Indian Journal of Chemistry Vol. 40A, July 2001, pp. 727-732

Simultaneous first derivative spectrophotometric determination of nickel(II) and copper(II) in alloys with diacetylmonoxime benzoylhydrazone

K Hussain Reddy· & K B Chandrasekhart

Department of Chemistry, Sri Krishnadevaraya University, Anantapur 515 003

Received 14 March 2000; revised 12 March 2001

Diacetylmonoxime benzoylhydrazone (DMBH), a novel class of oxime-hydrazone has been synthesized and characterized based on elemental analysis, IR, NMR and mass spectra data. The reagent gives intense colour reactions with nickel(II) and copper(II) in basic medium. Hence direct spectrophotometric methods for the determination of nickel(II) and copper(II) have been developed in aqueous medium. The molar absorptivity and Sandell's sensitivity of the methods for Ni(II) and .Cu(II) are 2.l3x104, l.36x104 L. mol-I cm-I and 0.0028 and 0.0047 p.glcm2 respectively. Beer's law is obeyed in the ranges 0.12-2.58 p.glml and 0.25-2.0 p.glml fornickel(II) and copper(II) respectively. First derivative spectrophotometric technique has been used for the simultaneous determination of nickel(II) and copper(ll) using DMBH in alloys.

Oximes I and hydrazones2 are the two important classes of reagents for the spectrophotometric determination of metal ions. It should be of interest to design, synthesize and use a novel type of reagent containing both functional groups viz. oxime and hydrazone. Recently, we have reported the spectrophotometric determination of lead(II) in water samples using benzil a-monoxime isonicotinoyl hydrazone.3 Only few derivative methods4- 8 are available for the simultaneous determination of metal ions. In the light of above and in continuation of our previous work, herein we report the synthesis, characterization and analytical properties of a novel class of reagent viz. diacetyl-monoxime benzoylhydrazone (DMBH) and simultaneous first derivative spectrophotometric determination of nickel(II) and copper(II) using DMBH in alloys.

Materials and Methods A Schimadzu 160 A microcomputer based UV

visible spectrophotometer equipped with 1.0 cm quartz cells was used for all the spectral measurements. An ELICO LI-120 digital pH-meter was used for pH adjustments. All reagents used were of AR grade unless otherwise stated. All solutions were prepared with doubly distilled water.

Stock solutions containing 590 ppm of nickel(II) and 635 ppm of copper(II) were prepared by dissolving 0.70 g of NiS04.7H20 and 0.50 g of

tDepartment of Chemistry, JNTU College of Engineering, Anantapur 515 002, India

Cu(CH3COOHhH20 in 250 ml of distilled water respectively. The solutions were suitably diluted to obtain standard working solution of metal ions.

The reagent (DMBH) was prepared by simple condensation of 1 mol of diacetylmonoxime with 1 mol of benzhydrazide. In a 250-ml round bottom flask, hot methanolic solution (50 ml) of diacetylmonoxime (2 g, 0.025 mol) and benzhydrazide (3.4 g, 0.025 mol) were mixed and heated under reflux for 4 h. On cooling the reaction mixture, a yellow coloured product was separated out, collected by filtration washed with cold methanol, yield 30%, m.p 206°C.

Elemental analysis, found C, 61.02%, H, 6.01% and N, 19.12%; Calculated for DMBH C, 60.27%, H, 5.94% and N, 19.17%.

The pKa values are determined by Phillips and Merritt method9• The values of the deprotonation of ligand are 7 (PK1) and 9 (PK2).

The infrared spectrum of DMBH shows bands at 3335 (b), 1648 (s) and 1017 (m) cm- I assigned to vOH, vC=N (imine), v(C=N) oxime and vN--O stretching vibration respectively.

Mass spectrum of DMBH shows molecular ion (M) peak at 219 (m1z) corresponding to its molecular weight. The other important peaks at m1z 202, 161, 120, 105, 28 are assigned to [M-OH]; [M-CH3CN(OH)CH3CNt; M-[CH3CN(OH)CH3CNNHt and [M-CH3CN(OH)CH3CNNHCJIst respectively.

