Zn(II), Cd(II), Pb(II) and Cu(II) can be simulta-neously determined inPittosporumleaves acid extract by placing into the electrochemical cell 0.1 ml of sample, 10.0 ml of ultrapure water, 1.0 ml of 1000 mg kg1 Hg(II) standard solution as the oxidant agent and 0.5 ml of 10.0lg ml
Ga(III), in order to prevent Cu–Zn complexes formation on the mercury film