Determination of remoxipride in human plasma and urine by reversed-phase ion-pair high-performance liquid chromatography.

A sensitive method is described for the measurement of remoxipride in human plasma and urine. Remoxipride and its internal standard are extracted from plasma or urine at pH 12 with a mixture of hexane and methyl tert.-butyl ether. After washing the organic phase with base, the compounds are extracted into acid and analyzed on a C18 column with ultraviolet detection at 214 nm. The mobile phase is composed of acetonitrile and aqueous buffer (sodium perchlorate and phosphoric acid, pH 1.7). The limits of reliable quantitation for remoxipride are 12.5 and 50 ng/ml for plasma and urine, respectively. The run times are 6 min for plasma and 3 min for urine. The method has been successfully used to assay remoxipride clinical study samples. This mobile phase has also been successfully applied to the analysis of other basic drugs such as cimetidine, codeine, diltiazem and quinidine with minor modifications.     

Optimization of a peak compression system for a remoxipride metabolite (FLA797) and its application to bioanalysis.

A peak compression system is optimized for FLA797 (I), a phenolic tertiary amine and a metabolite to the antipsychotic drug remoxipride. An application is described where this effect is used to give a 6-7-fold improvement of the quantification limit in an assay of I in plasma. The liquid chromatographic system is constructed so that the injection of I dissolved in a solution of a competing amine gives a very high and narrow analyte peak with an apparent efficiency of 1.5 x 10(6) plates/m. When the levels of I in plasma are determined, an internal standard, giving a normal isocratic peak, is added to the plasma sample before the extraction. Concentrations of I down to 0.5-1.0 nM can be determined with reasonable precision. FLA908, another phenolic remoxipride metabolite and a regioisomer to I, eluting as a normal isocratic peak, can be determined simultaneously although only at concentrations higher than 10-15 nM.     

A New Sensitive Reversed‐phase High‐performance Liquid Chromatography Method for the Quantitative Determination of Metoclopramide in Canine Plasma

Abstract

A specific and sensitive high‐performance liquid chromatographic method was developed for the determination of metoclopramide in canine plasma. The procedure involves fast liquid–liquid extraction and analysis on an octadecyl silane (ODS) column. A preliminary pharmacokinetic study was performed by applying the developed method to a single oral administration of metoclopramide (MCP) to a dog. The validation method yielded good results regarding linearity, precision, accuracy, and specificity. The procedure is suitable for separation and quantification of MCP in canine plasma, enough to quantify 0.2 ng/ml when 0.5 ml of plasma is used. This assay procedure might be useful for the pharmacokinetic study of MCP in dogs.     

Rapid HPLC measurement of buflomedil in plasma in poisoning cases

A rapid high-performance liquid chromatographic method for the determination of buflomedil in human plasma is described. It requires a single liquid-liquid extraction step from 1 mL of plasma with diethyl ether followed by chromatography on a Nova Pak C(18) reversed-phase column and detection by ultaviolet light. Metoclopramide was used as internal standard. The method is sensitive with a quantification limit at 500 ng/mL. It was used for the determination of buflomedil in biological fluids in poisoning cases.     

A simplified assay of furosemide in plasma and urine by high-pressure liquid chromatography.

A simplified high-pressure liquid chromatograhic method for determination of furosemide in plasma and urine has been developed using a fluorometric detector directly coupled to the column effluent. The method includes an ether extraction from acidified biologic samples. The mobile phase used for chromatography on a reversed-phase column (C15 hydrocarbon permanently bonded to silica particles) is sufficiently acidic to induce fluorescence of furosemide. The methylester of furosemide is employed as an internal standard. The sensitivity is 0.1 and 0.25 microgram per ml plasma and urine, respectively. The applicability to pharmacokinetic studies of furosemide is shown.     

Determination of penicillin G in bovine plasma by high-performance liquid chromatography after pre-column derivatization.