The reagent solution (0.01 M) was prepared by dissolving 220 mg of the compound in 100 ml of DMF. The reagent solution is stable for 24 h.

728 INDIAN J CHEM, SEC A, JULY 2001

Hydrochloric acid (1 M)-Sodium acetate (1 M) (PH 0.5-3.5); 0.2 M NaOAc-O.2 M AcOH (PH 4-6) and 2 M NH4CI-2 M NH40H (PH 7.5-11) were used.

Solutions of diverse ions of suitable concentration were prepared using AR grade chemicals.

Reactions with metal ions The reactions of some important metal ions were

tested at different pH values. The samples were prepared in 25-ml volumetric flasks by adding 10 ml of buffer (pH, 1-10), metal ion (1 ml of lxlO-3 M), and 1 ml of 0.01 M DMBH solution. The reaction mixture was diluted to the mark with distilled water. The absorbance was measured in 350-600 nm range against the reagent blank. The results are summarized in Table I.

Recommended procedures (a) Determination of nickel( II) and copper( II) (Zero order)

An aliquot of the solution containing 0.25 to 2.50 j.l.g/ml (or ppm) of nickel(II) or copper(II), 10 rnl of NH4Cl-NH40H buffer solution (PH 9.0) and I ml of 0.0 I M DMBH were combined in a 25-ml volumetric flask and the reaction mixture diluted to the mark with distilled water. The absorbance of this solution was read at 362 nm for the determination of nickel(II) or at 346 nm for the determination of copper(II).

(b) Determination of Ni( II) and cur II) using first derivative spectrophotometry

The first derivative spectra of Ni(II) and Cu(II) with DMBH complexes were recorded for the above solution of zero order. The peak height method (h) was followed for the determination of metal ions. The peak height at 392 and 420 nm is proportional to the concentration of Ni(II) and Cu(II) respectively. Therefore, peak heights were measured at these wavelengths for the construction of calibration plots.

(c) Simultaneous first derivative spectrophotometric determination ofnickel(lI) and copper(lI)

An aliquot of the solution containing nickel(II) and copper(II) in the optimum concentration range, 10 rnl of NH4Cl-NH40H buffer solution (PH 9.0) and 1 ml of 0.01 M DMBH solution were mixed in a 25-ml standard flask and the reaction mixture was made up to the mark with distilled water. The derivative amplitude was measured at 392 and 420 nm and the amounts of Ni(lI) and Cu(Il) were computed from corresponding equations (Eqs 1-4).

Table I-Analytical characteristics of diacetylmonoxime benzoyl hydrazone (OMBH)

Metal ion pH Ama. (nm) Molar absorptivity

Pb(II) 10.5 Cd(II)* 9.3 Ni(I1) 9.0 Cu(II) 9.0 Fe(II) 8.5 Co(ll) 8.5

* Borate buffer

Results and Discussion

372 348 362 346 364 331

I mol- J cm- J

I.Ox lO4

1.6x l04 2.l x 104 1.4x lO4

1.5x lO4

l.l x 104

Diacetylmonoxime benzoylhydrazone (DMBH) is easily obtained as any other Schiff base reagent. It is a blend of two functional groups viz. oxime and hydrazone. Oxime-hydrazones are not exploited so far for the spectrophotometric determination of metal ions. The bathochromic shift of strong absorption band of DMBH in solution from 285 to 305 nm indicates that in solution on increasing the pH, the acid (=N-OH ~ -N-O- + H+) is neutralized and> C=O group is enolized and dissociated.

The colour reactions of some important metal ions with DMBH are summarized in Table 1. The colour reactions are mainly due to complex formation of DMBH with divalent metal ions such as, Ni(II), Cu(II), Co(ll), Pb(II), Fe(II) and Cd(II) in basic medium to give intense coloured complexes. In basic medium, the ligand presumably exist in enolic form and coordinates the metal ion as dianion to give neutral complexes.

