Comparison Between Two Assays for Plasma Cortisol

Abstract

We have compared the results obtained for plasma cortisol when two methods were used to measure this steroid. The first method, a Competitive protein binding (CPB) assay, used transcortin as binding protein for cortisol. The second method is a radioimmunoassay (RIA) utilizing as binding reagent, a specific antibody against cortisol. Nineteen samples were tested covering a wide range of values. The CPB assay consistently overestimated the levels of plasma cortisol compared to the RIA method.     

HPLC Measurement of Cyclosporine in Blood Plasma and Urine and Simultaneous Measurement of its Four Metabolites in Blood

Abstract

A high performance liquid chromatographic assay has been developed for the estimation of cyclosporine and its four major metabolites in blood and for cyclosporine alone in plasma and urine samples. This assay employs a rapid and very reproducible solid-liquid extraction system. Isocratic chromatographic conditions allow the simultaneous measurement of cyclosporine and its four major metabolites in blood. The method is linear up to 2500 ng/ml and the minimum quantifiable limit for cyclosporine is 30 ng/ml, when 1 ml of sample is analyzed.     

Pattern Recognition as a Procedure for Selecting Analytical Methods for Solving Analytical Problems. A Preliminary Investigation

Abstract

A first step towards developing a calculation method, predicting the analytical method suitable to solve a distinct analytical problem, is described.

With pattern recognition, a binary decision maker is calculated, deciding the analytical method from two alternatives, w-vie spectrometry and atomic absorption spectrometry. This procedure yielded a 85% predicting accuracy.     

Rapid Determination of Teicoplanin in Human Plasma by High Performance Liquid Chromatography

Abstract

A rapid isocratic reversed-phase HPLC method for the determination of the major component of teicoplanin in plasma is described.

By using solid phase extraction C18 and UV detection at 240 nm, this method is specific, and sufficiently sensitive.

We found a good linearity over the range: 5 – 40 mg/1 of teicoplanin plasma concentrations. The coefficients of variation did not exceed 5.4% both within-day and between-day assays.

With the small plasma sample required for the analysis (250 μl) and the good accuracy, this rapid procedure appears to be suitable for the therapeutic drug monitoring.     

A Radioimmunoassay for Serum and Urine Aldosterone by Celite Column Chromatography

Abstract

A relatively simple and rapid radioimmunoassay (RIA) for the measurement of aldosterone in serum and urine has been developed. The method involves extraction of 1 ml of serum or urine (after acid hydrolysis) with dichloromethane, followed by partition chromatography on celite microcolumns prior to RIA. Dextran coated charcoal is used for separation of free from antibody-bound aldosterone. The method is very sensitive, blanks are negligible and recovery is approximately The%. 80 coefficient of variation is 4. 3% (within assay) and 10. 4% (between assay). When known amounts of aldosterone were added to serum and urine pools containing low endogenous levels of this steroid recovery was quantitative. Aldosterone concentrations measured under various physiological conditions were in agreement with published data. Up to 150 samples can be assayed by 1 technician during 5 working days.     

HPLC Determination of Cyclosporine in Whole Blood

Abstract

A rapid sensitive method for measuring cyclosporine concentration in whole blood by HPLC has been developed. The pre-chromatography isolation steps are convenient and rapid and are based on salting out acetonitrile with simultaneous extraction of cyclosporine from the blood. A reversed phase column is used with detection by absorbance at 200 nm.     

Rapid Colorimetric Assay of 5-Aminosalicylate

Abstract

The drug 5-aminosalicylate is an anti-inflammatory agent used in the treatment of ulcerative colitis. Recent studies have suggested that the amino substituent plays an important role in both the toxicity and the therapeutic effect of the drug. In view of these findings, a rapid and convenient method of analysis would be useful for monitoring selected patients receiving 5-aminosalicylate. A colorimetric assay based upon schiff base formation with the amino substituent was compared to the ferric nitrate method of salicylate analysis. the results indicate that the arylamine assay is more sensitive than the salicylate method and in contrast to the latter, the absorbance versus substrate curve is linear over clinically relevant concentrations. the arylamine assay is simple, rapid, convenient, and suitable for monitoring procedures where only the measurement of the active drug concentration is required.     

