Experiment
Chemicals and Equipments. Ibuprofen (>_98%, GC grade) and ciprofloxacin (>_98%,HPLC grade) were purchased from sigma-aldrich (UK). HPLC-grade methanol (MeOH), acetonitrile (ACN), and 98% formic acid were obtained from Fisher Scientific (UK). Deionized reagent water was prepared by an ELGACAN B 114 deionizer with a C 114 cartridge (ELGA) Labwater). Ibuprofen (1000 mg/L) and ciprofloxacin (20 mg/L) stock solutions for calibration were both prepared in MEOH and stored in a freezer (at -18 C) . Both stock solutions were used within 2 weeks. Stock solutions of ibuprofen and ciprofloxacin for recovery study were prepared in deionized water in the concentration of 10 mg/l and used within 1 week.