05 mM) on k and k was investigated using constant perylene
uct in the photoinitiated PO-CL reaction. To determine if the
reactive intermediate of the slow decay curve observed in Fig. 1
is a six-membered cyclic peroxide, we added DNP from 0 to
0.04 mM for conditions similar to curve 1 in Fig. 1. As shown in
Fig. 4, with the gradual increase of DNP concentration, the
relative CL intensity of the slow decay curves increased and
then at a certain point began to decrease whereas the opposite
trend was observed for the time required to reach the maximum
emission, τmax. In this reaction, DNP acts as a nucleophile to
generate the reactive intermediate (six-membered cyclic per-
oxide) up to a certain point and then acts as an inhibitor. When
DCP, PCP or TCP was used in the experiment instead of DNP
under the same reaction condition as Fig. 4 they also acted
as nucleophiles as shown in Fig. 5. Based on these results, we
r
f
(
(
0.05 mM) and H O (340 mM) concentrations in ethyl acetate
data not shown). There was no significant change, suggest-
2 2
ing that the pseudo-first-order rate constants k and k are
r
f
Ϫ1
independent of DNPO concentration (k = 1.90 ± 0.03 s
,
r
Ϫ1
kf = 0.095 ± 0.004 s ). In other words, when the H O concen-
2
2
tration greatly exceeded the DNPO concentration in ethyl
acetate, the effect of DNPO concentration was not observed in
the reaction.
The effect of varying the perylene concentration (0.006
to 0.25 mM) on k and k was investigated using constant
r
f
DNPO (0.05 mM) and H O (340 mM) concentrations in ethyl
2
2
acetate (data not shown). Both kinetic parameters were inde-
Ϫ1
pendent of the concentration of perylene (k = 1.85 ± 0.02 s
,
r
J. Chem. Soc., Perkin Trans. 2, 2002, 1653–1657
1655

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1
0 hours of storage in a Pyrex borosilicate glass bottle the pres-
ence of DNP formed by the decomposition of DNPO (0.4 mM)
in acetonitrile was observed by absorbance at 420 nm. Thus, we
always prepared fresh DNPO solutions in organic solvent every
4
hours because DNPO dissolved in organic solvents is unstable
in Pyrex borosilicate glass bottles for longer storage periods.
Effects of H O
2
Fig. 6 shows the effect of varying H O concentration with
2
Fig. 4 Effect of DNP concentration on the DNP-catalyzed nucleo-
philic CL reaction in ethyl acetate. [DNP] (mM) = 0 (1), 0.006 (2), 0.032
(
1
3), and 0.160 (4), [perylene] = 0.025 mM, [DNPO] = 2.0 mM, [H O ] =
2 2
0.0 mM.
Fig. 6 Effect of H O concentration in the DNPO-CL reaction without
2
an added catalyst in acetonitrile. [H O] (M) = 0 (1), 1.11 (2), 1.67 (3) and
2
2
.22 (4), [DNPO] = 0.2 mM, [H O ] = 20.0 mM, [perylene] = 0.02 mM.
2 2
constant DNPO, H O , and perylene concentrations in aceto-
2
2
nitrile. Curve 1 in Fig. 6, obtained without H O, shows that the
2
slow decay curve predominates. However, the fast decay curve
becomes dominant with increasing H O concentration. In par-
2
ticular, curve 4, obtained by adding a large excess of H O,
2
shows that the slow decay curve disappears and the CL
intensity of the fast decay curve increases.
To understand the mechanistic details of the reaction of aryl
oxalates with H O, several research groups have studied the
2
2
0,21
hydrolysis kinetics of DNPO in aqueous solution using UV
2
2
and IR spectroscopies. These researchers have suggested that
DNPO is hydrolyzed in aqueous solution (such as acetonitrile–
water mixtures) with low water content, forming 2 moles of
the corresponding DNP from 1 mole of DNPO. An overall
hydrolysis reaction of DNPO in aqueous acetonitrile solution
proposed by Neuvonen is consistent with the concept of the
occurrence of aryl hydroperoxyoxalate ester as an intermediate
generated in the reaction between aryl oxalate and H O .
