Identification of Two Aliphatic Position Isomers between α-and β

Article pubs.acs.org/ac

Identification of Two Aliphatic Position Isomers between α- and β‑Ketoglutaric Acid by Using a Briggs−Rauscher Oscillating System Yu Zhang,† Gang Hu,*,† Lin Hu,‡ and Jimei Song† †

Department of Chemistry, Anhui University, Hefei, 230601, People’s Republic of China Institute of Applied Chemistry, East China Jiaotong University, Nanchang, 330013, People’s Republic of China

‡

ABSTRACT: This paper reports a novel method for identification of two aliphatic position isomers between α-ketoglutaric acid (α-KA) and β-ketoglutaric acid (β-KA) by their different perturbation effects on a Briggs−Rauscher oscillating system, in which tetraaza-macrocyclic complex [NiL](ClO4)2 is used as the catalyst. The ligand L in the complex is 5,7,7,12,14,14-hexamethyl1,4,8,11-tetraazacyclotetradeca-4,11-diene. The experimental results have shown that addition of α-KA into the system does not affect the oscillating patterns, while the presence of β-KA in a dynamic system influences the oscillatory amplitude. A more interesting feature is that, in the presence of a higher concentration of β-KA, there are damped oscillations after the initial spike, followed by quenching (more exactly: very small oscillations) of the oscillations before the subsequent regeneration of oscillations. A qualitative approach was thus established by employing a Briggs−Rauscher system for identification of these two isomers. The concentrations of these two isomers that can be distinguished lie over the range between 5.0 × 10−6 and 2.5 × 10−3 mol/L. A reaction mechanism based on the FCA model has been proposed. An explanation is that β-KA reacts with HOO• radicals to form acetone, whereas the α-KA does not. Scheme 1. (a) Structure of α-Ketoglutaric Acid (α-KA); (b) Structure of β-Ketoglutaric Acid (β-KA)

A

s a typical kind of self-organization, oscillating chemical reactions have attracted considerable attention from researchers over the past few decades due to their complex dynamics and the applications in the areas of theoretical and experimental chemistry.1,2 Among the model systems that have been utilized in the analytical field, the Belousov−Zhabotinskyi (BZ)3−12 and Briggs−Rauscher (BR)13−18 oscillating reactions are two of the most extensively studied. Quantitative measurements of some organics,19−22 ions,23,24 and antioxidants25−28 have been reported that involve these two types of oscillating systems with metal ions (Ce4+/Mn2+/Fe(phen)33+) or macrocyclic complexes as catalysts. However, previously reported analytical methods based on chemical oscillations have been confined to quantitative technique. In an attempt to broaden the scope of application of oscillating reaction in analytical field, we have managed to utilize a novel BR system in qualitative analysis: identification of two aliphatic position isomers (α-ketoglutaric acid (α-KA) and β-ketoglutaric acid (β-KA)). As shown in Scheme 1, the single difference of these two aliphatic position isomers lies in the position of the ketone functional group, alpha or beta. The novel BR system that we used here refers to the system of H2SO4− KIO3−malonic acid−H2O2−[NiL](ClO4)2, where the ligand L is 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene. © XXXX American Chemical Society

This qualitative accomplishment has been successfully achieved by identifying two aliphatic position isomers by their different perturbation effects on this BR oscillator. The addition of α-KA in the system does not affect the oscillating patterns, while the presence of β-KA in the dynamic system influences the oscillatory amplitude. A more interesting feature is that, in the presence of higher concentration of β-KA, there are damped oscillations after the initial spike, followed by quenching (more exactly: very small oscillations) of the oscillations, before the subsequent regeneration of oscillations. A new qualitative approach was thus established by employing a BR reaction for identification of these two isomers. Received: July 15, 2015 Accepted: August 31, 2015

