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Modified iron oxide nanoparticles as solid phase extractor for spectrophotometeric determination and separation of basic fuchsin
Talanta 77 (2009) 1328–1331
Contents lists available at ScienceDirect
Talanta journal homepage: www.elsevier.com/locate/talanta
Modified iron oxide nanoparticles as solid phase extractor for spectrophotometeric determination and separation of basic fuchsin B. Zargar ∗ , H. Parham, A. Hatamie Chemistry Department, College of Science, Shahid Chamran University, Ahvaz, Iran
a r t i c l e
i n f o
Article history: Received 23 July 2008 Received in revised form 3 September 2008 Accepted 4 September 2008 Available online 18 September 2008 Keywords: Iron oxide nanoparticles Sodium dodecyl sulfate Preconcentration Basic fuchsin Determination Spectrophotometry
a b s t r a c t This study presents a novel separation, preconcentration and determination of basic fuchsin (BF) in an aqueous solution by sodium dodecyl sulfate (SDS)-bounded iron oxide nanoparticles (S-IONPs). It is shown that the novel magnetic nano-adsorbent is quite efficient for the adsorption and desorption of BF at 25 ◦ C. Different parameters such as pH, temperature, ionic strength and composition of desorbent solvent were optimized. The effect of some co-existing ions on the determination was investigated. The nanoparticles were analyzed by transmission electron microscopy (TEM) and the sizes of S-IONPs were in the range of 20–100 nm. The method showed good linearity for the determination of BF in the range of 10–300 ng mL−1 with a regression coefficient of 0.9989. The limit of detection (LOD) (signal-to-noise ratio of 3:1) was 0.0073 g L−1 and the relative standard deviation (RSD) for 0.03 g mL−1 and 0.2 g mL−1 of BF were 4.53% and 4.73%, respectively. The BF was determined successfully in spiked samples of Karoon River water. © 2008 Elsevier B.V. All rights reserved.
1. Introduction The treatment of industrial effluents is a challenging topic in environmental sciences, since control of water pollution has become of increasing importance in recent years [1]. Effluents from the textile industries are important sources of water pollutions, because wastewater dyes undergoes chemical as well as biological changes, consume dissolved oxygen, and destroy aquatic life. Moreover, some dyes and their degradation products may be carcinogenic and/or toxic. Therefore, it is necessary to treat textile effluents prior to their discharge into receiving water [2]. Basic fuchsin (BF) (Fig. 1) is a triphenylmethane dye with molecular formula of C20 H20 ClN3 and is one of those rare dyes that are inflammable in nature. It is widely used as coloring agent in textile and leather industries and also is used to stain collagen, muscle, mitochondria, and tubercle bacillus. BF possesses anesthetic, bactericidal (Gram positive), and fungicidal properties. The physical contact with the dye may cause severe eye and skin irritation. Its ingestion may cause gastrointestinal irritation with nausea, vomiting, and diarrhea and the inhalation of the dye causes irritation to the respiratory tract [3]. Keeping the toxicity of the dye in mind, there is a need to develop effective methods for its removal, recovery and determination in
∗ Corresponding author. Tel.: +98 611 3331094 fax: +98 611 3331098. E-mail address: zargar [email protected] (B. Zargar). 0039-9140/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.talanta.2008.09.011
wastewater. Several methods have been tried to remove various dyes with different adsorbents [2]. Recently magnetic nanoparticles as a new adsorbent with large surface area and small diffusion resistance have been recognized [4]. Ferrofluids are colloidal dispersions of small single domain magnetic particles suspended in a carrier fluid. Ferrofluids characteristically have both magnetic and fluid properties [5]. Nanosized magnetic iron oxide particles have been studied extensively due to their wide range of applications in ferrofluids, high-density information storage, magnetic resonance imaging (MRI), biological cell labeling and sorting, separation of biochemicals, targeting, and drug delivery. For many of these applications, surface modification of nanosized magnetic particles is a key of challenge [6–10]. In general, surface modification can be accomplished by physical and/or chemical adsorption of the desired molecules to coat the surface, depending on the specific applications [11]. Several methods for the separation and removal of chemical species such as metals [12–16], dyes [2,17–19] and gases [20] have been reported. The stability of dispersed particles and magnetic properties are of most importance. The nanoparticles which have a large ratio of surface area to volume, tends to agglomerate in order to reduce their surface energy by strong magnetic dipole–dipole and London-van der Waals attractions between particles. These nanoparticles can be coated with surfactants and as a result prevent their aggregation in liquids and improve their chemical stability. The repulsive interactions between particles can be created by coating a surfactant layer on particle surfaces [21].
