Three-phase hollow fiber liquid-phase microextraction based on a magnetofluid for the analysis of aristolochic acids in plasma by high-performance liquid chromatography.

A new and fast sample preparation technique based on three-phase hollow fiber liquid-phase microextraction with a magnetofluid was developed and successfully used to quantify the aristolochic acid I (AA-I) and AA-II in plasma after oral administration of Caulis akebiae extract. Analysis was accomplished by reversed-phase high-performance liquid chromatography with fluorescence detection. Parameters that affect the hollow fiber liquid-phase microextraction processes, such as the solvent type, pH of donor and acceptor phases, content of magnetofluid, salt content, stirring speed, hollow fiber length, extraction temperature, and extraction time, were investigated and optimized. Under the optimized conditions, the preconcentration factors for AA-I and AA-II were >627. The calibration curve for two AAs was linear in the range of 0.1-10 ng/mL with the correlation coefficients >0.9997. The intraday and interday precision was <5.71% and the LODs were 11 pg/mL for AA-I and 13 pg/mL for AA-II (S/N = 3). The separation and determination of the two AAs in plasma after oral administration of C. akebiae extract were completed by the validated method.

Orthogonal array design for optimization of hollow-fiber-based liquid-phase microextraction combined with high-performance liquid chromatography for study of the pharmacokinetics of magnoflorine in rat plasma.

In this work, a new sample-preparation method based on hollow-fiber liquid-phase microextraction (HF-LPME) was developed for analysis of magnoflorine in rat plasma. Analysis was accomplished by reversed-phase high-performance liquid chromatography (HPLC), with ultraviolet detection by use of a photodiode-array detector. An orthogonal array design (OAD) was found to be effective for optimization of major conditions which may affect the efficiency of HF-LPME. Under the optimized conditions (pH of donor and acceptor phases 12 and 2.0, respectively; extraction time 20 min; stirring speed 800 rpm; and addition of 10 % (w/v) salt), the preconcentration factor for magnoflorine was 355. Calibration curves with reasonable linearity (r(2)≥0.9994) were obtained in the range 10-1000 ng mL(-1). Intra-day and inter-day precision (RSD) were <5.5 % and the limit of detection (LOD) for the analyte was 3.0 ng mL(-1) (S/N=3). The validated method was successfully used for pharmacokinetic studies of magnoflorine in rat plasma after intravenous administration.

Application of a reversed-phase ionic liquid dispersive liquid-liquid microextraction method for the extraction and preconcentration of domoic acid from urine samples.

A simple and efficient sample extraction and preconcentration method based on reversed-phase ionic liquid dispersive liquid-liquid microextraction (RP-IL-DLLME) had been developed and used to quantify the domoic acid in human urine samples. The analysis was performed by ultra-performance liquid chromatography and photodiode array detection. During the procedure, hydrophilic ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate [C4mim] BF4 as dispersive solvent and NaOH solution was chosen as extraction solvent. Some important parameters in the method were investigated to get high enrichment factors. Under optimal conditions, the linearity of the method was in the range of 0.1-10 ng mL-1 and the correlation coefficient was above 0.9996. The relative standard deviations (RSDs) of the developed methods for intra-day (n = 5) and inter-day (n = 5) precision ranged from 1.9 to 3.9%. Meanwhile, limit of detection (LOD) was 0.03 ng mL-1(S/N = 3) and that of quantification (LOQ) was 0.1 ng mL-1(S/N = 10) with the enrichment factors (EF) being 230. Eventually, the proposed method was successfully applied to the determination of Dominic acid in human urine samples.

Determination of isoquercitrin in rat plasma by high performance liquid chromatography coupled with a novel synergistic cloud point extraction.

A novel improved preconcentration method known as synergistic cloud point extraction was established for isoquercitrin preconcentration and determination in rat plasma prior to its determination by high performance liquid chromatography. Synergistic cloud point extraction greatly simplified isoquercitrin extraction and detection. This method was accomplished at room temperature (about 22°C) in 1min with the nonionic surfactant Tergitol TMN-6 as the extractant, n-octanol as cloud point revulsant and synergic reagent. Parameters that affect the synergistic cloud point extraction processes, such as the concentrations of Tergitol TMN-6, volume of n-octanol, sample pH, salt content and extraction time were investigated and optimized. Under the optimum conditions, the calibration curve for the analyte was linear in the range from 5 to 500ngmL-1 with the correlation coefficients greater than 0.9996. Meanwhile, limit of detection (S/N=3) was less than 1.6ngmL-1 and limit of quantification (S/N=10) was less than 5ngmL-1. It demonstrated that the method can be successfully applied to the pharmacokinetic investigation of isoquercitrin.

Application of mixed cloud point extraction for the analysis of six flavonoids in Apocynum venetum leaf samples by high performance liquid chromatography.