A

DOI: 10.1021/acs.analchem.5b02649 Anal. Chem. XXXX, XXX, XXX−XXX

Article

Analytical Chemistry Scheme 2. Structure of [NiL](ClO4)2a

Isolating or distinguishing some isomers can be difficult because isomers share physical and chemical properties that arise from their same molecular formula and similar structure. Some methods for identification of isomers have been reported, such as MS,29,30 GC-MS,31 and LC-MS.32,33 As MS technology relies on the distribution of ions by mass (more correctly: mass-to-chargeratio) in a sample, directly using MS in identifying sometimes meets challenges because fragments obtained from two broken isomers may be similar: having the same mass-to-charge-ratio (m/z) with similar distribution. Thus, MS method has to be coupled with other techniques like two-colored femtosecond laser fields,34 polarized femtosecond laser pulses,35 binary phases shaping (BPS) space mapping,36 making the analysis process more complex. Gas chromatography−mass spectrometry (GC-MS) have been utilized to isolate or identify mixed components, but a drawback to this method is that it could not be employed to detect unstable substances due to GC-MS’s higher operating temperature. Liquid chromatography−mass spectrometry (LC-MS) also has been introduced to distinguish isomers owing to its better separation efficiency and higher sensitivity. However, LC-MS technique also has a limitation in identification of isomers in that it is difficult to choose an applicable mobile phase. Thereby, a novel method for identification of isomers is required. In this paper, an achievement in identification of two aliphatic position isomers (α-KA and β-KA) was finalized by using a variation of the Briggs−Rauscher oscillating reaction. The concentrations of α-KA and β-KA that can be distinguished lie over the range from 5.0 × 10−6 to 2.5 × 10−3 mol/L. Not only does such a method witness the novel transition from quantitative technique to qualitative one involving a chemical oscillator, but it presents a new approach in identification of isomers with simpler equipment and a lower limit as well. Moreover, this qualitative approach also could be extended to identify other position isomers, on the condition that such isomers are prone to have different perturbation mechanism on a BR system due to the position difference to a functional group in the molecule.

a

The ligand L is 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca4,11-diene.

catalyst [NiL](ClO4)2 (Scheme 2), which was synthesized according to the literature37,38 and which was identified by IR and elemental analysis. The 2.00 mol/L malonic acid, 1.4 × 10−1 mol/L KIO3, 1.73 × 10−2 mol/L [NiL](ClO4)2, and 4.00 mol/L H2O2 were prepared with 2.5 × 10−2 mol/L H2SO4, which was diluted from 98% H2SO4. Solutions of 1.0 mol/L α-KA and β-KA were dissolved in double redistilled water. Solutions with lower concentrations of α-KA and β-KA were prepared prior to use. The 3 mol/L NaOH was prepared with double redistilled water and was used in neutralization titration.

■

RESULTS AND DISCUSSION Identification of Aliphatic Position Isomers. Unperturbed BR oscillating systems were obtained by directly mixing reactants in the following order: 14.5 mL of 2.5 × 10−2 mol/L H2SO4, 6.5 mL of 1.4 × 10−1 mol/L KIO3, 1.5 mL of 1.73 × 10−2 mol/L [NiL](ClO4)2, 3.5 mL of 2.00 mol/L malonic acid, and 14 mL of 4.00 mol/L H2O2. The periodic change of solution color (yellow-brown-yellow) was noticed during the oscillation. This can be explained by a one-electronic transfer process for catalyst:39 [NiL]2 + (yellow) ⇔ [NiL]3 + (green)

