Environmentally Friendly Slow Release Formulations of Alachlor Based on Clay-Phosphatidylcholine

Abstract

A new clay-liposome complex was developed for reducing leaching of herbicides and contamination of groundwater. The liposomes were composed of the neutral and Environmental Protection Agency approved phospholipid phosphatidylcholine (PC). Adsorption of PC liposomes on the clay mineral montmorillonite could exceed the cation exchange capacity of the clay, and was well simulated by the Langmuir equation. X-ray diffraction results for 6 mM PC and 1.6 g/L clay (3 day incubation) yielded a basal spacing of 7.49 nm, which was interpreted as the formation of a supported planar bilayer on montmorillonite platelets. Fluorescence methods demonstrated structural changes which reflected adsorption of PC followed by loss of vesicle integrity as measured by the penetration of dithionite into the internal monolayer of fluorescently labeled liposomes, resulting in a decrease in fluorescence intensity to 18% of initial after 4 h. Energy transfer was demonstrated after 1 h from labeled liposomes to montmorillonite labeled by an acceptor. The neutral herbicide alachlor adsorbed on the liposome-clay complex, yielding a formulation of up to 40% active ingredient, and 1.6-fold reduction in herbicide release in comparison to the commercial formulation. Hence, the PC-montmorillonite complex can form a basis for environmentally friendly formulations of herbicides, which would yield reduced leaching.

Poly(ɛ-caprolactone)nanocapsules as carrier systems for herbicides: Physico-chemical characterization and genotoxicity evaluation

“…Materials used in agriculture for this purpose include liposomes [4], cyclodextrins [5][6][7], clays [8][9][10], silica [11], lignin [12,13], polymeric microparticles [14][15][16][17][18] and nanoparticles [19,20]. Biodegradable micro and nanoparticles are especially suitable as carriers for pesticides, due to their low toxicity and good biocompatibility.…”

Reduced metribuzin pollution with phosphatidylcholine–clay formulations

“…In a previous study, the authors optimised the adsorption of PC on montmorillonite for the preparation of slow‐release herbicide formulations 9. This system proved to be very effective at reducing the leaching of poorly water‐soluble herbicides such as atrazine and alachlor 10.…”

Factors Affecting the Design of Slow Release Formulations of Herbicides Based on Clay-Surfactant Systems. A Methodological Approach

“…This provided a binding coefficient for each surfactant, that allowed to predict their sorption for several surfactant/clay ratios. The validity of this approach has been extensively proven for other surfactants [16], [36]. In a second stage, once the amount of sorbing surfactant was determined for particular surfactant/clay ratios, the maximal amount of herbicide which could be sorbed for the employed surfactant concentration was calculated from the solubility studies by considering the same ratio between the solubilized (included in micelles) herbicide and the surfactant in solution as in the formulation with the clay.…”

“…It has been previously reported that incorporation of active ingredients in the micelles and vesicles formed by surfactant molecules which adsorbed on clays, such as montmorillonite, provided a slow release system [14]–[16]. The fraction of the pesticide encapsulated in surfactant-clay complexes prolonged their action.…”