Fluorometric analysis of chlorite via oxidation of 9-anthracenecarboxaldehyde

Article abstract of DOI:10.1016/j.jphotochem.2021.113309

We investigated a simple fluorescence signaling method for the convenient analysis of a practical oxidant—chlorite—via the oxidation of 9-anthracenecarboxaldehyde to the corresponding carboxylic acid. 9-Anthracenecarboxaldehyde exhibited a marked ratiometric fluorescence signaling toward chlorite through manipulating its aggregation-induced emission property. The probe showed high chlorite-selectivity over other oxychlorine species as well as common metal ions, anions, and oxidants. Interference from a closely related oxidant, hypochlorite, was efficiently removed using DMSO as a scavenger. The proposed probe also exhibited a prominent ratiometric response through changes in UV–vis absorption behavior. Among the tested aromatic aldehydes (naphthaldehydes, anthracenecarboxaldehyde, and pyrenecarboxaldehyde), anthracene-based carboxaldehyde exhibited the most pronounced signaling contrast and the fastest signaling speed. The detection limit of chlorite determination was found to be 1.1 × 10^–7 M. Exploitation of the probe for the convenient analysis of chlorite in tap water via a recovery test was conducted.

Full text of DOI:10.1016/j.jphotochem.2021.113309

Journal of Photochemistry & Photobiology, A: Chemistry 415 (2021) 113309
Contents lists available at ScienceDirect
Journal of Photochemistry & Photobiology, A: Chemistry
journal homepage: www.elsevier.com/locate/jphotochem
Fluorometric analysis of chlorite via oxidation of
9-anthracenecarboxaldehyde
Kang Min Lee, Myung Gil Choi, Jae Hoon Yoo, Sangdoo Ahn*, Suk-Kyu Chang*
Department of Chemistry, Chung-Ang University, Seoul, 06974, Republic of Korea
A R T I C L E I N F O
A B S T R A C T
Keywords:
We investigated a simple fluorescence signaling method for the convenient analysis of a practical oxidant—-
chlorite—via the oxidation of 9-anthracenecarboxaldehyde to the corresponding carboxylic acid. 9-Anthracene-
carboxaldehyde exhibited a marked ratiometric fluorescence signaling toward chlorite through manipulating its
aggregation-induced emission property. The probe showed high chlorite-selectivity over other oxychlorine
species as well as common metal ions, anions, and oxidants. Interference from a closely related oxidant, hypo-
chlorite, was efficiently removed using DMSO as a scavenger. The proposed probe also exhibited a prominent
ratiometric response through changes in UV–vis absorption behavior. Among the tested aromatic aldehydes
(naphthaldehydes, anthracenecarboxaldehyde, and pyrenecarboxaldehyde), anthracene-based carboxaldehyde
exhibited the most pronounced signaling contrast and the fastest signaling speed. The detection limit of chlorite
determination was found to be 1.1 × 10–7 M. Exploitation of the probe for the convenient analysis of chlorite in
tap water via a recovery test was conducted.
Chlorite
9-anthracenecarboxaldehyde
Aggregation-induced emission
Aldehyde oxidation
Fluorescence signaling
Oxychlorines
1. Introduction
higher levels of exposure can lead to an increase of methemoglobin [6].
Therefore, the chlorite level in drinking waters generated by chlorine
Chlorite (ClO–2) has a broad range of applications in the chemical,
environmental, and industrial fields. It is used as a disinfectant and
chemical purification agent for municipal drinking water treatment
because it liberates chlorine dioxide in an acidic medium [1]. Further-
more, it is employed in the textile industry as an effective bleaching agent
because controlled bleaching is possible using the oxidation potential of
chlorites [2]. In addition, chlorite ions have many practical applications in
organic synthesis, such as the preparation of amides, enones, and epoxides
as well as in osmium-catalyzed asymmetric dihydroxylation and in the
oxidative deprotection of 1,3-dithiane groups [1]. In particular, the
increasing use of chlorine dioxide as a substitute sanitizer to chlorine in
water treatment processes has aroused a critical health issue. Treatment
with chlorine dioxide generates hazardous chlorite ions as a major
byproduct.
dioxide treatment must be regularly monitored.