However, instead of green, brown was observed during the oscillations. The periodic generation of I2 was responsible for this phenomenon: iodine was produced and dissolved periodically during oscillation. Recordings of redox potential (Pt) as a function of time is shown in Figure 1a. Identification experiments were carried out by adding equal amounts of α-KA (in Figure 1b,d,f) or β-KA (in Figure 1c,e,g) into active BR oscillators, respectively. Several injection points were tested for the sake of the experimental accuracy and repeatability. The experimental results have shown that the presence of α-KA in the system does not affect the oscillating patterns (in Figure 1b,d,f), while addition of β-KA in the dynamic system influences the oscillatory amplitude (in Figure 1c,e,g). A more interesting feature is that, in the presence of a higher concentration of β-KA, there are damped oscillations after the initial spike, followed by quenching (more exactly: very small oscillations) of the oscillations, before the subsequent regeneration of oscillations (Figure 1e,g). There is an inhibition time, which is defined as the time elapsed between the end of the damping oscillations and the first regenerated oscillation. This behavior is different from the behavior perturbed by other inhibitors like polyphenols. When polyphenols were added into an active BR oscillator, the oscillations would be immediately quenched for a period of time before its regeneration.27 As it can be seen in Figure 1b,d,f, the entire oscillating profiles exhibit unchanged features after the addition of the α-KA solution to make its concentration in the system reach 1.0 × 10−4 mol/L, 6.5 × 10−4 mol/L, or 1.1 × 10−3 mol/L, respectively. On the contrary, in Figure 1c, when 1.0 × 10−4 mol/L of β-KA was added into this mixed medium, the potential decreased

■

EXPERIMENTAL SECTION Apparatus. Oscillating experiments were carried out in a 50 mL vessel thermostated at 4 ± 0.5 °C by using a thermostat (DZCS-IIC, Nanjing Dazhankejiao Institute of Instrument, China). A model 79−3 magnetic stirrer (Jiangsu, China) was applied to homogenize the reaction solution, and the stirring rate was kept at 500 rpm. A type of 213 platinum electrode (Shanghai, China) connected to a model 217 saturated calomel electrode (SCE; Shanghai, China) via a salt bridge containing 1 mol/L Na2SO4 as reference electrode was utilized to monitor the changes of potential. Both sides of these two electrodes were linked to an amplifier (Vernier Software Technology, U.S.A.) and a GO!Link sensor interface (Vernier Software Technology, U.S.A.) that was connected to a personal computer with a Logger Lite data-acquisition program. A pH sensor (Vernier Software Technology, U.S.A.) was also used to measure the value of pH for solutions. GC-MS (Varian, U.S.A.) and FT-IR (Thermo Nicolet Corporation, U.S.A.) was introduced to identify triiodomethane. Reagents and Procedure. Malonic acid, H2SO4 (98%), KIO3, and H2O2 (30%) were obtained commercially from Chinese Medicine Group Chemical Reagent Co., Ltd.; iodine standard, α-KA, and β-KA were purchased from TCI Development Co., Ltd.; and acetone and NaOH were obtained from Aladdin Chemistry Co., Ltd. All reagents were of analytical quality and used without further purification except for the B

DOI: 10.1021/acs.analchem.5b02649 Anal. Chem. XXXX, XXX, XXX−XXX

Article

Analytical Chemistry

Figure 1. Oscillation profiles for the proposed oscillation system using a platinum electrode in the conditions: (a) unperturbed oscillator; (b) perturbation of 1.0 × 10−4 mol/L of α-KA in the system; (c) perturbation of 1.0 × 10−4 mol/L of β-KA in the system; (d) perturbation of 6.5 × 10−4 mol/L of α-KA in the system; (e) perturbation of 6.5 × 10−4 mol/L of β-KA in the system; (f) perturbation of 1.1 × 10−3 mol/L of α-KA in the system; (g) perturbation of 1.1 × 10−3 mol/L of β-KA in the system. Common conditions: [H2SO4] = 2.5 × 10−2 mol/L, [KIO3] = 2.275 × 10−2 mol/L, [[NiL](ClO4)2] = 6.4875 × 10−4 mol/L, [MA] = 1.75 × 10−1 mol/L, [H2O2] = 1.4 mol/L, T = 4 ± 0.5 °C.

to the minimum instantaneously and then increased to the maximum, which resulted in the increase of the amplitude of

oscillation. This oscillating system, after such an increase of the amplitude of oscillation, went into a new oscillatory state with the C

