Determination of Polymyxin E1 and E2 in Human Cerebrospinal Fluid by High Performance Liquid Chromatography-Tandem Mass Spectrometry
Objective To establish a new salting-out-assisted liquid-liquid extraction combined with high performance liquid chromatography tandem mass spectrometry(HPLC-MS/MS)technique for the rapid determina-tion of polymyxin E1 and E2 concentrations in human cerebrospinal fluid.Methods Polymyxin B1 was used as an internal standard,the cerebrospinal fluid samples were extracted with acetonitrile,and ammonium formate was used as the salting-out agent for liquid-liquid extraction.The concentration and volume of the salting-out agent as well as the volume of the extracting agent were optimized.A Waters Xselect ® HSS T3 column(2.1 mm × 150 mm.2.5 pm)was used.The mobile phase consisted of acetonitrile and water containing 0.1％formic acid.The detec-tion length was 6 min by gradient elution.Results Under the optimal experimental conditions,the calibration curves of analytes in cerebrospinal fluid showed good linearity within the range of 0.20-8.00 pg·ml-1 for poly-myxin E1(r=0.9960)and 0.36-14.4 pg·ml-1 for polymyxin E2(r=0.9984).The accuracies of the analytes ranged from 91.4％to 109.0％,and the relative standard deviations(RSD)of intra-and inter-day precisions were less than 9.5％.The recoveries of polymyxin E1 and polymyxin E2 were 77.7％-84.3％and 60.3％-68.3％respectively.The analytes had no obvious matrix effect in cerebrospinal fluid.The cerebrospinal fluid samples were stable during collection,storage and pretreatment.Conclusion This method is simple,inexpensive,highly accurate and reproducible,which can be applied to determination of polymyxin E1 and E2 in human cerebrospinal fluid.
liquid chromatography-tandem mass spectrometrysalting-out-assisted liquid-liquid extractioncerebrospinal fluidpolymyxin E
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