In preliminary test, the liquid chromatography system Shimadzu Prominence (Shimadzu, Kyoto, Japan) was equipped with two LC-20AD pumps, a DGU-20A3 vacuum degasser, a SIL-HTC autosampler, a CTO-20AD column oven and a controller module.
In order to solve the back conversion problem of clopidogrel, an online SPE system (Symbiosys, Spark, Holland) was used. The system integrated the liquid chromatography unit with solid phase extraction unit including binary pumps (in this method, isocratic pump was used), an autosampler, an automatic cartridge exchanger unit, two high pressure dispensers and a column oven.
The chromatographic separation was achieved on an Eternity-2.5-C18-UHPLC column (50 mm×2.1 mm, 2.5 μm, Kromasil, Sweden) with a C18 guard column (4 mm×3 mm, 5 μm, Phenomenex, USA). The column oven temperature was set at 45 °C. The samples were kept at 4 °C in an autosampler. The mobile phase consisted of 0.04% formic acid, 3 mmol/L ammonium acetate in acetonitrile/water (65:35, v/v). Mobile phase at the first minute was set at 0.15 mL/min, and flow rate returned to 0.35 mL/min in the remaining 4.5 min. Besides, a peak focusing mode was used to obtain the acquire sensitivity. Peak focus mode included mobile phase and focus reagent (water). Focus reagent was set at 200 μL/min for 1 min, propelling by a high pressure dispenser detailed inFig. 1 11 .
In order to solve the back conversion problem of clopidogrel, an online SPE system (Symbiosys, Spark, Holland) was used. The system integrated the liquid chromatography unit with solid phase extraction unit including binary pumps (in this method, isocratic pump was used), an autosampler, an automatic cartridge exchanger unit, two high pressure dispensers and a column oven.
The chromatographic separation was achieved on an Eternity-2.5-C18-UHPLC column (50 mm×2.1 mm, 2.5 μm, Kromasil, Sweden) with a C18 guard column (4 mm×3 mm, 5 μm, Phenomenex, USA). The column oven temperature was set at 45 °C. The samples were kept at 4 °C in an autosampler. The mobile phase consisted of 0.04% formic acid, 3 mmol/L ammonium acetate in acetonitrile/water (65:35, v/v). Mobile phase at the first minute was set at 0.15 mL/min, and flow rate returned to 0.35 mL/min in the remaining 4.5 min. Besides, a peak focusing mode was used to obtain the acquire sensitivity. Peak focus mode included mobile phase and focus reagent (water). Focus reagent was set at 200 μL/min for 1 min, propelling by a high pressure dispenser detailed in