Because chlorite is such widely employed in many chemical and
industrial applications, the development of a simple and selective
analytical method for this important oxidant is highly desired. Analyt-
ical methods for chlorites have not been developed substantially
compared to those of the closely related practical oxidant, hypochlorite.
In routine analytical applications, iodometry is a standard method for
chlorite determination [7]. The determination of chlorite in drinking
water is conducted using ion chromatography [8] and capillary elec-
trophoresis [9]. Flow injection analysis has also been employed to
analyze chlorite levels in chlorinated and chloraminated drinking water
[10]. On the other hand, UV spectrophotometry, by direct absorbance
measurement of chlorite absorption at 260 nm, has also been used [11].
Representative chlorite determination methods, including their appli-
cations, are summarized in Table S1 (Supplementary data).
Chlorites are strong oxidants that can cause hemolysis, methemo-
globinemia, and kidney failure [3]. The World Health Organization has
recommended that the chlorite level in drinking water should be less
than 0.2 mg/L [4]. In addition, US EPA established a chlorite content
within 1.0 mg/L as the allowable level for safe drinking water [5].
Low-level exposure to chlorite may cause hemolytic anemia, whereas
One of the most essential processes in the organic synthesis is
transforming aldehydes to carboxylic acids, which has numerous
applications for academic research and industrial processes. Alde-
hydes are prone to oxidation, and the transformation to carboxylic
acids can usually be performed by various oxidants, such as ClO–2 [12,
* Corresponding authors.
E-mail addresses: sangdoo@cau.ac.kr (S. Ahn), skchang@cau.ac.kr (S.-K. Chang).
https://doi.org/10.1016/j.jphotochem.2021.113309
Received 13 January 2021; Received in revised form 9 March 2021; Accepted 14 April 2021
Available online 19 April 2021
1010-6030/© 2021 Elsevier B.V. All rights reserved.

K.M. Lee et al.
Journal of Photochemistry & Photobiology, A: Chemistry 415 (2021) 113309
13], MnO–4 [14], periodic acid (H5IO6) [15], chromium trioxide (CrO3)
[16], Oxone [17], and molecular oxygen [18] (Scheme 1). Among
these, chlorite has been successfully used as chemo-selective reagents
for the aldehyde-to-carboxylic acid conversion with the toleration of
many labile coexisting functional groups in the reactants [19]. After
the reaction, in contrast to many metal-based oxidants, chlorite dis-
charged environmentally more friendly waste products.
high-resolution mass spectrum was acquired using a JEOL JMS-700 mass
spectrometer with fast atom bombardment (FAB) ionization. Column
chromatography was conducted using silica gel (Merck, 240 mesh).
2.2. Preparation of stock solutions
Stock solutions of probes 1–4 (5.0 × 10–4 M) were prepared in spec-
troscopic grade dimethyl sulfoxide (DMSO). A stock solution of chlorite
(1.0 × 10–2 M) was prepared by dissolving sodium chlorite in deionized
water and was standardized according to the reported literature [39].
Stock solutions of other oxidants (1.0 × 10–2 M) were prepared according
to a published procedure [40]. Stock solutions of the metal ions and an-
ions (1.0 × 10–2 M) were prepared by dissolving the metal perchlorate
salts or sodium salts of anions in deionized water.
Based on this viewpoint, we constructed a novel fluorescence probe
for detecting chlorite through oxidative aldehyde-to-carboxylic acid
transformation. Aldehyde-functionalized dyes have been widely utilized
as essential starting materials for designing various reaction-based
probes (Table S2, Supplementary data). For instance, they are used as
a platform for the preparation of imines [20] and oximes [21,22] for
hypochlorite sensing and dithianes or dithiolanes for Cd(II) [23] and Hg
(II) determination [24] and for the introduction of a removable moiety
by 2-aza-Cope sigmatropic rearrangement for formaldehyde sensing
purposes [25].
