- Email: [email protected]
Catalytic-oxidation of Janus green in the presence of AgNPs: Application to the determination of iodate
G Model
JIEC-1866; No. of Pages 3 Journal of Industrial and Engineering Chemistry xxx (2014) xxx–xxx
Contents lists available at ScienceDirect
Journal of Industrial and Engineering Chemistry journal homepage: www.elsevier.com/locate/jiec
Catalytic-oxidation of Janus green in the presence of AgNPs: Application to the determination of iodate S.S. Mortazavi a,*, A. Farmany b a b
Young Researchers & Elite Club, Hamedan Branch, Islamic Azad University, Hamedan, Iran Departments of Chemistry, Hamedan Branch, Islamic Azad University, Hamedan, Iran
A R T I C L E I N F O
Article history: Received 20 December 2013 Accepted 6 January 2014 Available online xxx Keywords: AgNPs Iodate Oxidation Catalytic reaction Real samples
A B S T R A C T
Catalytic-oxidation of Janus green was made in the presence of AgNPs. The reaction was monitored spectrophotometrically at 610 nm. The system was optimized for the trace analysis of iodate. The method is featured with good accuracy and reproducibility for iodate monitoring in real samples without any pre-concentration and separation step. ß 2014 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.
1. Introduction As a trace element, iodine is essential to animal and plants. It is an essential part of the thyroid hormones that play an important role in the growth of cell. Deficiency of iodine causes serious delay in neurological development. On the other hand, an excess of iodine or iodide can cause goiter and hypothyroidism as well as hyperthyroidism [1]. Drugs, specially, table salt is iodized by iodate as a source of iodine in order to prevent iodine deficiency. At this time a few reports are present concerning the determination of iodate [2–9]. The aim of this present work was to develop a rapid, simple, sensitive and accurate method for the determination of iodate ion in water, based on the reaction of iodate with Janus greed in acidic media. The system was monitored spectrophotometrically by measuring the decrease in absorbance of the dye at 610 nm. 2. Materials and methods 2.1. Apparatus All absorbance measurements were carried out on a Scinco’s PDA UV–vis spectrophotometer (photodiode array) using a quartz cell with an optical path of 1 cm. All pH measurements were made with a 780 pH meter (Metrohm, Switzerland) combined with a
glace-calomel electrode. TEM image of the Ag nanoparticles was obtained using a JEOL model JEM-100CX microscope at an acceleration voltage of 80 kV. 2.2. Reagents All chemicals were of analytical-reagent grade double-distilled water was used throughout the study. A stock solution of Janus green (103 M) was prepared by dissolving the appropriate amount of Janus green in double-distilled water. Potassium iodate solution (0.1 M) was prepared by dissolving appropriate amount of potassium iodate salt in 100 mL double-distilled water. Acetate– acetic acid buffer was used. 2.3. Procedure In a 25 mL test tube, 0.2 M acetate–acetic acid, 0.3 M AgNPs solution and 2.5 mM Janus green solution were placed. After diluting the solution with double-distilled water, the solution was put in a 1.0 cm quartz cell. The initial absorbance (Ai) at 610 nm was recorded. After addition of different amounts of iodate, the mixture was equilibrated at room temperature for 100 s. Then the final absorbance (Af) was recorded at 610 nm. The absorbance difference was defined as DA610 ¼ Ai Af . 2.4. Synthesis of silver nanoparticles
* Corresponding author. Tel.: +98 811 4494143; fax: +98 811 4494143. E-mail address: [email protected] (S.S. Mortazavi).
The AgNPs were synthesized in a one-step reduction process in an aqueous solution. In a typical preparation, a 400 mL aliquot of a
http://dx.doi.org/10.1016/j.jiec.2014.01.024 1226-086X/ß 2014 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.
