Simultaneous spectrophotometric determination of Cu(II), Co(II), Ni(II) using 1-(2-pyridylazo)-2- naphthol (PAN) by chemometric method

Abstract. A spectrophotometric determination of copper(II), cobalt(II) and nickel(II) is carried out using PAN as the complexing reagent in aqueous phase and using surfactant Tween 80 and result in high repeatability. The λmax molar absorption of Cu(II), Co(II) and Ni(II) are 550 nm, 580 nm and 569 nm. The pH value appropriate for complex formation between Cu(II), Co(II), Ni(II) and PAN is 5. The most suitable Tween 80 concentration is 5%. This method has been applied to determine Cu(II), Co(II) and Ni(II) in laboratorial samples.

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JOURNAL OF SCIENCE OF HNUE DOI: 10.18173/2354-1059.2015-00081 Chemical and Biological Sci. 2015, Vol. 60, No. 9, pp. 77-82 This paper is available online at Received October 26, 2015. Accepted November 30, 2015. Contact Nguyen Duc Vuong, e-mail address: vuongqb@yahoo.com 77 SIMULTANEOUS SPECTROPHOTOMETRIC DETERMINATION OF Cu(II), Co(II), Ni(II) USING 1-(2-PYRIDYLAZO)-2- NAPHTHOL (PAN) BY CHEMOMETRIC METHOD Nguyen Duc Vuong1, Nguyen Duc Minh1 and Nguyen Xuan Tong2 1Faculty of Chemistry, Quang Binh University 2 University of Industry, Ho Chi Minh City Abstract. A spectrophotometric determination f copper(II), cobalt(II) and nickel(II) is carried out sing PAN as the complexing reagent in aqueous phase and usingsurfactant Tween 80 and result in high repeatability. The λmax molar absorption of Cu(II), Co(II) and Ni(II) are 550 nm, 580 nm and 569 nm. The pH value appropriate for complex formation between Cu(II), Co(II), Ni(II) and PAN is 5. The most suitable Tween 80 concentration is 5%. This method has been applied to determine Cu(II), Co(II) and Ni(II) in laboratorial samples. Keywords: Chemometric, PAN, copper, cobalt, nickel. 1. Introduction Copper, cobalt and nickel are trace elements that are essential for plant and animals. Copper is a component of many enzymes, but too much copper in the body could lead to illnesses such as Wilson's disease. A nickel deficiency can lead to health problems such as bones deformation, however, excess nickel could lead to lung cancer and heart attack. Cobalt is a central component of vitamin B12 [1, 2]. PAN reagent reacts with metal ions to form colored-c mplexes often used in photometric analysis [1, 3-5]. The complexation of metal ions Cu (II), Ni (II) and Co (II) with PAN, insoluble in water but a soluble medium when containing surfactant such as Tween 80 [1]. In addition, PAN was a colored reagent and absorption at a wavelength near to the wavelength of maximum absorbance of PAN complexes with metal ions lead to the mutual overlap between the reagent and the complex spectrum. 2. Content 2.1. Experiment * Reagent and chemicals - A solution of (1- 2-pyridylazo)-2-naphthol (Merk) in ethanol was prepared and used. Nguyen Duc Vuong, Nguyen Duc Minh and Nguyen Xuan Tong 78 A standard solution Cu2+ 10-2M (PA); a standard solution Ni2+ 10-2M (PA); a standard solution Co2+ 10 -2M (PA); acid buffer solution at pH 4.8 sodium acetate - Tween 80 (Polyoxyetlen (20) sorbitan monooleat, C644H124O26, M = 1310 g/mol) of 5% (v/v) * Apparatus - PH meter: WTW 330 i/set; UV- VIS spectrophotometr Jasco V360 (Japan). - Program phochuan.exe, program SIMULAN1.exe 2.2. Results and discussion 2.2.1. Survey additive property of PAN reagent and complex Cu-PAN2, , Co-PAN2, Ni- PAN2 Proceed PAN reagent reacts with metal ions to form c lored-complexes Cu-PAN2, Co-PAN2 and Ni-PAN2, then scan spectra in wavelengths ranging from 400 - 700 nm. 400 450 500 550 600 650 700 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 spetrum of mixture at fact spectrum of mixture at theory Ni-PAN 2 Co-PAN 2 Cu-PAN 2 PAN A Wave length (nm) Figure 1. The absorption spectra of PAN 1,00.10-5M, Cu-PAN2 5,00.10 -6 M, Co-PAN2 5,00.10 -6 M, Ni-PAN2 5,00.10 -6 M and their mixture Figure 1 shows the sp ctral features of Cu-PAN2, Co - PAN2, Ni-PAN2, PAN and their mixture in Tween-80. According to this figure, Cu-PAN2, Co-PAN2 and Ni-PAN2 complexes show an absorption maximu at λ = 550 nm, 580 nm and 569 nm and PAN shows an absorption maximu at 470 nm. Spectral of colored-complexes are additivity (absorption spectrum of complex mixtures in theory and in fact overlap in tolerance limit (RE (%) = 5.79)). Thus, we use the chemometric method to determine the concentration Cu (II), Co (II) and Ni (II) in the mixture. 