Determination of Ciprofloxacin in Roast Eel by Hyphenation of High Performance Liquid Chromatography and Mass Spectrometry

Ciprofloxacin (CPXC) in roast eel sample was extracted twice with acetonitrile acidified with formic acid (1+99).The supernatant liquid was collected and diluted to 25.0 mL with acetonitrile.An aliquot of 10 mL was taken,dried by blowing with nitrogen at 40 ℃ and the residue was dissolved in 2.0 mL of the mobile phase solution,which was further extracted with 2 mL of n-hexane.Ten μL of the lower layer was taken and introduced into the HPLC/MS analyzer.In HPLC,the XBridgeTM Shield RP18 column (250 mm×3.0 mm,5 μm) was used as stationary phase,a solution containing methanol,acetonitrile and dil.formic acid (2+998) mixed in the ratio of 15+15+70 was used as mobile phase,and fluorescence detection at λex 275 nm/λem 445 nm was used in the determination.In MS,SIM technique under the mode of ESI(+) was used for the detection,and the quantitative ion used was m/z 331.9M+H+.Linear relationships between the values of peak area of detection signals and concentration of CPXC were obtained in the ranges of 100.0-2 500.0 μg·L-1 for HPLC-FD,and 20.0-500.0 μg·L-1 for MS-SMI-ESI(+),with detection limits of 50.0 μg·kg-1 and 10.0 μg·kg-1 respectively.Tests for precision and recovery were made by addition of standard solution of CPXC at 3 different concentrations.Values of RSD′s (n=6) found were less than 6.5% and values of recovery in the range of 83.0%-99.0%.