Determination of nickel( II) and copper( II) Nickel(II) and copper(II) reacts with DMBH in

basic medium to give yellow coloured species. The colour reactions are instantaneous even at room temperature in the pH range 8.0-11.0. The absorbance of the yellow coloured species remain constant for 2 h in both cases. The maximum colour intensity is observed in the pH range 8.0-10.0 and 8.0-11.0 for Ni-DMBH and Cu-DMBH complexes respectively.

A lO-fold molar excess of reagent is adequate for full colour development in both systems. Addition of excess reagent has no adverse effect on absorbance. The· order of addition of metal ion, reagent and buffer solution has no adverse effect on the absorbance. Important analytical characteristics of Ni-DMBH and Cu-DMBH complexes are summarized in Table 2.

Derivative spectrophotometry is a very useful technique in the sense that (1) it decreases the interference i.e., increases the tolerance limit value of

REDDY et al.: DETERMINA nON OF Ni(II) & Cu(II) IN ALLOYS

Table 2-Physicochemical and analytical characteristics of complexes

Characteristics

pH range (optimum)

A.ma• (nm)

Complexes of Ni(I1)-DMBH Cu(I1)-DMBH

8.0-10.0 8.0-11.0

Mole of reagent required per mole of metal ion for complete complexation

Beer's law validity range (ppm)

362

lO-fold

0.12-2.60

0.50-2.10

2.13x104

0.0028

1:2

4.5x109

0.006'

346

lO-fold

0.25-2.00

0.50-2.3

1.36x 104

0.0047

Optimum concentration range (ppm)

Molar absorptivity (L mole-I cm-I)

Sandell's sensitivity p.g of metal cm-2

Composition (M:L) (Job's and Mole ratio methods)

Stability constant

Standard deviation for ten determinations

• In the determination of 1.20 ppm of nickel

t In the determination of 1.30 ppm of copper

0.4

0.3

0.2

0.1

a

O~~~~~~==~~

0.2

0.1

1: 1

3.0x105

O.003t

a'

O+---~~----~~-------

-0.1

-0.2

-O.3+---~-----r----r----r----'

300 350 400 450 500 550 300 350 400 450 500 550

(1)

-g 0.3 .~

"S. 1=. 0.2

~ u 0.1 ~

b

~ 11 __ -r ____ r-__ ~~~==~ o 0+ VI

400 450 500 550

0.1

0.08

0.06

0.04

0.02

b'

O+---~----r----r--~~--~

300 350 400 450 500 550 .0 300 350

< I--------------------------~--------------------~~ c' c 0.6

0.5 0.4

0.3

0.2 0.1

0.3 0.2 0.1

O+-----r---------~---------0.1 '{).2 -0.3

0+L--~--~~r===~=9 -O.4+----,-----r----r----r----, 300 350 400 450 500 550 300 350 400 450 500 550

Wavelength (run)

729

Fig. I-Zero order and first order derivative spectrum of nickel(I1), copper(II) and mixture of nickel(II) and copper(II) at pH 9.0; a Zero order spectrum of Ni(I1)-DMBH system [Ni(II) 2xlO-5 M and DMBH 4xlO-4 M]; a' First order spectrum of Ni(II)-DMBH system [Ni(II) 2xlO-5 M and DMBH 4xlO-4 M]; b Zero order spectrum of Cu(II)-DMBH system [Cu(II) 2xlO-5 M and DMBH 4xlO-4 M]; b' First order spectrum of Cu(II)-DMBH system [Cu(I1) 2xlO-5 M and DMBH 4xlO-4 M]; c Zero order spectrum of Ni(II) and Cu(II) mixture-DMBH system [Ni(II) and Cu(II) mixture 2xlO-5 M and DMBH 4xlO-4 M]; c' First order spectrum of Ni(I1) and Cu(II) mixture-DMBH system lNi(Il) and Cu(Il) mixture 2xl0-5 M and DMBH 4xl0-4 M]

730 . INDIAN J CHEM, SEC A, JULY 2001

foreign ions and (2) it may be advantageously used for the simultaneous determination of metal ions having overlapping spectra. The recommended procedures have been employed for the derivative spectrophotometric determination of nickel(II) and copper(II) and simultaneous determination of metal ions.