B. Zargar et al. / Talanta 77 (2009) 1328–1331
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Fig. 2. Suggested mechanism for the adsorption of sodium dodecyl sulfate on the surface of IONP.
Fig. 1. Chemical structure of basic fuchsin.
Diluted ferrofluid dispersions are not stable. Therefore anionic and cationic surfactants are used as stabilizer. In this study, we used sodium dodecyl sulfate (SDS) which is an anionic surfactant and tends to interact with surface of nanoparticles and coated them. Iron oxide magnetic nanoparticles as cores and SDS as ionic exchange groups were used for recovery and determination of BF dye. 2. Experimental 2.1. Chemicals and reagents
separated magnetically and the initial red colored solution became colorless. The mixture was decanted and the solution above the nanoparticles was removed completely. Finally 2.5 mL of desorbent solution (a mixture of methanol and acetic acid with a ratio of 80:20, v/v) was added to the BF-S-IONPs in a beaker. The beaker was placed on the magnet and the mixture was decanted. The absorption of the solution which has been separated from IONPs by magnet was measured spectrophotometerically at 547 nm. 3. Results and discussion The synthesis of nanoparticles is based on the reaction of ferric and ferrous ions in an aqueous ammonia solution to form magnetite (Fe3 O4 ). Suggested reaction for the formation of nanoparticles is as follow [20]: 2FeCl3 + FeCl2 + 8NH3 + 4H2 O → Fe3 O4 + 8NH4 Cl Experimental conditions such as temperature, rate of ammonia addition and rate of solution stirring have critical effect on the size of nanoparticles.
All chemicals and reagents were of analytical grade. Basic fuchsin, phosphoric acid (85% m/m), methanol (99.9% m/m), ammonia solution (25% m/m), hydrochloric acid (37% m/m), acetic acid (99.9% m/m), FeCl3 (96% m/m), FeCl2 ·4H2 O (99.9% m/m), and sodium dodecyl sulfate were purchased from Merck (Darmstadt, Germany). Phosphate buffer solutions (pH 7) were prepared by adding appropriate amounts of 0.1 M sodium hydroxide solution into a mixture of 0.1 M of phosphoric acid. 2.2. Apparatus The spectrophotometric measurements were carried out with a Cintra 101 spectrophotometer (GBC SCIENTIFIC EQUIPMENT, Australia). A transmission electron microscope (906E, LEO, Germany), pH-meter (632 Metrohm, Herisau, Switzerland) and a super magnet (1.2 T, 10 cm × 5 cm × 2 cm) were used. 2.3. Preparation of SDS-bounded iron oxide nanoparticles (S-IONPs) Iron oxide nanoparticles were prepared according to a previous work [22]. In order to coat the particles, 5 mL of SDS solution (5% m/v) was added to about 5 g of damped nanoparticles in a beaker. The solution was stirred for 1 min by a glassy rod and the beaker was then placed on the magnet. After complete precipitation of S-IONPs occurred the solution was decanted and ferroflouid was washed with distillated water for several times (3 times on average) to eliminate extra amount of surfactant from nanoparticles. 2.4. Adsorption and desorption of BF About 0.6 g of damped S-IONPs (equivalent to 0.06 g dry SIONPs) were added to the 50 mL of BF solution (0.01–1 g mL−1 ) in a beaker. The pH of the solution was adjusted to 7 by addition of 2 mL of 0.03 M of phosphate buffer pH 7. The mixture was stirred by a glassy rod for about 100 s and the beaker was then placed on the magnet. The S-IONPs which adsorbed BF (BF-S-IONPs) were
Fig. 3. Transmission electron microscope images of (a) IONPs and (b) S-IONPs.
