Journal of Analytical Methods in Chemistry
Volume 2019 (2019), Article ID 2173671, 8 pages
https://doi.org/10.1155/2019/2173671

Research Article

A Visible Colorimetric Fluorescent Probe for Hydrogen Sulfide Detection in Wine

Haitao Chen, Xiaoming Wu, Shaoxiang Yang, Hongyu Tian, Yongguo Liu, and Baoguo Sun

Beijing Advanced Innovation Center for Food Nutrition and Human Health, Beijing Key Laboratory of Flavor Chemistry, Beijing Technology and Business University, No. 11 Fucheng Road, Haidian District, Beijing 100048, China

Correspondence should be addressed to Shaoxiang Yang; yangshaoxiang@th.btbu.edu.cn

Received 11 September 2018; Revised 13 November 2018; Accepted 26 November 2018; Published 10 January 2019

Academic Editor: Jose Vicente Ros-Lis

Copyright © 2019 Haitao Chen et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract.

A new efficient and practical fluorescent probe 6-(benzo[d]thiazol-2-yl)naphthalen-2-yl-thiophene-2-carboxylate (probe 1) was synthesized to detect hydrogen sulfide (H₂S). The addition of H₂S caused the solution of probe 1 to change from colorless to yellow, and the solution of probe 1 changes to different colors with respect to different concentrations of H₂S. Importantly, probe 1 could help detect H₂S efficiently by a distinct color response as a visible detection agent. Probe 1 reacted with various concentrations of H₂S (0–200 μM), and the detection limit for H₂S was 0.10 μM. Particularly, probe 1 can be applied as a sensor to detect H₂S accurately in wine samples.

1. Introduction

Hydrogen sulfide (H₂S) has unpleasant rotten egg smell [1, 2]. H₂S is a significant compound in wine, and a detection threshold value is measured from 1.1 to 1.6 μg/L [3]. Alcoholic fermentation is mainly a way to generate H₂S because of enzymatic catabolism of S-amino acid and yeast from elemental sulfite pesticide residues, sulfate, or sulfur [4]. Due to abiotic storage of wine, the level of hydrogen sulfide keeps an increasing trend. Other sources of H₂S are investigated all the time [5, 6]. H₂S affects the quality of wines and causes economic losses [7, 8].

H₂S is an important part in the processes of physiological and pathophysiological responses, and abnormal levels of H₂S cause various diseases [9, 10], including cardiac ischemia disease [11], hypertension [12], atherosclerosis [13], diabetes [14], tumor [15], and other diseases. Therefore, the sensitive and selective methods for detecting H₂S in wine are required.

The methods to detect H₂S include colorimetry [16], electrochemical precipitation [17], metal-induced sulfide precipitation [18], gas chromatography [19], high-performance liquid chromatography-mass spectrometry [6], and sulfide precipitation [20]. Recently, fluorescent probes have been considered a practical tool for H₂S detection [21–24]. The H₂S fluorescent probes are designed by some approaches, such as sulfide-induced precipitation of quantum dots [25, 26], reduction of azide and nitro group to amines [27–32], substitution reaction [33], nucleophilic reactions [34, 35], high adsorption of S²⁻ to Cu²⁺ [36], and the reaction with the unsaturated double bond [37]. Recently, different kinds of fluorescent probes have been designed and compounded to detect H₂S in living cells, and development of efficient and practical sensors to detect H₂S in wine is still crucial [38]. In order to discover a more responsive and visible colorimetric fluorescent probe, a new fluorescent probe (probe 1) was introduced in this work, with naphthalene and benzothiazole ring moiety as the fluorophore and thiophene-2-carboxylate as the reaction site. Probe 1 shows responsive and visible colorimetric precipitation for H₂S with naked eye. Especially, the solution of probe 1 poses different colors at different H₂S concentrations under ambient light. Probe 1 could be used as a sensor to obtain H₂S levels and to obtain high recovery in real wine samples.

