A Validated HPLC Method with Fluorescence Detection for the Determination of Droperidol in Pharmaceutical Tablets,Human Serum,and Human Milk

A sensitive and simple HPLC method with fluorimetric detection has been developed for determination of droperidol in pharmaceutical tablets, human serum, and human milk. Chromatography was performed on a 100 mm × 3 mm i.d. C₁₈ column with methanol–water, 30:70 (v/v), pH 3.5, as mobile phase at a flow-rate of 0.8 mL min⁻¹. The injection volume was 5 μL and detection was by monitoring emission at 324 nm after excitation at 283 nm. Droperidol and p-hydroxybenzoic acid (internal standard) eluted after 5.3 and 6.1 min, respectively. The method was validated over the concentration range 1.14 × 10⁻⁷ to 9.12 × 10⁻⁶ M. Selectivity was good and the limits of detection and quantitation of the method were approximately 3.54 × 10⁻⁸ and 1.07 × 10⁻⁷ M, respectively, corresponding to 13 and 40 ng mL⁻¹. The applicability of the method to determination of droperidol in pharmaceuticals, human serum, and human milk was demonstrated.

     

Determination of Sotalol in Tablets and Serum by CZE

A validated capillary zone electrophoretic method for analysis of sotalol is described. Analysis was performed in a fused-silica capillary with 20 mM phosphate buffer (pH 4.20) containing 10% (v/v) acetonitrile as background electrolyte. The applied potential was +20 kV, the injection time 0.08 min, signal detection was at 200 nm, and 3,4-dihydoxybenzylamine was used as internal standard. The method was validated over the concentration range 1.98 × 10⁻⁵ to 9.90 × 10⁻⁵ M; repeatability was good and there was no interference. Highly satisfactory results were obtained from analysis of tablets and serum, indicating the method is specific, accurate, and precise, and suitable for routine analysis of sotalol in pharmaceutical tablets and in pharmacokinetic studies.

     

Determination of Folic Acid by CE in Various Cultivated Variety of Lentils

A simple extraction and determination method for folic acid (FA) in lentil samples was developed employing capillary electrophoresis. The analysis was performed in a 75 μm ID fused silica capillary using a running buffer of 10 mM sodium borate (10%, v/v, methanol, pH 9) at +18 kV and a detection wavelength at 200 nm. Methylparaben was used as the internal standard. FA signal response was linear in the range between 1.2 × 10^?5 and 4.8 × 10^?5 M. Limit of detection (inter-day) was determined at 6.12 × 10^?7 M (3.3 σs^?1). The amount of FA found in green, red and mignon lentils was found to range between 0.408 and 0.742 mg g^?1.     

Sensitive and efficient determination of gabapentin in human serum based on capillary electrophoresis with laser-induced fluorescence detection

A sensitive and efficient analytical method for gabapentin (GBP) in human serum based on capillary electrophoresis (CE) with laser-induced fluorescence (LIF) detection has been established. 6-Oxy-(N-succinimidyl acetate)-9-(2′-methoxycarbonyl) fluorescein (SAMF), a new synthesized fluorescent reagent, was used for precolumn derivatization of the non-fluorescent drug in serum. γ-Aminobutyric acid (GABA) was used as an internal standard (I.S.). The best derivative condition was obtained in phosphate buffer (pH 8) at room temperature for 10 min. Optimal separation and detection were obtained with a background electrolyte (BGE) of 3.5 × 10^?2 M phosphate buffer (pH 5.5) and laser-induced fluorescence detection excited at 473 nm. The method developed for GBP was linear over the concentration range of 4.0 × 10^?9 to 4.0 × 10-7 M. The concentration limit of detection was 2.0 × 10^?10 M (signal-to-noise ratio = 3). The sensitive method was used for the determination of GBP in serum samples.     