A simple, selective, and sensitive liquid chromatographic method with ultraviolet detection was developed for the analysis of penicillin G in bovine plasma. The assay utilizes a simple extraction of penicillin G from plasma (with a known amount of penicillin V added as internal standard) with water, dilute sulphuric acid and sodium tungstate solutions, followed by concentration on a conditioned C18 solid-phase extraction column. After elution with 500 microliters of elution solution, the penicillins are derivatized with 500 microliters of 1,2,4-triazole-mercuric chloride solution at 65 degrees C for 30 min. The penicillin-mercury mercaptide complexes are separated by reversed-phase liquid chromatography on a C18 column. The method, which has a detection limit of 5 ng/ml (ppb) in bovine plasma, was used to quantitatively measure the concentrations of penicillin G in plasma of steers at a series of intervals after the intramuscular administration of a commercial formulation of procaine penicillin G.     

Solid-phase extraction of vinblastine and vincristine from plasma and urine: variable drug recoveries due to non-reproducible column packings

A sensitive and selective high-performance liquid chromatographic (HPLC) method for the determination of vinblastine and vincristine in plasma and urine is described. The drugs are isolated from 1.0 ml of the biological fluid with a solid-phase extraction column (Bond-Elut Diol). The HPLC method was combined with electrochemical detection at +850 mV versus an Ag/AgCl reference electrode. The detection limit is 100 pg for vinblastine and 250 pg for vincristine with a signal-to-noise ratio of 3, which permits the determination of these compounds in biological fluids at the nanogram level. Evaluation of the isolation method revealed that the drug recoveries and the reproducibility of the extraction procedure depend on the batch number of the solid-phase extraction column used.     

Determination of a platelet activating factor antagonist (CV-3988): methodology and clinical application

A high-performance liquid chromatographic method was developed for determination of the platelet activating factor antagonist CV-3988 in human plasma and urine. After development of a column extraction procedure without an internal standard, a more satisfactory organic extraction procedure was set up with amiodarone as internal standard. Linearity of the calibration curves was found in the range 0.0625-10 micrograms/ml CV-3988. Reproducibility was higher than 10% for the column extraction and lower than 10% for the organic extraction procedure. Recovery of CV-3988 from plasma averaged 81.7% for the column procedure and 40% for the organic extraction. Urine samples could be extracted only by the organic extraction procedure. The organic extraction procedure was applied to the determination of CV-3988 in plasma and urine samples after intravenous administration to normal volunteers.     

Determination of free 3-methoxy-4-hydroxyphenylglycol with several other monoamine metabolites in plasma by high-performance liquid chromatography with amperometric detection

A reversed-phase liquid chromatographic method with amperometric detection has been developed for determining free 3-methoxy-4-hydroxyphenylglycol in plasma. The method is based on a simple and rapid extraction procedure employing a small C18 column. Vanillyl alcohol was used as an internal standard to obtain a good reproducibility. The 3-methoxy-4-hydroxyphenylglycol concentrations measured with the present method were in reasonable agreement with recently published data using high-performance liquid chromatography with amperometric detection and gas chromatography with mass spectrometry. The additional advantage of the present assay is that it can be performed in parallel with the quantification of other monoamine metabolites in plasma.     

A Rapid Sample Preparation Method of Adriamycin from Plasma for HPLC Analysis

A rapid and comprehensive sample preparation method used to extract adriamycin from plasma has been investigated. The samples were passed through an Adsorbex extraction column with an elution solvent. The eluate was directly analyzed by reversed-phase high performance liguid chromatography (HPLC) with fluorescence detector. This solid/liquid extraction method is simpler than the conventional liquid/liquid extraction method. Different elution solvents were used to extract the adriamycin from samples with and without serum. The mobile phase was found to be the optimal elution solvent: 5 mM orthophosphoric acid 62.5% in methanol; acetonitrile; isopropanol = 15:15:7.5, pH 3.2. This method has the merits of better recovery (98%), higher reproducibility, and reguires shorter time and consumes less solvent.     