Please cite this article in press as: S.S. Mortazavi, A. Farmany, J. Ind. Eng. Chem. (2014), http://dx.doi.org/10.1016/j.jiec.2014.01.024
G Model
JIEC-1866; No. of Pages 3 S.S. Mortazavi, A. Farmany / Journal of Industrial and Engineering Chemistry xxx (2014) xxx–xxx
2
0.1 M AgNO3 aqueous solution was added into 100 mL of an aqueous solution containing 0.10 wt% of the soluble starch and vigorously stirred for 1 h. The pH of resulting solution was adjusted to 8.0 by adding a 0.1 M NaOH solution. Under this experimental condition, the initial reaction mixture was colorless and the growth of the AgNPs was monitored at different intervals using UV–vis absorption spectroscopy. After about 1 h the solution turned light yellow, which indicated the initial formation of the AgNPs. The mixture was maintained at 50 8C for 24 h and the color of the reaction solution became yellow. 3. Results and discussions 3.1. Monitoring the reaction Formation of AgNPs in the colloidal solution was monitored from their absorption spectra as the small noble metal particles reveal absorption band in the UV–vis spectral region due to surface plasmon resonance (SPR) [10]. The process of reduction of the silver ions using the starch was slow, yielding a broad absorption band centered at about 400 nm until 1 h of reaction, which was assigned to the SPR of AgNPs (see Fig. 1). The broadband indicates a relatively high polydispersity, both in size and shape of the Ag particles (see Fig. 2). The intensity of the SPR band increased systematically with the increase of reaction time, to reach a maximum after about 24 h. There after, the intensity of the SPR band did not change. The reduction of silver ions with starch aqueous solution at 50 8C leads to the formation of AgNPs that are stable in solution for several months. This indicates that the soluble starch serves as both reducing and protecting agent. The broad spectrum of nanotechnology is important in the major fields of chemistry, physics, biology, and material sciences. Nanotechnology deals with the study of materials at the nanometers. Metal nanoparticles have been an extensive area of research because of their unique chemical, physical, and optical properties. These make them potential candidates in the field of catalysis, labeling, biosensing, etc. [11–14]. At this time, several work reported the catalytic oxidation/reduction of organic dyes using AgNPs [14–16]. In the present work, we use the AgNPs as catalytic agent of the reaction between iodate and Janus green. It is interesting that AgNPs, increase the oxidation of Janus green by potassium iodate, dramatically 3.2. Effects of variables Primary study shows that the reaction rate depends strongly on the concentrations of buffer, Janus green dye, and AgNPs and the
Fig. 2. TEM of AgNPs.
temperature. The reaction conditions were carefully set so that the uncatalyzed reaction was suppressed and the catalyzed dominated. Several types of buffers with different concentrations were used. The result shows that acetate–acetic acid gives greater sensitivity. The optimum value of acetate–acetic acid concentration is obtained as 0.2 M of acetate–acetic acid buffer. Whereas the greater amounts of acid decreased the sensitivity of the method. The effect of AgNPs concentration on the catalytic system is explored. The data obtained were used for the plot of DA versus concentration of AgNPs. The results show that 0.3 M AgNPs was the best. The effect of Janus green concentration on the catalytic determination of iodate is studied. The results demonstrate that A610 value increased with an increase in Janus green concentration to 2.0 mM Janus green concentration. Greater amounts of Janus green decrease the sensitivity. This is due to the fact that at higher concentration of Janus green, the coagulation of azo dye diminishes the analytical signal. The effect of the temperature on the reaction rate was studied m the range 10–45 8C. The results show that the initial slopes of the reaction curve become steeper with the temperature, while the uncatalyzed reaction, under the previously mentioned conditions, was negligible in this temperature range. A temperature of 25 8C (room temperature) was adopted for the analytical applications. 3.3. Calibration curve & limit of detection (LOD) and interference study Under the optimum working conditions reported above, calibration graphs were constructed covering the ranges of 70– 320 ng/ml while further extension to higher values could be achieved. The regression equation was A610 = 0.0350X nM + 0.170, where X is the iodate concentration. The limit of detection (LOD) was calculated as 25 ng/ml on the basis of 10 blank measurements. To study the selectivity of the proposed method, the effect of foreign species on the determination of 100 ng/ml of iodate was tested. The tolerance limit was defined as the concentration at which the species caused an error less than 3s. The results show that BrO3, I, Br, Cu2+, Fe3+ Ni2+, Mn2+ are interfering in the quantification of iodate. 3.4. Application
Fig. 1. Temporal evolution of UV–vis absorption spectra after addition of AgNO3 solution into soluble starch solution at 50 8C.
