The recoveries of all three QC levels are consistent, precise and reproducible, indicating the suitability of liquid extraction procedures for separation of YH-8 from rat plasma samples.
A liquid-liquid extraction procedure was optimized by varying the following parameters: type of extraction solvent (cyclohexane, n-hexane, 1,1,2-trichlorotrifluoroethane), the ratio extraction solvent/sample volume (1∶1 to 50∶1) and the number of extraction repetitions (1 10).
The use of the optimized liquid-liquid extraction procedure and a normal-phase HPLC separation with a fluorescence detector provided high sensitivity and selectivity for the determination of tocopherols and tocotrienols.
Besides the tedious liquid-liquid extraction procedures using large volumes of organic solvents in the methods based on formation of ion-pair associates [15].
These drawbacks included tedious liquid-liquid extraction procedures using large volumes of organic solvents in the methods based on formation of extractive ion-pair associates [11 15], and the employment of multiple-steps and long time for completing the whole procedure [16, 17].
The calibration and liquid-liquid extraction procedures as well as chromatographic conditions have been described previously [ 23].
Liquid-liquid extraction procedures for plasma samples were as follows: 2 μL of internal standard solution (1 mg/mL of evodiamine in methanol) was added into 5 mL polypropylene screw-capped conical tubes and then evaporated under a stream of nitrogen, followed by addition of 100 μL of the plasma and 100 μL acetonitrile.
Plasma concentrations of ABZ, ABZ-NH3, ABZ-SO and ABZ-SO2 were estimated by high performance liquid chromatography (HPLC) with a liquid-liquid phase extraction procedure adapted from that described by Marriner and Bogan [ 3].
A pressurised liquid extraction (PLE) procedure, by using methanol/water mixture, was developed for extracting arsenical species from marine biological material (mussel and fish) and standard reference materials (CRMs).
These two methods offered adequate sensitivities; however they employed the expensive mass detectors that are not available in most laboratories, and involved laborious liquid-liquid sample extraction procedures that negatively affected the accuracy of the results.