Electrophoretic determination of 1-methyl-2-mercaptoimidazole in the pharmaceutical preparation mercazolyl

The conditions for the quantitative determination of 1-methylimidazoline-2-thione with the use of a Kapel’ 103-R capillary electrophoresis system were optimized (acetate buffer; pH 4.5; U = 20 kV). The analytical range of the procedure is 1.5 × 10^?4?1.8 × 10^?3 M (the limit of detection is 4.6 × 10^?5 M; RSD = 2.5%). The tablets of Mercazolyl from Akrikhin (Moscow) and Zdorov’e (Kharkov) were analyzed.     

Simultaneous Determination of Neuroactive Amino Acids in Serum by CZE Coupled with Amperometric Detection

A quantitative determination of six neuroactive amino acids (NAAs) was performed by capillary zone electrophoresis with amperometric detection (CZE-AD). This CZE-AD method utilized two electrolytes: the borate solution flowing in a capillary has the NAAs-separation effects, and the sodium hydroxide (NaOH) solution filled in the detection reservoir for the amperometric analysis of NAAs. The following experimental parameters were optimized: the working electrode potential, the pH value, the component, and the concentration of running buffer, the separation voltage, and the injection time on CZE-AD. Then, under the optimum conditions, the six NAAs could be completely separated in 30 min and had well-shaped AD responses at 0.75 V (versus SCE) on a copper electrode. The linear calibration range of NAAs was from 5 × 10^?4 to 5 × 10^?6 mol L^?1 with the limits of detection (LODs) ranging from 10^?6 to 10^?7 mol L^?1 (signal-to-noise ratio = 3), and the relative standard deviations (RSDs) of the migration time and peak area were 0.45–0.55 and 3.8–6.3 %, respectively. Moreover, this method has succeeded in human serum analysis, and the determined contents of the six NAAs in human serum were in an average recovery range of 85.3–117.9 %, which confirmed the validity and practicability of this method.     

Surface analysis of tablets by room-temperature phosphorimetry

The feasibility of surface analysis of homogeneous tablets by room-temperature phosphorimetry is studied for propranolol, p-aminobenzoic acid and acetylsalicylic acid as model compounds. Potassium iodide is used to provide the heavy atom; starch or carboxymethylcellulose is used as the excipient. The analytically useful ranges were found to be 3 × 10^?5?3 × 10^?4% for p-aminobenzoic acid, 5 × 10^?4?5 × 10^?2% for propranolol, and ? 10% for acetylsallicylic acid (all by weight in tablets).     

Simultaneous Determination of Levodopa and Its Metabolite in Human Blood by Capillary Electrophoresis with Laser‐induced Fluorescence Detection

A rapid, sensitive and reproducible method is described for the analysis of levodopa and its metabolite dopamine (DA) in human blood. The influence of carbidopa as the inhibitor againist the decarboxylase activity on the metabolism has been also studied. After derivatization in a dark pulsator for 12 h at room temperature, the fluorescein isothiocyanate (FITC) derivative of levodopa and other components were separated by capillary zone electrophoresis (CZE) within 13 min and detected with laser-induced fluorescence (LIF). Under the optimum analysis conditions, the linear range is 3.0×10^－8—4.0×10^－6 mol/L and 1.0×10^－8—2.0×10^－6 mol/L for levodopa and DA, respectively. The detection limits of levodopa and DA were 7.8×10^－9 mol/L (39.0 amol) and 3.1×10^－9 mol/L (15.5 amol), respectively. The method was successfully applied to monitoring the levodopa and DA in human blood after one took tablets orally.     

Direct potentiometric titration of thiosulfate,thiourea, and ascorbic acid with lodate using an iodide ion-selective electrode

A potentiometric method has been developed for the semi-automatic direct titration of thiourea, thiosulfate, and ascorbic acid with potassium iodate in strongly acidic solutions using an iodide ion-selective electrode to monitor the reaction and locate the endpoint. The method is simple, fast, precise, and accurate. Amounts ranging from 0.15–1.5 mg of thiourea (3.9 × 10^?4–3.9 × 10^?3, M), 0.3–3.0 mg of thiosulfate (5.4 × 10^?4–5.4 × 10^?3, M), and 0.5–5.0 mg of ascorbic acid (5.7 × 10^?4–5.7 × 10^?3, M) have been determined with an average error of about 1%. The method has been applied to the determination of ascorbic acid in tablets. Results checked closely with those obtained with a standard titrimetric method.     