Comparison Of Highly Sensitive Sandwich Enzyme Immunoassay And Radioimmunoassay For Human Ferritin

Abstract

A highly sensitive sandwich enzyme immunoassay (EIA) for human ferritin was developed using rabbit anti-ferritin IgG-coated polystyrene balls and affinity-purified rabbit anti-ferritin Fab' labelled with β-D-galactosidase from Escherichia coli and compared with the corresponding sandwich radioimmuno assay (RIA). The specific and nonspecific binding of labelled anti-ferritin to the polystyrene balls were examined in relation to the amount of labelled anti-ferritin used per tube, and the highest sensitivity of each immunoassay (0.2 amol/tube in EIA and 2.5 amol/tube in RIA) was obtained by using the minimal amount of the corresponding labelled anti-ferritin (0.71 fmol in EIA and 4.5 fmol=4436 cpm in RIA) which gave a reliable calibration curve. The sandwich RIA was less sensitive, largely because the specific radioactivity of ¹²⁵I-labelled anti-ferritin used was not sufficiently high.     

Ciclosporin: HPLC routine method with column switching

Conclusion It seems to be a major advantage of the described method that standard HPLC equipment with column switching can be used. The procedure proved to be precise, accurate and specific. According to our experience with CyA determinations in more than 1,000 blood samples, this method is well suited for routine monitoring despite the necessity of sample preparation.

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Ciclosporin: Eine HPLC-Routinemethode mit Säulenschaltung

     

A Microtiter Plate Assay for Sulfonamides

Abstract

Sulfamethoxazole, sulfisoxazole, and sulfadiazine are sulfonamides used in the treatment of several infectious diseases. Several studies have demonstrated that the amino substituent plays an important role in both the toxicity and the therapeutic effect of these drugs. In view of these findings, a rapid and convenient method of analysis would be useful for monitoring selected patients receiving these drugs. With the increasing use of microtiter plate methodology in the clinical laboratory, an assay based upon the Bratton-Marshall reaction with the amino substituent was adapted to the microtiter plate format. The results indicate that the microtiter plate assay for sulfonamides retains the sensitivity and linearity necessary for analysis of sulfonamides in biological fluids at clinically relevant concentrations. The assay is simple, rapid, convenient, and suitable for monitoring procedures where only the measurement of the active drug concentration is required.     

Potentiometric Titration of Trace Concentrations of Penicillamine Using Ion Selective Electrodes

Abstract

Penicillamine (PA) has shown promise as a therapeutic agent in the treatment of rheumatoid arthritis (RA), and a sensitive analytical procedure applicable to physiological fluids is needed. PA is a metal chelating agent which forms very strong complexes with heavy metal ions (e.g., Hg²⁺, Cu²⁺, Pb²⁺). This characteristic has been applied to the analytical problem presented. The method developed is based on potentiometric titration of the ligand with a metal ion solution utilizing for endpoint detection an indicator electrode selective for this metal ion. The procedure described used lead (II) as the titrant and a lead (II) selective electrode. Demonstrated precision was ±2.0% when 7.5 μg PA was determined in 50 ml solution.     

Rapid Analysis of Trace Quantities (1 PPM) of Bromide in Natural Water

Abstract

An analytical procedure for the rapid assay of trace quantities of bromide ion is described. An exchange resin contained in a filter disk is used to separate the ion and the bromide concentration is then measured as an emission intensity on the x-ray spectrograph. Analytical error is estimated at 5% and 0.05 ppm Br is the statistical detectability limit when compared with a standard disk containing 100 ppm Br^?.     

HPLC Analysis of Methoxamine in Rabbit Plasma and Pharmaceutical Formulations

Abstract

A rapid, selective and simple high performance liquid chromatographic (HPLC) assay for methoxamine HC1 has been developed. The analytical procedure involved the use of internal standardization method (1-norephedrine). It has been applied for the qualitative and quantitative determination of methoxamine HC1 in rabbit plasma and in pharmaceutical formulations using an adsorption column in an isocratic mode, with resulting relative standard deviations of 1.7% and 3.3%, respectively. The applicability of the assay procedure to pharmacokinetic studies was demonstrated. Detection limits were as low as 15ng for a 30 ul injection and the determination time was less than 6 minutes.     

Quantitative Determination of Acenocoumarin in Anticoagulated Patients

Abstract

A new procedure of pre-concentration on Tenax GC followed by high performance liquid chromatography analysis has been developed for the quantitative determination of acenocoumarin in human plasma. The recovery of acenocoumarin was greater than 90% over a concentration range of 0.10 to 1.00 μg/ml and the limit of quantitation by the assay was 10 ng/ml of plasma. This method allows quantitative determinations in patients under acenocoumarin therapy and can be used as a routine clinical monitoring.     

Applications of Optimization Strategies in the Design of Intelligent Laboratory Robotic Procedures

Abstract

Laboratory robots are being used to perform sample preparation and routine analytical determinations 1,2. In addition to these routine applications, laboratory robots should be able to analyze the analytical procedure itself and select the optimal experimental condition for any analytical method. The application of the fixed-sized SIMPLEX algorithm, the Nelder and Mead variable sized SIMPLEX algorithm and response surface fitting methods in analytical robotics is presented ³.     

