title: [Detection of plasma and urine furosemide based on online enrichment and restricted- access media coupled with high-performance liquid chromatography].
abstract: OBJECTIVE
  To establish a method based on restricted access media-high performance liquid chromatography for direct online sample injection and detection of plasma and urine furosemide in rats.
  
  
  METHODS
  The column of restricted access media was used as the pre-treatment column and a C18 column as the analytical column. The mobile phase of the pre- treatment column was water-methanol (95:5, V/V) with a volume percentage of formic acid of 0.1%. The mobile phase of the analytical column was methanol-water (65:35, V/V) for plasma and methanol-water (55:45, V/V) for urine samples, all containing a volume percentage of formic acid of 0.1% with a flow rate of 1 ml/min. The detection wavelength was 274 nm and the column temperature was maintained at 25 degrees celsius.
  
  
  RESULTS
  The calibration curve showed an excellent linear relationship in rat plasma furosemide concentration range of 0.1-3.2 µg/ml (r=0.9995) and in urine concentration range of 0.5-32 µg/ml (r=0.9991). The average recoveries of furosemide at 3 spiked levels ranged from 101.82% to 113.36% for plasma and from 98.75% to 112.27% for urine samples. The detection showed good intra- and inter-day assay precisions and accuracies with the relative standard deviations all below 5%. The pharmacokinetic parameters AUC(0→24) was 6.265 g/(ml·h) with a t(1/2) of 2.447 h and a C(Max) of 1.414 g/ml. The mean cumulative excretory rate of furosemide in the urine of rats over 24 h was 32.50%-39.08%.
  
  
  CONCLUSIONS
  Detection of furosemide in plasma and urine samples using restricted access media-high performance liquid chromatography is simple and efficient and allows direct online injection of the samples.
authors.affiliation: School of Pharmacy, Lanzhou University, Lanzhou 730050, China.E-mail: gsggzxh@163.com.
authors.forename: Xiao-Hui
authors.initials: XH
authors.lastname: Zhang
authors.forename: Rong
authors.initials: R
authors.lastname: Wang
authors.forename: Hua
authors.initials: H
authors.lastname: Xie
authors.forename: Qiang
authors.initials: Q
authors.lastname: Yin
authors.forename: Wen-Bin
authors.initials: WB
authors.lastname: Li
authors.forename: Zheng-Ping
authors.initials: ZP
authors.lastname: Jia
authors.forename: Juan-Hong
authors.initials: JH
authors.lastname: Zhang
mesh_terms: D000818:Animals; D002138:Calibration; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D005665:Furosemide / Q000097:blood* / Q000652:urine*; D051381:Rats; D015203:Reproducibility of Results
chemical_list: D005665:Furosemide