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B. Zargar et al. / Talanta 77 (2009) 1328–1331
Fig. 4. Effect of different pH values on the BF separation [conditions: 50 mL of 1 g mL−1 solution of BF; 1 g of damped IONPs; 2.5 mL of desorbent solution (methanol/acetic acid 80:20, v/v)].
The suggested mechanism for the coating of IONP with sodium dodecyl sulfate is shown in Fig. 2. The S-IONPs have bigger sizes compared to the initial IONPs as can be seen by TEM pictures (Fig. 3). IONPs without coating did not adsorb BF but S-IONPs adsorbed BF and separated it from the bulk of solution. The presence of trace amount of IONPs in the spectrophotometer cell could affect the absorption of the solution. It could be eliminated by holding the cell on the magnet for a few second before measuring. Absorption of the desorbed solution was measured at 547 nm instead of 542 nm (as a result of solvent changing from water to a mixture of methanol and acetic acid the max was shifted to higher wavelengths). The pH of the solutions was adjusted by NaOH and HCl to find the optimum pH value. Separation and Determination of BF was performed in the pH range from 2 to 12. The obtained results are shown in Fig. 4. In low pH values, the solution was darkly because iron oxide nanoparticles had begun to dissolve; on the other hand, at high pH values the IONPs were converted to colloidal particles and did not respond to the magnetic field (adsorption of hydroxide ions on the particles surfaces produce a dark colloid suspension). The amount of separation and desorption of BF in the pH range from 5 to 8 was constant and therefore this range was chosen as optimum range for pH. However pH 7 was selected for all other experiments and phosphate buffer was used to obtain this value. The amount of added buffer was investigated and it was demonstrated that with the amount of buffer volume exceeding 2 mL of 0.03 M solution in the 50 mL test sample solution; the amount of separation and adsorption of BF decreases.
Fig. 6. Effect of different compositions of desorbent solution on the desorption of BF from IONPs (conditions: 50 mL of 0.2 g mL−1 solution of BF; pH 7; 0.6 g of damped IONPs; 2.5 mL of desorbent solution).
The required amount of iron nanoparticles for the complete separation of BF in 50 mL solution (containing 1 g mL−1 of BF) at pH 7 was investigated. To this end, different amounts of damped iron nanoparticls were added to the solution following mixing and separation of IONPs with magnet. The adsorption of solution was then measured at 542 nm. The results are shown in Fig. 5. Addition of 0.6 g of damped iron nanoparticls (equivalent to 0.06 g dry IONPs) separated the BF from this solution completely. In order to find the best composition for desorbent solution, we used solutions with different ratios of methanol and acetic acid reported in references to be suitable for this purposes [2]. The obtained results are shown in the Fig. 6. Adsorption of BF by IONPs and it’s desorption by different compositions of desorbent solutions were studied in a constant volume of desorbent solution. Pure methanol and acetic acid (1 M) were used as stock solutions. The obtained results are showed that with 50–70% methanol in the final desorbent solution, the BF can be completely desorbed from nanoparticles surfaces. Addition of desorbent solution in multiple steps (3 steps) can improved the desorption process. The effect of ionic strength on the system was examined in different concentrations of KCl as an electrolyte. The adsorption of BF decreases with increasing the ionic strength of the solution. This implied that electrostatic attraction between the negatively charged SDS ions on the IONPs and positively charged of BF ions was affected by the KCl under the examination conditions. The adsorption of BF was studied in four different temperatures. The recovery of BF was slightly increased with increasing the temperature. The optimum experimental conditions which have been described were used to study the effect of some ions and two red dyes (Rodamin B, Allura red) on the determination process. To this end separation and determination of BF was performed in the presence of co-existing ions. The maximum acceptable error was ±5%. The obtained results are shown in Table 1. The table shows that Ca2+ , Mg2+ and Rodamin B strongly interfered even in the same Table 1 Effect of co-existing ions (conditions: 100 mL BF 0.2 g mL−1 ; pH 7. IONPs: 0.6 g; volume of desorbent solution: 2.5 mL (methanol/acetic acid 60:40, v/v)). Ionsa +
Tolerance ratio (w/w) +
−
−
2+
−
K , Na , Cl , Br , Pb , NO3 I− , F− CO3 Ni2+ Co2+ Ca2+ , Mg2+ , Rodamin B, Allura red Fig. 5. Effect of different amounts of IONPs on the BF separation [conditions: 50 mL of 1 g mL−1 solution of BF; pH 7; 2.5 mL of desorbent solution (methanol/acetic acid 80:20, v/v)].
