Urinary Tyramine Assay by High-Performance Liquid Chromatography

Abstract

An assay for urinary tyramine based on its reaction with fluorescamine and subsequent separation on reverse phase column has been described. The method is simple, sensitive and free from interferences. Patients with neuroblastoma, pheochromocytoma and Parkinson's disease have elevated levels of urinary tyramine.     

Determination of Ascorbic Acid in Blood Plasma or Serum and in Seminal Plasma Using a Simplified Sample Preparation and High-Performance Liquid Chromatography Coupled with Uv Detection

Abstract

A simplified method of sample preparation and high-performance liquid chromatography procedure using UV detection is described for the determination of ascorbic acid (AA) in blood plasma or serum and seminal plasma. Within two hours from collection samples are treated with dithioerythritol (DTE) and then stored under Argon at -80°C. Prior to analysis, protein precipitation is initiated with the addition of cold methanol. AA elution is carried out on a C₁₈ reverse phase column using dodecyltrimethylammonium bromide as an ion-pairing agent. the detection is accomplished by measuring ultraviolet absorption at 265 nm. the analysis time for sample is 10.5 min, the retention time of AA being 9.7 min. Within- and between-day coefficients of variation are 2.9% and 4.9% for blood serum, 1.0 % and 2.3 % for seminal plasma. Mean analytical recovery of 102.5 ± 3.7% was found analyzing a serum pool after addition of a standard amount of AA. AA levels are stable for at least 43 days under the described storage conditions.     

Simple and Sensitive Assay of Torasemide in Human Plasma by High-Performance Liquid Chromatography Using a Monolithic Silica Column

A rapid and sensitive method to assay torasemide in plasma was developed using a simple liquid-liquid extraction technique followed by high-performance liquid chromatography. Torasemide and the internal standard furosemide were extracted from 0.5 mL of plasma using ethyl acetate in the presence of 0.1M HCl. The analysis of the extracts was performed on a monolithic silica column with ultraviolet spectrophotometric detection. The calibration curve was linear over the concentration range of 0.05-5 μg mL^?1 in plasma. Recoveries were reasonable for routine analyses (>80%); the limit of quantification was 0.05 μg mL^?1 with a signal-to-noise ratio of 5. The coefficient of variation of the assay precision was less than 6.1%, and the accuracy exceeded 98%. This method was used to measure the torasemide concentration in plasma from healthy subjects after a single 20-mg oral dose of torasemide. This method provides a very simple, sensitive, and accurate way to determine torasemide concentrations in plasma.     

Determination of Reserpine in Plasma Using High-Performance Liquid Chromatography with Fluorescence Detection

Abstract

A high-performance liquid chromatographic method for determining reserpine in plasma has been developed. The procedure involves extraction of reserpine from buffered plasma into benzene, oxidation of reserpine to a fluorophor by treatment with vanadium pentoxide in phosphoric acid, and chromatographic separation of the reserpine fluorophor on an octadecylsilane column by ion-pairing with heptanesulfonate ions. Fluorescence monitoring of the column effluent provides high sensitivity of detection and increases the specificity of the procedure. A detection limit of approximately 100 pg of reserpine per ml of plasma was obtained following analysis of 2 ml samples. Analysis of a number of samples demonstrated the applicability of this method in confirming the presence of reserpine in equine plasma specimens collected at various horse shows and in evaluating the pharmacokinetic behavior of reserpine following intramuscular administration to horses.     

Rapid Determination of Apomorphine in Brain and Plasma Using High-Performance Liquid Chromatography

Abstract

A new method for quantitative determination of apomorphine in mouse brain and rat plasma is described. The drug was extracted utilizing SEP-PAK C₁₈ cartridge, and quantified by high performance liquid chromatography with electrochemical detector. The average recovery was 92 ± 2.8% with a day-to-day coefficient of variation of 10.2%. Apomorphine concentration in mouse brain and in rat plasma, as a function of dose and time, after injection with apomorphine-HCl were determined. The results indicate that the method is adequate for pharmacokinetic studies.     

Micro-Scale Method for Determination of Tobramycin in Serum Using High-Performance Liquid Chromatography

Abstract

A rapid, simple, accurate, and micro-scale method for the determination of tobramycin, sisomicin and netilmicin in serum using high-performance liquid chromatography has been developed. The method is sensitive to 0.3 pg/ml using only 20 μl of serum. The serum is deproteinized with methanol containing an internal standard: sisomicin for the tobramycin, netilmicin for the sisomicin, and sisomicin for the netilmicin. After centrifugation, a counter-ion reagent is added to the supernatant, then an aliquot of the solution is injected into the chromatograph. Tobramycin, sisomicin and netilmicin are separated by reversed-phase, ion-pair chromatography and detected by fluorescence using continuous-flow, post-column derivatization with o-phthalaldehyde. For the tobramycin, within-run and day-to-day variation was below 2.5%. Correlation of this method with microbiological assay and homogeneous enzyme immunoassay was good.     