Determination of Dothiepin in Human Plasma by LC–ESI–MS and its Application to Bioequivalence Studies

An LC–MS method for the determination of dothiepin in human plasma was developed and validated. Sample preparation involved extraction with n-hexane:2-propanol (95:5). Separation was on an Ultimate XB C18 column (2.1 × 150 mm, 5 μm). A single-quadrupole mass spectrometer with an electrospray interface was operated in the selected-ion monitoring mode to detect the [M+H]⁺ ions at m/z 296 for dothiepin and at m/z 278 for the internal standard (amitriptylene). The method demonstrated good linearity from 0.78 ng mL^?1 (the LOQ) to100 ng mL^?1. The mean extraction recovery was 82.4% for dothiepin and and 84.2% for the internal standard. The intra-day and inter-day precision ranged from 8.5 to 11.4% and 9.7 to 12.1% (RSD), respectively. The method was successfully applied to bioequivalence studies of dothiepin hydrochloride tablets to obtain the pharmacokinetic parameters.     

Optimization,Validation and Application of a Capillary Zone Electrophoresis Method for the Assay of Sparfloxacin in Pharmaceutical Formulation

Abstract

A capillary zone electrophoresis (CZE) method has been developed for the determination of the antibiotic sparfloxacin in tablets. The CZE separation was performed using 75 µm×35 cm fused-silica capillary under the following conditions: 25°C; applied voltage, 12 kV; 25 mM H₃PO₄-NaOH running buffer (pH 8.5). The detection wavelength was 254 nm. Flumequine was used as internal standard (IS). The method was suitably validated with respect to linearity, limit of detection and quantification, accuracy, precision, specificity, and robustness. The calibration was linear from 10 to 60 µg mL^?1 and the limit of detection and quantification were 5.38 and 9.46 µg mL^?1, respectively. Recoveries ranging from 95.68%–102.4% were obtained in the determination of sparfloxacin that were spiked to placebos. Excipients in the commercial tablets and degraded products from different stress conditions did not interfere in the assay. The method was successfully applied to the determination of sparfloxacin in pharmaceutical tablets.     

Cyclodextrin-Modified Gold Nanoparticle Capillary Electrochromatography with Online Sample Stacking for Simultaneous and Sensitive Determination of Aminobenzoic Acid Isomers

A newly-developed method of complete separation and sensitive determination of o-, m-, and p-aminobenzoic acid isomers was achieved by combining open-tubular columns for capillary electrochromatography (OT-CEC) and online sample stacking. In this study, spherical gold nanoparticles were modified by a covalent attachment of mono-6-thio-β-cyclodextrin, and OT-CEC was formed by immobilizing cyclodextrin-modified gold nanoparticles (CD-AuNP) on prederivatized 3-mercaptopropyl-trimethoxysilane fused-silica capillaries. Based on the theory of moving chemical reaction boundary, effects of several important factors such as the pH and concentration of running buffer and the conditions of stacking analytes were optimized. The optimized separations were carried out in 58 mmol/L HAc buffer at pH 3.0 using a capillary coated with CD-AuNP, while the optimized concentration was carried out in 50 mmol/L disodium hydrogen phosphate (pH 9.5). The linear ranges for m-, p-, and o-aminobenzoic acid were from 5.0 × 10^?4–0.1, 5.0 × 10^?4–0.1 and 1.0 × 10^?4–0.1 mmol/L, respectively. And the detection limits (S/N = 3) were as low as 8.22 × 10^?5, 8.21 × 10^?5, and 3.76 × 10^?5 mmol/L for m-, p-, and o-aminobenzoic acid, respectively. The run-to-run, day-to-day, and column-to-column reproducibilities of migration time were satisfactory with relative standard deviation values of less than 4.5 % in all cases. This method was successfully used in determining procaine hydrochloride injection sample with recoveries in the range of 96.1–106.6 % and relative standard deviations less than 5.0 %.     

