title: Centrifuge microextraction coupled with on-line back-extraction field-amplified sample injection method for the determination of trace ephedrine derivatives in the urine and serum.
abstract: Although sample stacking has enjoyed some degree of success in electrophoretic separation techniques, there is still a major problem with complex matrix sample as it suffers tremendously from sample matrix effects. A novel method that combines two concentration techniques, centrifuge microextraction (CME) and on-line back-extraction field-amplified sample injection (OLBE-FASI), is used to determine trace ephedrine derivatives in urine and serum by capillary zone electrophoresis. The CME, integrating the sample cleanup and preconcentration into a single step, is a promising sample preparation method for biological samples. The CME technique provided 9-14-fold enrichment within 10 min. The OLBE-FASI eliminated the need to perform solvent exchange and provided a further concentration of the analytes. Using CME coupled with OLBE-FASI, over a 3800-fold increase in sensitivity could be obtained as compared with the normal hydrodynamic injection without sample stacking. For a 1-mL urine sample, the linear range was 5/10-200 ng/mL with the square of the correlation coefficients (r(2)) ranging from 0.9988 to 0.9994. Detection limits were from 0.15 to 0.25 ng/mL using a photodiode array UV detection at wavelength 192 nm. The possibility of this method to determine ephedrine derivatives in 20-muL serum samples was also demonstrated.
authors.affiliation: Department of Chemistry, Wuhan University, Wuhan 430072, China.
authors.forename: Huaifang
authors.initials: H
authors.lastname: Fang
authors.forename: Zhaorui
authors.initials: Z
authors.lastname: Zeng
authors.forename: Lan
authors.initials: L
authors.lastname: Liu
mesh_terms: D002498:Centrifugation / Q000379:methods*; D004563:Electrochemistry; D004809:Ephedrine / Q000031:analogs & derivatives* / Q000097:blood / Q000652:urine; D006801:Humans; D007700:Kinetics; D009862:Online Systems
chemical_list: D004809:Ephedrine