42

Z. Anal. Chem. 284, 42 (1977) - �9 by Springer-Verlag 1977

Z. Anal. Chem., Band 284 (1977)

Spectrophotometric Determination of Cobalt(II), Nickel(II) and Copper(II) with 1-(2-Quinolylazo)-2-acenaphthylenol

Ishwar Singh I , B. S. Garg, and R. P. Singh

Department of Chemistry, University of Delhi, Delhi-110007, India

Received May 11, 1976; revised July 6, 1976

Spektralphotometrische Bestimmung yon Kobalt( II) , Nickel( II) und Kupfer( II) mit 1- ( 2-Chinolylazo )-2-acenaphthylenol

Best. von Kobalt(II), Nickel(II), Kupfer(II) mit 1-(2-Chinolylazo)-2-acenaphthylenol; Spektralphotometrie

1-(2-Quinolylazo)-2-acenaphthylenol (QAAc) forms red coloured water insoluble complexes with cobalt(II) , nickel(II) and copper(II) , which were found to be extractable in mos t o f the water immiscible organic solvents, having m a x i m um absorbance at 550 rim, 560 n m and 545 nm and composi t ions ( M : L ) 1:3, 1 :2 and 1:2, respectively. Sandell 's sensitivities and mola r extinction co-efficients were 0.0011 gg Co /cm 2 and 5 .4x 1041 �9 m o l e . cm -~, respectively, at 550 nm for c o b a l t ( I I ) - Q A A c complex; 0.0013 lag Ni /cm / and 4.4 x 104 1 �9 mole �9 cm -~, respectively, at 560 nm for n i c k e l ( I I ) - Q A A c complex and 0.0015 lag Cu/cm 2

and 4.25 x 104 1 �9 mole - cm -1, respectively, at 545 nm for c o p p e r ( I I ) - Q A A c complex. The r a n g e s for Beer's Law validity o f the complexes were 0 - 1.06 ppm, 0 - 1 . 0 ppm and 0 . 1 6 - 1 . 5 9 ppm, respectively.

Working Procedure. To a suitable aliquot containing 2.2 to 9.0 lag of cobalt(II) or 5.75-23.25 lag of nickel(II) or 2.4 to 14 lag of copper(II), add sufficient excess [5 ml of 2 x 10 -3 M for cobalt(II) or copper(II) but 10ml of 2 x 1 0 - 3 M for nickel(II)] of methanolic ligand solution followed by 2 - 4 ml of 2 M sodium acetate. Raise the volume of the content to 10 ml in the determination of cobalt(II) or copper(II), but 25 ml in case of nickel(II), keeping 50~ (v/v) methanol aqueous system and then extract in 10 ml of freshly distilled carbon tetrachloride. Measure the absorbance against reagent blanks prepared under identical conditions.

Effect of Diverse Ions. The ions C I - , B r - , I - , SO 2 - , S/O 2- , N O 3 , NO2-, Ca(II) , Ba(II), Sr(II), AI(III) , Sb(V), Mn(II) , Pt metals except Pd (in cold) did no t interfere, but the ions C N - , P O ] - , citrate, E D T A , Fe(II), Zn(II) , Co(II ) and Ni(II ) interfered seriously. The tolerence limits (in ppm) upto which other ions did not cause an error more o f than 2 ~ in absorbance are given in Table 1.

Acknowledgement. One of the authors (I.S.) is thankful to the Council of Scientific and Industrial Research, New Delhi, India, for providing the necessary financial assistance.

Table 1. Effect of diverse ions**

Anions Cations

Foreign ions Co-QAAc Ni-QAAc Cu-QAAc Foreign ions Co-QAAc Ni-QAAc Cu-QAAc

F - 1000 Int. 500 Cd(II) * 5 c Int. Int. CNS- 1000 500 Int. Hg(II)* 20a 5 c 5" SO~- 20 500 100 Cu(II)* 15 c Int. - 8 2 0 2 - 1000 200 Int. Ag(I) * 15 b 5 b 5 a Oxalate Int. 100 Int. Au(III)* 10c 10d 10a Tartrate 250 200 250 Pd(II)* t0c 5 ~ 5 a BO~- 1000 500 Int. Pb(II)* 5a _ 5" Thiourea 1000 500 Int.

* Masked with a F - ; b CNS- ; c $20~- ; a I - . ** In the determination of cobalt(II) and nickel(II) = 0.59 ppm and copper(II) = 0.635 ppm.

1 Corresponding author.