Journal of Chemical and Pharmaceutical Research

Transcription

1 Available on line Journal of hemical and Pharmaceutical Research I o: ODE(UA): JPR5 J. hem. Pharm. Res., 2011, 3(2): Derivative spectrophotometric determination of cobalt (II) and ickel (II) using 2-acetylpyridine-4-methyl-3-thiosemicarbazone (APMT) K. Vasudeva Reddy 1,2*, D. agarjunareddy 2 and K. Hussain Reddy 2 1Department of hemistry, Govt. ollege for Women, hintamani(ka) 2 Deptartment of hemistry, ri Krishnadevaraya University, Anantapur(AP) ABTRAT 2-Acetylpyridine-4-methyl-3-thiosemicarbazone (APMT) gives yellow coloured water soluble complexes in aqueous medium with oblt(ii)and nickel(ii) show maximum and constant absorbance in the ph range respectively. The molar absorptivity and andell s sensitivity of o(ii) ( λ max 360) and i(ii) (λ max 375 nm) are found to be 1.86 X 10 4, 2.16 X 10 4 L mol -1 cm -1 and 3.2 X 10-3, 3 X 10-3 µg cm -2. obalt(ii) and ickel(ii) form 1:2 complexes with APMT respectively. econd derivative spectrophotometric method has been developed and used for the determination of o(ii) and i(ii) in alloys. Keywords: Derivative spectrophotometry, 2-acetylpyridine -4-methyl-3thiosemicarbazone. ITRODUTIO Derivative spectrophotometry is a very useful approach for determining the concentration of single component in mixtures with overlapping spectra as it may eliminate interferences. It has been widely used in pharmaceutical analysis, amino acid and protein analysis, clinical and environmental chemistry etc [1], but less often in inorganic analysis.[2,3] In this paper a second order derivative spectrophotometric method is described for the determination of cobalt(ii) and nickel(ii) in alloys. 835

2 K. Vasudeva Reddy et al J. hem. Pharm. Res., 2011, 3(2): EXPERIMETAL ETIO Apparatus A himadzu 240 UV-VI spectrophotometer with 1.0 cm quartz cell was used for absorbance studies. An Elico LI-120 digital ph meter was used for ph adjustment. Reagents The reagent 2-Acetylpyridine-4-methyl-3-thiosemicarbazone (APMT) prepared by simple procedure. 2-acetylpyridine (4ml, mol) in 5ml of methanol, 4-methyl-3- thiosemicarbazide(3.75 g, mol) dissolved in 10ml of hot water) were taken in 250-ml round bottom flask. uitable quantity (~ 2ml) of glacial acetic acid was added to the reaction mixture and refluxed for 3 hours. On cooling the reaction mixture, light brown coloured product was separated out. It was collected by filtration and washed several times with hot water and 50 percent cold methanol. This compound was recrystallised from ethanol and dried in vacuum. Yield 3.8g; m.p The reagent solution was stable upto 48 h (cheme 1). O H 3 + H 2 H H H 3 H 3 OOH H 2 O H H H 3 H 3 cheme 1 The standard o (II) solution (1 x10-2 ) and i(ii) (1 x10-2 ) were prepared by using analytical reagent grade obalt chloride and ickel sulphate (AR,BDH), respectively and standardized gravimetrically and iodometrically 4. The solutions were suitably diluted to obtain standard working (10-3 M) solutions of the metal ions.hydrochloric acid (1M) - sodium acetate (1M) (ph ); 0.2M aoac 0.2M AcOH (ph 4 6) and 2M H 4 l -2 M H 4 OH (ph ) were used in the preparation of buffer solutions [4,5]. Recommended procedure Direct spectrophotometry: An aliquot of the solution containing µg/ml of obalt(ii) or ickel(ii), 10 ml of aoac AcOH buffer solution (ph 6) and 1ml of 0.01M APMT was transferred to 25 ml volumetric flask and diluted upto the mark with distilled water. The absorbance was measured at 360 nm and 375 nm for the obalt (II) and ickel (II) against the corresponding reagent blank respectively. The measured absorbance was used to compute the o(ii) and i(ii) from pre-determined calibration plot. econd derivative spectrophotometry: for the above solutions, second order derivative spectra were recorded with scan speed having a degree of freedom 9, in the wavelength range from nm. The derivative peak height was measured by peak-zero method at 455 and 424 nm for o(ii) and i(ii) respectively. REULT AD DIUIO The absorption spectra of APMT (1 x 10-4 M) solution were recorded at different ph values. The compound shows single absorption maximum (Position depends on ph) which may be due to π 836

