Facilitated transport and preconcentration of the herbicide glyphosate and its metabolite AMPA through a solid supported liquid-membrane

A solid supported liquid-membrane (SLM) system for the transport and preconcentration of the herbicide glyphosate and its main metabolite aminomethylphosphonic acid (AMPA) has been designed and characterised. The influence of the chemical composition of the system as well as membrane configuration on the transport properties were investigated. The best extraction conditions were achieved by adjusting the pH of the aqueous feed phase to 12 (0.1 M NaOH). Among the different options tested, a 0.1 M HCl solution was found to be the most effective to strip glyphosate and AMPA from the loaded organic phase. The effect of carrier concentration and the nature of the organic solvent were also tested and the best results were obtained when working with 0.2 M Aliquat 336 in dodecane modified with 4% dodecanol. Under these chemical conditions some preconcentration experiments were run using two different geometries of the membrane: a hollow fiber liquid-membrane (HFSLM) and a laminar membrane system (LSLM) where the stripping solution can be recirculated. The best results were obtained for the liquid-membrane system in HF configuration, with concentration factors of 19 and 2.5 for glyphosate and AMPA, respectively.