Simultaneous Quantitation of Quinolone Residues in Biological Fluid by CE Combined with Electrogenerated-Chemiluminescent Detection

A simple, rapid and sensitive method has been proposed for simultaneous electrogenerated-chemiluminescent detection of quinolone residues in biological fluid after effective separation by capillary electrophoresis. Enrofloxacin, levofloxacin and ciprofloxacin can be assayed in the range of 3.0 × 10^?8–5.0 × 10^?6 g mL^?1 within 10 min. The relative standard deviations of the signal intensity and the migration time were less than 4.9 and 2.4% for a standard sample containing 1.0 × 10^?7 g mL^?1 of each quinolone (n = 5), respectively. The presented method has been successfully applied to determine the amounts of quinolones in pig urine after clean-up by C₁₈ solid phase extraction column.     

Determination of Abacavir, Lamivudine and Zidovudine in Pharmaceutical Tablets, Human Serum and in Drug Dissolution Studies by HPLC

A simple, accurate, precise and fully automated method for the simultaneous determination of abacavir, lamivudine and zidovudine in pharmaceutical tablets, human serum samples and drug dissolution studies has been developed. Separation was performed on a 5 μm Zorbax^® C₁₈ column (150 × 4.6 mm ID) with methanol:water:phosphate buffer at pH 5.65 (80:10:10; v/v/v) isocratic elution in less than 7 min with a flow rate of 0.6 mL min^?1.Good sensitivity for all analytes was observed with UV detection at 275 nm. The method allowed quantitation over the 500–3,000 ng mL^?1 range for abacavir and 500–5,000 ng mL^?1 range for lamivudine and zidovudine. The method has been applied, without any interference from excipients or endogenous substances, for the simultaneous determination of these three compounds in tablets. Human serum and drug dissolution studies.     

Determination of enoxacin and ofloxacin by capillary electrophoresis with electrochemiluminescence detection in biofluids and drugs and its application to pharmacokinetics

A novel and sensitive method for the simultaneous determination of enoxacin and ofloxacin has been established using capillary electrophoresis (CE) coupled with electrochemiluminescence (ECL) detection based on the ECL enhancement of tri(2,2‐bipyridyl)ruthenium(II). The conditions for sample solvent type, CE separation and ECL detection were investigated systematically. The analytes were well separated and detected within 7 min. The limits of detection (S/N = 3) of enoxacin and ofloxacin are 9.0 × 10^?9 and 1.6 × 10^?8 mol/L, respectively. The precisions (RSD%) of intraday and interday are less than 2.1 and 4.0%, respectively. The limits of quantitation (S/N = 10) of enoxacin and ofloxacin are 3.2 × 10^?7 and 5.4 × 10^?7 mol/L in human urine samples and 4.1 × 10^?7 and 6.9 × 10^?7 mol/L in human serum samples, respectively. The recoveries of enoxacin and ofloxacin at different concentration levels in human urine, serum and eye drop samples are between 94.0 and 106.7%. The proposed method was successfully applied to the determination of the enoxacin and ofloxacin in human urine, serum and eye drop samples and the monitoring of pharmacokinetics of ofloxacin in human body. Copyright © 2009 John Wiley & Sons, Ltd.     

