Enantiomer Separation Of Chiral Phenoxypropionic Herbicides By Supercritical Fluid Chromatography

The enantiomers of chiral herbicides often show different biologicalactivities, and the use of too much chiral herbicides will produce greatrisks to organism and environment. Some European countries have strictrequirements for the use of these chemicals and announced to cut theamounts of chiral pesticides.Therefore to abtain pure and high efficientenantiomers of chiral pesticedes is of great importance to improvingpesticides’ effect and reducing environmental pollution. In this study, theenantiomeric separation of11chiral phenoxypropionic herbicides werecarried out using supercritical fluid chromatography(SFC). Morever, theinfluence of type and concentration of organic modifier (1%-10%),column temperature (25℃-45℃), system pressure (130bar-170bar) andtype of chiral stationary phases(CSPs)(Sino-Chiral OJ, Chiralcel OD-H,Chiralpak IB and Chiralpak AD-H column) were studied.9of11chiral phenoxypropionic herbicides investigated werecompletely or partially separated. Fluazifop-butyl, quizalofop-ethyl,dichlorprop-methyl, fenoprop-methyl and mecoprop-methyl obtainedoptimal separation on Sino-Chiral OJ column with resolution1.73,7.18,1.75,2.67,3.16separately. Diclofop-methyl and fenoxaprop-ethyl got optimal separation on Chiralcel OD-H column, their resolution were2.84and2.48. Cyhalofop-butyl achieved resolution0.83on Chiralpak AD-Hcolumn as optimal separation.At last, propaquizafop got resolution0.44onChiralpak IB column.The type and concentration of organic modifier added in mobilephase had great influence on the enantiomeric separation. With thesequence of methanol, ethanol and isopropyl, the capacity factor andresolution of chiral phenoxypropionic herbicides increased gradually. Withthe increase of modifier addition, the capacity factor and resolutiongradually decreasedSome influence on the enantiomeric separation were made as thecolumn temperature changes. As the temperature increases, the capacity ofthe chiral separation factor increased gradually, but the separation factor,and resolution reduced gradually. The isoenantioselective temperature ofquizalofop-ethyl, fenoprop-methyl and mecoprop-methyl were453K,419K, and461K, which were above the range of temperature assayed. Inadditon, the enantiomeric separation is an enthalpy driven process.The system pressure also had effects on enantiomeric separation, ascapacity factor and resolution reduced when pressure increased.By comprehensive comparison of separation results on4CSPs wecan conclude that6chiral phenoxypropionic herbicides were totallyseparated while4herbicides failed to be separated on Sino-Chiral OJ column.2chiral phenoxypropionic herbicides could be totally separated,5chemicals were partially separated wehile another4herbicides couldn’tget separated on Chiralcel OD-H column. There were only4herbicidesseparated on Chiralpak IB column. Finally could separete the majority of11chiral phenoxypropionic herbicides except3chemicals, yet theresolution obtained were relatively low.