200 100 60 40 10 1
a All cations were prepared from nitrate salts and anions were prepared from sodium and potassium salts.
B. Zargar et al. / Talanta 77 (2009) 1328–1331 Table 2 Determination of BF in spiked Karoon River water samples. Added BF (g mL−1 ) 0.100 0.150 a
Found BF (g mL−1 ) a
0.096 0.147a
1331
than 5 min. The proposed method is recommended for removal and/or determination of BF in different water samples. Recovery (%) 96.0% 98.0%
Average of three determinations.
concentration with BF. A solution of EDTA was used to eliminate the interference affect of Ca2+ and Mg2+ . 4. Analytical characteristics The calibration curve was linear in the range of 0.01 g mL−1 to 0.3 g mL−1 of BF with an equation of y = 4.2113 x + 0.1222 (R = 0.9989) in which y is absorbance and x is concentration of BF (g mL−1 ). The relative standard deviation (n = 8) for 0.2 g mL−1 and 0.03 g mL−1 of BF were 4.53% and 4.73%, respectively and the LOD of the method was 0.0073 g mL−1 . The enrichment factor of the method was calculated to be 40. 5. Analysis of Karoon River water sample To determine the ability of the proposed method for the analysis of BF in a real sample, Karoon River water was spiked. The spiked levels were 100 ng mL−1 and 150 ng mL−1 of BF. The spiked solutions were successfully determined in two different river waters samples. The results are summarized in Table 2. Excellent recoveries indicated that the complex matrix of river water samples does not interfere with the analysis of BF. 6. Conclusion Basic fuchsin could be removed from an aqueous solution by the SDS-bounded iron oxide nanoparticles. The nanoparticles can rapidly adsorbed BF and desorbed it in a suitable solution in less
Acknowledgement The authors wish to thank Shahid Chamran University Research Council for financial support of this work (Grant 1386). References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16]
[17] [18] [19] [20] [21] [22]
V. Rocher, J.M. Siaugue, V. Cabuil, A. Bee, Water Res. 42 (2008) 1290. S.Y. Mak, D.H. Chen, Dyes Pigments 61 (2004) 93. V.K. Gupta, A. Mittal, V. Gajbe, J. Mittal, J. Colloid Interface Sci. 319 (2008) 30. M.H. Liao, D.H. Chen, Biotechnol. Lett. 24 (2002) 1913. C.L. Lin, C.F. Lee, W.Y. Chiu, J. Colloid Interface Sci. 291 (2005) 411. H.Y. Shen, Y. Zhu, X. Wen, Y. Zhuang, Anal. Bioanal. Chem. 387 (2007) 2227. S.S. Banerjee, D.H. Chen, J. Hazard. Mater. 147 (2007) 792. I. Safarik, L.F.T. Rego, M. Borovska, E.M. Szablewskae, F. Weyda, M. Safarikova, Enzyme Microb. Technol. 40 (2007) 1551. J. Li, X. Zhao, Y. Shi, Y. Cai, S. Mou, G. Jiang, J. Chromatogr. A 1180 (2008) 24. Y.C. Chang, D.H. Chen, J. Colloid Interface Sci. 283 (2005) 446. M. Takafuji, S. Ide, H. Ihara, Z. Xu, Chem. Mater. 