2. Materials and Methods

2.1. General Methods

The chemicals and reagents were purchased from Beijing Huaxue Shiji (Beijing, P.R. China). The reagents were all analytically pure. ¹H-NMR and ¹³C-NMR spectra were recorded at 400 MHz and 100 MHz, respectively. Chemical shifts (δ) were expressed in ppm relative to TMS, and coupling constants (J) are in Hz. The high-resolution mass spectrum (HRMS) was performed at a Bruker Apex IV FTMS. Fluorescence spectra were recorded on a Hitachi F-4600 fluorescence spectrometer with a temperature controller.

2.2. Preparation of Probe 1

6-(benzo[d]thiazol-2-yl)naphthalen-2-ol. 6-hydroxy-2-naphthaldehyde (0.86 g, 5 mmol) and 2-aminothiophenol (0.63 g, 5 mmol) were dissolved in ethanol (25 mL) and stirred for 15 min. And then, p-toluenesulfonic acid (0.34 g, 2 mmol) in ethanol (5 mL) was added into the mixture slowly. The reaction mixture was heated in an oil bath at 80°C overnight. After the mixture was cooled to room temperature, the mixture was added 50 mL distilled water. The precipitate was collected by evaporation and dried to yield 6-(benzo[d]thiazol-2-yl)naphthalen-2-ol as a yellow solid (1.29 g, 93.5%, Scheme 1).

Scheme 1: Synthesis of probe 1.

¹H NMR (300 MHz, DMSO), δ (ppm): 10.11 (s, 1H), 8.54 (s, 1H), 8.06 (m, 4H), 7.84 (d, J = 8.67 Hz, 1H), 7.53 (td, J = 7.29, 1.17 Hz, 1H), 7.43 (td, J = 7.95, 1.17 Hz, 1H), and 7.16 (m, 2H). ¹³C NMR (75 MHz, DMSO): δ (ppm): 168, 158, 154, 137, 135, 131, 128, 127, 126, 125, 123, 120, and 109.

Probe 1: 6-(benzo[d]thiazol-2-yl)naphthalen-2-yl-thiophene-2-carboxylate. 6-(benzo[d]thiazol-2-yl)naphthalen-2-ol (0.50 g, 1.8 mmol), CHCl₃ (20 mL), and thiophene-2-carbonyl chloride (0.29 g, 1.8 mmol) was added. After stirring 20 min, a drop of trimethylamine was dissolved in CHCl₃ (5 mL) and added slowly. The reaction mixture was heated at 80°C for 4 h. The precipitate used evaporation to be collected and then used column chromatography to purify probe 1 as a solid (0.570 g, 81.8%; Scheme 1).

¹H NMR (300 MHz, DMSO), δ (ppm): 8.78 (s, 1H), 8.28 (d, J = 4.35 Hz, 2H), 8.20 (d, J = 3.96 Hz, 1H), 8.12–8.14 (m, 4H), 8.11 (d, J = Hz, 1H), 7.96 (s, 1H), 7.58 (t, J = 4.41 Hz, 2H), 7.50 (t, J = 3.78 Hz, 1H), and 7.35 (s, 1H). ¹³C NMR (75 MHz, DMSO): δ (ppm): 168, 161, 154, 150, 136, 135, 132, 131, 130, 129, 128, 127, 126, 125, 123, and 120. HRMS: calcd. [M]⁺ 387.0388; 387.0390.

2.3. Preparation of Solutions of Probe 1 and Analytes

The HPLC-grade DMSO as reagent was used to dissolved probe 1. After mixing, probe 1 stock solution was obtained. Analytes NaF, Na₂SO₃, NaCl, NaHSO₃, NaNO₃, NaBr, Na₂SO₄, Na₂S₂O₃, Na₂S₂O₅, NaS₂O₆, CH₃COONa, NaHCO₃, and Na₂S used distilled water to be dissolved and obtained 10 mM aqueous solutions. Various concentrations could be obtained by using distilled water to dilute the stock solutions.

2.4. Preparation of Wine Samples

Three kinds of beers and four kinds of red wines were bought from wumart supermarket (Beijing) and different concentrations of Na₂S were added (Na₂S is the H₂S source), and the 504 nm fluorescence signals of samples were recorded.

