Tahnfa, Printed
Vol. 31, No. 11, pp. 1008-1009,
1984
0039-9140/84$3.00+ 0.00 Copyright 0 1984Pergamon Press Ltd
in Great Britain. All rights reserved
DETERMINATION OF NICKEL BY FLAME ATOMIC-ABSORPTION SPECTROPHOTOMETRY AFTER SEPARATION BY ADSORPTION OF ITS NIOXIME COMPLEX ON MICROCRYSTALLINE NAPHTHALENE TOHRU NAGAHIRO and BAL KRISHAN PURI Himeji Institute of Technology, 2167, Shosha, Himeji-shi, Hydgo, Japan MOHAN KATYAL and MASATADA SATAKE Faculty of Engineering, Fukui University, Fukui 910, Japan (Received 31 December
1983. Accepted
1 June 1984)
Summary-A method has been developed for the determination of nickel in alloys by flame atomicabsorption spectrophotometry after formation of a water-insoluble complex, its adsorption on microcrystalline naphthalene, and dissolution of the complex and naphthalene in nitric acid and xylene.
Nioxime forms a water-insoluble, thermally stable red complex with nickel, which can be determined spectrophotometrically in the presence of gum arabic in aqueous medium, ‘J but the complex is only partially soluble in the common organic solvents and so cannot be determined by extraction and spectrophotometry. Like may other complexes,3-8 nickel nioximate is readily and quantitatively adsorbed on microcrystalline naphthalene, however, and thus easily separated from the aqueous phase. The nickel can then be stripped by dissolving the solid with nitric acid and xylene, and determined by atomicabsorption. EXPERIMENTAL
Eflect
Reagents Standard nickel solution, 5 ppm. Nioxime solution in ethanol, 0.1%. Acetic acid/ammonium acetate buffer, 1M, pH 4.0 Naphthalene solution in acetone, 20%. Procedure
To a known volume (up to 40 ml) of sample solution containing 5-100 pg of nickel, in an 80-ml stoppered Erlenmeyer flask, add 2.0 ml of pH 4.0 buffer and I .5 ml of nioxime solution, mix, then after a few minutes add 2.0 ml of naphthalene solution and shake the mixture vigorously for 30 sec. Filter off the nauhthalene on a filter paper (No. 5C, Toyo Roshi Co., Japai) placed flat on a perforated Teflon disc (3 cm in diameter) placed in an ordinary filter funnel or on a sintered glass filter (porosity 2). Wash with water, then add 13 ml of 3M nitric acid and 2 ml of xylene to the filter to dissolve the naphthalene and nickel complex. The nickel is then in the aqueous phase and the naphthalene in the xylene. Filter the aqueous phase into a 20-ml standard flask, and wash the paper with water until the solution is diluted to the mark. Aspirate the solution into an air-acetylene flame and measure the absorbance at 232.0 nm, using a nickel hollow-cathode lamp. RESULTS AND
of the nioxime solution, and l-5 ml of buffer can be used. The nickel complex forms completely in a few minutes. Adsorption is complete with 0.54.0 ml of the naphthalene solution and takes only a few seconds of shaking. Mineral acids of various concentrations were tried for dissolution of the nickel complex and 3M nitric acid was found the most suitable. The adsorption yield with the 0.4 g of naphthalene is constant for aqueous phase volumes up to 200 ml, but decreases for larger volumes. Beer’s law is obeyed for nickel up to 5 pg/ml in the final aqueous solution. For ten replicate determinations of 40 pg of nickel, the relative standard deviation was less than 1.4%.
DISCUSSION
The optimum pH range is 3.2-l 1.2. The adsorption of the complex is quantitative with use of 0.3-6.0 ml
of diverse
ions
In determination of 40 pg of nickel the following compounds did not interfere, even at the lOO-mg level: KI, NaClO,, KNO,, NaCl, CH3COONa.3H,0, NH&l, sodium tartrate, Na,SO,, KSCN, NaF, KH,PO, .12H,O. Only relatively low amounts (1 mg) of sodium citrate and oxalate could be tolerated. EDTA and KCN interfered seriously. Mg, Mo(VI), Ca, W(VI), Mn(II), Pb, Cd, Hg(I1) and Ag (adsorbed at pH 11.2), could be tolerated even at the lOOO-mg level. Pd(I1) can be removed by prior extraction into molten naphthalene at pH 1.0. The following metal ions (amounts, mg, in parentheses) could be tolerated: Al (1.50), V(V) (loo), Zn (SO), Cr(V1) (20), Pt(V1) (15), Bi(II1) (2), Fe(II1) (1.5) and Co (0.1). Cu(I1) (4 mg) could be completely masked with 5 ml of 5% thiourea. In analysis of steels, if the iron concentration is higher than the tolerance limit, it can be lowered by extraction from 6M hydrochloric acid medium with methyl isobutyl ketone or diethyl ether. Generally, metal ions such as Fe(III), Co and Cu(II), which form complexes, interfere with the determination, and hence they must be eliminated with masking agents or by prior extraction with organic solvents.