To investigate the applicability of the proposed method to real sample analysis, the method was applied to monitoring of iodate in water samples. The standard addition method is used to quantify the iodate concentration in real samples. The reason for using the standard additions method is that the matrix of real sample may contain other components that interfere with the analyte signal
Please cite this article in press as: S.S. Mortazavi, A. Farmany, J. Ind. Eng. Chem. (2014), http://dx.doi.org/10.1016/j.jiec.2014.01.024
G Model
JIEC-1866; No. of Pages 3 S.S. Mortazavi, A. Farmany / Journal of Industrial and Engineering Chemistry xxx (2014) xxx–xxx Table 1 Determination of iodate in three water samples (n = 3). Iodate added (nM)
Iodate found (nM)
Recovery (%)
A
80 100 120
78.5 100.3 119.4
98.1 100.3 99.5
B
80 100 120
79.3 99.5 120.2
99.1 99.5 100.1
80 100 120
78.5 98.8 119.4
98.2 98.8 99.5
Sample
C
causing inaccuracy in the determined concentration. The results show Table 1 that the proposed method is sensitive and selective for the determination of trace iodate in real samples with the satisfactory results. 4. Conclusion In this paper, a direct, simple, relatively rapid, low cost, highly sensitive and selective method is proposed for the quantification of
3
trace level of iodate based on the catalytic effect of AgNPs on the oxidation of Janus green in acetate–acetic acid buffer media. The method was directly applied to the determination of iodate in water samples without any pre-concentration step.
References [1] A.G. Gilman, L.S. Goodman, T.W. Rad, F. Murad, The Pharmacological Basis of Therapeutics, 7th edition, Macmillan, New York, 1985p. 964. [2] M. Kamburova, Talanta 39 (1992) 997. [3] A. Afkhami, A.R. Zarei, Talanta 53 (2001) 815. [4] A.A. Ensafi, G.B. Dehaghi, Anal. Sci. 16 (2000) 61. [5] M.S. El-Shahawi, F.A. Al-Hashemi, Talanta 43 (1996) 2037. [6] A. Afkhami, F. Mosaed, Microchem. J. 68 (2001) 35. [7] N. Jie, X. Sun, J. Yang, Q. Zhang, Z. Liu, Anal. Lett. 30 (1997) 2441. [8] N. Jie, D. Yang, Q. Zhang, J. Yang, Z. Song, Anal. Chim. Acta 359 (1998) 87. [9] O.F. Kamson, Anal. Chim. Acta 179 (1986) 475. [10] H. Huang, X. Yang, Carbohydr. Res. 339 (2004) 2627. [11] J. Zhong-Jie, L. Chun-Yan, S. Lu-Wei, J. Phys. Chem. B 109 (2005) 1730. [12] A.M. Signori, K.de O. Santos, R. Eising, B.L. Albuquerque, F.C. Giacomelli, J.B. Domingos, Langmuir 26 (2010) 17772. [13] K.de O. Santos, W.C. Elias, A.M. Signori, F.C. Giacomelli, H. Yang, J.B. Domingos, J. Phys. Chem. C 116 (7) (2012) 4594. [14] Z.J. Jiang, C.Y. Liu, L. Sun, J. Phys. Chem. B 109 (2005) 1730. [15] C. Dong, J. Zhang, D.-Z. Zhou, J. Meas. Sci. Instrum. 1 (2010) 61. [16] N.R. Jana, T.K. Sau, T. Pal, J. Phys. Chem. B 103 (1999) 115.
