Quantitation of zolpidem in biological fluids by electro-driven microextraction combined with HPLC-UV analysis

In this study, for the first time, an electro-driven microextraction method named electromembrane extraction combined with a simple high performance liquid chromatography and ultraviolet detection was developed and validated for the quantitation of zolpidem in biological samples. Parameters influencing electromembrane extraction were evaluated and optimized. The membrane consisted of 2-ethylhexanol immobilized in the pores of a hollow fiber. As a driving force, a 150 V electric field was applied to facilitate the analyte migration from the sample matrix to an acceptor solution through a supported liquid membrane. The pHs of donor and acceptor solutions were optimized to 6.0 and 2.0, respectively. The enrichment factor was obtained >75 within 15 minutes. The effect of carbon nanotubes (as solid nano-sorbents) on the membrane performance and EME efficiency was evaluated. The method was linear over the range of 10-1000 ng/mL for zolpidem (R2 >0.9991) with repeatability (%RSD) between 0.3 % and 7.3 % (n = 3). The limits of detection and quantitation were 3 and 10 ng/mL, respectively. The sensitivity of HPLC-UV for the determination of zolpidem was enhanced by electromembrane extraction. Finally, the method was employed for the quantitation of zolpidem in biological samples with relative recoveries in the range of 60-79 %

Determination of tricyclic antidepressants in human urine samples by the three-step sample pretreatment followed by HPLC-UV analysis

In this work, an efficient sample pretreatment method has been developed by combining salt induced– homogenous liquid–liquid extraction, dispersive solid phase extraction, and dispersive liquid–liquid microextraction based on the solidification of floating organic droplet for the extraction of some widely used tricyclic antidepressant (TCA) drugs (nortriptyline, amitriptyline, desipramine, clomipramine, and imipramine) in human urine samples before their determination by high performance liquid chromatography–ultraviolet detection. In brief, the target analytes are first isolated from urine samples into acetonitrile (ACN) separated by adding a salt. Then the obtained ACN phase is treated with a mixture of appropriate sorbents to remove interferences. Afterward, the purified ACN is mixed with menthol as an extractant and rapidly injected into alkaline HPLC–grade water as a preconcentration step. Next, the obtained solution is placed in an ice bath and menthol collects on top of the solution after solidification. The solidified drop is then withdrawn and injected into separation system after dissolving in 10 μL ACN. Under the optimum experimental conditions, extraction recoveries and enrichment factors of the selected drugs ranged from 69–84 % and 345–420, respectively. The limits of detection and quantification were obtained at the ranges of 0.22–0.31, and 0.71–1.1 μg L–1, respectively. The relative standard deviations of the proposed method were ≤ 6 % for intra– (n=6) and inter–day (n=4) precisions at a concentration of 10 μg L–1 (each drug). Finally, the suggested approach was applied to determine of TCA drugs in different patients' urine samples. The method could be applied in further TCAs pharmacokinetic and forensic studies

Quantitative analysis of phenobarbital in biological fluids: Analyte enrichment by an electrically-assisted microextraction technique

An electrically-assisted microextraction method called electromembrane extraction, followed by a simple high performance liquid chromatography and ultraviolet detection was developed and validated for determining phenobarbital in biological samples. The major parameters influencing the electromembrane extraction procedure including solvent composition, voltage, pH of acceptor and donor solutions, salt effect, and time of extraction were evaluated and optimized. The drug was extracted from the donor aqueous sample solution (pH 9) to the acceptor aqueous solution (pH 13). The donor and acceptor phases were separated by a hollow fiber dipped in 1-octanol as a supported liquid membrane. A voltage of 40 V during 20 minutes was applied as the driving force. The enrichment factor was obtained >51 which enhanced the sensitivity of the instrument. Limit of detection and limit of quantitation were 7.5 and 25 ng/ mL, respectively. The method was linear over the range of 25-1000 ng/mL for phenobarbital (R2 >0.9998) with repeatability (%RSD) between 0.4% and 6.8% (n = 3). The proposed method was successfully applied to human plasma and urine samples with relative recovery of 70-80% and %RSD < 6.8%