2.5. The Procedures of H₂S Determination and Samples Analysis

The ready of the detection system: dimethyl sulfoxide (0.48 mL) and probe solution (0.02 mL) were mixed. And then buffer solution was added and made up to 2 mL in the cuvette. After mixing, the spectrum was tested by recording the fluorescence signals.

Fluorescence spectrophotometer parameters: excitation wavelength, 330 nm; emission wavelength, 504 nm; temperature, 37°C; voltage, 700 v; slit width, 5 nm/5 nm.

3. Results and Discussion

3.1. Fluorescent Probe Preparation

Probe 1 was synthesized in just a two-step reaction. First, the intermediate compound 3 was manufactured by nucleophilic addition reaction and cyclodehydration of compound 1 with compound 2. Second, probe 1 was obtained so that compound 3 and thiophene-2-carbonyl chloride (compound 4) performed an esterification reaction. This synthetic process and the purification of silica gel column chromatographic separation were easy. ¹H NMR and ¹³C NMR (Figures S1 and S2) were used to determine the structure of 6-(benzo[d]thiazol-2-yl)naphthalene-2-ol, light yellow powder. The structure of Probe 1 was characterized by ¹H NMR, ¹³C NMR, and HRMS (Figures S3–S5).

3.2. Sensing Property of Probe 1 towards H₂S

The fluorescence response of probe 1 (10 μM) to Na₂S (we used Na₂S for H₂S production) was firstly verified in 10 mM phosphate buffer saline (PBS; pH 7.4) in DMSO at 37°C. According to Figure 1(a), the fluorescence intensity was detected at 1, 3, 5, 7, 9, 11, 15, 20, 25, 30, and 35 min after 200 μM H₂S was added, and the fluorescence intensity increased almost three times. The fluorescence signal at 504 nm increased all the time until 30 min (Figure 1(b)). The results suggest that probe 1 shows good response to H₂S in neutral environment.

(a)

(b)

Figure 1: (a) Time-dependent fluorescence spectra of probe 1 (10 μM) in the presence of H₂S (200 μM) in phosphate buffer saline (PBS; pH 7.4) with DMSO (v/v, 3 : 1) at 37°C; (b) time-dependent fluorescence intensity changes of probe 1 (10 μM) in the presence of H₂S (200 μM) at 504 nm. λex = 307 nm, λem = 504 nm, and slit width = 5 nm/5 nm. The test was repeated 3 times.

The fluorescent response of probe 1 to H₂S in different pH values (Table S1) from 3.0 to 10.0 was investigated (Figure 2(a)). The data suggest that the fluorescent intensity of probe 1 did not change in various pH values. However, as H₂S was added, the fluorescent intensity of probe 1 increased quickly from 3.0 to 4.0 and decreased from 4.0 to 9.0. The fluorescence intensity showed largest differences between probe 1 and probe 1-H₂S in pH 4.0. The water solubility of H₂S was reported as an equilibrium between molecular and ionic forms (H₂S ⇌ HS⁻ ⇌ S²⁻) [39]. The pKa values for the first and second dissociation steps are 7.0 and 12.0, respectively [39]. The major form of hydrogen sulfide exists as HS⁻ with a minor form of free H₂S in pH 7.4 [39] and exists as free H₂S in pH 4.0. The fluorescent intensity of probe 1-H₂S decreased indicating that the reaction activity of probe 1 to H₂S decreased. So, the reaction activity of probe 1 to H₂S decreased from 4.0 to 7.0, increased from 4.0 to 7.4, and then decreased from 7.4 to 9.0. As probe 1 can identify H₂S, HS⁻, and S²⁻ [40], the reaction activity of probe 1 to H₂S with pH is generally not too obvious regularity. The above results reveal that the pH value of 4.0 is better suitable for further studies.

(a)

(b)

(c)

Figure 2: (a) Fluorescent intensity of probe 1 (10 μM) in the absence and presence of H₂S (200 μM) in different pH buffer solutions with DMSO (v/v, 3 : 1). The test was repeated 3 times; (b) fluorescence spectra of probe 1 (10 μM) and probe 1 (10 μM) with H₂S (200 μM) in buffer solution (pH 4.0) with DMSO (v/v, 3 : 1) at 37°C; (c) the color change of probe 1 (10 μM) in the absence and presence of H₂S (200 μM).