DOI: 10.1021/acs.analchem.5b02649 Anal. Chem. XXXX, XXX, XXX−XXX

Article

Analytical Chemistry

Figure 2. (a) Cyclic voltammograms of the reactions between α-KA and [KIO3]. (b) Cyclic voltammograms of the reactions between α-KA and [[NiL](ClO4)2]. (c) Cyclic voltammograms of the reactions between β-KA and KIO3. Conditions: (a) [H2SO4] = 2.5 × 10−2 mol/L, [KIO3] = 2.275 × 10−2 mol/L; (b) [H2SO4] = 2.5 × 10−2 mol/L, [[NiL](ClO4)2] = 6.4875 × 10−4 mol/L; (c) [H2SO4] = 2.5 × 10−2 mol/L, [KIO3] = 2.275 × 10−2 mol/L; Scan rate = 100 mV/s.

reduced amplitude. Moreover, as shown in Figure 1e,g, there is an interval of inhibition time between the increase and the decrease of amplitude of oscillation in the presence of 6.5 × 10−4 and 1.1 × 10−3 mol/L of β-KA, respectively. The upper limit to β-KA addition is 2.5 × 10−3 mol/L. The repetition experiments proved that these two isomers could have markedly different perturbation effects on a [NiL]2+catalyzed BR oscillator, so a new method could be expected to exploit this behavior to identify α-KA and β-KA. Such a qualitative approach, based on an active BR system, shows a higher accuracy and lower limit of detection. The concentrations of these two isomers that can be identified lie over the range between 5.0 × 10−6 and 2.5 × 10−3 mol/L. Mechanism of Action of α-KA and β-KA on the Oscillating System. The reason why α-KA and β-KA could exhibit such distinct perturbation effects on a macrocyclic nickel(II) complex-catalyzed BR system can be explained by the analogous mechanism of BR reaction. Compared to the conventional BR oscillators, the [NiL]2+-catalyzed oscillating systems possess some specific features.7,17 Compared to the conventional Mn(II) catalyst, which is a common ion, Ni(II) complex catalyst possesses a macrocyclic ligand L, which occupies the extended π-system. Such an extended π-system, during the course of the oscillations, ensures a high rate for reactions involving electron transfer at individual steps of the oscillating process.7 Besides, compared with the apparent activation energy for the Mn(II)-catalyzed BR reaction, the [NiL]2+-catalyzed one is much lower.40 On the basis of the original NF and DE models, which put forward some conjectural skeleton processes under flow conditions,41 a new FCA mechanism was reported by Furrow et al.26,42 Based on the well-known FCA model, the oscillating reactions can be simplified into the following 12 processes: HOI + I− + H+ ⇔ I 2 + H 2O

(1)

HIO2 + I− + H+ → 2HOI

(2)

IO3− + I− + 2H+ ⇔ HIO2 + HOI

(3)

2HIO2 → IO3− + HOI + H+

(4)

IO3− + HIO2 + H+ ⇔ 2IO2• + H 2O

(5)

•

2HOO → H 2O2 + O2

(6)

HOI + H 2O2 → I− + O2 + H+ + H 2O

(7)

IO2• + [NiL]2 + + H+ ⇔ HIO2 + [NiL]3 +

(8)

[NiL]3 + + H 2O2 → [NiL]2 + + HOO• + H+

(9)

HOO• + IO3− + H+ → O2 + H 2O + IO2•

(10)

HOOCCH 2COOH ⇔ HOOCCHC(OH)2 (enol) (11)

HOOCCHC(OH)2 (enol) + I 2 → HOOCCHICOOH + I− + H+

(12)

