I942
Anal. Chem. 1983, 55, 1942-1946
Engineering, Inc. (Austin, TX), for supplying capillary columns and Analect Instruments (Irvine, CA) for the loan of the fx-6200 spectrometer. Registry No. COz, 124-38-9;anisole, 100-66-3;acetophenone, 98-86-2;nitrobenzene, 98-95-3.
LITERATURE CITED (1) Board, R.; McManlgill, 0.; Gere, D. R. Anal. Chem. 1982, 54, 736-740. (2) Peaden, P. A.; Fjeidsted. J. C.; Springston, S. R.; Novotny, M.; Lee, M. L. Anal. Chem. 1981, 53, 407A-414A. (3) Peaden, P. A.; Lee, M. L. J . Liq. Chromafogr. 1982, 5, 179-221. (4) Shafer, K. H.; Lucas, S. V.; Jakobsen, R. J. J . Chromafogr. Scl. 1979, 17, 464-470. (5) Kuehi, D.; Grlffiths, P. R. Anal. Chem. 1980, 52, 1394-1399. (6) VMrine, D. W. “Fourier Transform Infrared Spectroscopy”; Ferraro, J. R., Baslle, L. J., Eds.; Academic Press: London, 1979; Vol. 2, Chapter 4.
(7) Randall, L. Q.; Wahrhaftfg, A. L Rev. Sc;. Instrum. 1981, 52, 1283-1295. (8) Shafer, K. H.; Cooke, M.; DeRoos, F.; Jakobsen, R. J; Rosario, 0.; Mulik, J. D. Appl. Specfrosc. 1981, 35, 469-472. (9) Glss, G. N.; Brissey, G. M.; Steiner, S.; Wilkins, C. L. Anal. Chem. 1981, 53, 113-117. (10) Hlrschfeld, T.; Sanborn, R. H.; Wong, C. M.; Crawford, R. W. Anal. Chem. 1982, 54,817-820. (11) Griffiths, P. R. Appl. Specfrosc. 1977, 3 1 , 284-288. (12) Van Lenten, F. J.; Rothman, L. D. Anal. Chem. 1976, 48, 1430-1432. (13) Peaden, P. A.; Fjeldsted, J. C.; Lee, M. L. Anal. Chem. 1982, 5 4 , 1090-1 093. (14) Herzberg, G. “Infrared and Raman Spectra of Polyatomic Molecules”; Van Nostrand: New York, 1949. (15) Gere, D. R., Hewlett-Packard Co., private communication. (16) Kuehl, D.;Griffiths, P. R. J . Chromatogr. Sc;. 1979, 17, 471-476.
RECEIVED for review May 9,1983. Accepted June 27, 1983.
Determination of Trace Titanium with the Catalytic Maximum Wave in Differential Pulse Polarography Yasuyuki Yamamoto Graduate School of Environmental Science, Hokkaido University, Sapporo 060, Japan Kiyoshi Hasebe* a n d Tomihito Kambara Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060, Japan
A differentialpulse polarographic method for the determination of tltanlum by use of the catalytic-maximum wave has been studied. A well-defined differential pulse polarographic peak of titanium( I V ) In Britton-Robinson buffer solution containing 1 mM EDTA, 5 mM KBrO,, and 40 mM HBO, is observed in the potential range 4-0.15 to -0.45 V vs. SCE. The peak current is very large and proportional to the concentration of titanlum(1V) between 10“ and lo-’ M. The relative standard deviation at 3.34 X lo-’ M TI(IV) was 2.24% (n = 6). This method has been applied successfully to the determination of titanium in copying paper and carbon steels.