Please cite this article in press as: S.S. Mortazavi, A. Farmany, J. Ind. Eng. Chem. (2014), http://dx.doi.org/10.1016/j.jiec.2014.01.024
JIEC-1866; No. of Pages 3 Journal of Industrial and Engineering Chemistry xxx (2014) xxx–xxx
Contents lists available at ScienceDirect
Journal of Industrial and Engineering Chemistry journal homepage: www.elsevier.com/locate/jiec
Catalytic-oxidation of Janus green in the presence of AgNPs: Application to the determination of iodate S.S. Mortazavi a,*, A. Farmany b a b
Young Researchers & Elite Club, Hamedan Branch, Islamic Azad University, Hamedan, Iran Departments of Chemistry, Hamedan Branch, Islamic Azad University, Hamedan, Iran
A R T I C L E I N F O
Article history: Received 20 December 2013 Accepted 6 January 2014 Available online xxx Keywords: AgNPs Iodate Oxidation Catalytic reaction Real samples
A B S T R A C T
Catalytic-oxidation of Janus green was made in the presence of AgNPs. The reaction was monitored spectrophotometrically at 610 nm. The system was optimized for the trace analysis of iodate. The method is featured with good accuracy and reproducibility for iodate monitoring in real samples without any pre-concentration and separation step. ß 2014 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.
1. Introduction As a trace element, iodine is essential to animal and plants. It is an essential part of the thyroid hormones that play an important role in the growth of cell. Deficiency of iodine causes serious delay in neurological development. On the other hand, an excess of iodine or iodide can cause goiter and hypothyroidism as well as hyperthyroidism [1]. Drugs, specially, table salt is iodized by iodate as a source of iodine in order to prevent iodine deficiency. At this time a few reports are present concerning the determination of iodate [2–9]. The aim of this present work was to develop a rapid, simple, sensitive and accurate method for the determination of iodate ion in water, based on the reaction of iodate with Janus greed in acidic media. The system was monitored spectrophotometrically by measuring the decrease in absorbance of the dye at 610 nm. 2. Materials and methods 2.1. Apparatus All absorbance measurements were carried out on a Scinco’s PDA UV–vis spectrophotometer (photodiode array) using a quartz cell with an optical path of 1 cm. All pH measurements were made with a 780 pH meter (Metrohm, Switzerland) combined with a
glace-calomel electrode. TEM image of the Ag nanoparticles was obtained using a JEOL model JEM-100CX microscope at an acceleration voltage of 80 kV. 2.2. Reagents All chemicals were of analytical-reagent grade double-distilled water was used throughout the study. A stock solution of Janus green (103 M) was prepared by dissolving the appropriate amount of Janus green in double-distilled water. Potassium iodate solution (0.1 M) was prepared by dissolving appropriate amount of potassium iodate salt in 100 mL double-distilled water. Acetate– acetic acid buffer was used. 2.3. Procedure In a 25 mL test tube, 0.2 M acetate–acetic acid, 0.3 M AgNPs solution and 2.5 mM Janus green solution were placed. After diluting the solution with double-distilled water, the solution was put in a 1.0 cm quartz cell. The initial absorbance (Ai) at 610 nm was recorded. After addition of different amounts of iodate, the mixture was equilibrated at room temperature for 100 s. Then the final absorbance (Af) was recorded at 610 nm. The absorbance difference was defined as DA610 ¼ Ai Af . 2.4. Synthesis of silver nanoparticles
* Corresponding author. Tel.: +98 811 4494143; fax: +98 811 4494143. E-mail address: [email protected] (S.S. Mortazavi).
The AgNPs were synthesized in a one-step reduction process in an aqueous solution. In a typical preparation, a 400 mL aliquot of a
http://dx.doi.org/10.1016/j.jiec.2014.01.024 1226-086X/ß 2014 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.
