A new green method for trace level quantification of four herbicides, glyphosate (GLYP), glufosinate (GLUF), and their main metabolites, aminomethylphosphonic acid (AMPA) 3-(methyl-phosphinico)-propionic (MPPA), was developed. The purification step without any derivatization conducted by solid-phase extraction using Chelex-100 resin in the Fe (III) form, followed elution with 5% NH4OH. analytes...