2.3. Investigation of chlorite signaling
Furthermore, aldehyde-functionalized compounds themselves have
been extensively used as optical probes for several important chemical
and biological species (Table S3, Supplementary data). Representative
examples of colorimetric or fluorescence probes are based on the adduct
formation for bisulfites [26–29], nucleophilic addition reactions for
cyanide [30,31], the formation of a cyclized product for cysteine or
homocysteine [32–34], and the addition and subsequent Michael addition
reaction [35] and thiolysis of dinitrophenyl ether [36] and nitro-
benzofurazan (NBD) ether for sulfide anions [37].
All measurements were performed under optimal conditions in a pH
3.0 citrate buffered solution containing 5% DMSO. For fluorescence
measurements, the probe stock solution (30
μ
L, 5.0 × 10–4 M), the stock
solution of the analyte (ClO–2, metal ion, anion, oxidant, or oxychlorine;
75
μ
L; 1.0 × 10–2 M), and pH 3.0 citrate-NaOH buffer (150
μL, 0.20 M)
were added to a vial and subsequently diluted with distilled water and
DMSO (3.0 mL, 95:5 (v/v) mixture of citrate-NaOH buffer and DMSO).
The final concentrations of the probe, analyte, and citrate-NaOH buffer
solution were 5.0 × 10–6 M, 2.5 × 10–4 M, and 1.0 × 10–2 M,
respectively.
Despite this meaningful progress in utilizing aldehydes in sensing
applications, developing a reaction-based probe for an oxidant using the
standard oxidation process of aldehydes to carboxylic acids remains
unexploited. This is unexpected because, as described earlier, the
oxidative aldehyde-to-carboxylic acid conversion is readily accom-
plished using numerous essential oxidants, such as permanganate,
periodate, chromate, Oxone, and molecular oxygen. We noticed that
chlorites could act as a mild oxidant for the smooth and clean trans-
formation of tested aromatic aldehydes to carboxylic acids [38].
Furthermore, the spectral changes induced by the chlorite-assisted
aldehyde-to-acid transformation were marked to allow a ratiometric
analysis of the resulting responses.
2.4. Detection limit of chlorite analysis
To estimate the limit of detection (LOD) of chlorite, a titration curve
was drawn by plotting the changes in the intensity ratio of the fluores-
cence at 411 and 519 nm (I411/I519) according to the change in the
chlorite concentration. Following the guidelines of the IUPAC, the LOD
for chlorite was calculated using the equation (3sbl/m), where sbl is the
standard deviation of the blank responses of probe 1 (10 measurements)
and m is the slope of the curve [41].
In this study, simple-structured aromatic aldehydes were studied as
fluorescence probes aimed at the selective and sensitive detection of
chlorite by oxidative transformation to carboxylic acids. The selectivity
toward chlorite was observed by comparing with those for common
metal ions and anions, oxidants, and other oxychlorines. Interference by
hypochlorite was effectively blocked using a hypochlorite scavenger
DMSO. Utilization of the probe for the convenient analysis of chlorite in
tap water via a recovery test was also conducted.
2.5. Evidence of chlorite signaling
Probe 1 (20.6 mg, 0.1 mmol) was dissolved in acetonitrile (1.0 mL).
Chlorite (45.2 mg, 0.5 mmol) solution in 1.0 mL of distilled water was
slowly added to the prepared probe solution. After signaling, the vola-
tiles were evaporated under reduced pressure. The residue was purified
by column chromatography (eluent: CH2Cl2:CH3OH = 5:1 (v/v), silica
gel). 1H and 13C NMR and mass spectroscopic results of the purified
chlorite signaling product were measured and compared with the
spectral data of the 9-anthracenecarboxylic acid.