The fluorescence response of probe 1 (10 μM) to H₂S was verified in 10 mM buffer solution (pH 4.0) in DMSO at 37°C, the fluorescence signal at 504 nm increases all the time until 30 min (Figure S6). The fluorescence response of free probe 1 (10 μM) and H₂S (200 μM) added to probe 1 in buffer solution (pH 4.0) is shown in Figure 2(b). Meanwhile, the solution color changed from colorless to yellow (Figure 2(c)). All results indicate that probe 1 was a turn-on fluorescent probe and could be applied to detect H₂S in this experimental condition by the naked eye.

The solution of probe 1 in buffer solution (pH 4.0) was added with different concentrations of H₂S (0–200 μM), and the change of fluorescence intensity was recorded. As shown in Figure 3(a), a highest fluorescence peak was shown at 504 nm, and the fluorescence intensity was increasing with the addition of H₂S. The highest of fluorescence intensity was reached in the presence of 200 μM H₂S. The data could make a good linearity, R² = 0.9959 (Figure 3(b)). The detection limit (LOD) of probe 1 for H₂S was 0.1 μM, based on Cim = 3 SD/B according to the definition from IUPAC. These results suggest that pH 4.0 was the best pH value for probe 1 to detect H₂S and provide a nice quantitative detection method for H₂S.

(a)

(b)

(c)

(d)

(e)

Figure 3: (a) Fluorescence spectra of probe 1 (10 μM) with H₂S (0–200 μM); (b) the plot of fluorescence intensity difference with H₂S from 0 to 200 μM in buffer solution (10 mM, pH 4.0) with DMSO (v/v, 3 : 1); (c) fluorescence intensity change of probe 1 (10 μM) upon addition of various species (200 μM for each. 0, blank; 1, GSH; 2, F⁻; 3, Cl⁻; 4, Br⁻; 5, SO₃²⁻; 6, HSO₃⁻; 7, S₂O₃²⁻; 8, S₂O₅²⁻; 9, S₂O₆⁻; 10, CH₃COO⁻; 11, SO₄²⁻; 12, HCO₃⁻; 13, CO₃²⁻. 200 μM for H₂S). Wavelength, 504 nm. The test was repeated 3 times; (d) the solution color of probe 1 with Na₂S and competing species (200 μM for each. 0, H₂S; 1, GSH; 2, F⁻; 3, Cl⁻; 4, Br⁻; 5, SO₃²⁻; 6, HSO₃⁻; 7, S₂O₃²⁻; 8, S₂O₅²⁻; 9, S₂O₆⁻; 10, CH₃COO⁻; 11, SO₄²⁻; 12, HCO₃⁻; 13, CO₃²⁻. 200 μM for H₂S); (e) photograph of probe 1 (10 μM) at different H₂S concentrations under ambient light in buffer solution (pH 4.0) with DMSO (v/v, 3 : 1) at 25°C.

To verify the selectivity of probe 1 for H₂S, GSH, F⁻, Cl⁻, Br⁻, SO₃²⁻, HSO₃⁻, S₂O₃²⁻, S₂O₅²⁻, S₂O₆⁻, CH₃COO⁻, SO₄²⁻, HCO₃⁻, and CO₃²⁻ in buffer solution (pH 4.0) was chosen as the complex condition to research the fluorescent response of probe 1. As shown in Figure 3(c), under this condition, the competitor did not cause the fluorescence change obviously. At the same time, competition experiments were conducted by adding H₂S to the probe 1 solutions containing the above analytes. Fluorescent response of probe 1 shows that fluorescence had no changes toward H₂S and H₂S + competitor. It clearly indicated that the presence of competitor did not interfere with H₂S detection. In addition, only H₂S caused the probe 1 solution to change color from colorless to yellow (Figure 3(d)). Based on the above result, it indicated that probe 1 has good recognition toward H₂S in complex environment. Using probe 1 solution develops a test strip system (10 μM; buffer solution: DMSO = 3 : 1, pH 4.0). The test strip system showed different color changes to different concentrations of H₂S ranging from 0 μM to 600 μM (Figure 3(e)). So, these data show that probe 1 can be used to develop an easy-to-detect test strip system for an effective method to monitor H₂S by the naked eye.