Electrochemical determination of tryptophan based on silicon dioxide nanopartilces modified carbon paste electrode

Silicon dioxide nanoparticles modified carbon paste electrode was fabricated and used for electrochemical investigation of tryptophan. Compared with the unmodified electrode, the peak current significantly increased. Experimental conditions for tryptophan determination were optimized. Linear relationship between the peak current and tryptophan concentration was obtained in the range of 1.0 × 10^?7?5.0 × 10^?6 mol L^?1 and 5.0 × 10^?6?5.0 × 10^?5 mol L^?1 with an estimated detection limit of 3.6 × 10^?8 mol L^?1 (S/N = 3). Tryptophan in pharmaceutical and human serum samples were successfully determined by the proposed method.     

Electrophoretic and gas-chromatographic analysis of an Afobazol pharmaceutical preparation

Procedures for determining 5-ethoxy-2-[2-(morpholino)ethylthio]benzimidazole dihydrochloride, an active component of the Afobazol medicinal preparation, and its potential impurities, 5-ethoxybenzimidazol-2-thione and N-(2-chloroethyl)morpholine hydrochloride by capillary zone electrophoresis in the range 2.0 × 10^?5 to 2.0 × 10^?3 M and ligand-exchange capillary electrophoresis in the range 1.0 × 10^?5 to 5.0 × 10^?3 M are developed. The optimum conditions for the separation and determination of these analytes using a quartz capillary tube are found. The reliability of the results obtained by capillary electrophoresis was confirmed by gas chromatography with a mass-selective detector.     

Man‐Tailored Biomimetic Sensor of Molecularly Imprinted Materials for the Potentiometric Measurement of Rivastigmine in Tablets and Biological Fluids and Employing the Taguchi Optimization Methodology to Optimize the MIP‐Based Membranes

This work proposes a novel biomimetic sensor for the potentiometric transduction of rivastigmine based on molecularly imprinted polymer (MIP). Using the Taguchi method, this study analyzed the optimum conditions for preparing the MIP‐based membranes. The rank order of each controllable factor was also determined. MIP‐based membranes exhibited a Nernstian response (30.7±1.1 mV decade^?1) in a concentration range from 1.0×10^?5 to 1.0×10^?2 mol L^?1 with a LOD of 6.3×10^?6 mol L^?1. The sensor was successfully applied to the determination of rivastigmine concentrations in human serum, plasma, urine, rat brain and tablets.     

A simple spectrophotometric procedure for determination of valaciclovir in dosage forms and biological fluids

A simple and selective spectrophotometric procedure for the determination of Valaciclovir (VALA) is proposed and applied to determine the substance in tablets and biological fluids. This procedure is proposed for the determination of VALA in Britton-Robinson (BR) buffer at pH 6.0, which allows quantification over the 4 × 10^?6 to 6 × 10^?5 M range for spectrophotometric measurements. The repeatability and reproducibilty of the procedure for serum and breast milk samples are estimated. Precision and accuracy are also checked. The standard additions method is used for biological fluids. The proposed produce was verified for the determination of VALA in real human serum, breast milk samples; the selectivity over the metabolites was found to be quite satisfactory.     

Determination of Piribedil in Human Serum, Urine and Pharmaceutical Dosage Form by LC-DAD

A rapid, selective and sensitive reversed-phase liquid chromatographic (LC) method was developed for the determination of piribedil in human serum, urine and pharmaceutical dosage form. LC analysis was carried out using reversed-phase isocratic elution with a C₁₈ column and a mobile phase of 0.01 M phosphate buffer-acetonitrile (50:50, v/v). The chromatograms showed good resolution and sensitivity with no interference of human serum and urine. Piribedil concentrations were determined using diode array detection at 240 nm. Sildenafil citrate was used as internal standard. The limit of quantification (LOQ) and limit of detection (LOD) concentrations were 107.2 and 321.6 pg mL^?1, 96.6 and 290.4 pg mL^?1, 161.7 and 53.9 pg mL^?1 for urine, serum and pharmaceutical dosage forms, respectively. The method was validated for its linearity, precision and accuracy and applied to the tablets, urine and human serum. In addition, the results were compared to those obtained from UV-spectrophotometry.