2. Experimental section
2.1. General
2.6. Chlorite analysis in tap water
9-Anthracenecarboxaldehyde, 1-naphthaldehyde, 2-naphthaldehyde,
and 1-pyrenecarboxaldehyde were acquired from Merck KGaA. Sodium
chlorite was purchased from Merck KGaA and standardized by iodometry
[39]. UV–vis and fluorescence spectra were obtained with a Scinco S-3100
spectrophotometer and a FluoroMate FS-2 fluorescence spectrophotom-
eter. 1H nuclear magnetic resonance (NMR) (600 MHz) and 13C NMR (150
MHz) spectra were measured using a Varian VNS NMR spectrometer. A
The solutions used for plotting a calibration curve for chlorite were
made by adding probe 1 stock solution (30
μ
L, 5.0 × 10–4 M), chlorite
solution (6, 12, 18, 24, 30, 36, 42, 48, 54, and 60
μ
L, 1.0 × 10–3 M), and
a citrate buffer solution (150
μ
L, pH 3.0, 2.0 × 10–1 M), followed by
dilution with distilled water and DMSO (3.0 mL, 95:5 (v/v) mixture of
buffer and DMSO). The final concentrations of probe 1, standard chlorite
solution, and buffer were 5.0 × 10–6 M, 0–2.0 × 10–5 M, and 1.0 × 10–2
M, respectively. The changes in the intensity ratio of the fluorescence at
411 nm and 519 nm (I411/I519) of each sample were measured using a
fluorescence spectrophotometer with excitation at 363 nm. From the
result, the calibration curve for chlorite was drawn by plotting the
fluorescence intensity ratio (I411/I519) concerning the variation of
chlorite concentration.
Scheme 1. Oxidation of aromatic carboxaldehyde to the carboxylic acid.
2

K.M. Lee et al.
Journal of Photochemistry & Photobiology, A: Chemistry 415 (2021) 113309
3. Results and discussion
We attempted to design a convenient optical probe for the efficient
determination of chlorite based on its oxidizing property. For this, many
well-established oxidative conversions, such as sulfide to sulfoxide,
amine to amine oxide, and alcohol to carboxylic acid, could be suitably
applied. However, we chose the typical aldehyde-carboxylic acid
conversion induced by chlorite because the photophysical properties,
especially fluorescence characteristics, of the two relevant species are
dramatically different in some aromatic aldehydes. We tested several
representative fluorescent aromatic aldehydes, such as 9-anthracenecar-
boxaldehyde (1), naphthaldehydes (2 and 3), and 1-pyrenecarboxalde-
hyde (4) (Fig. 1), and found that anthracene-based aldehyde 1 showed
the most pronounced signal contrast suitable for the ratiometric analysis
and high signaling speed toward the targeting chlorite (Figs. 2 and S1,
Supplementary data).
The chlorite signaling property of probe 1 was studied by absorption
and fluorescence spectroscopy. An initial survey indicated that the fluo-
rescence responses of the probe were superior to UV–vis absorption
behavior. In the fluorescence spectrum, probe 1 displayed a broad band
positioned around 519 nm in citrate-buffered solution (pH 3.0) containing
5% DMSO. The broad band of probe 1 at a rather longer wavelength
region (460ꢀ 650 nm) is owing to the aggregation-induced excimer
emission of anthracene derivatives. 9-Anthracenecarboxaldehyde has
limited solubility in water-rich media and is known to form aggregates
which resulted in the aggregation-induced excimer emission [42]. To
check this, we measured the fluorescence spectrum of probe 1 as a func-
tion of water content in aqueous DMSO solution. The result shown in
Fig. S2 (Supplementary data) implies that the excimer emission band of
probe 1 at 519 nm became more prominent with the increases in water
content in aqueous DMSO solution. Based on this observation, we can
conclude that probe 1 exists mainly as an aggregate under the signaling
conditions and exhibits prominent aggregation-induced excimer emission.
Upon treatment with chlorite, a distinct difference in the fluorescence
spectral profile was perceived. For instance, the excimer emission band of
probe 1 wholly vanished, and new emissions at significantly shorter
wavelengths (390, 411, and 433 nm), which are characteristic of the
monomeric state of the parent anthracene fluorophore, were observed
(Fig. 2). The large spectral change induced by the chlorite is ascribable to
the enhanced solubility of the oxidized signaling product, 9-anthracene-
carboxylic acid, in the aqueous signaling conditions. The enhanced solu-
bility of the product rendered the aggregated form to a monomeric state
and resulted in the monomer emission at 411 nm at the expense of the
excimer emission of probe 1 [43]. Because the fluorescence spectral
change was pronounced, the target-induced responses were ratiometri-
cally analyzed. Pronounced chlorite-selective signaling behavior was
confirmed by the fluorescence intensity ratio between 411 nm and 519 nm
(I411/I519 = 35.8 for probe 1 in the presence of chlorite). At the same time,
the ratiometric response to representative metal ions and anions was
insignificant (I411/I519 fluctuated from 0.002 of Fe2+ and 0.02 of Cu2+ for
metal ions and 0.001 for Cl– and 0.01 for S2– for anions) (Fig. 3).
