A simple, cheap but reliable method for evaluation of zinc chelating properties

Zinc is an essential trace element. Both its lack and excess are associated with pathological states. The former is more common and can ensue from the excessive treatment with clinically used iron/copper chelators.

The aim of this work was to prepare a reliable, rapid and cheap method for the screening of zinc chelation. Spectrophotometric assessment using a known zinc indicator dithizone was selected.

Initial screening performed by comparison of spectra of dithizone and its complex with zinc suggested 530 and 570 nm as suitable wavelengths for determination of zinc at pH 4.5 while 540 and 590 nm for pH 5.5-7.5. Additional research showed the lower wavelengths to be more suitable. The sensitivity of the method was always bellow 1 μM with good linearity relationship between absorbance and zinc concentration. The method suitability was confirmed by use of two known zinc chelators, ethylenediaminetetraacetic acid (EDTA) and N,N,N',N'-tetrakis(2-pyridylmethyl)-1,2-ethylenediamine (TPEN).

This method represents a sufficiently precise method for zinc chelation screening usable at pathophysiologically relevant pH conditions. Such method can be employed for both screening of novel zinc chelators and for testing affinity of other metal chelators for zinc.