3.3. Reaction Mechanism

A possible response mechanism may attribute to H₂S-induced hydrolysis of thenoic acid ether moiety in probe 1 and thereby generate 6-(benzo[d]thiazol-2-yl)naphthalen-2-ol (compound 3) and 2-thiophenecarboxylic acid (compound 5), as shown in Scheme 2. To verify the response mechanism mentioned above, reaction of probe 1 with H₂S was analyzed by GC-MS (Figure S6). A peak at 5.40 min, m/z = 142.0 was the reaction product generated by the esterification reaction of compound 6 with methanol. Peak at 22.18 min, m/z = 277.1, which correlated to the formation of compound 3. The results suggest that probe 1 can react with H₂S efficiently and verify the proposed mechanism.

Scheme 2: The mechanism for probe 1 with H₂S.

3.4. Detection of H₂S in Wine

As H₂S negatively affects wine quality, it is an important reason to cause faulty wine. The data of probe 1 to detect H₂S in real samples were recorded to prove the actual practicability of probe 1. Three kinds of beers and four kinds of red wines were bought from Wumart supermarket (Beijing) and were added to the solution of probe 1 (10 μM; pH 4.0). Then, H₂S of different concentration levels (50 μM and 100 μM) were added. The fluorescence intensity of all these samples was investigated at 504 nm.

As shown in Table 1, 0.53, 0.69, 0.74, and 0.49 μM were obtained in four red wine samples. 0.41, 0.28, and 0.32 μM were founded in three beer samples. Probe 1 can detect H₂S concentration in red wine and beer, and the recovery ranged from 90.65% to 110.00% showing that probe 1 has good practicability to detect H₂S levels in real samples. The results show that the probe 1 as a testing method is feasible and practical to determinate H₂S in wine.

Table 1: Determination of H₂S concentrations in wine.

Sample
H₂S level found (µmol)
Added (µmol)
H₂S level found (µmol)
Recovery (%)
s²

Red wine A
0.53
50
53.02
104.88
0.007

100
100.21
99.68
0.005

Red wine B
0.69
50
48.90
96.47
0.001

100
98.14
97.33
0.004

Red wine C
0.74
50
46.10
90.65
0.005

100
97.14
96.28
0.005

Red wine D
0.49
50
47.96
94.99
0.004

100
98.12
97.64
0.006

Beer A
0.41
50
50.71
100.59
0.004

100
100.32
99.91
0.005

Beer B
0.28
50
49.10
97.65
0.002

100
100.34
100.00
0.006

Beer C
0.32
50
55.36
110.00
0.001

100
105.43
105.09
0.005

The test was repeated 3 times.

Probe 1 is compared with some previously reported H₂S fluorescent probe in terms of detection range, detection limit, and practical applications as listed in Table S2. Majority of H₂S fluorescent probes have been designed and used for biological imaging, but H₂S fluorescent probes for wine are rare. In this work, probe 1 has different color changes for different concentrations of H₂S ranging from 0 μM to 600 μM. Probe 1 has a wider detection range (0–200 μM) than our previous fluorescent probes and reported H₂S fluorescent probes (Table S2). Furthermore, probe 1 has successfully been used to detect H₂S concentrations in red wine and beer. In addition, the visual change indicates that probe 1 can be used to develop a naked eye detection agent to detect H₂S levels.

4. Conclusions

In summary, we developed a sensitive and visible colorimetric fluorescent probe to detect H₂S. The function of probe 1 relies on H₂S-induced make thenoic acid ether group cleave, and the produced fluorophores (6-(benzo[d]thiazol-2-yl)naphthalen-2-ol and compound 3 were verified by GC-MS studies. When probe 1 reacted with H₂S, the solution color changed from colorless to yellow, and addition of different concentrations of H₂S posed different color changes, indicating that probe 1 could be employed as a testing tool for H₂S. Furthermore, our work shows that probe 1 has been successfully applied to test H₂S levels in red wine and beer samples.