From the above processes, it is reasonable for us to believe that either intermediate species generated during the oscillation or initial reactants could react with the additives (α-KA or β-KA). In an attempt to confirm whether the redox reaction between α-KA and the initial reagents exists, cyclic voltammetry was performed in the absence and presence of α-KA, in the following media: (i) H2SO4 + KIO3, (ii) H2SO4 + [[NiL](ClO4)2], (iii) H2SO4 + MA, and (iv) H2SO4 + H2O2. In Figure 2a,b, the cyclic voltammograms have shown that the oxidation or reduction potentials were invariable. It implies that there is no reaction between α-KA and KIO3, nor reaction between α-KA and [NiL]2+. For the purpose of illustrating the changed oscillating profiles perturbed by β-KA, the same cyclic voltammetry was performed in the absence and presence of β-KA, in the following media: (i) H2SO4 + KIO3; (ii) H2SO4 + [[NiL](ClO4)2]; (iii) H2SO4 + MA; and (iv) H2SO4 + H2O2. According to the cyclic voltammetry (in Figure 2c), it may be concluded that β-KA can be oxidized by KIO3. Figure 2c has shown that the value of oxidation and reduction peak changed after the injection of β-KA into the acidic KIO3 solution. It must be emphasized strongly that the concentration of β-KA being added into the oscillating system is around the micromolar level or less, whereas there is a large amount of KIO3 compared with β-KA concentration. So if β-KA reacts directly with KIO3 in the mixture, it could be iodinated rapidly. That assumption causes some difficulties to explain the perturbed behavior of the system: the existence of inhibition time. The possibility of reaction between β-KA and intermediate species iodine should be taken into consideration. As β-KA has two active methylene hydrogens, which are easily replaced by iodine, and so the iodination and di-iodination of β-KA is probable. Therefore, β-KA could be iodized into the corresponding iodine compound, and di-iodine compounds, which are rather unstable. D

DOI: 10.1021/acs.analchem.5b02649 Anal. Chem. XXXX, XXX, XXX−XXX

Article

Analytical Chemistry

reaction 13, the direct reaction of β-KA with HOO• results in a decrease of IO2• in reaction 10, and such a decrease of IO2• leads to a decrease in [NiL]3+ by reaction 8. Due to the decrease of [NiL]3+, there will not be sufficient [NiL]2+ formed through reduction of [NiL]3+ in reaction 9, and this insufficiency in [NiL]2+ cause insufficiency in [NiL]3+ via reaction 8. As a result, oscillations between the [NiL]2+ and [NiL]3+ were terminated. Therefore, oscillations temporarily cease and this is why an interval of inhibition time was observed in Figure 1e,g. Process of reactions 8, 9, and 10 will become predominant when the whole amount of β-KA has completely reacted via reaction 13 and oscillations will restart. Determination for Acetone in the BR System Perturbed by β-KA. We held an assumption that β-KA may be oxidized by HOO• to form acetone via reaction 13. Although ref 44 indicates that β-KA could be oxidized into acetone, we still need experimental verification of acetone, the oxidation product in such a system. Although instrumental analytical methods for the identification of acetone, such as capillary GC45 and GC-MS,46 have been reported, they are inapplicable to this BR mixture because of the difficulty of selecting a suitable mobile phase. Besides, other instrumental methods like 13C NMR may not work here owing to a lower amount of acetone oxidized from β-KA and also due to strong evaporation of acetone.47 Hence, the iodoform test (haloform reaction), which needs to be operated in an alkaline medium, was used to recognize whether acetone has been generated in BR oscillators or not. The iodoform test was run in following procedure in order to confirm the generation of acetone: to the oscillating system, 200 μL of 2.4 mol/L β-KA solution (this concentration is much higher than that in perturbation experiments because we need to collect sufficient amount of oxidation product of β-KA− acetone) was added after several oscillation cycles; after the acidic oscillating mixture has been changed into alkaline (pH = 9) by dropwise addition of 3 mol/L NaOH solution, standard iodine solution was added. In approximately 3 min, a little pale yellow precipitate was observed. This precipitate was collected and analyzed for further study by using GC-MS and FT-IR, respectively, and the results are shown in Figures 3 and 4. The GC spectrum was shown in Figure 3a. The MS spectrum in Figure 3b indicates that the ion peaks are consistent with the triiodomethane standard diagram in Figure 3c. Moreover, as shown in Figure 4, the absorption peak near 2981 cm−1 is assigned to the stretching vibration absorption of C−H; absorption peaks in 1060 and 573 cm−1 belong to the C−I stretching vibration band. And all these absorption peaks of precipitates are in accordance with the iodoform standard IR spectra. The GC-MS and FT-IR spectra have demonstrated that triiodomethane formed finally in the iodoform test. The iodoform test confirms the generation of acetone in this BR system, because iodoform comes from the reaction of iodine and base with acetone. However, it is difficult to track if acetone would be oxidized to aldehyde or carboxylic acid under the existing experimental conditions. In an effort to investigate the role of acetone in the oscillator, acetone perturbation experiments were performed, and the result is shown in Figure 5. The result has shown that acetone almost has no perturbation responses to this BR oscillator. This phenomenon indicates that perturbation effects of β-KA on the oscillation are attributed to the interaction between β-KA and intermediates (like HOO• radicals) to form acetone, but acetone itself has no further perturbation effects.

