PARENT SESSION

1A - Environmental Analytical Methods
Hall 8
8:30 AM - 12:30 PM, Monday, 28 April 2003
Chair: Schäffer, A.¹, ¹
Co-chair: Bester, K.², ²

(MO8/9) Analysis of copper-complex lability in aqueous systems using high-specific activity ⁶⁴Cu.

van Doornmalen, Jacco¹, de Goeij, Jeroen J.M.¹, ¹ Interfaculty Reactor Institute, Delft University of Technology, Delft, The Netherlands

ABSTRACT- The behaviour of copper in aqueous systems is regulated by its speciation. Usually, a state of chemical equilibrium is assumed when speciation is assessed, although many aquatic systems are in fact dynamic systems. A more realistic description of copper behaviour will therefore be obtained, when kinetic parameters of copper speciation are considered. One kinetic aspect of copper speciation, viz. the lability of copper complexes, was studied with the aid of high-specific activity ⁶⁴Cu (> 10¹⁶ Bq ⁶⁴Cu per g Cu), which was produced via the ⁶⁴Zn(n,p)⁶⁴Cu nuclear reaction. The general procedure was to add the radioactive copper isotope in one specific chemical form to a sample and follow its transformation into another. Analytical techniques (chromatography, ion extraction) were used able to physically separate free copper ions from copper complexes as a function of time, in order to quantify this transformation. Both association and dissociation reactions of a range of artificial as well as natural copper complexes could be studied in this way and values for their dissociation rate constant (k_d), a measure for complex lability, could be determined. Thus, the ⁶⁴Cu radiotracer proved to be an excellent tool for copper-complex lability determinations in aquatic systems. Due to its high-specific activity, only minute amounts of the tracer needed to be used, which may be important for samples of which initial speciation has to be preserved.

Key words: speciation dynamics, copper-complex lability, ⁶⁴Cu radiotracer, dissociation rate constant