ABSTRACT
A rapid, simple and sensitive method for the detection of piperazinyl phenothiazine drugs using dispersive liquid-liquid microextraction (DLLME) combined with field-amplified sample stacking (FASS) in CE was developed. Sensitivity parameters that affect the extraction and FASS efficiency, such as the type and volume of disperser solvent, extraction time, addition of salt, and efficiency of FASS, were investigated and optimized. Note that the conductivity ratio between BGE and sample zone was measured to be 2300. Under optimal extraction and stacking conditions, the calibration curve, which ranged from 0.3 to 160 ng/mL, demonstrated good linearity with a correlation coefficient r⧠0.9900. The LODs of prochlorperazine (Pcp), trifluoperazine (Tfp), perphenazine (Ppa), and fluphenazine (Fpa) at an S/N of 3 were 0.1, 0.1, 0.07, and 0.08 ng/mL, respectively. An approximately 1000-fold to 2500-fold improvement in sensitivity was achieved for the four tested analytes compared to conventional CZE without DLLME. The recoveries of all phenothiazines in urine and plasma ranged from 85.7 to 107.6% and 95.6 to 105.4%, respectively. The proposed method was demonstrated to be a rapid and convenient method for the determination of four piperazinyl phenothiazine drugs in human urine and plasma.
ABSTRACT
High-speed capillary electrophoresis (CE) enables the simple, rapid, and inexpensive analysis of large sets of chiral samples in the pharmaceutical industry. Hence, we developed a novel method for separating enantiomers of d,L-phenothiazines simply and rapidly, based on using poly(diallyldimethylammonium chloride) (PDDAC) as an additive and hydroxypropyl-γ-cyclodextrin (Hp-γ-CD) as a chiral selector in capillary electrophoresis. Adding 0.9% PDDAC to the background electrolyte generated a stable, high, and reversed electroosmotic flow (EOF). Hp-γ-CD not only worked as a complexing agent to increase the chiral resolution between d,L-phenothiazines but also decreased the effective electrophoretic mobility of these drugs. Combining PDDAC and Hp-γ-CD as buffer additives enabled CE to achieve a high-speed enantioseparation of five pairs of d,L-phenothiazines. A decrease in capillary length and an increase in the intensity of the electric field further shortened the separation time. When the background electrolyte contained 0.9% PDDAC, 5mM Hp-γ-CD, and 75 mM formic acid (pH 3.0), enantioseparation of the d,L-phenothiazines was attained within 230 s by applying a capillary length of 32.5 cm and an electric field of 292 V cm(-1). The limit of detection (LOD) of the d,L-phenothiazines at a signal-to-noise ratio of 3 ranged from 2 to 8 µM. We demonstrated the feasibility of this method by detecting the five pairs of d,L-phenothiazines in urine samples.