The first derivative spectra of nickel(II) and copper(II) complexes of DMBH are given in Fig. 1. The spectra indicate that at 392 nm difference amplitude between Ni(II) and Cu(II) is maximum such that copper(II) has less amplitude compared to nickel(II), while at 420 nm the difference is negligible. It may be inferred that the total derivative amplitude either at 392 or 420 nm is equal to the sum of the derivative amplitudes due to the individual nickel(II) and copper(II) species. Hence 392 and 420 nm were chosen for the simultaneous first order derivative spectrophotometric determination of Ni(II) and Cu(II).

Calibration plots were construCted at 392 and 420 nm by plotting the derivative amplitude against the concentration of nickel(II) and copper(II). The plots thus obtained (Fig. 2) are linear for obeying the relationships.

For Ni(II), A392=0.1354C + 0.0001 and ~20 = 0.0678C + 0.0007

For Cu(II), A392=0.0387C + 0.0008 and A420 = 0.059IC + 0.0018

The simultaneous first derivative spectrophoto-metric determination of Ni(1I) and Cu(II) was therefore carried out by solving the following pair of simultaneous equations.

... (1)

0.4 ,..-----------------,

.. ~

=

0.3

::: 0.2 co. E «

0.1

o

Ni(lI) 1 at :l92 nm

0.5 1.5 2 2.5 3 Amount of Ni(/J) and Cu(U) (Ilg/ml)

Fig. 2-Calibration plot for the determination of nickel(II) and copper(II) at pH 9.0

. . . (2)

where CNi and Ccu are the amount of Ni(II) and Cu(II) in ppm respectively. Solving Eqs 1 and 2,

A392 oCu42o-A42o OCU392 Ni=------------x58. 71 x 1000

.. . (3)

A420 oNb92-A392 oNi42o Cu :---------x63.54x lOOO ... (4)

OCU420 oNi392-0Ni42o OCU392

where A392 and ~20 are the first derivative amplitude of the solution mixtures of Ni(II) and Cu(II) at 392 and 420 nm respectively. The 0 values represents the coefficients of linear variation of Ni(II) and Cu(II) at the wavelengths specified.

The simultaneous first derivative spectrophoto-metric determination of nickel(II) and copper(II) in synthetic mixtures was carried out by employing the recommended procedure and the results are presented in Table 4.

Table 3-Simultaneous first derivative determination of nickel (II) and copper(II) in synthetic mixtures

Amount Taken (~~m) Amount found* ~~m Error % Nickel (II) Copper (II) Nickel (II) Copper (II) Nickel (II) Copper (II)

0.705 1.018 0.690 0.994 -2. \0 -2.20

0.705 1.273 0.695 1.236 -1.40 -2.60

0.705 1.527 0.692 1.540 -1.80 +0.85

0.705 1.782 0.692 1.726 -1 .80 -2.90

0.705 2.036 0.720 2.080 +2. \0 +2.60

0.705 0.762 0.686 0.754 -1.00 -0.78

1.409 0.762 1.435 0.765 +1.80 +0.40

1.643 0.762 1.604 0.751 -2.40 -1.40

REDDY et al.: DETERMINATION OF Ni(II) & Cu(II) IN ALLOYS 731

Table 4-Tolerance limit of foreign ions in the determination of 1.20 ppm of nickel(II) and 1.30 ppm of copper(II)

Ion added Tolerance limit (22m) Nickel(IQ C022er(II)