16 (2004) 1977. L. Wang, Z. Yang, J. Gao, K. Xu, H. Gu, B. Zhang, X. Zhang, B. Xu, J. Am. Chem. Soc. 128 (2006) 13358. J.T. Mayo, C. Yavuz, S. Yean, L. Cong, H. Shipley, W. Yu, J. Falkner, A. Kan, M. Tomson, V.L. Colvin, Sci. Technol. Adv. Mater. 8 (2007) 71. A. Uheida, G. Salazar-Alvarez, E. Björkman, Z. Yu, M. Muhammed, J. Colloid Interface Sci. 298 (2006) 501. C. Huang, B. Hu, Spectrochim. Acta Part B 63 (2008) 437. J.E. Macdonald, J.A. Kelly, J.G.C. Veinot, Iron/Iron Oxide Nanoparticle Sequestration of Catalytic Metal Impurities from Aqueous Media and Organic Reaction Products, Langmuir 23 (2007) 9543. N. Yang, S. Zhu, D. Zhang, S. Xu, Mater. Lett. 62 (2008) 645. Y.C. Chang, D.H. Chen, Macromol. Biosci. 5 (2005) 254. M.H. Liao, K.Y. Wu, D.H. Chen, Chem. Lett. 6 (2003) 488. P. Li, D.E. Miser, S. Rabiei, R.T. Yadav, M.R. Hajaligol, Appl. Catal. B: Environ. 43 (2003) 151. G. Gnanaprakash, J. Philip, T. Jayakumar, B. Raj, J. Phys. Chem. B 111 (2007) 7978. P. Berge, N.B. Adelman, K.J. Beckman, D.J. Campbell, A.B. Ellis, G.C. Isensky, J. Chem. Educ. 7 (1999) 943.
Contents lists available at ScienceDirect
Talanta journal homepage: www.elsevier.com/locate/talanta
Modified iron oxide nanoparticles as solid phase extractor for spectrophotometeric determination and separation of basic fuchsin B. Zargar ∗ , H. Parham, A. Hatamie Chemistry Department, College of Science, Shahid Chamran University, Ahvaz, Iran
a r t i c l e
i n f o
Article history: Received 23 July 2008 Received in revised form 3 September 2008 Accepted 4 September 2008 Available online 18 September 2008 Keywords: Iron oxide nanoparticles Sodium dodecyl sulfate Preconcentration Basic fuchsin Determination Spectrophotometry
a b s t r a c t This study presents a novel separation, preconcentration and determination of basic fuchsin (BF) in an aqueous solution by sodium dodecyl sulfate (SDS)-bounded iron oxide nanoparticles (S-IONPs). It is shown that the novel magnetic nano-adsorbent is quite efficient for the adsorption and desorption of BF at 25 ◦ C. Different parameters such as pH, temperature, ionic strength and composition of desorbent solvent were optimized. The effect of some co-existing ions on the determination was investigated. The nanoparticles were analyzed by transmission electron microscopy (TEM) and the sizes of S-IONPs were in the range of 20–100 nm. The method showed good linearity for the determination of BF in the range of 10–300 ng mL−1 with a regression coefficient of 0.9989. The limit of detection (LOD) (signal-to-noise ratio of 3:1) was 0.0073 g L−1 and the relative standard deviation (RSD) for 0.03 g mL−1 and 0.2 g mL−1 of BF were 4.53% and 4.73%, respectively. The BF was determined successfully in spiked samples of Karoon River water. © 2008 Elsevier B.V. All rights reserved.