Please cite this article in press as: S.S. Mortazavi, A. Farmany, J. Ind. Eng. Chem. (2014), http://dx.doi.org/10.1016/j.jiec.2014.01.024
G Model
JIEC-1866; No. of Pages 3 S.S. Mortazavi, A. Farmany / Journal of Industrial and Engineering Chemistry xxx (2014) xxx–xxx
2
0.1 M AgNO3 aqueous solution was added into 100 mL of an aqueous solution containing 0.10 wt% of the soluble starch and vigorously stirred for 1 h. The pH of resulting solution was adjusted to 8.0 by adding a 0.1 M NaOH solution. Under this experimental condition, the initial reaction mixture was colorless and the growth of the AgNPs was monitored at different intervals using UV–vis absorption spectroscopy. After about 1 h the solution turned light yellow, which indicated the initial formation of the AgNPs. The mixture was maintained at 50 8C for 24 h and the color of the reaction solution became yellow. 3. Results and discussions 3.1. Monitoring the reaction Formation of AgNPs in the colloidal solution was monitored from their absorption spectra as the small noble metal particles reveal absorption band in the UV–vis spectral region due to surface plasmon resonance (SPR) [10]. The process of reduction of the silver ions using the starch was slow, yielding a broad absorption band centered at about 400 nm until 1 h of reaction, which was assigned to the SPR of AgNPs (see Fig. 1). The broadband indicates a relatively high polydispersity, both in size and shape of the Ag particles (see Fig. 2). The intensity of the SPR band increased systematically with the increase of reaction time, to reach a maximum after about 24 h. There after, the intensity of the SPR band did not change. The reduction of silver ions with starch aqueous solution at 50 8C leads to the formation of AgNPs that are stable in solution for several months. This indicates that the soluble starch serves as both reducing and protecting agent. The broad spectrum of nanotechnology is important in the major fields of chemistry, physics, biology, and material sciences. Nanotechnology deals with the study of materials at the nanometers. Metal nanoparticles have been an extensive area of research because of their unique chemical, physical, and optical properties. These make them potential candidates in the field of catalysis, labeling, biosensing, etc. [11–14]. At this time, several work reported the catalytic oxidation/reduction of organic dyes using AgNPs [14–16]. In the present work, we use the AgNPs as catalytic agent of the reaction between iodate and Janus green. It is interesting that AgNPs, increase the oxidation of Janus green by potassium iodate, dramatically 3.2. Effects of variables Primary study shows that the reaction rate depends strongly on the concentrations of buffer, Janus green dye, and AgNPs and the
Fig. 2. TEM of AgNPs.
temperature. The reaction conditions were carefully set so that the uncatalyzed reaction was suppressed and the catalyzed dominated. Several types of buffers with different concentrations were used. The result shows that acetate–acetic acid gives greater sensitivity. The optimum value of acetate–acetic acid concentration is obtained as 0.2 M of acetate–acetic acid buffer. Whereas the greater amounts of acid decreased the sensitivity of the method. The effect of AgNPs concentration on the catalytic system is explored. The data obtained were used for the plot of DA versus concentration of AgNPs. The results show that 0.3 M AgNPs was the best. The effect of Janus green concentration on the catalytic determination of iodate is studied. The results demonstrate that A610 value increased with an increase in Janus green concentration to 2.0 mM Janus green concentration. Greater amounts of Janus green decrease the sensitivity. This is due to the fact that at higher concentration of Janus green, the coagulation of azo dye diminishes the analytical signal. The effect of the temperature on the reaction rate was studied m the range 10–45 8C. The results show that the initial slopes of the reaction curve become steeper with the temperature, while the uncatalyzed reaction, under the previously mentioned conditions, was negligible in this temperature range. A temperature of 25 8C (room temperature) was adopted for the analytical applications. 3.3. Calibration curve & limit of detection (LOD) and interference study Under the optimum working conditions reported above, calibration graphs were constructed covering the ranges of 70– 320 ng/ml while further extension to higher values could be achieved. The regression equation was A610 = 0.0350X nM + 0.170, where X is the iodate concentration. The limit of detection (LOD) was calculated as 25 ng/ml on the basis of 10 blank measurements. To study the selectivity of the proposed method, the effect of foreign species on the determination of 100 ng/ml of iodate was tested. The tolerance limit was defined as the concentration at which the species caused an error less than 3s. The results show that BrO3, I, Br, Cu2+, Fe3+ Ni2+, Mn2+ are interfering in the quantification of iodate. 3.4. Application
Fig. 1. Temporal evolution of UV–vis absorption spectra after addition of AgNO3 solution into soluble starch solution at 50 8C.
