Search PubMed⌕ Search

Biomedical subjects

D Farthing

Publications and source records attributed to D Farthing.

15 recordsLinked to original sources
PubMed1999

High-performance liquid chromatographic method for determination of vanillin and vanillic acid in human plasma, red blood cells and urine.

A simple high-performance liquid chromatographic method was developed for the determination of vanillin and its vanillic acid metabolite in human plasma, red blood cells and urine. The mobile phase consisted of aqueous acetic acid (1%, v/v)-acetonitrile (85:15, v/v), pH 2.9 and was used with an octadecylsilane analytical column and ultraviolet absorbance detection. The plasma method demonstrated linearity from 2 to 100 microg/ml and the urine method was linear from 2 to 40 microg/ml. The method had a detection limit of 1 microg/ml for vanillin and vanillic acid using 5 microl of prepared plasma, red blood cells or urine. The method was utilized in a study evaluating the pharmacokinetic and pharmacodynamic effects of vanillin in patients undergoing treatment for sickle cell anemia.

Benzaldehydes↗
PubMed1998

Simple method for determination of hydrochlorothiazide in human urine by high performance liquid chromatography utilizing narrowbore chromatography.

A simple high performance liquid chromatographic (HPLC) method utilizing narrowbore chromatography was developed for the determination of hydrochlorothiazide in human urine. A mobile phase of 0.1% aqueous acetic acid--acetonitrile (93:7, v/v) pH 3 was used with a C18 analytical column and ultraviolet detection (UV). The method demonstrated linearity from 2 to 50 micrograms ml-1 using 50 microliters of urine with a detection limit of 1 microgram ml-1. The method was utilized in a study evaluating if racial differences are present in the pharmacokinetic and pharmacodynamic effects of hydrochlorothiazide.

Black People↗
PubMed1997

Simple high-performance liquid chromatographic method for determination of losartan and E-3174 metabolite in human plasma, urine and dialysate.

A simple high-performance liquid chromatographic (HPLC) method was developed for the determination of losartan and its E-3174 metabolite in human plasma, urine and dialysate. For plasma, a gradient mobile phase consisting of 25 mM potassium phosphate and acetonitrile pH 2.2 was used with a phenyl analytical column and fluorescence detection. For urine and dialysate, an isocratic mobile phase consisting of 25 mM potassium phosphate and acetonitrile (60:40, v/v) pH 2.2 was used. The method demonstrated linearity from 10 to 1000 ng/ml with a detection limit of 1 ng/ml for losartan and E-3174 using 10 microl of prepared plasma, urine or dialysate. The method was utilized in a study evaluating the pharmacokinetic and pharmacodynamic effects of losartan in patients with kidney failure undergoing continuous ambulatory peritoneal dialysis (CAPD).

Antihypertensive Agents↗
PubMed1997

Solid-phase extraction and determination of ranitidine in human plasma by a high-performance liquid chromatographic method utilizing midbore chromatography.

An improved high-performance liquid chromatographic (HPLC) method utilizing solid-phase extraction (SPE) and midbore chromatography was developed for the determination of ranitidine in human plasma. A mobile phase of 20 mM K2HPO4-acetonitrile-triethylamine (87.9:12.0:0.1, v/v) pH 6.0 was used with a phenyl analytical column and ultraviolet detection (UV). The method demonstrated linearity from 25 to 1000 ng/ml in 500 microliters of plasma with a detection limit of 10 ng/ml. The method was utilized in a pharmacokinetic study evaluating the effects of pancreatico-biliary secretions on ranitidine absorption.

Anti-Ulcer Agents↗
PubMed1994

Novel high-performance liquid chromatographic method using solid-phase on-line elution for determination of metolazone in plasma and whole blood.

A novel solid-phase on-line elution HPLC method employing fluorescence detection to measure metolazone in plasma and whole blood has been developed. The method is sensitive and selective for metolazone and linear over a dynamic range of 1-50 ng/ml with a sample requirement of 250 microliters. The limit of quantitation for the method is 1 ng/ml and combined intra- and inter-day accuracy and precision had an error and coefficient of variation of 2.9 and 5.5%, respectively.

Chromatography, High Pressure Liquid↗
PubMed1992

External-standard high-performance liquid chromatographic method for quantitative determination of furosemide in plasma by using solid-phase extraction and on-line elution.

A rapid and simple external-standard high-performance liquid chromatographic (HPLC) method has been developed for the determination of the concentration of furosemide in plasma. The analyte is extracted with a C-2 ethyl sorbent. On-line elution of the analyte into the HPLC system is accomplished with an advanced automated sample processor (Varian). Furosemide is quantified by fluorescence detection within a linear range of 25 to 1000 ng/mL (average correlation coefficient, 0.9998), with a limit of detection of 1.8 ng/mL. Both internal- and external-standard procedures were evaluated, and the external-standard procedure demonstrated superior characteristics. The external-standard procedure was precise to within a relative standard deviation of 8% and accurate with less than 3% error throughout the concentration range studied. The external-standard HPLC method was used to analyze the concentration of furosemide in greater than 1000 plasma samples obtained from patients with either normal kidney function or renal failure who had received furosemide either orally or intravenously in an experimental setting.

Aged↗
PubMed1990

Solid-phase extraction and liquid chromatography of torsemide and metabolites from plasma and urine.