1. Introduction The treatment of industrial effluents is a challenging topic in environmental sciences, since control of water pollution has become of increasing importance in recent years [1]. Effluents from the textile industries are important sources of water pollutions, because wastewater dyes undergoes chemical as well as biological changes, consume dissolved oxygen, and destroy aquatic life. Moreover, some dyes and their degradation products may be carcinogenic and/or toxic. Therefore, it is necessary to treat textile effluents prior to their discharge into receiving water [2]. Basic fuchsin (BF) (Fig. 1) is a triphenylmethane dye with molecular formula of C20 H20 ClN3 and is one of those rare dyes that are inflammable in nature. It is widely used as coloring agent in textile and leather industries and also is used to stain collagen, muscle, mitochondria, and tubercle bacillus. BF possesses anesthetic, bactericidal (Gram positive), and fungicidal properties. The physical contact with the dye may cause severe eye and skin irritation. Its ingestion may cause gastrointestinal irritation with nausea, vomiting, and diarrhea and the inhalation of the dye causes irritation to the respiratory tract [3]. Keeping the toxicity of the dye in mind, there is a need to develop effective methods for its removal, recovery and determination in
∗ Corresponding author. Tel.: +98 611 3331094 fax: +98 611 3331098. E-mail address: zargar [email protected] (B. Zargar). 0039-9140/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.talanta.2008.09.011
wastewater. Several methods have been tried to remove various dyes with different adsorbents [2]. Recently magnetic nanoparticles as a new adsorbent with large surface area and small diffusion resistance have been recognized [4]. Ferrofluids are colloidal dispersions of small single domain magnetic particles suspended in a carrier fluid. Ferrofluids characteristically have both magnetic and fluid properties [5]. Nanosized magnetic iron oxide particles have been studied extensively due to their wide range of applications in ferrofluids, high-density information storage, magnetic resonance imaging (MRI), biological cell labeling and sorting, separation of biochemicals, targeting, and drug delivery. For many of these applications, surface modification of nanosized magnetic particles is a key of challenge [6–10]. In general, surface modification can be accomplished by physical and/or chemical adsorption of the desired molecules to coat the surface, depending on the specific applications [11]. Several methods for the separation and removal of chemical species such as metals [12–16], dyes [2,17–19] and gases [20] have been reported. The stability of dispersed particles and magnetic properties are of most importance. The nanoparticles which have a large ratio of surface area to volume, tends to agglomerate in order to reduce their surface energy by strong magnetic dipole–dipole and London-van der Waals attractions between particles. These nanoparticles can be coated with surfactants and as a result prevent their aggregation in liquids and improve their chemical stability. The repulsive interactions between particles can be created by coating a surfactant layer on particle surfaces [21].
B. Zargar et al. / Talanta 77 (2009) 1328–1331
1329
Fig. 2. Suggested mechanism for the adsorption of sodium dodecyl sulfate on the surface of IONP.
Fig. 1. Chemical structure of basic fuchsin.
Diluted ferrofluid dispersions are not stable. Therefore anionic and cationic surfactants are used as stabilizer. In this study, we used sodium dodecyl sulfate (SDS) which is an anionic surfactant and tends to interact with surface of nanoparticles and coated them. Iron oxide magnetic nanoparticles as cores and SDS as ionic exchange groups were used for recovery and determination of BF dye. 2. Experimental 2.1. Chemicals and reagents
separated magnetically and the initial red colored solution became colorless. The mixture was decanted and the solution above the nanoparticles was removed completely. Finally 2.5 mL of desorbent solution (a mixture of methanol and acetic acid with a ratio of 80:20, v/v) was added to the BF-S-IONPs in a beaker. The beaker was placed on the magnet and the mixture was decanted. The absorption of the solution which has been separated from IONPs by magnet was measured spectrophotometerically at 547 nm. 3. Results and discussion The synthesis of nanoparticles is based on the reaction of ferric and ferrous ions in an aqueous ammonia solution to form magnetite (Fe3 O4 ). Suggested reaction for the formation of nanoparticles is as follow [20]: 2FeCl3 + FeCl2 + 8NH3 + 4H2 O → Fe3 O4 + 8NH4 Cl Experimental conditions such as temperature, rate of ammonia addition and rate of solution stirring have critical effect on the size of nanoparticles.
