Determinação polarografica do zinco em plantas, após a sua separação em resina trocadora de íons

Abstract

This paper deals with the polarographic determination of zinc in plants after its separation with an anion exchange resin column. One gram of plant was ashed in a 20 ml beaker at 4505009C for 90-100 minutes. The solution of plant ash in 2N hydrochloric acid was passed through the column formed by a resin bed (Amerlite IRA-401) of 9 cm of length, which adsorbed zinc in the form of an anion an allowed to pass all the interfering ions. Twenty ml of 0,125 N sodium nitrate solution was used to elute the zinc and the effluent was dried in silica dish in vapour bath. Ten ml of 0, 35 N ammonium hydroxide with 0, 0125 % of gelatin, were added to the dish and the solution was stirred in order to dissolve the zinc. Three to five ml of solution were transferred to one special cell of the Sargent Visible Recording Polarograph Model XXI and the polarogram were obtained with the dropping mercury electrode and the stationary pool of mercury as the second electrode. Some of the obtained data are presented: PLANT Micrograms of zinc Micrograms %Recuperation added to the sample of zinc found (average) Coffee (leaves) 0,0 9,2 Coffee (leaves) 0,0 9,2 Coffee (leaves) 0,0 9,2 Coffee (leaves) 20,0 29,2 Coffee (leaves) 20,0 30,4 101,4 Coffee (leaves) 20,0 29,2 Sweet Clover (aerial part) 0,0 22,4 Sweet Clover (aerial part) 0,0 22,4 Sweet Clover (aerial part) 0,0 21,2 Sweet Clover (aerial part) 20,0 42,4 Sweet Clover (aerial part) 20,0 43,6 101,9 Sweet Clover (aerial part) 20,0 42,4 Sugar Cane (leaves) 0,0 12,0 Sugar Cane (leaves) 0,0 12,0 Sugar Cane (leaves) 0,0 10,8 Sugar Cane (leaves) 20,0 31,8 Sugar Cane (leaves) 20,0 31,8 100,6 Sugar Cane (leaves) 20,0 31,8 With the proposed method it is possible to analyse ten to twelve plant samples in six hours.