Zero order Fi rst deri vati ve Zero order First derivative

Triethanolamine 5200 7150 2000 2000 Thioglycolic acid 450 530 400 420 Citrate 818 1057 836 840 Tartrate 722 800 656 670 Iodide 560 701 508 530 Thiosulphate 471 575 516 525 Oxalate 412 465 470 485 Bromide 336 420 384 400 Thiourea 304 370 335 350 Nitrate 275 301 273 285 Urea 264 292 288 305 Acetate 260 310 Thiocyanate 255 282 260 265 Chloride 150 170 142 145 Phosphate 95 500 190 195 Fluoride 91 95 99 100 Sulphate 384 396 Tungsten(VI) 147 150 150 165 Molybdenum(VI) 97 100 77 80 Tin(I1) 22 25 47 50 Cr(VI) 8 10 8 II Pd(I1) 10 15 Iron(I1I) 6' 8 6' 8 Manganese(II) 5 II 5 5 Silver(I) 4 5 30 35 Aluminium(lII) 8 22' 50 60 Copper(ll) 2.0t 2.0 Zinc(I1) 13 15 6 0.3 Vanadium(V) 12 41 5 31 'Masked with 1000 ppm of triethanolamine tMasked with 280 ppm of thiourea

Table 5-Simultaneous determination of nickel(II) and copper(II) in alloy samples

Sample Certified Value (%) Amount Found (%)* Error (%) Nickel(II) Copper(II) Nickel(II) Copper(II) Nickel(II) Copper(II)

Al alloy'

BAS 106b 1.025 1.175 1.020 1.170 -0.5 -0.4

1.93 4.10 1.890 4.13 -2.0 +0.7

NTPC baW bearing material 10.00 4.50

* Average of five determinations a = 0.3% Fe; 1.2% Mn; 18.5% Si; 77% Al b = 0.43% Fe; 0.19% Mn; 0.29% Si; 1.61% Mg; rest Al c = 6.5% Cr; 2% Mn Aluminium is masked with triethanolamine.

Interference The effect of some of the ions which often

accompany nickel and copper has been studied by adding different amounts to 1.2 p.g/ml of nickel(II) and 1.3 p.lIml of copper. The colour is developed as described in the standard procedure. An error of ± 2% in the absorbance or amplitude reading in the case of derivative methods considered tolerable. The results are given in Tahle 3. The data obtained in first

9.85 4.55 -1.5 +1.1

derivative method are also incorporated. The data suggest that several associated anions and cations do not interfere when they are present in large excess. The tolerance limit values for many anions and cations are more in derivative methods. The interference of associated metal ions such as Fe(III) and AI(III) is decreased with triethanolamine. In the detetermination of Ni(II), the tolerance limit of value for copper(II) is more in the presence of thiourea.

732 INDIAN J CHEM, SEC A, JULY 2001

Applications The method developed was applied to the

simultaneous determination of Ni(1I) and Cu(II) in aluminium alloys and NTPC ball bearing materials.

Analysis of alloys Alloy material (0.25 g) was dissolved in aqua-regia

(15 ml) by warming and the solution was evaporated to dryness. The residue was dissolved in dil . HCI (10 ml) and the resulting solution concentrated to -5 ml, diluted to -50 ml with doubly distilled water, filtered and made up to 100 mi. Suitable aliquots of sample containing nickel and copper (in the optimum concentration range) were analysed according to the derivative procedure for the simultaneous determination of Ni(II) and Cu(lI). The results are presented in Table 5.

Acknowledgement The authors thank the CSIR, New Delhi [No.

01(1558)/98/EMR-II] for financial support.

References 1 Singh R B, Garg B S & Singh R P, Talanta. 26 (1979) 425. 2 Jain P & Singh R P, Talanta, 29 (1982) 77. 3 Ramesh M, Chandrasekhar K B & Hussain Reddy K, Indian J

Chern, 39A (2000) 1337. 4 Wang N X, Liang W A & Qi P, Talanta, 40(6) (1993) 897. 5 Costa A C S, Ferrerira S L C, Andrade M G M & Loba I P,

Talanta, 40(8) (1993) 1267. 6 Sayed E I, Youssef A & Khali M N, Talanta, 43(4) (1996) 583. 7 Toral M, Ines, Richter, Poblo, Rodriguez & Cecilia, Talanta,

45(1) (1997) 147. 8 Baraj B, Cortina J L, Sastre A & Grandos M, J Anal Chern,

360(2) (1998) 263.

9 Phillips J P & Merritt L L, J Arn chern Soc, 70 (1948) 410.