2.2.2. Effect of pH on complex formation Conducting experiments complexation be ween Cu (II), Co (II), Ni (II) and PAN but changes in pH values for 3 to 8 by addition of NaOH solution or CH3COOH into acetate buffer solution pH = 4.8 and pH meter used to check the pH value, then record the absorption spectrum in the wavelength range of 400-700 nm. Results in Table 1 and Figure 2 Simultaneous spectrophotometric determination of Cu(II), Co(II), Ni(II) using... 79 Table 1. Results of the survey of pH influence on the formation of complexes pH 3 4 5 6 7 8 ACu- PAN2 (λ = 550) 0,088 0,090 0,093 0,092 0,106 0,107 ACo-PAN2 (λ = 580) 0,064 0,093 0,090 0,088 0,088 0,085 ANi-PAN2 (λ = 569) 0,062 0,109 0,158 0,140 0,135 0,131 Figure 2 shows that the absorbance of the complex Cu-PAN2 increases when pH increases but light increased, complex Ni - PAN2 increased then decreased and reached its maximum value at pH = 5, the absorbance of Co-PAN2 changes significantly. Hence, we choose pH = 5 for further research. 2.2.3. Effect of time on complex formation Complexation reactions proceed between Cu (II), Co (II), Ni (II) and PAN and brought record absorption spectrum in the wavelength range of 400-7 0 nm. The results are shown in Table 2 and Figure 3. Table 2 and Figure 3 shows that in 120 minutes, the absorbance of the complex Cu-PAN2, Co-PAN2 are little changed (Complex reliability) and Ni-PAN2 stable complexes between 20 to 40 minutes. So that, we choose the scan interval after forming a complex spectrum is 20 minutes. Table 2. Results of the survey of complex absorption color over time Time (minute) ACu-PAN2 (λ = 550) ACo-PAN2 (λ = 580) ANi-PAN2 (λ = 569) 1 0.093 0.086 0.077 5 0.093 0.093 0.117 10 0.093 0.093 0.139 15 0.092 0.093 0.151 20 0.092 0.093 0.158 25 0.092 0.093 0.159 30 0.092 0.093 0.159 35 0.092 0.093 0.158 40 0.092 0.093 0.156 45 0.092 0.093 0.152 50 0.092 0.093 0.150 60 0.092 0.093 0.149 80 0.092 0.093 0.146 100 0.092 0.093 0.142 120 0.092 0.093 0.140 Nguyen Duc Vuong, Nguyen Duc Minh and Nguyen Xuan Tong 80 3 4 5 6 7 8 0.06 0.08 0.10 0.12 0.14 0.16 A pH Cu-PAN 2 Co-PAN 2 Ni-PAN 2 0 10 20 30 40 50 0.08 0.10 0.12 0.14 0.16 A time (minute) Cu-PAN 2 Co-PAN 2 Ni-PAN 2 Figure 2. Effect of pH on complex formation Figure 3. Reliability of colored-complex dependence on time 2.2.4. UV-Vis spectrum of PAN By doing spectral scans of PAN reagent solution in the 400 - 700 nm wavelength range, we achieved the standard spectrum of the PAN solution (Figure 4). 400 450 500 550 600 650 700 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 A Wave length (nm) PAN 400 450 500 550 600 650 700 0.00 0.05 0.10 0.15 0.20 A Wave length (nm) Cu-PAN 2 Figure 4. UV-Vis spectral of PAN 1,00.10 -5 M Figure 5. UV-Vis spectral of the complexes Cu-PAN2 5,00.10 -6 M 2.2.5. UV-Vis spectral of the complex Cu-PAN2, Co-PAN2 and Ni-PAN2 The program phochuan.exe [6] is used to determine the standards spectrum of complex Cu-PAN2, Co-PAN-2, Ni-PAN2 if the exact amount of excess reagent is known. The results are shown in Figure 5. 2.2.6. Determining the concentration of mixture Cu (II), Co (II)) and Ni (II) by chemometric methods Having identified standard spectrum PAN reagents and complexes of metal ions with PAN, we will determine the concentration of metal ions present in the mixture and balances the reagents using the SIMULAN1.exe program [7] (T ble 3). Simultaneous spectrophotometric determination of Cu(II), Co(II), Ni(II) using... 