Analytical and Bioanalytical Chemistry

, Volume 381, Issue 7, pp 1373–1380 | Cite as

Kinetic catalytic determination of trace Cu(II) in water samples with the thioglycolic/thiolactic acid–chromate reaction

Special Issue Paper

Abstract

The use of two novel similar indicator reactions as applied to the kinetic determination of Cu(II) in water is investigated. The methods rely on the catalytic effect of the analyte on the oxidation of thioglycolic (TGA) and thiolactic (TLA) acids by chromate in acidic media. The extent of the reactions was followed spectrophotometrically at 345 nm. Pseudo-first-order rate coefficients, kobsd, were determined as a function of catalyst concentration. Interference of Fe(III) and Pb(II) was suppressed by complexation with pyrophosphate. For the reaction of TGA, a linear regression for kobsd versus [Cu(II)] was obtained for the entire concentration range considered. Although the plot corresponding to TLA oxidation exhibits a sharp change of slope at approximately 1.8×10−5 M Cu(II), it can still be described effectively by two linear regressions with different slopes. The reaction of TGA is more sensitive than that of TLA at low Cu(II) concentration. The opposite is true for higher catalyst contents. The detection limits were 65 μgL−1 for TGA and of 80 μgL−1 for TLA oxidation, respectively. The relative standard deviations, of 0.4% for TGA and 1.1% for TLA oxidation, respectively, were obtained for five replicate runs at 1000 μg L−1. Samples of river and wastewater from the mining region of Baia-Mare, Northern Romania were analyzed using the more sensitive reaction of thioglycolic acid. Results were compared to those obtained by the officially standardized methods. Good agreement was obtained, even for an untreated sample. Measurements did not require prior separation of interfering species.

Keywords

Kinetic catalytic method Thiol oxidation Cu(II) determination Water analysis Slope technique 

Notes

Acknowledgements

This study was carried out with the financial support of the CNCSIS—Romania Ministery of Education, Grant No 33965/8.07.2003, code no. 37/31. We also gratefully thank Dr. Onorica Meteş from the Water Management Office—Baia-Mare, Maramureş County, Romania for her kind advice and for the AAS determinations.

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Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  1. 1.Department of Physical Chemistry, Faculty of Chemistry and Chemical Engineering“Babeş-Bolyai” UniversityCluj-NapocaRomania

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