3-Hydroxy-3-n-Propyl-1-(4-Sulphonamidophenyl) Triazene: A New Reagent for Spectrophotometric Determination of Nickel (Ii)

Introduction

A number of hydroxytriazenes^1-7 have been used as spectrophotometric as well as metalochromic indicators. We report here spectrophotmetric determination of Nickel (II) using one such hydroxytriazene, 3-hydroxy-3-n-propyl-1-(4-sulphonamidophenyl) triazene.

Experimental

3 – Hydroxy – 3 -n- propyl-1- (4 -sulphonamidophenyl) triazene was synthesized by the reported method⁸ (Scheme:1).

Synthesis of 3-hydroxy-3-n-propyl-1-(4 -sulphonamidophenyl) triazene:&nbsp

Synthesis of n-propylhydroxylamine

In a one litre beaker 19.00g (0.30 mol) of nitropropane, 30 g of NH₄Cl and 300 ml of distilled water were mixed, stirred mechanically and cooled to 0°C by surrounding the beaker with ice salt mixture. To the reaction mixture 30 g Zn dust was added in small lots in few minutes interval taking about an hour for complete addition. During this period, the temperature was maintained between 0° to 15°C by adding ice to the reaction mass occasionally. The reaction mixture was stirred mechanically for another 40 min keeping temperature between 0 to 15°C. The solution was filtered under suction and washed with 100 ml ice cold water. The filtrate was taken in a beaker and kept in freezer and used as such for coupling with diazotized product.

Diazotization of sulphanilamide

In a 500 ml beaker 0.2 mol of sulphanilamide was dissolved in warm mixture of 50 mL of concentrated HCl and 50 mL of water. After constant stirring the mixture was kept in a freezer to cool. In another beaker 13.9g of NaNO₂ was dissolved in 40 mL of distilled water and kept it in the freezer. The beaker which contained sulphanilamide solution was put in an ice bath to maintain temperature between 0 to 5ºC. To this The NaNO₂ solution was added drop by drop with continuous stirring. The diazotized product so obtained was directly used for coupling.

Coupling

The n-propylhydroxylamine prepared in step (a) was coupled with the diazotized product of (b) step at 0 to 5°C under mechanical stirring with occasional addition of sodium acetate solution for maintaining the pH close to 5 during coupling process. The compound 3-hydroxy-3-n-propyl-1-(4-sulphonamidophenyl) triazene was obtained as yellowish green powder after crystallization from ethanol. Melting points of all synthesized compounds were taken in open capillaries and are uncorrected. C H N analysis corroborated the purity of compound. The compound was subjected to IR spectral analysis and following bands were observed. IR (KBr) cm-1: 3290 (O-H str.), 3078 (C-H str. Ar), 2981 (C-H str., CH₃), 1632 (N=N str.), 1419 (N-N str.).The spectra showed the compound to be in pure state. IR spectra (KBr) were recorded on FT IR RX1 Perkin Elmer Spectrometer.  Physical and analytical data are given in Table 1 and the structure has been given in Figure 1.

Table 1: Elemental analysis of 3 – hydroxy – 3 -n-propyl – 1 – (4 -sulphonamidophenyl)

triazene (HPSPT)

 

Molecular Formula of HPSPT	Molecular Weight	M.P. ºC	Elemental Analysis
				C%	N%	H%
C9H14N4O3S	258.30	180	Th.	41.85	21.69	5.46
			Exp.	41.65	21.53	5.01

 

Figure 1 Click here to View Figure

 

Scheme 1 Click here to View Scheme

 

SPECTROPHOTOMETRIC DETERMINATION OF NICKEL (II) WITH   HPSPT

Stock Solution                                            

A 1.0x 10^-2 M stock solution of Nickel chloride hexa hydrate (BDH) was prepared in distilled water. Few drops of (1 M) concentrated hydrochloric acid were added to prevent hydrolysis. The solution was standardized with EDTA solution at pH 10-11 using murexide⁹ as an indicator. A 1×10^-2 M solution of the reagent 3-hydroxy-3-n-propyl-1-(4-sulphonamidophenyl) triazene was prepared in alcohol. Tris-buffer (1%, w/v) was prepared. A UV/VIS. Systronic 106 Spectrophotometer and a pH Scan 2 tester were used.

