Bull. Chem. Soc. Ethiop. 2007, 21(3), 451-456. ISSN 1011-3924
Printed in Ethiopia 2007 Chemical Society of Ethiopia
CATALYTIC KINETIC SPECTROPHOTOMETRIC DETERMINATION OF TRACE
TITANIUM BASED ON TITANIUM(IV)-(DBS-ARSENAZO)-POTASSIUM BROMATE
Research Center for Nanotechnology, South Campus, Changchun University of Science and
Technology, 7186 Weixing Road, Changchun 130022, P.R. China
(Received September 26, 2006; revised December 22, 2006)
ABSTRACT. Based on the property that in 0.12 M sulfuric acid medium titanium(IV) catalyzes the discoloring
reaction of DBS-arsenazo oxidized by potassium bromate, a new catalytic kinetic spectrophotometric method for
the determination of trace titanium (IV) was developed. The linear range of the determination of titanium is 0-2.4
µg/25 mL. The detection limit of the method is 0.47 ng/mL. The effects of fifty coexisting substances were
studied and most of common substances do not interfere with the determination of titanium. The method has good
selectivity. The present method was used in the determination of trace amount of titanium in cabbage and potato
samples with satisfactory results. The relative standard deviations of ten replicate determinations of the method
are 1.4-1.5 % and the recoveries of standard addition are 97.6-98.0 %, respectively.
KEY WORDS: Titanium(IV), Catalytic kinetic spectrophotometry, DBS-Arsenazo, Potassium bromate,
*Corresponding author. E-mail: Zhaiqingzhou@sohu.com, firstname.lastname@example.org
Titanium is one of necessary microamount of elements for the health of human body.
Mocroamount of titanium in human body has the function of strengthening the immunity ability
and titanium may participate in physiological and biochemical reaction as the active centers of
some enzymes. People absorb titanium by food and drink. The development of new methods for
the determination of trace amount of titanium has important significance in life science.
Catalytic kinetic spectrophotometry has the advantages of high sensitivity and simplicity of
operation . The catalytic kinetic spectrophotometric method is especially suitable for the
determination of trace component. Most of the indicator reaction of the catalytic kinetic
spectrophotometric determination of titanium used base dyes such as indirubin , neutral red
 and nile blue hydrochloride . However, the determination of titanium based on an
unsymmetric bis-arylazo derivatives reagent of chromotropic acid as an indicator reaction is
few. Also, there is no commonly accepted catalytic kinetic spectrophotometric method for
titanium due to the limit of selectivity. Thus, the development of a new system of the
determination of titanium is still of interest. DBS-Arsenazo(DBS-ASA), 3-(2,6-dibromo-4-
dibromo-p-sulfonic acid-arsenazo, is an unsymmetric bis-arylazo derivative of chromotropic
acid and has been used for the spectrophotometric determination of rare earths . It was found
that in 0.12 M sulfuric acid potassium bromate can oxidize DBS-arsenazo to fade using DBS-
arsenazo as an indicator and trace titanium(IV) has the catalytic effect on this reaction. Based on
this property, the optimum conditions of the catalytic reaction were studied in detail in this
paper and a novel method for the determination of trace titanium was developed by catalytic
Bull. Chem. Soc. Ethiop. 2007, 21(3)
Where Red and Ox are the reactants of a redox system and P and Q are the reaction
products. When an ion M(n + 1)+ is a catalyst, it accelerates the formation of the product P and is
then reduced to a lower oxidation state, Mn+. If Mn+ is oxidized again to M(n + 1)+ by reaction (2),
the oxidation of Red to P is catalysed by a minute amount of M(n + 1)+. As the concentration of the
catalyst is directly proportional to the rate of reaction, the reaction rate can be used for the
determination of the catalyst. In present study, the Red and the Ox are DBS-arsenazo and
potassium bromate, respectively, and the catalyst is Ti(IV). The proposed catalytic reaction
occurs in a cyclic manner according to equations (4) and (5):
6H+ + Ti(IV) + C22H15AsBr2N4O14S3 → Ti(III) + C6H7AsO3 + C10H10O8S2 + C6H4Br2SO3 + 2N2 (4)
6H+ + 5Ti(III) + BrO3
- → 5T i(IV) + 1/2Br2 + 3H2O (5)
The proposed non-catalytic reaction occurs according to equation (6):
6H+ + C22H15AsBr2N4O14S3
- → C6H7AsO3 + C10H10O8S2 + C6H4Br2SO3 + 2N2 + 1/2Br2 (6)
To evaluate the analytical applicability of the method, it was applied to the determination of
titanium in cabbage and potato samples. The analytical results are shown in Table 1. It can be
seen from the Table that when the present method was used to the determination of trace
titanium in cabbage and potato samples, the analytical results were in excellent agreement with
those by atomic absorption spectrometry. The relative standard deviation of ten replicate
determinations was 1.4-1.5 % and the recovery of addition standard was 97.6-98.0 %,
respectively. The analytical results were quite satisfactory.
Table 1. Analytical results of samples.
(µg·g-1, n = 10)
6.18, 6.22, 6.14, 6.29, 6.41,
6.14, 6.25, 6.16, 6.14, 6.19
9.81, 9.75, 9.86, 9.97, 9.83,
9.79, 9.64, 9.95, 9.54, 9.99
6.21 1.4 0.500 0.490 98.0
A novel catalytic kinetic spectrophotometric method for the determination of titanium was
developed in this paper. The linear range of the determination of titanium is 0-2.4 µg/25 mL
with the limit of detection 0.47 ng/mL. The selectivity of the system is good and common
substances do not interfere in the determination of titanium. The method is suitable for the
determination of some cabbage and potato biological samples.
1. Mmottola, M.A.; Berez-Bendito, D. Anal. Chem. 1994, 66, 131R.
2. Wang, Y.F.; Zhou, S.M.; Chen, G.S. Rock. Miner. Anal. (in Chinese) 1997, 16, 307.
3. Liu, L.W. Chin. J. Anal. Lab. 2001, 20, 34.
4. Yang, Y.; Luo, C.N.; Du, C. Chem. World (in Chinese) 1998, 39, 319.
5. Luo, Q.Y.; Lei, Z.H.; Yu, X.M. Chin. J. Anal. Chem. 1984, 12, 985.
6. Motolla, H.A. Kinetic Aspects of Analytical Chemistry, Wiley: New York; 1998; p 123.
7. Bontchev, P.R. Talanta 1970, 17, 499.