PHOSPHONIC-ACIDS AND BIPHOSPHONATES AS EXTRACTANTS OF MICROELEMENTS FROM SANDY SOILS

The purpose of this investigation was the evaluation of four chelating agents with phosphonic groups (BHAMP: N,N-bis(2-hydroxyethyl) amineme thylene phosphonic acid; EDPA: N,N,N',N-ethylenediaminetetra(methylene phosphonic) acid; OAPMP: 2-hydroxy-2-oxo-1, 4,2-oxa-aza-phospha (V) c yclohexane-4-methylenephosphonic acid; and DMAPD: monosodium salt of d imethyl-3-amine-1-hydroxypropane-1,1-diphosphonic acid), as extractant s of Cu, Zn, Mn, and Fe from sandy soils from Medanos, Buenos Aires Pr ovince, Argentina. The studies were carried out using different concen trations of the chelating agents at different pH values in the range 5 .0-9.0. The extracted elements were determined using atomic absorption spectrophotometry. The amounts extracted using OAPMP and DMAPD were h igher than those extracted by BHAMP and EDPA with the exception of Fe, where the amounts were similar, with an increase in the values in the alkaline pH range. The complexation was in the order DMAPD greater th an or equal to OAPMP > EDPA > BNAMP.