Method

Spectrum of 3-hydroxy-3-n-propyl-1-(4-sulphonamidophenyl) triazene was measured in the wavelength region 360 – 460nm against solvent blank. Nickel and 3-hydroxy-3-n-propyl-1-(4- sulphonamidophenyl) triazene solutions were taken in 1:5 ratio and the spectrum of Nickel complex was recorded against reagent blank in the range 360-460 nm. The working wavelength was found to be 400 nm. A set of solutions containing Ni(II) and 3-hydroxy-3-n-propyl-1-(4-sulphonamidophenyl) triazene reagent in ratio 1:5 was prepared and ph was varied between 5 to 8. The pH range of constant maximum absorbance was found to be between 6.9 to 7.3. Composition of the complex was determined by Job’s method and moles ratio method of Yoe and Jones. The study revealed that composition of Nickel (II) complex is 1:2 (M:R).  Absorbance of set of six solutions containing Ni(II) to 3-hydroxy-3-n-propyl-1-(4-sulphonamidophenyl) triazene in ratio 1:5 was measured at corresponding working wavelength against reagent blank. Beer’s law was obeyed in concentration range 1×10^-5 to 6×10^-5 M. Interference of 23 cations and  anions in the determination of nickel was studied. To the set of solutions containing nickel to reagent 1:5 ratio, 10 ppm of different foreign ions were added at optimum conditions. Absorbance was measured against reagent blank. Those ions, which did not interfere at 10 ppm level their interference was again studied at 50 ppm level. In case no or little change in absorbance was seen as compared to the absorbance without any foreign ion, then for those ions interference was studied again at 100 ppm level. However tolerance of still higher concentration was not studied.

Results and Discussion

Nickel (II) forms 1:2 complex with 3-hydroxy-3-n-propyl-1-(4-sulphonamidophenyl) triazene.

Stability constants

Harvey and Manning’s method¹⁰ and Purohit’s method¹¹ have been used to determine the stability constants. Validity of the methods can be confirmed from the value of log β obtained from both the methods. Values of log β obtained by Harvey and Manning method and Purohit’s method were 9.57 and 9.53 respectively. The log β values agree quite well. Further the precision studies were carried out by measuring the absorbance of 10 sets of solution containing 5.86 ppm of Nickel (II), and title reagent in 1:5 ratio, under optimum conditions. The absorbance was measured against reagent blank at working wavelength (400 nm). Nickel was successfully determined at 5.86 ppm level with good precision. The value of ΔG obtained for the Harvey and Manning method and Purohit’s method were – 13.13 and –13.14(kcal/mole) at 27°C respectively.

Interference Studies

Interference of several cations and anions in the determination of nickel was studied at 10, 50 and 100 ppm level. Interference was studied using following 23 cations and anions viz. Na⁺, K⁺, NH₄⁺,Ba²⁺, Mn²⁺ Co²⁺, Pb²⁺, Cu ²⁺, Zn ²⁺, Cd²⁺, Mg²⁺, F^–,Cl^–, Br ^–, I^–, NO₂^–, NO₃^–, SO₄^-2, WO₄^-2, CO₃^2-, S₂O₃^2-  ,C₂O₄^2- ,CH₃COO^–. It was seen that at 100 ppm levelthe ions which still did not interfere are, Na⁺, K⁺,NH₄⁺, Ba²⁺, Mg²⁺, Cl^– , Br ^–, I^–. F^–, SO₄^-2, WO₄^-2, NO₂^–, NO₃^–, CO₃^2-, CH₃COO^–. However tolerance of higher concentration was not studied. Thus it can be seen that Nickel (II) can be determined even in presence of number of interfering species present at 100 ppm level.

Sandell’s Sensitivity

The molar absorptivity of complex was calculated from the Beer’s law graph and was found to be ε=6743 dm³ mol^-1 cm^-1.The value thus obtained was used for determining Sandell’s spectrophotometric sensitivity of the complex which was 8.61 ng cm^-2. This value is very low as compared to the following most commonly used reagents viz., 2-Acetylthiophenethiocyanate (48.92 ng cm^-2)¹², N,N’-Bis-(2-hydroxy-4-n-butoxyaceto-phenylidine) ethylenediamine (41.65 ng cm^-2)¹³,1-(2,3,5Triazolylazo)-2-naphthol(17.26 ng cm^-2)¹⁴, Sulphosalicylic acid(87.73 ng cm^-2)¹⁵, Ethylenediaminetetraaceticacid (3952.19 ng cm^-2)¹⁶, Dimethylglyoxime(14.67 ng cm^-2)¹⁷, 4-Methyl-2,3-pentanedionedioxime(19.31 ng cm^-2)¹⁸.

Conclusions

Thus the present studies have introduced 3-hydroxy-3-n-propyl-1-(4-sulphonamidophenyl) triazene as new reagent for nickel (II) determination spectrophotometrically which is quite comparable to most of the spectrophotometric reagents being used in the nickel (II) determination. Its easy synthesis, higher yields and economic method for preparation further enhance its applicability as spectrophotometric reagent for nickel(II) determination.Thus from the above studies it can be concluded that 3-hydroxy-3-n-propyl-1-(4-sulphonamidophenyl) triazene can be used successfully for spectrophotometric determinationof Nickel(II). The tentative structure of 1:2 complex of Ni (II) with HPSPT has been given in Figure2.

 

Figure 2 Click here to View Figure

 

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