Chlorite signaling was realized by the oxidation of the aldehyde
function of probe 1 to a carboxylic acid (Scheme 2). The initial step in
the conversion involves a nucleophilic attack on the carbon atom of the
aldehyde by ClO–2, which subsequently expels HOCl from the activated
complex to yield carboxylic acid. The suggested transformation was
confirmed by NMR and mass spectroscopic data. For this, the signaling
Fig. 2. (a) UV–vis and (b) fluorescence changes of probe 1 upon treatment with
chlorite. For UV–vis measurement; [1] = 1.0 × 10–5 M, [chlorite] = 5.0 × 10–4
M, and for fluorescence measurement; [1] = 5.0 × 10–6 M, [chlorite] = 2.5 ×
10–4 M. Citrate-NaOH buffer (pH = 3.0, 1.0 × 10–2 M) containing 5% DMSO
was used. λex =363 nm.
Fig. 3. Chlorite-selective fluorescence signaling expressed by the intensity ratio
at 411 nm and 519 nm (I411/I519) of probe 1 over common metal ions and
anions (inset). [1] = 5.0 × 10–6 M, [chlorite] = [Mn+] = [An–] = 2.5 × 10–4 M,
[buffer] = 1.0 × 10–2 M (citrate, pH = 3.0) containing 5% DMSO. λex =363 nm.
product obtained by the reaction of probe 1 with chlorite (5 equiv) was
purified by chromatography (silica gel, eluent = dichloromethane:
methanol = 5:1, v/v). The 1H NMR spectral data of the purified product
revealed that the aldehyde proton resonance at 11.5 ppm of the probe
disappeared (Fig. S3, Supplementary data). 13C NMR data also
supported the postulated transformation by revealing a carbon reso-
nance, which could be attributed to the carboxylic acid group at 170.6
ppm instead of the aldehyde carbon resonance at 194.7 ppm of the probe
(Fig. 4). The mass spectral data of the purified product further supported
Fig. 1. Structures of the tested aromatic carboxaldehydes.
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K.M. Lee et al.
Journal of Photochemistry & Photobiology, A: Chemistry 415 (2021) 113309
Scheme 2. Chlorite signaling by oxidation of 9-anthracenecarboxaldehyde.
Fig. 4. Partial 13C NMR spectra of 1 and purified product of (1 + ClO2–) in DMSO-d6. [1] = [purified product of (1 + ClO–2)] = [9-anthracenecarboxylic acid] = 1.0 ×
10–2 M. The spectral data of (1 + ClO2–) was obtained after purifying the reaction product of (1 + ClO–2) by column chromatography. The peaks highlighted by blue
and red asterisks are the resonances of the carbonyl carbon of aldehyde of 1 and carboxylic acid carbon of the signaling product, respectively.
the reaction by disclosing an indicative peak at m/z = 221.0601
(calculated for C15H9O–2 [M–H]–: 221.0608) (Fig. S4, Supplementary
data).
nearly the same (before: pH 3.12, after: pH 3.12) owing to the presence of
the pH stabilizing buffer solution. Therefore, pH 3.0 citrate-buffered
solution, containing 5% DMSO as a masking agent for hypochlorite was
employed for the signaling conditions. In addition, the time plot of chlo-
rite signaling showed that a constant response was obtained within 15
min, whereas the fluorescence change of the probe itself was negligible
(Fig. S5, Supplementary data).