Development and Validation of a Stability-Indicating RP-HPLC Method for Rapid Determination of Doxycycline in Pharmaceutical Bulk and Dosage Forms

Background: A rapid stability-indicating RP-HPLC method for analysis of doxycycline in the presence of its degradation products was developed and validated. Methods: Forced degradation studies were carried out on bulk samples and capsule dosage forms of doxycycline using acid, base, H2O2, heat, and UV light as described by ICH for stress conditions to demonstrate the stability-indicating power of the method. Separations were performed on a Perfectsil® Target ODS column (3-5µm, 125 mm×4 mm), using a mobile phase consisting of methanol-50 mM ammonium acetate buffer (containing 0.1% v/v trifluoroacetic acid and 0.1% v/v triethylamine, pH 2.5) (50:50 v/v) at room temperature. The flow rate was 0.8 mL/min. Results: The method linearity was investigated in the range of 25–500 µg/mL (r > 0.9999). The LOD and LOQ were 5 and 25 µg/mL, respectively. The method selectivity was evaluated by peak purity test using a diode array detector. There was no interference among detection of doxycycline and its stressed degradation products. Total peak purity numbers were in the range of 0.94-0.99, indicating the homogeneity of DOX peaks. Conclusion: These data show the stability-indicating nature of the method for quality control of doxycycline in bulk samples and capsule dosage forms

Quantitation of zolpidem in biological fluids by electro-driven microextraction combined with HPLC-UV analysis

In this study, for the first time, an electro-driven microextraction method named electromembrane extraction combined with a simple high performance liquid chromatography and ultraviolet detection was developed and validated for the quantitation of zolpidem in biological samples. Parameters influencing electromembrane extraction were evaluated and optimized. The membrane consisted of 2-ethylhexanol immobilized in the pores of a hollow fiber. As a driving force, a 150 V electric field was applied to facilitate the analyte migration from the sample matrix to an acceptor solution through a supported liquid membrane. The pHs of donor and acceptor solutions were optimized to 6.0 and 2.0, respectively. The enrichment factor was obtained >75 within 15 minutes. The effect of carbon nanotubes (as solid nano-sorbents) on the membrane performance and EME efficiency was evaluated. The method was linear over the range of 10-1000 ng/mL for zolpidem (R2 >0.9991) with repeatability ( %RSD) between 0.3 % and 7.3 % (n = 3). The limits of detection and quantitation were 3 and 10 ng/mL, respectively. The sensitivity of HPLC-UV for the determination of zolpidem was enhanced by electromembrane extraction. Finally, the method was employed for the quantitation of zolpidem in biological samples with relative recoveries in the range of 60–79 %

Inhibition of Growth and Induction of Apoptosis in Fibrosarcoma Cell Lines by Echinophora platyloba DC: In Vitro Analysis

Echinophora platyloba DC plant (Khousharizeh) is one of the indigenous medicinal plants which is used as a food seasoning and medicine in Iran. The objective of this study was to examine the in vitro cytotoxic activity and the mechanism of cell death of crude methanolic extracts prepared from Echinophora platyloba DC, on mouse fibrosarcoma cell line (WEHI-164). Cytotoxicity and viability of methanolic extract was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and dye exclusion assay. Cell death ELISA was employed to quantify the nucleosome production result from nuclear DNA fragmentation during apoptosis and determine whether the mechanism involves induction of apoptosis or necrosis. The cell death was identified as apoptosis using terminal deoxynucleotidyl transferase- (TdT-) mediated dUTP nick end labeling (TUNEL) assay. Our results demonstrated that the extract decreased cell viability, suppressed cell proliferation, and induced cell death in a time- and dose-dependent manner in WEHI-164 cells (IC50 = 196.673 ± 12.4 μg/mL) when compared with a chemotherapeutic anticancer drug, Toxol. Observation proved that apoptosis was the major mechanism of cell death. So the Echinophora platyloba DC extract was found to time- and dose-dependently inhibit the proliferation of fibrosarcoma cell possibly via an apoptosis-dependent pathway