However, this iodination assumption could not explain the perturbed behavior, quick decrease and increase of potential, nor could it explain the rapid spiking of oscillation. In order to interpret perturbed behavior, a reaction between β-KA and intermediates (such as HOO•) should be taken into account. For β-KA perturbed BR system, the existence of changed amplitude of oscillation and interval of inhibition time correlates with HOO• radical. Thus, reaction 13 was put forward possibly to enrich the FCA model.43 The detailed mechanism of reaction 13 can be split up into five different steps, which are shown in reaction 13a−e.

Reaction of β-KA with HOO• radical forms acetone and carbon dioxide. The reaction 13 and reaction 10 are competitive because both of them can consume the HOO• radical, but reaction 10 is faster in the presence of low concentrations of β-KA, which would influence the amplitude of the oscillation. The extra consumption of HOO• radical via reaction 13 leads to the increase of the concentration of [NiL]2+ in reaction 9, and this increase causes the decrease of minimum potential (corresponds to maximum concentration of [NiL]2+). As a result of the accumulation of [NiL]2+ through reaction 9, the concentration of [NiL]3+ increases in reaction 8, which results in the increase in the maximum potential (corresponds to maximum concentration of [NiL]3+). Thus, the value of ln{[NiL]3+/[NiL]2+} increases accordingly, and an increased oscillation amplitude (from minimum potential to maximum potential) was observed in Figure 1c. With the increase of concentration of β-KA, reaction 13 would consume more HOO• radicals than reaction 10. According to E

DOI: 10.1021/acs.analchem.5b02649 Anal. Chem. XXXX, XXX, XXX−XXX

Article

Analytical Chemistry

Figure 3. GC-MS information on precipitates.

Figure 5. Typical oscillation profiles for the proposed oscillation system using a platinum electrode perturbed by 3.0 × 10−3 mol/L acetone in the conditions: [H2SO4] = 2.5 × 10−2 mol/L, [KIO3] = 2.275 × 10−2 mol/L, [[NiL](ClO4)2] = 6.4875 × 10−4 mol/L, [MA] = 1.75 × 10−1 mol/L, [H2O2] = 1.4 mol/L, and T = 4 ± 0.5 °C.

Figure 4. FT-IR information on precipitates.

In β-KA perturbation experiments, acetone may be generated from two sources: it comes either from oxidation of β-KA by HOO•, or it is from decomposition of β-KA itself. It was noticed that the changes of platinum electrode potential were instantaneous after addition of β-KA. As decomposition of β-KA would usually require significant time (several minutes or even more, for example), an instantaneous change in potential indicates that acetone could be produced from oxidation of β-KA by HOO•, which goes very fast and is shown in reaction 13. Iodoform Test for the BR System Perturbed by α-KA. Same iodoform test processes were introduced into the oscillating system that was perturbed by α-KA, just like the processes we had applied in the oscillating system that was perturbed by β-KA. After the pH of BR oscillator was changed to 9 by the addition of 3 mol/L of NaOH, iodine standard solution were added into this mixture. It was observed that the color of the solution turned to brown gradually and no precipitates were

observed. It implies that no acetone was generated in the BR system perturbed by α-KA.

