Determination of Zeatin in plant extracts by square wave stripping polarography and differential pulse stripping polarography

The electrochemical behaviour of the phytohormone trans-Zeatin at a hanging mercury drop electrode was studied. Three adsorption waves are observed, the first is due to the complexation reaction between Hg(II), produced at the electrode, and Zeatin and the other two by specific adsorption of Zeatin and reduction of the C = N group, respectively. The methodological and instrumental variables were studied in order to develop a determination method based on stripping differential pulse and stripping square wave polarography. The determination limits were between 15.5 and 53.6 ng ml−1 and a linear variation of peak intensity versus Zeatin concentration was observed for the three waves. The procedure was applied to the determination of Zeatin in plant extracts, after separation of cytokinins by means of a column packed with Amberlite XAD-4 ion exchange resin. The proposed procedure was compared with the determination by gas chromatography-mass spectrometry with prior methylation of Zeatin.