Eco-friendly method for the estimation of cobalt (II) in real samples using 1-(2-Thiazolylazo)-2-naphthol|JBES-Vol-15-No-1

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J. Bio. & Env. Sci. 2019Investigation of Cobalt (II) in hair samplesThe hair samples were washed and subjected toultrasonic vibration for 1 hour in acetone, water,water and acetone separately in the 100mL volume.The samples were filtered and dried. After weighingthe samples, they were digested in nitric acid 2.5mLvolume and kept at 60 o C overnight in oven. Thesesamples were taken in calibrated flask (DaAntonio,1982). Then NaOH was mixed to neutralize thesamples and working solutions were made in 50mLmeasuring flask. Though the solutions weretransferred into measuring flask and mixed 2mLvolume TAN, 0.02 M CTAB 2mL volume and 2mL ofbuffer solutions of 9.5 pH for formation of metalchelate and determined spectrophotometrically forcobalt (II) metal ion. The amount of cobalt wascalculated and the results are shown in Table 7.Determination of Cobalt (II) in nail samplesThe samples were collected, washed with doubledistilled water and dried in oven. Then the sampleswere digested by adding the 10mL of nitric acid conc.and perchloric acid in the ratio of 6:1 ratio of mixtureand kept them at room temperature overnight. Thenthe obtained solution was promoted for preconcentrationby placing in oven at about 160-180 o Cto get 1mL of solution at last (Mehra and Juneja,2005). Then NaOH was mixed to neutralize thesamples and working solutions were made in 50mLmeasuring flask. Though the solutions weretransferred in measuring flask and mixed the suitableTAN volume, 0.02 M CTAB 2mL volume and 2mL ofbuffer solutions of 9.5 pH for formation of metalchelate and determined spectrophotometrically forcobalt (II) metal ion. The amount of cobalt wascalculated and is shown in Table 7.Investigation of Cobalt (II) in Pharmacologicaltablet samplesThe samples of known amount were taken anddigested with 3mL volume of HNO3 0.01M, heated todryness and residue was dissolved in alcohol. Thesolution was then filtered and made it diluted upto100mL with deionized water. The stock solutions ofthe lower concentrations were made by suitablesuccessive dilution method. Then the sample wastransferred in measuring flask and mixed the 2mLvolume TAN, 0.02 M CTAB 2mL volume and 2mL ofbuffer solutions of 9.5 pH for formation of metalchelate and determined spectrophotometrically forcobalt (II) metal ion. The amount of cobalt wascalculated and the results are shown in Table 8.Results and discussionTAN is tridentate chelate reacts with Co(II) bybonding through two atoms of nitrogen and one atomof oxygen in TAN after deprotonation. The structureof the complex bis [1-(2-Thiazolylazo)-2-naphthol]cobalt is shown in Fig. 1. UV-vis spectrum of TANshowed broad peak (π→π*) electron transitions fromone ligand to another (L→L) of nitrogen atom of nitrogroup at λmax 488.5 of C=N group, OH group andN=N double bonds is shown in Fig. 2. UV-Visspectrum of Co(II)-TAN compound gavebathochromic shift termed as red shift by 84.2 nm.Transformation of charge from TAN to Co(L→M) wasobserved from the orbitals of TAN (pπ) to Co(dπ) atλmax 572.7 (ε1.89×10 4 L mol -1 cm -1 ). Co(II)-TAN spectrashowed that after deprotonation of -OH atom andC=N group and N=N are taking part in TAN-chelateare shown in Fig. 3. The Co-complex gave reddishbrown colour rapidly and gave the same constantmaximum absorbance up to 60 minutes. Co-TANcomplex at room temperature showed no any changein absorbances until 24 h. The TAN reagentconcentration effect on the Co-TAN complexformation was investigated by varying TAN reagentconcentration (Khadem et al., 2010) 0.5 to 10.0×10 -4M, while Co (II) ions concentration was kept constant1m.mole. Concentration of the reagent TAN wasoptimized by taking 1m.mole Co ions reacted withTAN in molar ratio of 1:3×10 -4 M forming Co-TANcomplex showing maximum absorbance. TAN 3×10 -4M concentration showed Co-TAN complex formationwith maximum absorbance is shown in Fig. 4.Therefore concentration of TAN reagent was kept3×10 -4 M constant in the throughout studies.Stoichiometric Co-TAN compositions weredetermined using Job’s method (Cherdantsevaa et al.,2010; Jayanna et al., 2010; Patel et al., 2016; Reddy15 | Korai et al.