All chemicals and reagents were of analytical grade. Basic fuchsin, phosphoric acid (85% m/m), methanol (99.9% m/m), ammonia solution (25% m/m), hydrochloric acid (37% m/m), acetic acid (99.9% m/m), FeCl3 (96% m/m), FeCl2 ·4H2 O (99.9% m/m), and sodium dodecyl sulfate were purchased from Merck (Darmstadt, Germany). Phosphate buffer solutions (pH 7) were prepared by adding appropriate amounts of 0.1 M sodium hydroxide solution into a mixture of 0.1 M of phosphoric acid. 2.2. Apparatus The spectrophotometric measurements were carried out with a Cintra 101 spectrophotometer (GBC SCIENTIFIC EQUIPMENT, Australia). A transmission electron microscope (906E, LEO, Germany), pH-meter (632 Metrohm, Herisau, Switzerland) and a super magnet (1.2 T, 10 cm × 5 cm × 2 cm) were used. 2.3. Preparation of SDS-bounded iron oxide nanoparticles (S-IONPs) Iron oxide nanoparticles were prepared according to a previous work [22]. In order to coat the particles, 5 mL of SDS solution (5% m/v) was added to about 5 g of damped nanoparticles in a beaker. The solution was stirred for 1 min by a glassy rod and the beaker was then placed on the magnet. After complete precipitation of S-IONPs occurred the solution was decanted and ferroflouid was washed with distillated water for several times (3 times on average) to eliminate extra amount of surfactant from nanoparticles. 2.4. Adsorption and desorption of BF About 0.6 g of damped S-IONPs (equivalent to 0.06 g dry SIONPs) were added to the 50 mL of BF solution (0.01–1 g mL−1 ) in a beaker. The pH of the solution was adjusted to 7 by addition of 2 mL of 0.03 M of phosphate buffer pH 7. The mixture was stirred by a glassy rod for about 100 s and the beaker was then placed on the magnet. The S-IONPs which adsorbed BF (BF-S-IONPs) were
Fig. 3. Transmission electron microscope images of (a) IONPs and (b) S-IONPs.
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B. Zargar et al. / Talanta 77 (2009) 1328–1331
Fig. 4. Effect of different pH values on the BF separation [conditions: 50 mL of 1 g mL−1 solution of BF; 1 g of damped IONPs; 2.5 mL of desorbent solution (methanol/acetic acid 80:20, v/v)].
The suggested mechanism for the coating of IONP with sodium dodecyl sulfate is shown in Fig. 2. The S-IONPs have bigger sizes compared to the initial IONPs as can be seen by TEM pictures (Fig. 3). IONPs without coating did not adsorb BF but S-IONPs adsorbed BF and separated it from the bulk of solution. The presence of trace amount of IONPs in the spectrophotometer cell could affect the absorption of the solution. It could be eliminated by holding the cell on the magnet for a few second before measuring. Absorption of the desorbed solution was measured at 547 nm instead of 542 nm (as a result of solvent changing from water to a mixture of methanol and acetic acid the max was shifted to higher wavelengths). The pH of the solutions was adjusted by NaOH and HCl to find the optimum pH value. Separation and Determination of BF was performed in the pH range from 2 to 12. The obtained results are shown in Fig. 4. In low pH values, the solution was darkly because iron oxide nanoparticles had begun to dissolve; on the other hand, at high pH values the IONPs were converted to colloidal particles and did not respond to the magnetic field (adsorption of hydroxide ions on the particles surfaces produce a dark colloid suspension). The amount of separation and desorption of BF in the pH range from 5 to 8 was constant and therefore this range was chosen as optimum range for pH. However pH 7 was selected for all other experiments and phosphate buffer was used to obtain this value. The amount of added buffer was investigated and it was demonstrated that with the amount of buffer volume exceeding 2 mL of 0.03 M solution in the 50 mL test sample solution; the amount of separation and adsorption of BF decreases.
Fig. 6. Effect of different compositions of desorbent solution on the desorption of BF from IONPs (conditions: 50 mL of 0.2 g mL−1 solution of BF; pH 7; 0.6 g of damped IONPs; 2.5 mL of desorbent solution).