Data Availability

The data used to support the findings of this study are included within the article.

Conflicts of Interest

The authors declare that there are no conflicts of interest regarding the publication of this article.

Acknowledgments

The authors thank the Scientific and Technological Innovation and Service Capacity Building (basic research business funding) for funding the study on the flavor of typical Chinese traditional dishes (PXM2018-014213-000033) and the Support Project of High-Level Teachers in Beijing Municipal Universities in the period of 13th Five-Year Plan (CIT&TCD201804021).

Supplementary Materials

Experiment section. Figure S1: ¹H NMR spectra of 6-(benzo[d]thiazol-2-yl)naphthalen-2-ol. Figure S2: ¹³C NMR spectra of 6-(benzo[d]thiazol-2-yl)naphthalen-2-ol. Figure S3: ¹H NMR spectra of probe 1. Figure S4: ¹³C NMR spectra of probe 1. Figure S5: HRMS spectra of probe 1. Figure S6: the time-dependent fluorescence spectra in pH 4.0 buffer. Figure S7: GC-MS spectra of probe 1-H₂S. Table S1: disposition of different pH buffer solutions. Table S2: comparison of fluorescent probes for H₂S. (Supplementary Materials)

References

E. Vela, P. Hernandez-Orte, E. Franco-Luesma, and V. Ferreira, “Micro-oxygenation does not eliminate hydrogen sulfide and mercaptans from wine; it simply shifts redox and complex-related equilibria to reversible oxidized species and complexed forms,” Food Chemistry, vol. 243, pp. 222–230, 2018.

M. I. Kinzurik, M. Herbst-Johnstone, R. C. Gardner, and B. Fedrizzi, “Hydrogen sulfide production during yeast fermentation causes the accumulation of ethanethiol, S-ethyl thioacetate and diethyl disulfide,” Food Chemistry, vol. 209, pp. 341–347, 2016.

L. D. Araujo, S. Vannevel, A. Buica et al., “Indications of the prominent role of elemental sulfur in the formation of the varietal thiol 3-mercaptohexanol in Sauvignon blanc wine,” Food Research International, vol. 98, pp. 79–86, 2017.

G. Y. Kreitman, J. C. Danilewicz, D. W. Jeffery, and R. J. Elias, “Copper(II)-Mediated hydrogen sulfide and thiol oxidation to disulfides and organic polysulfanes and their reductive cleavage in wine: mechanistic elucidation and potential applications,” Journal of Agricultural and Food Chemistry, vol. 65, no. 12, pp. 2564–2571, 2017.

J. A. Jastrzembski, R. B. Allison, E. Friedberg, and G. L. Sacks, “Role of elemental sulfur in forming latent precursors of H₂S in wine,” Journal of Agricultural and Food Chemistry, vol. 65, no. 48, pp. 10542–10549, 2017.

E. Franco-Luesma and V. Ferreira, “Formation and release of H₂S, methanethiol, and dimethylsulfide during the anoxic storage of wines at room temperature,” Journal of Agricultural and Food Chemistry, vol. 64, no. 32, pp. 6317–6326, 2016.

N. Kontoudakis, A. Guo, G. R. Scollary, and A. C. Clark, “The impact of aging wine in high and low oxygen conditions on the fractionation of Cu and Fe in Chardonnay wine,” Food Chemistry, vol. 229, pp. 319–328, 2017.

E. Vela, P. Hernández-Orte, E. Franco-Luesma, and V. Ferreira, “The effects of copper fining on the wine content in sulfur off-odors and on their evolution during accelerated anoxic storage,” Food Chemistry, vol. 231, pp. 212–221, 2017.

H. Peng, Y. Cheng, C. Dai et al., “A fluorescent probe for fast and quantitative detection of hydrogen sulfide in blood,” Angewandte Chemie International Edition, vol. 50, no. 41, pp. 9672–9675, 2011.