81 Table 3. Concentrations of ion metals Cu 2 + , Co 2 + , Ni 2 + and PAN balance Cu2+ Co2+ Ni2+ PANbalance Cprepare (10 -6M) 5,00 5,00 5,00 10,00 Cfound (10 -6M) 4,96 5,02 4,88 9,63 RE (%) 0,8 0,4 2,4 3,7 Table 3 shows the concentration of metals Cu (II), Co (II) and Ni (II) as determined using the chemometric method through program simulan1.exe range tolerance. These results are acceptable. This method differs from the method in references [1, 5]. 2.2.7. Assess the reliability of the method * Repeatability Based on the results calculated in RSD (Table 4), we see that the value of RSD <RSDH should result in better measurement repeatability. Besides the small errors in measurement (Table 3), we can identify three simultaneous mixtures containing metal ions Cu (II), Co (II) and Ni (II) along with reagent PAN using the SIMULAN1.exe program. Table 4. Results calculated RSD (%) as determined metal Cu 2+ , Co 2 + , Ni 2+ and PAN balance Metal ions Cfound (10 -6M) PC (10-6M) RSD (%) RSDH (%) 1st 2nd 3rd Cu2+ 5,00 4,96 4,93 4,96 0,71 12,57 Co2+ 5,15 4,95 4,97 5,02 2,19 12,55 Ni2+ 4,95 4,92 4,77 4,88 1,98 12,6 PANbalance 9,45 10,04 9,4 9,63 3,7 11,39 Table 5. Confidence interval when determining metals Cu 2 + , Co 2 + , Ni 2 + and PAN balance Metal ions x (10-6M) ε μ (10 -6M) Cu2+ 4,96 0,09 4,87 – 5,05 Co2+ 5,02 0,28 4,74 – 5,5 Ni2+ 4,88 0,24 4,64 – 5,12 PAN 9,63 0,9 8,73 – 10,53 * Confidence interval Table 5 shows the concentration of metals Cu (II), Co (II) and Ni II) as determined by photometric chemometric method within the confidence interval. Measurement results are acceptable. 3. Conclusion 1-Having examined and found suitable conditions to determine Cu (II), Co (II) and Ni (II) reagent residue using PAN, in which the metal complexes with mixed PAN absorption spectrum popular with excess reagent. The surface Tween 80 is used to soluble the metal complexes. This method is simple and helps to quickly determine metal ion concentration. 2-Identify standard spectrum of PAN reagents and complexes Cu-PAN2, Co-PAN2, Ni- PAN2 using the phochuan.exe program. Nguyen Duc Vuong, Nguyen Duc Minh and Nguyen Xuan Tong 82 3-Identified concentrations of Cu (II), Co (II) and Ni (II) when there is an excess of PAN reagent using the SIMULAN1.exe program. REFERENCES [1] G. A. Shar, G. A. Soomro, 2004. Spectrophotometric determination of Cobalt(II), Nikel(II) and Copper(II) with 1-(2-pyridylazo)-2-naphthol in micellar medium. The Nucleus, 41 (1-4), pp. 77-82. [2] J. Ghasemi, Sh. Ahmadi, K. Torkestani, 2003. Simultaneous determination of copper, nickel, cobalt and zinc using zincon as a metallochromic indicator with partial least squares. Analytica Chimica Acta, Vol. 487, Issue 2, pp. 181- 8. [3] Chu Dinh Binh, Pham Luan, 2006. Look at the reaction to form complexes between Co (II) and Ni (II) with a reagent in environmental PAN micelles, assess the applicability to analyze simultaneously Co (II) and Ni (II). Journal of Analytical Chemistry, Physics and Biology, Vol. 11, No. 4. [4] A. Gallardo Melgarejo, A. Gallaardo Céspedes, J. M. Canopavon, 1989. Simultaneous determination of Nickel, Zinc and Copper by second-derivative spectrophotometry using 1-(2-pyridylazo)-2-naphthol as reagent. Analyst, Vol. 114, pp. 109-111. [5] Habibohllah Eskandari, Ali Ghanhari Saghseloo, Mansour Arab Chamjangali, 2006. First-and second-derivative spectrophotometry for simultaneous determination of copper and cobalt by 1-(2-pyridylazo)-2-naphthol in Tween 80 micellar solutions. Turk. J. Chem, 30, pp. 49-63. [6] Tran Thuc Binh, Tran Tu Hieu, 2008. Research methods for determining the standard spectrum of metal complexes have the common use of excess reagent overlap with universal reagent of complexes with metal ions. Journal analytical Chemistry, Physics and Biology, Vol. 13, No. 1, pp. 116-120. [7] Tran Thuc Binh, 2002. Research methods for determining the quality and absorption spectra overlap with one another using the computer. PhD Thesis Chemistry, College of Natural Sciences, Hanoi.