Determination of diclofenac in plasma using a fully automated analytical system combining liquid-solid extraction with liquid chromatography

A fully automated analytical system based on liquid-solid extraction combined with column liquid chromatography is described for the determination of diclofenac in plasma. After addition of pH 5 buffer and the internal standard solution to the plasma sample, both sample preparation via a C18 disposable extraction column and injection were performed by a Gilson ASPEC system. Diclofenac and the internal standard were separated on a reversed-phase column, using methanol-pH 7.2 phosphate buffer (56:44, v/v) as mobile phase at a flow-rate of 0.4 ml/min. The reproducibility and accuracy of the method were acceptable over the concentration range 31-3140 nmol/l in plasma.     

Liquid chromatographic determination of sotalol in plasma and urine employing solid-phase extraction and fluorescence detection

A liquid chromatographic method using a solid-phase extraction procedure for the quantification of sotalol in plasma and urine is described. Sotalol is eluted from an extraction column with ethyl acetate-acetonitrile (1:2) and, after separation by reversed-phase high-performance liquid chromatography on a mu Bondapak C18 column, is quantified by fluorescence detection at excitation and emission wavelengths of 240 and 310 nm, respectively. The method has been demonstrated to be linear over the concentration ranges 10-6000 ng/ml in plasma and 0.5-100 micrograms/ml in urine. Mean inter-assay accuracy of the method for plasma ranged from 93 to 100% and for urine from 102 to 114%; precision ranged from 0.5 to 1.6% for plasma over a concentration range of 200-4000 ng/ml and for urine from 0.7 to 2.0% at concentrations of 2-50 micrograms/ml. Mass spectrometry confirmed the presence of sotalol in isolated chromatographic fractions of plasma and urine extracts from subjects given sotalol orally.     

High-throughput biological sample analysis using on-line turbulent flow extraction combined with monolithic column liquid chromatography/tandem mass spectrometry

A high-throughput liquid chromatography/tandem mass spectrometry (LC/MS/MS) method, which combines on-line sample extraction through turbulent flow chromatography with a monolithic column separation, has been developed for direct injection analysis of drugs and metabolites in human plasma samples. By coupling a monolithic column into the system as the analytical column, the method enables running 'dual-column' extraction and chromatography at higher flow rates, thus significantly reducing the time required for the transfer and mixing of extracted fraction onto the separation column as well as the time for gradient separation. A strategy of assessing and reducing the matrix suppression effect on the on-line extraction LC/MS/MS has also been discussed. Experiments for evaluating the resolution, peak shape, sensitivity, speed, and matrix effect were conducted with dextromethorphan and its metabolite dextrorphan as model compounds in human plasma matrix. It was demonstrated that the total run time for this assay with a baseline separation of two analytes is less than 1.5 min.     

Rapid and sensitive liquid chromatographic determination of carbamazepine suitable for use in monitoring multiple-drug anticonvulsant therapy.

A rapid, sensitive and selective method for the determination of carbamazepine and its major metabolite in plasma has been developed. Other commonly used anticonvulsants can be determined in the same procedure without interference. After extraction with dichloromethane, the components are separated by high-pressure liquid chromatography without further clean-up or concentration on a column packed with small-particle silica gel. The mean recovery from plasma is 98.6% with a relative standard deviation of 1.6%. The detection limit for carbamazepine is approximately 2 ng/ml, requiring 1 ml of plasma.     

Reversed-phase ion-pair liquid chromatographic method for the determination of low concentrations of haloperidol in plasma

A sensitive liquid chromatographic method for the determination of haloperidol in plasma is described. The efficient and simple extraction procedure, followed by reversed-phase ion-pair liquid chromatography on a 3-micron octadecylsilica column and UV absorbance detection, makes it possible to determine concentrations down to 0.5 nmol/l with acceptable precision. In a pharmacokinetic study, in which 5 mg of haloperidol were given orally, the plasma levels were followed for 48 h.     