J. W. Calvert, S. Jha, S. Gundewar et al., “Hydrogen sulfide mediates cardioprotection through Nrf2 signaling,” Circulation Research, vol. 105, no. 4, pp. 365–374, 2009.

B. Geng, L. Chang, C. Pan et al., “Endogenous hydrogen sulfide regulation of myocardial injury induced by isoproterenol,” Biochemical and Biophysical Research Communications, vol. 318, no. 3, pp. 756–763, 2004.

J. Ma, M. J. Stampfer, C. H. Hennekens et al., “Methylenetetrahydrofolate reductase polymorphism, plasma folate, homocysteine, and risk of myocardial infarction in US physicians,” Circulation, vol. 94, no. 10, pp. 2410–2416, 1996.

P. A. van Zwieten, “Hydrogen sulphide,” Journal of Hypertension, vol. 21, no. 10, pp. 1819-1820, 2003.

P. Kamoun, M. C. Belardinelli, A. Chabli, K. Lallouchi, and B. Chadefaux-Vekemans, “Endogenous hydrogen sulfide overproduction in down syndrome,” American Journal of Medical Genetics, vol. 116A, no. 3, pp. 310-311, 2002.

K. Eto, T. Asada, K. Arima, T. Makifuchi, and H. Kimura, “Brain hydrogen sulfide is severely decreased in Alzheimer’s disease,” Biochemical and Biophysical Research Communications, vol. 293, no. 5, pp. 1485–1488, 2002.

D. Jiménez, R. Martínez-Máñez, F. Sancenón, J. V. Ros-Lis, A. Benito, and J. Soto, “A new chromo-chemodosimeter selective for sulfide anion,” Journal of the American Chemical Society, vol. 125, no. 30, pp. 9000-9001, 2003.

N. S. Lawrence, J. Davis, L. Jiang, T. G. J. Jones, S. N. Davies, and R. G. Compton, “The electrochemical analog of the methylene blue reaction: a novel amperometric approach to the detection of hydrogen sulfide,” Electroanalysis, vol. 12, no. 18, pp. 1453–1460, 2000.

M. T. Alvarez, C. Crespo, and B. Mattiasson, “Precipitation of Zn(II), Cu(II) and Pb(II) at bench-scale using biogenic hydrogen sulfide from the utilization of volatile fatty acids,” Chemosphere, vol. 66, no. 9, pp. 1677–1683, 2007.

J. Furne, A. Saeed, and M. D. Levitt, “Whole tissue hydrogen sulfide concentrations are orders of magnitude lower than presently accepted values,” American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, vol. 295, no. 5, pp. R1479–R1485, 2008.

T. Ubuka, “Assay methods and biological roles of labile sulfur in animal tissues,” Journal of Chromatography B, vol. 781, no. 1-2, pp. 227–249, 2002.

Y. Ding, W. H. Zhu, and Y. Xie, “Development of ion chemosensors based on porphyrin analogues,” Chemical Reviews, vol. 117, no. 4, pp. 2203–2256, 2016.

J. Wang, Y. Hao, H. Wang et al., “Rapidly responsive and highly selective fluorescent probe for bisulfite detection in food,” Journal of Agricultural and Food Chemistry, vol. 65, no. 13, pp. 2883–2887, 2017.

Y. Ji, L. J. Xia, L. Chen, X. F. Guo, H. Wang, and H. J. Zhang, “A novel BODIPY-based fluorescent probe for selective detection of hydrogen sulfide in living cells and tissues,” Talanta, vol. 181, pp. 104–111, 2018.

J. Ou-Yang, W. L. Jiang, K. Y. Tan et al., “Two-photon fluorescence probe for precisely detecting endogenous H₂S in lysosome by employing a dual lock system,” Sensors and Actuators B: Chemical, vol. 260, pp. 264–273, 2018.

P. Wu, J. Zhang, S. Wang, A. Zhu, and X. Hou, “Sensing during in situ growth of Mn-doped ZnS QDs: a phosphorescent sensor for detection of H₂S in biological samples,” Chemistry-A European Journal, vol. 20, no. 4, pp. 952–956, 2013.