To investigate the applicability of the proposed method to real sample analysis, the method was applied to monitoring of iodate in water samples. The standard addition method is used to quantify the iodate concentration in real samples. The reason for using the standard additions method is that the matrix of real sample may contain other components that interfere with the analyte signal
Please cite this article in press as: S.S. Mortazavi, A. Farmany, J. Ind. Eng. Chem. (2014), http://dx.doi.org/10.1016/j.jiec.2014.01.024
G Model
JIEC-1866; No. of Pages 3 S.S. Mortazavi, A. Farmany / Journal of Industrial and Engineering Chemistry xxx (2014) xxx–xxx Table 1 Determination of iodate in three water samples (n = 3). Iodate added (nM)
Iodate found (nM)
Recovery (%)
A
80 100 120
78.5 100.3 119.4
98.1 100.3 99.5
B
80 100 120
79.3 99.5 120.2
99.1 99.5 100.1
80 100 120
78.5 98.8 119.4
98.2 98.8 99.5
Sample
C
causing inaccuracy in the determined concentration. The results show Table 1 that the proposed method is sensitive and selective for the determination of trace iodate in real samples with the satisfactory results. 4. Conclusion In this paper, a direct, simple, relatively rapid, low cost, highly sensitive and selective method is proposed for the quantification of
3
trace level of iodate based on the catalytic effect of AgNPs on the oxidation of Janus green in acetate–acetic acid buffer media. The method was directly applied to the determination of iodate in water samples without any pre-concentration step.
References [1] A.G. Gilman, L.S. Goodman, T.W. Rad, F. Murad, The Pharmacological Basis of Therapeutics, 7th edition, Macmillan, New York, 1985p. 964. [2] M. Kamburova, Talanta 39 (1992) 997. [3] A. Afkhami, A.R. Zarei, Talanta 53 (2001) 815. [4] A.A. Ensafi, G.B. Dehaghi, Anal. Sci. 16 (2000) 61. [5] M.S. El-Shahawi, F.A. Al-Hashemi, Talanta 43 (1996) 2037. [6] A. Afkhami, F. Mosaed, Microchem. J. 68 (2001) 35. [7] N. Jie, X. Sun, J. Yang, Q. Zhang, Z. Liu, Anal. Lett. 30 (1997) 2441. [8] N. Jie, D. Yang, Q. Zhang, J. Yang, Z. Song, Anal. Chim. Acta 359 (1998) 87. [9] O.F. Kamson, Anal. Chim. Acta 179 (1986) 475. [10] H. Huang, X. Yang, Carbohydr. Res. 339 (2004) 2627. [11] J. Zhong-Jie, L. Chun-Yan, S. Lu-Wei, J. Phys. Chem. B 109 (2005) 1730. [12] A.M. Signori, K.de O. Santos, R. Eising, B.L. Albuquerque, F.C. Giacomelli, J.B. Domingos, Langmuir 26 (2010) 17772. [13] K.de O. Santos, W.C. Elias, A.M. Signori, F.C. Giacomelli, H. Yang, J.B. Domingos, J. Phys. Chem. C 116 (7) (2012) 4594. [14] Z.J. Jiang, C.Y. Liu, L. Sun, J. Phys. Chem. B 109 (2005) 1730. [15] C. Dong, J. Zhang, D.-Z. Zhou, J. Meas. Sci. Instrum. 1 (2010) 61. [16] N.R. Jana, T.K. Sau, T. Pal, J. Phys. Chem. B 103 (1999) 115.
Please cite this article in press as: S.S. Mortazavi, A. Farmany, J. Ind. Eng. Chem. (2014), http://dx.doi.org/10.1016/j.jiec.2014.01.024