ION-SELECTIVE ELECTRODES BASED ON CALIX[4]ARENE TETRAESTER IN THE DETERMINATION OF FORMALDEHYDE VIA IN-SITU GENERATION OF IONIC LIPOPHILIC HYDRAZONE

A formaldehyde-selective electrode was designed based on the host-guest interaction between p-tert-butylcalix[4]arene tetraester and lipophilic hydrazone generated in situ from formaldehyde and a modified Girard's reagent G2. The poly(vinyl chloride) membrane electrode contains 4.5% mim of a tetraester derivative of calix[4]arene as the neutral carrier and dioctyl phthalate as the plasticizer. At pH 5.4, the electrode exhibits a dicationic Nernstian response in the range 4 x 10(-5)-0.1 mol l(-1) formaldehyde with a slope of 32.4 mV per decade. In contrast, at pH 9.2, the electrode shows a near Nernstian response with a slope of 50.3 mV per decade in a narrower working concentration range. The electrode has a Past response time and a long working lifetime. The viability of using the electrode for the micro-determination of formaldehyde was also demonstrated.