AN ATR-FTIR STUDY OF GLYPHOSATE AND ITS FE(III) COMPLEX IN AQUEOUS-SOLUTION

An ATR-FTIR study of the vibrational spectrum of glyphosate (N-phospho nomethylglycine) in aqueous solution 1 M in NaCl is reported. Band ass ignments are given in the 1800-850 cm(-1) range based on the analysis of the spectral changes from low to high pH values (2-11). Potentiomet ric titrations of glyphosate are performed at 0.1, 0.5, and 1 M ionic strengths in NaCl and the pK(a2), pK(a3), and pK(a4) values determined . A chemometric analysis of the spectral data has been carried out to support the assignments and reproduce the pK(a) values. In addition, t he ATR-FTIR spectrum of the 1:1 Fe(III)/glyphosate complex in aqueous solution is analyzed by comparison with that of the free ligand.