Determination of Arteether in Plasma Using a Simple and Rapid High-Performance Liquid Chromatographic Assay

Abstract

A simple and rapid high-performance liquid chromatographic (HPLC) assay for the determination of the antimalarial drug arteether in plasma was developed and validated in this report. Perchloric acid was used in this method as a plasma protein precipitant and to attain an acidic medium suitable for the decomposition of arteether to a derivative possessing UV absorption. This derivative and the internal standard (progesterone) were separated from the plasma on a 10 μm μ-Bondapack C₁₈ reversed-phase column at ambient temperature with a mobile phase composed of acetonitrile:water (60:40 v/v) and at a flow rate of 1.5 ml/min. The effluent was monitored at 254 nm with a UV detector. Linear relation between drug concentrations and peak height ratios of arteether derivative to the internal standard was achieved in the range of 0.25-10 μg/ml arteether with a detection limit of 50 ng/ml arteether in plasma. The within-day and between-days precisions were evaluated using 3 different concentrations of arteether. The values of the coefficients of variation were 1.35-1.68% and 1.65-2.82% for within-day and between-day, respectively. This method was applied to determine some pharmacokinetic parameters of arteether after intramuscular injection of 50 mg/kg arteether oily solution to rabbits.     

A Rapid and Sensitive Method for The Determination of Diclofenac Sodium in Plasma By High-Performance Liquid Chromatography

Abstract

A rapid and sensitive high-performance liquid chromatographic method for the determination of diclofenac sodium in plasma has been developed. The method is specific and free of interference from metabolites and common anti-inflammatory agents. The UV detector (215 nm) response was linear over a range of 5-1000 ng/ml. Day-to-day and within-day calibration curves were reproducible. The method was validated by analysis of spiked human plasma samples, partly in a blind fashion. The accuracy and precision of the method are satisfactory over the range of 5-1000 ng/ml. The method was cross-checked with the GC method. Results show a correlation coefficient of 0.983 and a slope of 1.04. The method is suitable for the routine analysis of large numbers of plasma samples usually obtained in bioavailability and pharmacokinetic studies.     

Analysis of Norethindrone In Plasma by High-Performance Liquid Chromatography

Abstract

A sensitive specific high-performance liquid chromatographic procedure for the determination of norethindrone in plasma is described. The organic solvent extract from plasma is chromatographed on a reversed phase column using a high-performance liquid chromatograph fitted with an ultraviolet detector (254 nm); quantitation from plasma samples containing 2 ng/ml norethindrone is reported. Metabolites and endogenous substances do not interfere with the assay. The determination of norethindrone concentrations in plasma following administration of single oral dose to a mini-pig is described.     

Measurement of Nicotine in Plasma by High-Performance Liquid Chromatography

Abstract

A new procedure has been developed to measure nicotine in blood plasma by high-performance liquid chromatography (HPLC). Nicotine is extracted from plasma by elution with cholorform. Final determination is achieved by isocratic HPLC with ultraviolet detection. Twenty microliters of plasma extract is deluted over a silica column at a flow rate of 1.0 ml/min with a dioxane:isopropanol:NH₄OH (80:3.0:0.4) mobile phase. The procedure is sensitive to 0.05 ug of nicotine per ml of plasma and is linear within the range of 0.05 to 10.0 ug/ml of plasma. When a known amount of nicotine was added to plasma, the concentration of nicotine measured averaged 99.9 + 3.9 (S.D.)% of the known concentration. The within-sample coefficient of variation was 3.9%     

Rapid Assay for the Determination of Tolfenamic Acid in Pharmaceutical Preparations and Biological Fluids by High-Performance Liquid Chromatography

Abstract

An improved reversed-phase High-Performance Liquid Chromatographic (HPLC) method using UV detection, at 282 nm, is described for the determination of tolfenamic acid in the presence of caffeine, as internal standard, in pharmaceutical preparations and biological fluids. Sample analyses are performed with a Lichrosorb-RP18, 10 μm, 250×4 mmLD., column using acetate buffer, (pH 4.6 and constant ionic strength 0.05 M) methanol (18:82) as eluent, at a flow rate of 1.9 ml/min. The retention time is 1.44 min for caffeine and 2.62 min for tolfenamic acid. The absolute detection limit is 0.5 ng in the presence and 0.9 ng in the absence of internal standard and linearity is observed up to 100 ng injected. The method involves the use of solid     

Rapid and Sensitive Method for Citrinin Determination Using High-Performance Liquid Chromatography with Fluorescence Detection

Citrinin is a toxic product of secondary metabolism of fungi, such as certain Aspergillus, Penicillium, and Monascus species that are usually contaminating cereals. A new sensitive liquid chromatographic method with fluorescence detection was developed, validated, and applied for citrinin determination. The method is based on reversed-phase separation at pH 2.5, where citrinin exhibits the highest fluorescence quantum yield. In this setup, no derivatization step is needed. The method shows linearity in the range between 0.2 μg/mL and 0.1 mg/mL. The detection limit reached is 90 ng/mL (3.6 × 10^?7 M). Validated method was successfully applied on analysis of spiked and real cereal samples.     