3 K. Vasudeva Reddy et al J. hem. Pharm. Res., 2011, 3(2): π * transitions. In alkaline medium (8 10), this band is shifted towards higher wavelength (lower energy) due to the formation of conjugated negative anion. The shifting of absorption maximum from lower wavelength to higher wavelength is known as bathochromic shift, a common spectral property of chiff reagent. A plot was prepared between absorbance and ph at different wavelengths of radiation by following Phillip and Merrit methods. The pka values are calculated as 4.1 (pk 1 ) and 8.2 (pk 2 ). The possible species that may be formed due to deprotonation of the ligand are given cheme 2. H 3 H H H 3 pk 1 = 4.1 H H 3 H H 3 pk 2 = 8.2 (-) H 3 Keto form Enol form H H 3 Mono anion + H + cheme 2 The complex formation reactions between o(ii) and i(ii) with APMT have been studied in detail. Various physico-chemical and analytical properties of cobalt (II) and ickel(ii) complexes respectively are : λ max (360,375 nm; optimum ph range ( ); Beer s law validity range( , µg/ml); molar absorptivity (1.86 X 10 4, 2.16 X 10 4 L mol -1 cm -1 ); andell s sensitivity(3.2 X 10-3, 3 X 10-3 µg cm -2 ); standard deviation(0.005,0.008), relative standard deviation(0.43,0.67); composition (M:L) of the complexes (1:2) and stability of the complex from Job s method( 4.05 X 10 11, 8.3 X ). The zero order and second derivative spectra of complexes are given in Fig. Interference The effect of foreign ions has been investigated. Many anions and cations do not interfere in the determination cobalt (II) and ickel(ii) using APMT reagent. The tolerance limit value was taken as the amount of foreign ion required to cause ± 2 percent error in the absorbance. The tolerance limit(µg/ml) values of diverse ions in the determination of 1.18 and1.17µg/ml and of o(ii) and i(ii) respectively are itrate(384), tartarate(296), urea(288), iodate(254), bicarbonate(244), oxalate(176), thiourea(152), bromide(16), W V (367), Mn II (22), Mo VI (30), Al III (34), Fe II ( 0.2), V V (0.2), d II ( 2.2 in the presence of 200 µg/ml of thiocyanate) and u II (0.3). The tolerance limit values determined in derivative method are higher those in zero order determination of o(ii) and i(ii). Applications The present method are applied for the determination of o(ii) and i(ii) in some synthetic samples whose composition corresponds to certified samples. The results are given in Table 1 and

4 K. Vasudeva Reddy et al J. hem. Pharm. Res., 2011, 3(2): sample Table 1 Determination of cobalt in alloy samples Amount of obalt * in µg/ ml ertified Found Error Eligiloy M 1712 a % High peed teel b % * Average of three determinations a. o 40%, r 20%, i 15%, Fe 15%, Mo 7% and Mn 2%. b. W 18.5%, o 9.25%, Mo 5.5%, r 4.15%, Mn 0.4%, i 0.53% and 0.25%. Table 2 Determination of ickel in alloy samples sample Amount of ickel * in µg/ ml ertified Found Error BA 106 a % TP Alloy b % B-RM38T c % Monel 400 d % Ookay e % * Average of three determinations a. i 1.93%, u 4.1%, Fe 0.43%, Mn 0.2% and Mg 1.61% b. i 10%, r 15%, Fe 6.5%, u 4.5% and Mn 2.1% c. i %; r 12-46%; Mo 5.83%; Ti 2.95%; e 0.28%; Al 0.29%; o 0.21%;Mn 0.08% and u 0.092%. d. i 63.01%; 0.15%; %; Mn 0.07%; i 0.5%; Fe 2.5%; u 31.0% e. i 60.00%; Pt 20%; V 9.5% and Pd 10.5% b Absorbance a b W a v e le n g t h a 1 Figure 1: Zero order and econd order derivative spectrum of obalt (II) and ickel (II) a Zero order spectrum of o(ii) APMT system [o(ii) 1x10-3 M and 1x10-2 M a econd order spectrum of o(ii) APMT system [o(ii) 1x10-4 M and 1x10-2 M b Zero order spectrum of i(ii) APMT system [i(ii) 1x10-3 M and 1x10-2 M b econd order spectrum of i(ii) APMT system [i(ii) 1x10-4 M and 1x10-2 M 838

5 K. Vasudeva Reddy et al J. hem. Pharm. Res., 2011, 3(2): OLUIO The present derivative spectrophotometric methods for the determination of obalt (II) and ickel (II) compares favorably with recently reported methods. The analytical properties of o- APMT and ickel-apmt complexes are investigated. The second order derivative methods are found to be more selective compared to zero order methods. Acknowledgement The authors thank to Dr.K.R.K. Prasad, Associate Professor II, Bangalore for his help in recording IR and MR spectra of reagent samples. REFEREE [1] nachez Rojas.F; Bosch-ojeda ; ano Pavon J.M; Talanta, 1988, 35, 753. [2] Bermejo.A; Bermoji, B.P; Bermejo Martinez.F; Analyst,1985, 110, [3] Kuroda. R; Kurosaki,M; Hayashibe, Talanta, 1990, 77, 619. [4] Bassett J; Danney R ; Jeffery G H, A Vogel s text book of quantitative inorganic analysis, 4 th edn ( Longman, London), ,448 [5] Perrin D.D; Boyd D; Buffers for ph and metal on control, ( hapman Hall) London 1974,