Titanium is an important substance in steel alloy production. Above all, demand of titanium dioxide production for disposable items, such as housing production, shows a yearly increase. A simple and highly sensitive method for the determination of titanium is needed. The determination can be carried out by the spectrophotometric method with diantipyrylmethane and 1,2-dihydroxybenzene-3,5-disulfonic acid, disodium salt (Tiron) (1-3). However, this method involves many steps for color development. Atomic absorption spectrometry also is an unfavorable method because of the difficult atomization of titanium. When a graphite furnance atomizer is used, the detection limit is improved from 4.18 X 10%to 8.35 X M (4).The inductively coupled radio frequency plasma (ICP) method is the most sensitive, its detection limit being 4.18 X M, but the ICP analysis is time-consuming and very expensive (5). In this paper, we describe the pulse polarographic behavior of titanium and the suitable conditions for analysis. There is little information in the literature about polarographic determinations for microamounts of titanium (6, 7). In trace analysis, the determination of titanium by anodic stripping voltammetry is not feasible because of the nonreduction of
titanium from 4+ to 0 (8). Only the reduction from Ti(1V) to Ti(III), or the reverse oxidation reaction, is effective by polarography. There are many reports of the electrochemical behavior of titanium (9-14), but these are not applicable to the analysis of trace quantities of titanium. The AC polarographic method for titanium(1V) in the presence of a large excess of iron(II1) is not very sensitive (15). Polarographic catalytic waves caused by metal ions or metal complexes in the presence of certain inorganic or organic compounds offer high sensitivity (16-20) and are used for the determination of analytes in low concentration. Toropova and Zabbarova (21) have examined the polarographic catalytic wave of the Ti(1V)-EDTA complex in the presence of bromate ions and determined titanium(1V) between lo4 and M. Kaneko and Kaneko (22)have also applied the polarographic catalytic wave to the determination of titanium in thin films of titanium carbide containing 0.6-25 Fg of titanium. We have studied the polarographic behavior of titanium(1V)-EDTA complexes by differential pulse polarography and observed the catalytic maximum wave of the titanium(1V)-EDTA complex in Britton-Robinson (B-R) buffer containing 5 mM KBr03 and 40 mM boric acid. In the differential pulse polarographic (DP) mode, the catalytic maximum peak is more than 200 times larger than that of the Ti(IV)-EDTA complex, using the same conditions. It is also larger than that of the so-called catalytic peak obtained in the Ti(IV)-EDTA-KBr03 system without boric acid, by as much as 10 times. This method has one of the most favorable limits of detection (ca. 1.5 x M), being comparable to that of the ICP method. In the present paper, the pulse polarographic behavior of the titanium complex in B-R buffer containing KBr03, with and without boric acid, and also the most suitable conditions for determination are described. EXPERIMENTAL SECTION Apparatus. Polarograms were recorded with a Model P-1000 voltammetric analyzer with a mechanical drop knocker (Yanag-
0003-2700/83/0355-1942$01.50/00 1983 American Chemical Society
ANALYTICAL CHEMISTRY, VOL. 55, NO. 12, OCTOBER 1983 1943
oL----
' 50
2.0
' 2 4.0
I
0
PH Figure 1. Effect of pH on peak potential arid peak current of the catalytic maximum wave: 2.088 X 10" M Ti(1V) in B-R buffer solution containing 1 mM EDTA, 5 mM KBrO,, and 40 mM HB02; drop time, f d = 2 s; scan rate, v = 5 mV s-'; pulse amplitude, A€ = -50 mV.
imoto Mfg. Co., Ltd., Kyoto, Japan) and a Watanabe X-Y recorder, Model WX 4401. The dropping mercury electrode (DME) had the following characteristics: mercury flow rate, m = 1.33 mg s-l in deionized double-distilledwater at open circuit; natural drop time, t d = (1.82 s in B-R buffer solution containing 1 mM EDTA and 5 mM KBrO,; mercury reservoir height, h ~ r o r r & d = 89.5 cm. The three-eleclrode system consisted of the DME, a double-junction SCE, and a Pt coil as the counterelectrode. A presaturated, purified nitrogen stream was used to deoxygenate the polarographic solutions and keep them oxygen-free. Except for temperature dependence studies, all measurements were carried out in a water bath at 20 & 0.5 "C. Measurements of pH were carried out with a digital pH meter, Model COM-10 (Denki Kagaku Keiki Co., Ltd. Japan). Controlled potential electrolysis was carried out with a Model 173 potentiostat/galvanostat with a Model 176 current-to-voltage converter (EG&G Princeton Applied Research, Princeton, NJ). Reagents. All. chemicalsused were of analytical reagent grade and dissolved in deionized and double-distilledwater. A standard titanium(IV) solution of lo00 ppm (2.089 X 10" M) was prepared from 99.9% titanium metal obtained from Koch-Light,Ihgland. Ethylenediaminetetraacetic acid (EDTA) and analogous compounds were obtained from Dojindo Laboratories, Kumamoto, Japan.
RESULT8 AND DISCUSSION Mechanism of Catalytic Maximum Wave. The catalytic waves of titanium complexes have been studied by many investigators (10,16-22). Toropova and Zabbarova (18),for example, proposed that the mechanism of the catalytic wave in the presence of bromate ion can be represented as follows: TiY 'TiY-
+ e-
+ Br03-
-
TiY-
(1)
TiYBr02-
(2)
-+
where Y4-denotes the EDTA anion. TiYBr032-, caused by a bimolecular reaction, decomposes rapidly to form TiY again. Pecsok and Maverick (23) also studied titanium-EDTA complexes in detail and polarographically determined the equilibrium constanta o l the complexes. Kaneko and Kaneko (22)have discussed in detail the mechanism of catalyst-oxidant interaction in the ielectrode process. From these reports, the catalytic wave of Ti (1V)-EDTA complex in the presence of bromate ion is an EC (heterogeneous electron transfer followed by homogeneous chemical reaction) mechanism, as shown by the following equations:
6Ti:"Y-
+ + + + Ti'"Y -t
+ e-
6H"
BrC),-
TiOY2-
pH