The oxidation power of chlorite is known to be strongly pH-dependent
[44]. The pH effect on the chlorite signaling of probe 1 was elucidated by
varying the pH of the citrate buffer solution. For controlling pH of the
solution, citrate buffer was used because it has a relatively wide working
pH range between pH 2.0 and 6.0 [45]. Chlorite signaling was the most
pronounced in the acidic pH region between 2 and 3.5, peaking at pH 3.0,
and became less prominent at a higher pH (pH 4) (Fig. 5). We also checked
the possible pH changes induced by the chlorite signaling and found that
the pH values before and after the chlorite signaling of probe 1 were
Because chlorite signaling is due to the oxidative conversion from
aldehyde to carboxylic acid, the response toward other common oxidants
was also elucidated. Under the measurement conditions, only chlorite
induced prominent responses. Actually, during the optimization process
using varying pH and solvent composition, we found that hypochlorite
also evoked considerable fluorescence enhancement of the probe in
acetonitrile (Fig. S6, Supplementary data). We attempted to suppress this
unwanted interference from hypochlorite to realize exclusive chlorite
selectivity of the probe using DMSO as a hypochlorite scavenger. It has
been reported that DMSO could act as an effective masking agent for the
discriminative analysis of chlorite over hypochlorite by utilizing its
specific reactivity with the latter [46,47]. By adding 5% DMSO in citrate
buffer solution, the response from hypochlorite was effectively
suppressed, and good chlorite selectivity of probe 1 was realized over
common oxidants (Fig. 6). The reason for the chlorite selectivity of the
probe over other employed oxidants is not clear at the moment. In fact, we
tried to find a reasonable explanation for the chlorite selectivity of the
probe using standard reduction potential (E0) of the oxidants but could not
find any useful correlation.
Discriminative chlorite signaling over other oxychlorine species of
hypochlorite, chlorate, and perchlorate is essential in the analysis of
chlorite. Particularly, the selective determination of chlorite in the
presence of hypochlorite is highly pertinent in practical applications
[48]. To gain more insights into this practical requirement, the effect of
the existence of oxychlorines on chlorite signaling was tested by varying
Fig. 5. pH effect on chlorite signaling by probe 1 as plotted by the fluorescence
intensity ratio at 411 nm and 519 nm (I411/I519). [1] = 5.0 × 10–6 M, [chlorite]
= 2.5 × 10–4 M, [buffer] = 1.0 × 10–2 M (citric acid-NaOH, pH = 2.0 – 6.0)
containing 5% DMSO. λex =363 nm.
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K.M. Lee et al.
Journal of Photochemistry & Photobiology, A: Chemistry 415 (2021) 113309
Fig. 6. Chlorite-selective fluorescence signaling of probe 1 as plotted by the
intensity ratio at 411 nm and 519 nm (I411/I519) over practical oxidants. Inset:
Fluorescence spectra of probe 1 in the presence of common oxidants. [1] = 5.0
× 10–6 M, [oxidant] = 2.5 × 10–4 M, [buffer] = 1.0 × 10–2 M (citrate, pH = 3.0)
containing 5% DMSO. λex =363 nm. PB: perborate, PC: percarbonate, APS:
ammonium persulfate, TBHP: tert-butyl hydroperoxide, PAA: peracetic acid.
Fig. 7. Ratiometric plot of the chlorite concentration dependent changes of the
probe as plotted by the fluorescence intensity ratio at 411 nm and 519 nm (I411
/
I519). [1] = 5.0 × 10–6 M, [chlorite] = 0 – 2.0 × 10–5 M, [buffer] = 1.0 × 10–2 M
(citrate, pH = 3.0) containing 5% DMSO. λex =363 nm.
Table 1
the ratio of the two relevant species, oxychlorine and chlorite ([oxy-
chlorine]/[chlorite]). Chlorite signaling was insignificantly influenced
by the presence of up to 100 equiv of each oxychlorine species and
chloride ions (Fig. S7, Supplementary data). This result signifies that the
present probe can be utilized for the discriminative signaling of chlorite
in the presence of other oxychlorines, especially of closely related and
possibly interfering hypochlorite, under the optimal measurement
conditions.