A simple, inexpensive and efficient method based on the mixed cloud point extraction (MCPE) combined with high performance liquid chromatography was developed for the simultaneous separation and determination of six flavonoids (rutin, hyperoside, quercetin-3-O-sophoroside, isoquercitrin, astragalin and quercetin) in Apocynum venetum leaf samples. The non-ionic surfactant Genapol X-080 and cetyl-trimethyl ammonium bromide (CTAB) was chosen as the mixed extracting solvent. Parameters that affect the MCPE processes, such as the content of Genapol X-080 and CTAB, pH, salt content, extraction temperature and time were investigated and optimized. Under the optimized conditions, the calibration curve for six flavonoids were all linear with the correlation coefficients greater than 0.9994. The intra-day and inter-day precision (RSD) were below 8.1% and the limits of detection (LOD) for the six flavonoids were 1.2-5.0 ng mL(-1) (S/N=3). The proposed method was successfully used to separate and determine the six flavonoids in A. venetum leaf samples.

Simultaneous separation and determination of four phenylethanoid glycosides in rat plasma sample after oral administration of Cistanche salsa extract by microemulsion liquid chromatography.

A simple, rapid and specific method was developed to separate as well as to determine the four phenylethanoid glycosides (PhGs) (echinacoside, tubuloside B, acteoside and isoacteoside) in rat plasma after oral administration of Cistanche salsa extract by reversed phase high performance liquid chromatography using a microemulsion as the mobile phase. The separations were performed on a Zorbax Extend-C18 column at 25°C. Photodiode-array detector was conducted at 322nm and with a flow rate of 0.8mLmin(-1). The optimized microemulsion mobile phase consisted of 0.3% triethylamine in 20mM phosphoric acid at pH 6.0, 0.8% (v/v) ethyl acetate as oil phase, 1.5% (v/v) Genapol X-080 as surfactant, 2.5% (v/v) n-propanol as co-surfactant. Under the optimal conditions, the calibration curve for four PhGs was linear in the range of 10-1000ngmL(-1) with the correlation coefficients greater than 0.9994. The intra-day and inter-day precision (RSD) were below 8.64% and the limits of detection (LOD) for the four PhGs were 0.4-1.3ngmL(-1) (S/N=3). The microemulsion liquid chromatography (MELC) method was successfully applied to separate and determine the four PhGs in rat plasma after oral administration of C. salsa extract.

Two-phase hollow fiber liquid phase microextraction based on magnetofluid for simultaneous determination of Echinacoside, Tubuloside B, Acteoside and Isoacteoside in rat plasma after oral administration of Cistanche salsa extract by high performance liquid chromatography.

A new and fast sample preparation technique based on two-phase hollow fiber liquid phase microextraction (HF-LPME) with magnetofluid was developed to quantitate and determine the four phenylethanoid glycosides (PhGs) (Echinacoside, Tubuloside B, Acteoside and Isoacteoside) in plasma after oral administration of Cistanche salsa extract. Analysis was accomplished by reversed-phase high performance liquid chromatography (RP-HPLC) with ultraviolet detection. Parameters that affect the HF-LPME processes, such as the content of magnetic powder, the solvent type, salt content, stirring speed, extraction time and hollow fiber length, were investigated and optimized. Under the optimized conditions, the preconcentration factors for PhGs were higher than 625. The calibration curve for PhGs was linear in the range of 0.1-100ngmL(-1) with correlation coefficients greater than 0.9996. The intra-day and inter-day precision (RSD) were below 8.74% and the limits of detection (LOD) for the four PhGs were 8-15pgmL(-1) (S/N=3). The validated method was successfully applied to separate and determine the four PhGs in rat plasma after oral administration of C. salsa extract.

Application of two-phase hollow fiber liquid phase microextraction coupled with high-performance liquid chromatography for the study of the echinacoside pharmacokinetics in Parkinson's disease rat plasma.

A simple and solvent-minimized sample preparation technique based on two-phase hollow fiber liquid phase microextraction (HF-LPME) was developed and used to quantify the echinacoside in Parkinson's disease rat plasma following oral administration. Analysis was accomplished by reversed-phase high performance liquid chromatography (HPLC) with ultraviolet detection. The influence factors relevant to the HF-LPME processes were optimized. Under the optimized conditions, the preconcentration factor for echinacoside was 337. Calibration curves with reasonable linearity (r(2) ≥ 0.9998) were obtained in the range of 5-750 ng mL(-1). Intra-day and inter-day precision (RSD) were ≤ 5.43% and the limit of detection (LOD) for the analyte was 2.0 ng mL(-1) (S/N=3). The validated method has been successfully applied for pharmacokinetic studies of echinacoside in Parkinson's disease (PD) rat plasma after oral administration.