■

CONCLUSIONS We demonstrated here that, for the first time, the macrocyclic Ni(II) complex-catalyzed BR oscillating system is an appropriate matrix for the qualitative identification of isomers between α-KA and β-KA. The presence of α-KA in the system does not affect the oscillations, while the addition of β-KA influences the oscillatory amplitude. A qualitative approach was thus established by employing a BR system for identification of these two isomers. The explanation is that β-KA reacts with HOO• radicals to form acetone, whereas the α-KA does not. Acetone, the oxidation product from β-KA, was identified by the iodoform F

DOI: 10.1021/acs.analchem.5b02649 Anal. Chem. XXXX, XXX, XXX−XXX

Article

Analytical Chemistry test. Because of the facts that α-KA’s anion, α-ketoglutarate, is an important intermediate in the Krebs cycle, whereas β-KA’s anion is not a biological compound, our mechanism studies regarding using oscillating reaction in distinguishing the isomers are helpful in understanding the different biological roles of some isomers (α- and β- ketoglutaric acid, for example).

■

(27) Cervellati, R.; Renzulli, C.; Guerra, M. C.; Speroni, E. J. Agric. Food Chem. 2002, 50, 7504−7509. (28) Hu, G.; Zeng, Q. L.; Hu, Y. Y.; Shen, X. F.; Song, J. M. Electrochim. Acta 2014, 136, 33−40. (29) Chen, Z.; Tong, Q. N.; Zhang, C. C.; Hu, Z. Chin. Phys. B 2015, 24, 043303. (30) Yuan, G.; Horiike, M.; Chul-Sa, Kim; Hirano, C. Chin. J. Chem. 1994, 12, 348−354. (31) Sheng, Y.; Chen, X. B. Health 2009, 1, 203−206. (32) Pan, C. X.; Xu, X. Z.; He, H. M.; Cai, X. J.; Zhang, X. J. J. Zhejiang Univ., Sci. 2005, 6, 74−78. (33) Chen, Z. W.; Tong, L.; Li, S. M.; Li, D. X.; Zhang, Y.; Zhou, S. P.; Zhu, Y. H.; Sun, H. J. Pharm. Anal. 2014, 4, 14−25. (34) Ohmura, H.; Ito, F.; Tachiya, M. Phys. Rev. A: At., Mol., Opt. Phys. 2006, 74, 043410. (35) Li, Y.; Bruder, C. Phys. Rev. A: At., Mol., Opt. Phys. 2008, 77, 015403. (36) Cruz, J. M. D.; Lozovoy, V. V.; Dantus, M. J. Phys. Chem. A 2005, 109, 8447−8450. (37) Curtis, N. F.; Hay, R. W. Chem. Commun. 1966, 15, 524−525. (38) Curtis, N. F. J. Chem. Soc., Dalton Trans. 1972, 13, 1357−1361. (39) Hu, G.; Hu, L.; Ni, S. S. React. Kinet. Catal. Lett. 2006, 88, 349− 355. (40) Hu, G.; Zhu, L.; Guo, M. M.; Liu, H. Y. Asian J. Chem. 2010, 22, 6393−6396. (41) Kepper, P. D.; Epstein, I. R. J. Am. Chem. Soc. 1982, 104, 49−55. (42) Cervellati, R.; HÖ ner, K.; Furrow, S. D.; Mazzanti, F.; Costa, S. Helv. Chim. Acta 2004, 87, 133−155. (43) Fujisawa, S.; Atsumi, T.; Kadoma, Y.; Sakagami, H. Toxicology 2002, 177, 39−54. (44) Ševčík, P.; Mišicák, D.; Adamčíková, L. J. Phys. Chem. A 2007, 111, 10050−10054. (45) Sitholé, B. B.; Sullivan, J. L.; Allen, L. H. Holzforschung 1992, 46, 409−416. (46) Reissell, A.; Harry, C.; Aschmann, S. M.; Atkinson, R.; Arey, J. J. Geophys. Res. 1999, 104, 13869−13879. (47) Xu, T.; Munson, E. J.; Haw, J. F. J. Am. Chem. Soc. 1994, 116, 1962−1972.

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS The authors gratefully acknowledge funding for this work from the National Natural Science Foundation of China (21171002). Proofreading of the manuscript by Prof. John Pojman from Louisiana State University is acknowledged.