Determination of Plasma Levels of Bupivacaine by High-Performance Liquid Chromatography

Abstract

We evaluate a method for determination of bupivacaine using HPLC, and the possibility of pharmacological interferences produced by seven commonly used drugs administered before, during and after surgery: diacepam, midazolam, epinephrine, naloxone, flumacenil, atropine and ephedrine. The method has an average recovery of 102.8 +/? 5.4%. The detection limit is 0.125 μg/mL. The within-day coefficient of variation is 5.88% and the between-day coefficient of variation is 15%. We haven't found drug interferences at generally encountered serum concentrations.     

Determination of Pyridostigmine in Human Plasma by High-Performance Liquid Chromatography

Abstract

An easy to perform, specific, reproducible and sensitive high performance liquid chromatographic (HPLC) method to measure pyridostigmine concentration in human plasma was developed and validated. Sample clean-up consists of ion-pair extraction into dichloromethane in the presence of neostigmine as internal standard, followed by back extraction into an aqueous phase. Mean recovery of 110% (with a standard deviation of 10%) was determined for concentrations of 5 – 100 ng/ml. Chromatography on a 125·4 mm CN-propyl column using a mobile phase composed of 10% acetonitrile in 3.5×10^?4M NaH₂PO₄ and UV detection at 270 nm, yields clean chromatograms without any interferences from endogenous plasma components. Using 1 ml plasma samples the method has a limit of detection (LD) of 3 ng/ml, with %CV (precision) and bias (accuracy) ≥ 10% for concentrations in the range of 0–100 ng/ml. The method is being used in human pharmacokinetic studies of oral dosage forms of pyridostigmine.     

Determination of Cefpirome in Human Plasma by High-Performance Liquid Chromatography

Abstract

Cefpirome is an investigational third-generation cephalosporin, which appears promising for the treatment of various pediatric infections. A high performance liquid chromatographic method was developed to measure cefpirome in small volumes of plasma for conducting pharmacokinetics studies in infants and children. the assay involved precipitation of plasma proteins with acetonitrile, using cefaclor as an internal standard. Chromatographic separation was accomplished using a reverse-phase     

Rapid Quantitation of Verapamil in Plasma by High-Performance Liquid Chromatography

Abstract

A simple and sensitive liquid chromatographic assay procedure using a fluorescence detector for the quantitative determination of verapamil in plasma without extraction was developed. After precipitating the protein with acetonitrile, the resulting supernatant liquid was injected onto the column for analysis. Chromatographic separation was achieved on C₁₈ reversed phase column and the eluting solvent was the isocratic mixture of methanol, acetonitrile and pH 3.0 glycine buffer (1:4:5). With this mobile phase the drug and its internal standard were well separated from the interference of the plasma sample. The average recovery of verapamil from 3 replicate samples of different concentration (100–600 ng/mL) were 95.5 ± 5.68%. The minimum amount of verapamil detectable by this method was 40 ng/mL of sample. The elimination half-life (β-phase) of this drug in rabbits was found to be 3.7 hours.     

Quantitation of Baclofen in Tablets Using High-Performance Liquid Chromatography

Abstract

A reverse phase high-performance liquid chromatography method has been developed to quantify baclofen in tablets. The method is accurate and precise with a percent relative standard deviation of 0.52 based on 5 readings. The recovery from the synthetic mixtures was quantitative. The results were in excellent agreement with the USP-NF colorimetric method. The method can be used to test the content uniformity of the tablets. Samples which were treated with either sulfuric acid or sodium hydroxide and boiled for 10 minutes did not show new peaks in the chromatogram. Baclofen appears to be a very stable compound.     

Quantification of Leukotriene B4 Using High-Performance Liquid Chromatography

Abstract

Leukotriene B₄ (LTB₄) was derivatized with p-(9-anthroyloxy) phenyl bromide forming the panacyl ester. The yield from this reaction was 95 percent. Subsequent separation of this ester using reversed phase high-performance liquid chromatography resulted in a greater than 10 fold increase in sensitivity as measured directly with ultraviolet light (absorption at 254 nm). Sensitivity was 16 ng and elution time was less than 15 minutes. We applied this technique to quantification of LTB₄ production by human polymorphonuclear leucocytes.     

Individual Carotenoid Determinations in Human Plasma by High-Performance Liquid Chromatography

Abstract

A high-performance liquid chromatographic technique is described to quantify beta carotene from alpha carotene and lycopene in human plasma. Total analysis time is 14.5 min. A reverse-phase column was employed with a mobile phase composed of 65% acetonitrile: tetrahydrofuran (90:10, v:v) in methanol. Use of the internal standard, beta-apo-8- carotenoic ethyl ester permitted a reliable way to quantify potential losses in plasma extractions. Plasma beta carotene levels obtained from subjects several days after supplement use were observed to increase three-fold or more.