A Simple Dried Blood Spot Assay for Therapeutic Drug Monitoring of Lamotrigine

Blood spot collection cards can be easily used to obtain specimens for analysis of drugs for the purpose of therapeutic drug monitoring. In this work, the development and validation of a simple technique for the determination of lamotrigine from dried blood spots is described. The method is based on liquid chromatography with ultraviolet detection. The intra- and inter-day precision (measured by CV%) was less than 11%. The accuracy (measured by relative error %) was less than 12%. The limits of detection and quantification were calculated to be 0.12 and 0.2 μg mL⁻¹ respectively. The small volume of blood required (10 μL), the short analysis time (less than 4 min), combined with the simplicity of the analytical technique makes this a useful procedure for monitoring lamotrigine concentrations. Our preliminary experience with the developed method indicated that it can be implemented in routine clinical setting.

     

A Rapid Liquid Chromatographic Method for Determination of Flecainide in Human Blood Plasma Using Ultraviolet Detection

Abstract

A liquid chromatographic method for the assay of the antiarrhythmic drug flecainide in plasma has been developed. The method is rapid, simple and with sufficient detection sensitivity to render it suitable for therapeutic drug monitoring. Flecainide and added internal standard, a non-fluorinated analogue, were extracted by a single ether extraction from alkalinized plasma followed by a back-extraction of the ether with dilute phosphoric acid. A portion of the acid extract was then applied directly to a 30 cm ODS column eluting isocratically with 30% acetonitrile in water containing 0.01M dibutylamine phosphate. Monitoring was by ultraviolet detection at 214 nm and the total run time was 8 min. This method is specific and can quantitate plasma levels to less than 30 ng/ml (free base) from 0.5 ml of plasma without interference from antiarrhythmic drugs commonly used in therapy.     

Determination of Ofloxacin,A New Oxazine Derivative in Human Serum,Urine, and Bile by High-Performance Liquid Chromatography

Abstract

A simple and precise high-performance liquid procedure has been developed for the determination of Ofloxacin (DL-8280), a new oxazine derivative in human serum, urine and bile using Norfloxacin as internal standard. The work-up procedure involves a chemical extraction step followed by isocratic chromatography on a anion-exchange analytical column, with ultraviolet detection. The run time for the assay was 11.5 minutes.     

High-Performance Liquid Chromatography of Domoic Acid,a Marine Neurotoxin,with Application to Shellfish and Plankton

Abstract

A recent outbreak of poisoning resulting from the consumption of cultured blue mussels (Mytilus edulis L.) from a localized area in Eastern Canada has been attributed to the presence of domoic acid (1), a relatively rare neurotoxic amino acid, previously found only in some algae of the family Rhodomelaceae. Studies on aqueous extracts of shellfish tissue indicated that the toxin and several of its isomers could be separated (and isolated in sufficient amounts for subsequent structural identification) by reversed-phase high-performance liquid chromatography (HPLC) with ultraviolet (UV) diode array detection (DAD). Aqueous acetonitrile containing 0.1% v/v trifluoroacetic acid was used as mobile phase. As the retention time and characteristic UV absorption spectrum of 1 (λ_max = 242 nm) permit unequivocal identification, the HPLC-DAD procedure was refined with a microbore column to provide a rapid (5 min), sensitive (0.3 ng detection limit) and reproducible assay method for the determination of 1 in shellfish tissue. Extraction was accomplished by boiling homogenized shellfish tissue for 5 min with distilled water. Extracts were taken through an octadecylsilica solid phase extraction clean-up prior to HPLC. This method has been applied to a variety of shellfish and phytoplankton samples.

BRIEF

Reversed-phase HPLC with ultraviolet diode array detection was used to analyze shellfish tissue and phytoplankton extracts for domoic acid. A rapid (5 min) and sensitive (0.3 ng detection limit) assay is presented.     

An Automated Method for the Determination of Enoximone and Its Major Sulfoxide Metabolite in Plasma Using Robotic Technology–High Performance Liquid Chromatography

Abstract

An automated analytical procedure for the determination of enoximone, a new cardiotonic agent, and its major oxidative metabolite in plasma using robotic technology is described. A Zymark robot is used to perform all the operations of solid phase extraction including column pretreatment, internal standard addition, sample mixing, sample pipetting, column rinsing, drying and sample elution. The processed sample is injected directly into the high performance liquid chromatography system which is equipped with an ultraviolet absorption detector. The assay has good precision and accuracy, equivalent to the manual method it replaces, and yet provides higher throughput of sample.