The required amount of iron nanoparticles for the complete separation of BF in 50 mL solution (containing 1 g mL−1 of BF) at pH 7 was investigated. To this end, different amounts of damped iron nanoparticls were added to the solution following mixing and separation of IONPs with magnet. The adsorption of solution was then measured at 542 nm. The results are shown in Fig. 5. Addition of 0.6 g of damped iron nanoparticls (equivalent to 0.06 g dry IONPs) separated the BF from this solution completely. In order to find the best composition for desorbent solution, we used solutions with different ratios of methanol and acetic acid reported in references to be suitable for this purposes [2]. The obtained results are shown in the Fig. 6. Adsorption of BF by IONPs and it’s desorption by different compositions of desorbent solutions were studied in a constant volume of desorbent solution. Pure methanol and acetic acid (1 M) were used as stock solutions. The obtained results are showed that with 50–70% methanol in the final desorbent solution, the BF can be completely desorbed from nanoparticles surfaces. Addition of desorbent solution in multiple steps (3 steps) can improved the desorption process. The effect of ionic strength on the system was examined in different concentrations of KCl as an electrolyte. The adsorption of BF decreases with increasing the ionic strength of the solution. This implied that electrostatic attraction between the negatively charged SDS ions on the IONPs and positively charged of BF ions was affected by the KCl under the examination conditions. The adsorption of BF was studied in four different temperatures. The recovery of BF was slightly increased with increasing the temperature. The optimum experimental conditions which have been described were used to study the effect of some ions and two red dyes (Rodamin B, Allura red) on the determination process. To this end separation and determination of BF was performed in the presence of co-existing ions. The maximum acceptable error was ±5%. The obtained results are shown in Table 1. The table shows that Ca2+ , Mg2+ and Rodamin B strongly interfered even in the same Table 1 Effect of co-existing ions (conditions: 100 mL BF 0.2 g mL−1 ; pH 7. IONPs: 0.6 g; volume of desorbent solution: 2.5 mL (methanol/acetic acid 60:40, v/v)). Ionsa +
Tolerance ratio (w/w) +
−
−
2+
−
K , Na , Cl , Br , Pb , NO3 I− , F− CO3 Ni2+ Co2+ Ca2+ , Mg2+ , Rodamin B, Allura red Fig. 5. Effect of different amounts of IONPs on the BF separation [conditions: 50 mL of 1 g mL−1 solution of BF; pH 7; 2.5 mL of desorbent solution (methanol/acetic acid 80:20, v/v)].
200 100 60 40 10 1
a All cations were prepared from nitrate salts and anions were prepared from sodium and potassium salts.
B. Zargar et al. / Talanta 77 (2009) 1328–1331 Table 2 Determination of BF in spiked Karoon River water samples. Added BF (g mL−1 ) 0.100 0.150 a
Found BF (g mL−1 ) a
0.096 0.147a
1331
than 5 min. The proposed method is recommended for removal and/or determination of BF in different water samples. Recovery (%) 96.0% 98.0%
Average of three determinations.
concentration with BF. A solution of EDTA was used to eliminate the interference affect of Ca2+ and Mg2+ . 4. Analytical characteristics The calibration curve was linear in the range of 0.01 g mL−1 to 0.3 g mL−1 of BF with an equation of y = 4.2113 x + 0.1222 (R = 0.9989) in which y is absorbance and x is concentration of BF (g mL−1 ). The relative standard deviation (n = 8) for 0.2 g mL−1 and 0.03 g mL−1 of BF were 4.53% and 4.73%, respectively and the LOD of the method was 0.0073 g mL−1 . The enrichment factor of the method was calculated to be 40. 5. Analysis of Karoon River water sample To determine the ability of the proposed method for the analysis of BF in a real sample, Karoon River water was spiked. The spiked levels were 100 ng mL−1 and 150 ng mL−1 of BF. The spiked solutions were successfully determined in two different river waters samples. The results are summarized in Table 2. Excellent recoveries indicated that the complex matrix of river water samples does not interfere with the analysis of BF. 6. Conclusion Basic fuchsin could be removed from an aqueous solution by the SDS-bounded iron oxide nanoparticles. The nanoparticles can rapidly adsorbed BF and desorbed it in a suitable solution in less
Acknowledgement The authors wish to thank Shahid Chamran University Research Council for financial support of this work (Grant 1386). References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16]
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