Fig. 5 Effect of phenols (0.01 mM) added in the four types of PO-CL
reactions; 1. no addition, 2. DCP, 3. TCP, 4. PCP, 5. DNP. [H O ] = 5.6
2
2
mM, [DNPO] = 3.0 mM, [perylene] = 0.1 mM.
2
1
believe that CL observed from the reaction between TCPO or
PCPO and H O in the absence of a weak base comes from
2
2
6,7,9,11
2
2
TCP- or PCP-catalyzed nucleophilic CL reactions.
2
0–22
Based on references,
we surmise that the CL decay curves
shown in Fig. 6 were obtained from three competitively reactive
pathways which are 1) the direct CL reaction, 2) the DNP-
catalyzed nucleophile CL reaction, and 3) the hydrolysis reac-
tion of DNPO. Therefore, the fast decay curve predominates
Stability of DNPO
Although DNPO is less stable in organic solution and has a
higher background intensity than other oxalates such as TCPO
and PCPO, it exhibits faster reaction kinetics and the greatest
CL intensity in PO-CL reactions. Several research groups have
measured the decomposition of TCPO in acetonitrile.
example, when Hanaoka used Pyrex borosilicate and sodium
borosilicate glass bottles as reservoirs for TCPO solution, no
deactivation of TCPO was observed for at least 6 hours in
acetonitrile. In the present study, we stored DNPO solutions
with increasing H O concentration under the reaction condi-
2
17
tions in Fig. 6 because the excess DNP produced from the
hydrolysis reaction of DNPO in aqueous solvent is an inhibitor
(quencher) rather than a nucleophile in DNP-catalyzed CL
reaction. In other words, the slow decay curve disappears
18–20
For
19
when a large excess of H O is present (curve 4 in Fig. 6) because
2
DNPO is hydrolyzed to DNP which acts as a quencher. There-
fore, the decay curves of Fig. 6 were obtained from the three
competitive reaction pathways (direct CL reaction, DNP-
catalyzed CL reaction and hydrolysis reaction of DNPO).
The results shown in Fig. 6 are inconsistent with those
obtained in Figs. 3 and 4. To determine the different spectral
trends shown in the figures, we separated the fast decay curve
(
0.4 mM) in a Pyrex borosilicate glass bottle for 10 hours and
every hour measured CL intensity with H O (9.0 mM) and
2
2
perylene (0.13 mM) (data not shown). There were negligible
changes in either the CL intensity or τmax over a 4-hour storage
period. However, after 6 hours of storage the CL intensity of
the slow decay curve increased sharply (data not shown). After
1
656
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Table 1 Comparison between the direct CL reaction and DNP-catalyzed nucleophilic CL reaction in the absence of base catalysts
Direct
DNP-catalyzed nucleophilic
τmax
H O
DNPO
Fast
Slow
Dominates in excess concentration
Dominates in low concentration
CL intensity decreases with its addition
CL intensity decreases with its addition
Dominates in relatively low concentration
Dominates in excess concentration
CL intensity increases with its addition
CL intensity increases with its addition
2
2
H O
2
DNP
(
direct CL reaction) and the slow decay curve (DNP-catalyzed
from DNPO molecules formed in the DNP-catalyzed CL
reaction might not be significant because large DNP concen-
trations produced from both the direct CL reaction and
DNP-catalyzed CL reaction act to inhibit (quench) the
two DNPO-CL reaction pathways. Table 1 summarizes the
major differences between the direct CL reaction and the
DNP-catalyzed CL reaction.
CL reaction) as shown previously in Figs. 3 and 4. The effect of
H O for each reactive condition (direct CL reaction: [DNPO] =
0
2
.01 mM, [H O ] = 34.0 mM, [perylene] = 0.025 mM; DNP-
2 2
catalyzed CL reaction: [DNPO] = 3.0 mM, [H O ] = 10.0 mM,
2
2
[perylene] = 0.025 mM) in acetonitrile was then investigated
(
data not shown). The results obtained under both reaction
conditions were consistent with those shown in Figs. 3 and 4. In
other words, the intensity obtained from the direct CL reaction
in the presence of H O decreased, whereas the intensity shown
Acknowledgements
2
in the DNP-catalyzed CL reaction with H O increased. The
2
This research was partially funded with the support of the US
Department of Energy (DOE) Cooperative Agreement No.