J. Bio. & Env. Sci. 2019et al., 2016) by varying both Co and TANconcentrations by molar-ratio method. Co-TAN metalagainst ligand ratio was found 1:2 (M:L2). 0.02MCTAB 2mL volume of surfactant solution showedmaximum constant absorbance, which was above thecmc value. In complex formation different pH waskept and investigated the optimum pH where theabsorbance was showed maximum. pH 9.5 wasmeasured optimum pH (Kuliyev, 2016) for Co (II)-(TAN)2 complex formation is given in Fig. 5.Calibration linear concentration graph was obtainedat 0.02-9.0μgmL -1 , with correlation coefficients0.9991 is given in Fig. 6. Coefficient of molarabsorptivity was obtained ε1.89×10 4 L mol -1 cm -1 atλmax572.7 is shown in Table 1. The Sandell’ssensitivity was found 3.1ngcm -2 is shown in Table 1,showed improvement. Detection limit was obtained tobe 3.1ngmL -1 is given in Table 1.Table 1. Analytical parameters of Co(II)- [TAN]2 inCTAB 0.02M.ParametersCobaltWavelength (λmax)572.7 nmpH 9.5CTAB (Surfactant) 0.02M 2.0mLTAN concentration3.0×10 -4 MMetal to Reagent ratio (M:R) 1:2Linear range 0.02-9.0 µgmL -1Coefficient of molarabsorptivity1.89×10 4 Lmol -1cm -1Sandell’s sensitivity 3.1 ngcm -2Detection limit 3.1 ngmL -1(R 2 ) 0.9991(% RSD) 0.802.0µg/mL of metal complex was chosen to examinethe effect of interference under definite for theformation of metal complex was measured. Thecations copper(II) and chromium(IV) were merelyinterfering species that exhibited the great influencein the formation of metal complex. 1.0mL of maskingagent EDTA was used to remove before moreperchloric acid addition. Both copper (II) andcadmium (II) showed greater interference at minutelevel, which was lowered using 0.01M NaCN 1.0mLvolume masking agent solution (Jain and Memon,2017). The high concentrations of SCN - , Br - , Cl - ,ascorbic acid and I - have not experiencedinterference. 1500µg/mL concentration of sodiumtartrate has not revealed any interfering influence inthe formation of metal chelate absorbance. Variousmasking agents such as thiocyanate, phosphate,citrate, and fluoride were utilized to eliminate themore effect of foreign interfering species (Rajni andUsha, 2012) as shown in Table 2.Table 2. Effect of foreign ions on the Co(II)-[TAN]2.Metal ions / saltsCobaltNa2tartarate 1500KSCN, KClO3 1100NaF, CH3COO - 2100Na2citrate, Pb(II) 500Al(III) 100Bromide, Iodide, Chloride, Borate, 200Na2C2O4EDTA, Cyanate, Cd(II), Mn(II), Hg(II), 10Fe(II) 100Ni(II) 100Zn(II) 100Co(II) -Cu(II) 10Cr(III) 60Cr(IV) 8FTIR spectra of TAN aqueous gave absorption band at3342.70cm -1 for ν (OH) group and 2948.39 for ν (C-H)(C-N) and 1651.39 for aromaticity are shown in Fig. 7.4000 cm -1 -1500 cm -1 showed the stretching while while1500 cm -1 -550 cm -1 showed finger print region (Korai,2019). The Co (II)-TAN complex showed lower wavenumbers by 3335.77 cm -1 for ν (OH) group and2940.55 for ν(C-H) (C-N) and decrease to 1657.06 foraromaticity of ν(Co-TAN). New bands suggested Co(II)-TAN bonding as shown in Fig. 8.Precision and accuracyNeurobion injection (Merck), Alloy JSS 607-6 andTap water were tested for reliability and accuracy ofmethod, % age recovery test by adding calculatedamount of Co (II) ions are given in Table 3-5.Table 3. Determination of Co(II) in reference material.Alloys(%) CertifiedcompositionMetalionsMetalsPresentMetalsfoundJSS 607-6 Co(II) 14.01 µg 13.98µg%RSD0.40%Relativeerror%Recovery0.14 99.78Table 4. Determination of Co(II) in pharmaceutical samples.SamplesNeurobion(Inj)21.74 µg/mLAnalyteionsProposedmethodµg/mLRSD%AASmethodµg/mLRSDRecovery% %Co(II) 21.68 0.4 21.69 0.4 98.016 | Korai et al.
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Eco-friendly method for the estimation of cobalt (II) in real samples using 1-(2-Thiazolylazo)-2-naphthol|JBES-Vol-15-No-1

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