A. Shamirian, H. Samareh Afsari, D. Wu, L. W. Miller, and P. T. Snee, “Ratiometric QD-FRET sensing of aqueous H₂S in vitro,” Analytical Chemistry, vol. 88, no. 11, pp. 6050–6056, 2016.

W. Chen, A. Pacheco, Y. Takano, J. J. Day, K. Hanaoka, and M. Xian, “A single fluorescent probe to visualize hydrogen sulfide and hydrogen polysulfides with different fluorescence signals,” Angewandte Chemie International Edition, vol. 55, no. 34, pp. 9993–9996, 2016.

Q. Han, Z. Mou, H. Wang et al., “Highly selective and sensitive one- and two-photon ratiometric fluorescent probe for intracellular hydrogen polysulfide sensing,” Analytical Chemistry, vol. 88, no. 14, pp. 7206–7212, 2016.

J. Zhang, X. Y. Zhu, X. X. Hu et al., “Ratiometric two-photon fluorescent probe for in vivo hydrogen polysulfides detection and imaging during lipopolysaccharide-induced acute organs injury,” Analytical Chemistry, vol. 88, no. 23, pp. 11892–11899, 2016.

S. Ding, W. Feng, and G. Feng, “Rapid and highly selective detection of H₂S by nitrobenzofurazan (NBD) ether-based fluorescent probes with an aldehyde group,” Sensors and Actuators B: Chemical, vol. 238, pp. 619–625, 2017.

Y. Zhou, X. Zhang, S. Yang et al., “Ratiometric visualization of NO/H₂S cross-talk in living cells and tissues using a nitroxyl-responsive two-photon fluorescence probe,” Analytical Chemistry, vol. 89, no. 8, pp. 4587–4594, 2017.

Y. Zhang, M. Zhao, and D. Chao, “A cyclometalated iridium(III) complex for selective luminescent detection of hydrogen sulfide,” Sensors and Actuators B: Chemical, vol. 248, pp. 19–23, 2017.

T. Liu, Z. Xu, D. R. Spring, and J. Cui, “A lysosome-targetable fluorescent probe for imaging hydrogen sulfide in living cells,” Organic Letters, vol. 15, no. 9, pp. 2310–2313, 2013.

H. Li, W. Peng, W. Feng et al., “A novel dual-emission fluorescent probe for the simultaneous detection of H₂S and GSH,” Chemical Communications, vol. 52, no. 25, pp. 4628–4631, 2016.

Q. L. Xie, W. Liu, X. J. Liu, F. Ouyang, Y. Q. Kuang, and J. H. Jiang, “An azidocoumarin-based fluorescent probe for imaging lysosomal hydrogen sulfide in living cells,” Analytical Methods, vol. 9, no. 19, pp. 2859–2864, 2017.

K. Sasakura, K. Hanaoka, N. Shibuya et al., “Development of a highly selective fluorescence probe for hydrogen sulfide,” Journal of the American Chemical Society, vol. 133, no. 45, pp. 18003–18005, 2011.

L. Wang, X. Chen, and D. Cao, “A nitroolefin functionalized DPP fluorescent probe for the selective detection of hydrogen sulfide,” New Journal of Chemistry, vol. 41, no. 9, pp. 3367–3373, 2017.

Q. Chen, P. Xing, Y. Xu, H. Li, and S. Sun, “A selective fluorescent sensor for fast detection of hydrogen sulfide in red wine,” Chinese Journal of Chemistry, vol. 35, no. 4, pp. 477–482, 2017.

Y. Zhao, T. D. Biggs, and M. Xian, “Hydrogen sulfide (H₂S) releasing agents: chemistry and biological applications,” Chemical Communications, vol. 50, no. 80, pp. 11788–11805, 2014.

X. Jin, S. Wu, M. She et al., “Novel fluorescein-based fluorescent probe for detecting H₂S and its real applications in blood plasma and biological imaging,” Analytical Chemistry, vol. 88, no. 22, pp. 11253–11260, 2016.