1008
SHORT
1009
COMhKJNlCATlONS
Table 1. Determination
of nickel in samples Nickel content. % ,”
Sample
-
N.B.S. SRM-163 Low alloy N.B.S., SRM-171 Magnesium alloy N.B.S., SRM-85 Aluminium alloy
JSS 157-3 Carbon steel JSS 503-4 Nickelchromium steel JSS 505-4 Ni-Cr-Mo steel
Composition, % Mn:0.897 c:o.933, S:O.O27 P:O.O07, Si:O.488, Cu:O.O87 Mo:0.029 Cr:0.982, N:0.007 Mn:0.45, Si:O.O118 Cu:O.O112, A1:2.98 Fe:0.0018 Pb:0.0033, Zn: 1.05 Mg: 1.49 cu: 3.99, Cr:0.21 Mn:0.61, Fe:0.24 Si:O.l8, Zn:0.03, Ti:0.022 Pb:0.021, Ga:0.019 V:O.O06 Si:O.21 c:o.21, Al:0.017 S:O.O25, Mn:0.61, P:O.O20 Cr:O.lO, Cu:O.lO Si:O.27 c:o.33, N:0.0115 s:o.o20, v:o.o04 Cu:O.O84, Mn:0.63, P:O.O29 Cr:0.70, Mo:0.013 Si:O.30 c:o.20, N:0.0061 S:O.O086, cuo.10, Al:0.026 Mn:0.64, P:O.O2 Mo:0.22 Cr:0.50,
Nickel certified value %
Present method
Direct AAS
0.081
0.085, 0.082, 0.082, 0.085, 0.082
0.082
0.0009
0.0007, 0.0007 0.0008, 0.0007 0.0006
0.0008
0.084
0.089, 0.093 0.089, 0.090 0.087
0.085
0.11
0.10, 0.10, 0.10 0.11, 0.11
0.11
1.24
1.28, 1.28, 1.27 1.26. 1.27
1.34
1.82
1.72, 1.75, 1.72 1.76, 1.76
1.93
0.009, 0.010, 0.030, 0.030,
0.010, 0.010, 0.030, 0.030,
CoSO,.7H,O* Co(NO,), .6HrO*
0.009, 0.009 0.010 0.031, 0.030 0.031
0.010, 0.011 0.010 0.030, 0.031 0.031
*Cobalt was removed from 8M HCl medium by extraction with three 30-ml portions of 5% tri-n-octylamine xylene.9 Analysis
of alloys
This method has been successfully applied to the analysis of nickel-containing alloys and metal salts. The results (Table 1) are in reasonable agreement with the certified values or those obtained by direct AAS determination. The method is not really suitable for alloys containing > -2% nickel, on account of the comparatively high relative standard deviation. REFERENCES
1. R. B. Singh, B. S. Garg and R. P. Singh, Tulanta, 1979, 26, 425.
solution in
2. R. C. Ferguson and C. V. Banks, Anal. Chem., 1951,X3, 448. 3. T. Fujinaga, Y. Takagi and M. Satake, Bull. Chem. Sot. Japan, 1979, 52, 2556.
4. M.
Satake,
Y.
Matsumura
and
M.
C. Mehra,
Mikrochim. Acta, 1980 I, 455.
5. M. Satake and M. C. Mehra. Microchem. J.. 1982. 27. 182. 6. M. Satake, M. C. Mehra and T. Fujinaga, Bull. Chem. Sot. Japan, 1982, 55, 2079. 7. M. Satake and H. B. Singh, Defence Science J., 1982, 32, 201. 8. M. Satake, M. C. Mehra, H. B. Singh and T. Fujinaga, Bunseki Kagaku, 1983, 32, El65. 9. G. Nakagawa, Nippon Kagaku Zasshi, 1961,82, 1042. I