■

REFERENCES

(1) Samjeské, G.; Osawa, M. Angew. Chem., Int. Ed. 2005, 44, 5694− 5698. (2) Jimenez-Prieto, R.; Silva, M.; Perez-Bendito, D. Anal. Chem. 1995, 67, 729−734. (3) Noszticzius, Z.; Bodiss, J. J. Am. Chem. Soc. 1979, 101, 3177−3182. (4) Guedes, M. C.; Faria, R. B. J. Phys. Chem. A 1998, 102, 1973−1975. (5) Kurin-Csörgei, K.; Zhabotinsky, A. M.; Orbán, M.; Epstein, I. R. J. Phys. Chem. 1996, 100, 5393−5397. (6) Zhao, L.; Hu, G. L.; Xie, F. X.; Xu, Z. Q.; Ni, S. S. Chin. Chem. Lett. 1996, 7, 579−580. (7) Yatsimirskii, K. B.; Tikhonova, L. P. Coord. Chem. Rev. 1985, 63, 241−269. (8) Ueki, T.; Watanabe, M.; Yoshida, R. Angew. Chem., Int. Ed. 2012, 51, 11991−11994. (9) Hu, G.; Zhang, Z. D. Chem. Lett. 2006, 35, 1154−1155. (10) Bánsági, T.; Leda, M., Jr.; Toiya, M.; Zhabotinsky, A. M.; Epstein, I. R. J. Phys. Chem. A 2009, 113, 5644−5648. (11) Horvath, V.; Gentili, P. L.; Vanag, V. K.; Epstein, I. R. Angew. Chem., Int. Ed. 2012, 51, 6878−6881. (12) Field, R. J.; Koros, E.; Noyes, R. M. J. Am. Chem. Soc. 1972, 94, 8649−8664. (13) Briggs, T. S.; Rauscher, W. C. J. Chem. Educ. 1973, 50, 496. (14) Rosokha, S. V.; Tikhonova, L. P.; Bakai, É. A. Theor. Exp. Chem. 1996, 32, 160−163. (15) Furrow, S. D. J. Phys. Chem. 1995, 99, 11131−11140. (16) Furrow, S. D.; Cervellati, R.; Amadori, G. J. Phys. Chem. A 2002, 106, 5841−5850. (17) Tikhonova, L. P.; Rosokha, S. V.; Bakay, E. A. React. Kinet. Catal. Lett. 1998, 63, 129−136. (18) Hu, G.; Zhao, F. S.; Hu, L. Helv. Chim. Acta 2011, 94, 903−913. (19) Hu, G.; Chen, P. P.; Wang, W.; Hu, L.; Song, J. M.; Qiu, L. G.; Song, J. Electrochim. Acta 2007, 52, 7996−8002. (20) Chen, P. P.; Hu, G.; Wang, W.; Song, J. M.; Qiu, L. G.; Wang, H. L.; Chen, L. L.; Zhang, J. F.; Hu, L. J. Appl. Electrochem. 2008, 38, 1779− 1783. (21) Hu, G.; Chen, L. L.; Zhang, J. F.; Chen, P. P.; Wang, W.; Song, J. M.; Qiu, L. G.; Song, J.; Hu, L. Cent. Eur. J. Chem. 2009, 7, 291−297. (22) Zeng, Q. L.; Chen, L. L.; Song, X. Y.; Hu, G.; Hu, L. Cent. Eur. J. Chem. 2014, 12, 325−331. (23) Hu, L.; Hu, G.; Xu, H. H. J. Anal. Chem. 2006, 61, 1021−1025. (24) Chen, L. L.; Hu, G.; Zhang, J. F.; Hu, L. Mendeleev Commun. 2009, 19, 224−226. (25) Cervellati, R.; HÖ ner, K.; Furrow, S. D.; Neddens, C.; Costa, S. Helv. Chim. Acta 2001, 84, 3533−3547. (26) Cervellati, R.; CresPi-Perellino, N.; Furrow, S. D.; Minghetti, A. Helv. Chim. Acta 2000, 83, 3179−3190. G

DOI: 10.1021/acs.analchem.5b02649 Anal. Chem. XXXX, XXX, XXX−XXX