Automatic on‐line solid‐phase extraction with ultra‐high performance liquid chromatography and tandem mass spectrometry for the determination of ten antipsychotics in human plasma

An automatic on‐line solid‐phase extraction with ultra‐high performance liquid chromatography and tandem mass spectrometry method was developed for the simultaneous determination of ten antipsychotics in human plasma. The plasma sample after filtration was injected directly into the system without any pretreatment. A Shim‐pack MAYI‐C₈ (G) column was used as a solid‐phase extraction column, and all the analytes were separated on a Shim‐pack XR‐ODS III column with a mobile phase consisting of 0.1% v/v formic acid in water with 5 mM ammonium acetate and acetonitrile. The method features were systematically investigated, including extraction conditions, desorption conditions, the equilibration solution, the valve switching time, and the dilution for column‐head stacking. Under the optimized conditions, the whole analysis procedure took only 10 min. The limits of quantitation were in the range of 0.00321–2.75 μg/L and the recoveries ranged from 75.9 to 122%. Compared with the off‐line ultra‐high performance liquid chromatography and the reported methods, this validated on‐line method showed significant advantages such as minimal pretreatment, shortest analysis time, and highest sensitivity. The results indicated that this automatic on‐line method was rapid, sensitive, and reliable for the determination of antipsychotics in plasma and could be extended to other target analytes in biological samples.     

High-performance liquid chromatographic analysis of 2',3'-dideoxyinosine in biological samples

A high-performance liquid chromatographic analysis for the anti-AIDS drug 2',3'-dideoxyinosine (ddI) in rat plasma and urine, with a limit of detection of 0.2 microgram/ml and requiring a sample size of 100 microliters is described. Diluted plasma or urine samples were extracted using a C18 solid-phase extraction column. Retention of ddI on more polar solid-phase extraction columns was insufficient for sample clean-up. This method is useful for pharmacokinetic studies of ddI in small rodents.     

Liquid Chromatographic Analysis of Plasma Melphalan with Amperometric Detection in a Patient with Breast Cancer

Abstract

We developed a liquid chromatographic method for the measurement of melphalan in plasma and studied a patient with breast cancer, given melphalan before an Autologous Bone Marrow Transplant (ABMT). A reverse phase C 18 column with isocratic elution and amperometric detection was used. The potential was set at + 0.95V. Sample pretreatment involved extraction of the drug with ethyl acetateethanol. The method is sensitive and precise and was used to study the pharmacokinetics of melphalan.     

Quantitative determination of cortisol in human plasma by high-pressure liquid chromatography.

A method is described for the determination of cortisol in human plasma by high-pressure liquid chromatography. The simplified extraction procedure makes the method applicable to routine clinical assays. Partition chromatography is carried out on a Zorbax-Sil column with the eluent system dichloromethane-ethanol-water. A 78% recovery was obtained for cortisol. The detection limit is 1 mug per 100 ml in 1 ml of plasma. Cortisol values were determined in samples from a random selection of patients.     

Determination of adriamycin in plasma and tissue biopsies.

A simple, rapid and sensitive method for the extraction and high-performance liquid chromatographic analysis of adriamycin in tissue and plasma is described. Tissue (5-100 mg) and plasma (1 ml) samples underwent a C18 Sep-Pak extraction into methanol. Chromatography was performed on a muBondapakphenyl column using a mobile phase of acetonitrile-0.1 M ammonium formate (pH 4.0) with a flow-rate of 2 ml/min. Fluorometric detection was used with an excitation of 480 nm and an emission of 550 nm. The procedure produced a linear curve for the concentration range 25-1000 ng/ml. The development of the assay produced rapid, repeatable and accurate results for both small tissue samples and plasma.