Enantiomeric Separations of Chiral Polychlorinated Biphenyls and Synthetic Pyrethroids by Supercritical Fluid Chromatography
|School||Zhejiang University of Technology|
|Keywords||Chiral polychlorinated biphenyls Synthetic pyrethroids Enantiomer separation Supercritical fluid chromatography Chiral stationary phase|
Polychlorinated biphenyls （PCBs） are one of the typical persistent organic pollutants. Different environmental behaviors （toxicity and metabolic pathways） of PCBs atropisomers display the chiral selectivety of PCBs, and the research on the environmental behaviors of PCBs has been the hot spot. Therefore, it is very important to develop an efficient analytical method enabling the enantiomeric separation of chiral PCBs. Synthetic pyrethroids （SPs） are a type of widely used pesticides. The biological activity and toxicity of SPs are always different, so it is significative to obtain pure enantiomers of SPs. In this study, enantiomeric separations of PCBs and SPs were conducted by supercritical fluid chromatography （SFC）. In addition, the influences of organic modifier, temperature and chiral stationary phases on enantiomeric separation were discussed.Sixteen of all the 18 chiral PCBs were absolutely separated into their two enantiomers: PCBs 45, 84, 88, 91, 131, 139, 144, 149, 171, 176 and 183 achieved satisfactory resolutions on Sino-Chiral OJ with their resolution 4.48, 3.12, 4.12, 4.47, 2.77, 4.32, 3.07, 3.41, 2.83, 1.86 and 3.41. PCBs 132, 174, 175 and 196 achieved satisfactory resolutions on Chiralcel OD with their resolution 1.87, 1.64, 2.03 and 1.55. Only PCB 197 got satisfactory resolution on Chiralpak IB with resolution 1.53. PCB 135 could be partially resoluted on Chiralpak IB with resolution 0.81. PCB 95 couldn’t be separated in this research.PCBs could achieve better resolution with less and smaller polar modifier added in the mobile phase. The thermodynamics reseach of 14 PCBs on Sino-Chiral OJ when the mobile phase containing 5% ethanol pointed out that the separation of chiral PCBs were enthalpy-driving process and the isoenantioselective temperature were all above the range of temperature assayed. It was also could be concluded that PCBs with less chlorine substitutived could achieved better resolution.The enantiomer separation of synthetic pyrethroids on Sino-Chiral OJ was much better than on Chiralcel OD. Lambda-cyhalothrin could be baseline separated （R1-2=2.61, R2-3=2.11, R3-4=3.19）. Permethrin could be separated into 4 enantiomers （R1-2=2.57, R2-3=3.29, R3-4=0.91） only when methanol was added in mobile phase, while fenvalerate achieved partially resolution （R1-2=0.72, R2-3=2.82, R3-4=0.84） as the mobile phase containing 3% ethanol. Seven chromatographic peaks of cypermethrin (R1-2=1.83, R2-3=1.56, R3-4=2.73, R4-5=1.17, R5-6=1.89, R6-7=4.26) were obtained when there was no modifier in the mobile phase. Both of bifenthrin and deltamethrin couldn’t be effectively separated, only 2 chromatographic peaks could be obtained.