DE-FC04-95AL85832 with the Amarillo National Resource
Center for Plutonium (ANRCP). However, any opinions, find-
ings, conclusions or recommendations expressed herein are
those of the authors and do not necessarily reflect the views of
DOE or ANRCP.
decay curve observed under either the direct CL reaction or the
DNP-catalyzed CL reaction in aqueous solution is obtained
from two competitive reaction pathways (the direct CL reaction
and the hydrolysis reaction of DNPO, or the DNP-catalyzed
nucleophilic CL reaction and the hydrolysis reaction of
DNPO). Therefore, DNP generated from the hydrolysis reac-
tion of DNPO with low water content acts as a quencher in the
direct CL reaction and acts as a nucleophile in the DNP-
catalyzed CL reaction.
References
1
2
3
4
L. J. Kricka and G. G. G. Thorp, Analyst, 1983, 108, 1274.
K. Honda and K. Imai, Anal. Chem., 1983, 55, 940.
J. K. DeVasto and M. L. Grayeski, Analyst, 1991, 116, 443.
M. M. Rauhut, L. J. Bollyky, B. G. Roberts and M. J. Loy, J. Am.
Chem. Soc., 1967, 89, 6515.
F. McCapra, K. Perring, R. J. Hart and R. A. Hann, Tetrahedron
Lett., 1981, 22, 5087.
C. L. R. Catherall, T. F. Palmer and R. B. Cundall, J. Chem. Soc.,
Faraday Trans. 2, 1984, 80, 823.
M. Orlovic, R. L. Schowen, R. S. Givens, F. Alvarez, B. Matuszeski
and N. Parekih, J. Org. Chem., 1989, 54, 3606.
Conclusions
Based on the present results observed under the most
fundamental PO-CL reaction conditions, we propose possible
high energy intermediates formed in DNPO-CL reactions in
the absence of catalysts (Scheme 1). The CL effects observed
5
6
7
8
9
F. Alvarez, N. J. Parekh, B. Matuszeski, R. S. Givens, T. Higuchi and
R. L. Schowen, J. Am. Chem. Soc., 1986, 108, 6435.
H. P. Chokshi, M. Barbush, R. G. Carlson, R. S. Givens, T. Kuwana
and R. L. Schowen, Biomed. Chromatogr., 1990, 4, 96.
1
1
1
1
0 R. E. Milofsky and J. W. Birks, J. Am. Chem. Soc., 1991, 113,
715.
1 J. H. Lee, S. Y. Lee and K.-J. Kim, Anal. Chim. Acta, 1996, 329,
17.
2 M. Stigbrand, E. Ponten and K. Irgum, Anal. Chem., 1994, 66,
766.
9
1
1
3 C. V. Stevani, D. F. Lima, V. G. Toscano and W. J. Baader, J. Chem.
Soc., Perkin Trans. 2, 1996, 989.
1
1
4 A. G. Hadd and J. W. Birks, J. Org. Chem., 1996, 61, 2657.
5 J. H. Lee, J. C. Rock, S. B. Park, M. A. Schlautman and
E. R. Carraway, J. Chem. Soc., Perkin Trans. 2, 2002, 802.
6 J. H. Espenson, Chemical kinetics and reaction mechanism, 2nd edn.;
McGraw-Hill, New York, 1995.
7 A. G. Hadd and J. W. Birks, Mechanism and Analytical Detection;
R. E. Sievers, Ed.; John Wiley and Sons, 1995, New York,
p. 222.
1
1
1
1
2
8 K. W. Sigvardson and J. W. Birks, Anal. Chem., 1983, 55, 432.
9 N. Hanaoka, Anal. Chem., 1989, 61, 1298.
0 R. N. Jennings and A. C. Capomacchia, Anal. Chim. Acta, 1988,
2
05, 207.
2
1 H. Neuvonen, J. Chem. Soc., Perkin Trans. 2., 1994, 89.
Scheme 1
22 G. Orosz and E. Dudar, Anal. Chim. Acta, 1991, 247, 141.
J. Chem. Soc., Perkin Trans. 2, 2002, 1653–1657
1657