Recovery test of chlorite in tap water
Sample
Chlorite spiked (
μM)
Chlorite founda
Recoveryb
(
μ
M, n = 3)
(%, n = 3)
0
Not detected
49.2 ± 0.1
98.5 ± 0.1
Not detected
49.8 ± 0.1
98.7 ± 0.1
–
Distilled water
50
100
0
98.5 (± 0.1)
98.5 (± 0.1)
–
Tap water
a
50
100
99.6 (± 0.1)
98.7 (± 0.1)
Next, the effect of foreign ions on chlorite analysis of the probe was
investigated under existence of common ionic species. Normally
encountered metal ions and anions, excepting easily oxidizable ions such
as Fe2+ and I–, showed little interference in the selective chlorite responses
(Figs. S8 and S9, Supplementary data). These redox-active ions merely
consume the chlorite analyte through the relevant redox reactions [39,
49]. We believe that the diminished response in the presence of these
oxidizable ions is not a pertinent issue in chlorite analysis. The analytical
purpose is to determine the residual target analyte after all the relevant
reactions and interactions have taken place.
All experiments were performed three times independently.
b
Recovery (%) was calculated by dividing the measurement value of the
spiked sample by the known amount added and multiplying by 100.
the most prominent and ratiometrically analyzable signaling behavior as
well as practically feasible signaling speed for chlorite. The signaling of
chlorite was not influenced by coexisting frequently encountered metal
ions and anions. Discriminative analysis of chlorite in the presence of
other oxychlorines and especially the closely related oxidant, hypo-
chlorite, was possible with the probe by employing DMSO as a hypo-
chlorite scavenger. The practical pertinency of the probe in the analysis
of chlorite in tap water was demonstrated by recovery tests. We believe
that the present probe could be employed as an expedient and sensitive
probe in the selective chlorite analysis for the various analytical appli-
cations, including municipal water treatment systems.
The quantitative analytical characteristic of the probe was assessed
through following the changes in the intensity ratio of the emission
bands at 411 and 519 nm (I411/I519) accompanying the changes in
chlorite concentration (Fig. 7). The plot revealed good linearity (R2
=
0.9982) ranging up to 2.0 × 10–4 M chlorite. Using this plot, the LOD for
chlorite analysis of the probe was estimated as 1.1 × 10–7 M according to
the IUPAC recommendations (3sbl/m) [41].
Author statement
Finally, we tested the practical pertinency of the probe by analyzing
chlorite in real samples. For this, a recovery test was performed by adding
calculated amounts of chlorite into distilled and tap water samples. The
developed responses of the probe were analyzed by ratiometric analysis
Kang Min Lee: Methodology, Investigation, Writing - Original Draft.
Myung Gil Choi: Investigation, Visualization, Writing - Original Draft.
Jae Hoon Yoo: Investigation, Visualization. Sangdoo Ahn: Writing -
Review & Editing, Supervision. Suk-Kyu Chang: Conceptualization,
Writing - Review & Editing, Supervision.
based on the variation of the intensity ratio at 411 and 519 nm (I411/I519
)
of the fluorescence. As shown in Table 1, satisfactory recoveries of 98.5 %
and 99.6 %, respectively, were observed for spiked chlorite levels of 50
μ
M
and 100 μM in tap water. This observation implies that the present probe
could be applied to the sensitive fluorescence analysis of chlorite in
various chemically and environmentally relevant targets, including
municipal water treatment applications.
Declaration of Competing Interest
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influence
the work reported in this paper.
4. Conclusion
We developed a simple and selective fluorescence signaling method
to analyze a chemically and industrially important oxidant, chlorite. The
selective oxidation of 9-anthracenecarboxaldehyde to its relevant car-
boxylic acid was employed for the optical analysis of chlorite. Among
the tested aromatic aldehydes, 9-anthracenecarboxaldehyde exhibited
Appendix A. Supplementary data
Supplementary material related to this article can be found, in the
online version, at doi:https://doi.org/10.1016/j.jphotochem.2021.
113309.
5

K.M. Lee et al.
Journal of Photochemistry & Photobiology, A: Chemistry 415 (2021) 113309
[26] X.F. Yang, M. Zhao, G. Wang, A rhodamine-based fluorescent probe selective for
bisulfite anion in aqueous ethanol media, Sens. Actuators. B-Chem. 152 (2011)
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