Torsemide is a new diuretic drug with a profile of action similar to that of furosemide. The high potency of torsemide results in low dose therapy and causes problems for the pharmacokinetic study of the drug due to low plasma levels. Described here are methods for the analysis of torsemide and two metabolites in plasma and urine using solid-phase extraction and liquid chromatography. The limits of quantitation are 10 ng/mL for plasma and 20 ng/mL for urine. The relative standard deviations for precision are less than 10% for most analytes at most concentrations in the calibration range. The recoveries from plasma were 94.3, 92.9, and 95.6%, and from urine were 77.5, 66.6, and 76.5% for torsemide and metabolites M1 and M5, respectively. The method was suitable for pharmacokinetic studies. Data from a normal volunteer are presented.

Chromatography, Liquid↗
PubMed1987

Automated solid-phase extraction and high-performance liquid chromatographic determination of ranitidine from urine, plasma and peritoneal dialysate.

Ranitidine is an H2-receptor antagonist primarily used to treat peptic ulcer. The present automated solid-phase extraction technique involves sorbent conditioning of a cyano (CN) cartridge with 0.5 ml of methanol and 1.0 ml of extraction buffer (0.005 M phosphate, pH 9). Plasma samples were applied by passing 1.0 ml of plasma through the cartridge and subsequently washing with 2 ml of the extraction buffer. Appropriate larger volumes of dialysate were used to concentrate ranitidine onto the cartridge so that the amount eluted was increased to within detectable limits. Urine samples were deluted with distilled water to decrease the ranitidine concentration to within the range of the standard curve. The high-performance liquid chromatographic method (mobile phase 88-89% of 0.02 M phosphate buffer pH 3 and 11-12% of methanol; Spherisorb phenyl cartridge column, 10 cm X 0.46 cm I.D., 5 micron particle diameter, flow-rate 1.1 ml/min; detection at 228 nm) is sensitive to 2 ng/ml in 1 ml of sample. The internal standard of choice was determined to be n-propionylprocainamide as compared to cimetidine and lidocaine. The method was cost-efficient, rapid and simple due to the automated sample processing. The coefficient of variation on replicate assays was less than 10% over all concentrations studied. Recoveries were between 97 and 110%, and the method was linear over the range 1.90-687.20 with a mean correlation coefficient of 0.999.

Autoanalysis↗
PubMed1987

Benzyl alcohol interference from heparin lock flush solutions in a high pressure liquid chromatographic procedure for mezlocillin.

During the course of a pharmacokinetic study of the antibiotic mezlocillin, we observed an interfering peak in the high pressure liquid chromatographic analytical procedure that was identified as benzyl alcohol. The benzyl alcohol interferent was traced to a preservative in heparin and saline solutions used to flush heparin locks and indicated that the heparin lock purge volume was inadequate to clean the flushing solution. The present study uses this as a model to study the amount of dilution and contamination interference observed in a controlled study where the purge volume was varied for two "real situation" concentrations of benzyl alcohol in the flush solution. It was found that only 0.5 ml of purge must be drawn to avoid significant contamination interference if benzyl alcohol-free saline is used for dilutions. Contamination interference from benzyl alcohol can also be avoided by spectroscopic or chromatographic resolution if the interference is identified and the particular analyte in question can be resolved. The results of this study provide valuable information for any study in which heparin locks are used and especially in procedures where benzyl alcohol may interfere with the method of analysis. If saline containing benzyl alcohol is used for the dilution of heparin solutions, 1.0 ml of purge must be drawn.

Benzyl Alcohol↗
PubMedDate not supplied

Simple method for simultaneous determination of halothane, enflurane, and isoflurane in Krebs solution using capillary gas chromatography.

A simple gas chromatography (GC) method for the simultaneous determination of halothane, enflurane, and isoflurane in Krebs buffer solution has been developed. The method utilizes methylene chloride as the internal standard and liquid-liquid extraction using chloroform as the solvent. The method demonstrated excellent recovery (100%) of each component and a linear calibration range of 100-700, 100-800, and 300-1,400 micrograms/mL for halothane, isoflurane, and enflurane, respectively. Intra-day accuracy and precision had an error and coefficient of variation of less than 5.1% and 2.7%, respectively.

Anesthetics, Inhalation↗
PubMedDate not supplied

High-performance liquid chromatography (HPLC) determination of inosine, a potential biomarker for initial cardiac ischaemia, using isolated mouse hearts.

Each year in the USA approximately 7-8 million patients with non-traumatic chest pain come to hospital emergency rooms. It is estimated that approximately 2-5% of these patients are experiencing cardiac ischaemia, but due to the shortcomings of the available testing methods they are incorrectly diagnosed and discharged without appropriate therapy having been provided. Preliminary data with a globally ischaemic mouse heart model has demonstrated that endogenous inosine might be a potential biomarker of initial cardiac ischaemia before cardiac tissue necrosis. A high-performance liquid chromatographic diode array detection (HPLC-DAD) method was utilized for the detection and quantification of inosine in Krebs-Henseleit (Krebs) buffer solution perfusing from surgically removed and isolated mouse hearts undergoing global cardiac ischaemia. A C18 column at a flow rate of 0.6 ml min-1 with an aqueous mobile phase of trifluoroacetic acid (0.05% trifluoroacetic acid in deionized water, pH 2.2, v/v) and methanol gradient was used for component separation. The assay detection limit for inosine in Krebs buffer solution was 500 ng ml-1 using a 100-microl neat injection. The HPLC results were used to determine total cardiac effluxed inosine into the Krebs effluent for each mouse during oxidative stress and compared with the per cent cardiac ventricular functional recovery rate to determine if a relationship exists amongst this cardiovascular parameter during periods of cardiac oxidative stress.

Animals↗