An inexpensive method for the determination of serum ionized calcium

The method described here may be used for the determination of serum ionized calcium. The physical conditions of the measurement, including sample volume (0.6 ml) and temperature (25 or 37 °C), are fixed. Stasis of the sample may contribute to a prolonged but not prohibitive response time. Other than the prolonged response time, the performance characteristics of the electrodes were not altered by incorporating them into the electrode chamber. Exemplifying the utility of this method were the results of protein-binding studies, in vitro and ex vivo CaCl₂ and EDTA administration and a comparison with the Orion SS-20. In consideration of the data presented, the cost and simplicity of construction, and method described should serve to make the determination of serum ionized calcium accessible to a greater number of investigators and encourage research in pharmacological and physiological processes thought to be mediated by serum ionized calcium.     

Potentiometric flow-injection system for determination of alkaline phosphatase in human serum

A flow-injection system for detection of alkaline phosphatase (ALP) activity in human serum samples has been developed. As a specific and inexpensive ALP substrate for this kinetic assay monofluorophosphate (MFP) was applied. For detection of fluoride ions, generated in the course of the biocatalytic hydrolysis of MFP, conventional fluoride ion-selective electrode based on LaF₃-crystalline membrane was applied. After optimization the system allows analysis of human serum with high selectivity and relatively short time of analysis (5–6 samples h⁻¹). Volume of serum required for analysis is 0.05 mL. The system is useful for determination of the enzyme activity in human serum samples at physiological and pathological levels as well as for detection of isoenzymatic forms of ALP.     

Simple and sensitive catalytic method for determination of copper in blood serum

Summary A new catalytic method is proposed for determination of copper in blood serum, based on the oxidation of sulphanilic acid with H₂O₂, catalysed by copper(II). Because of its high sensitivity the method requires a serum sample of only 0.10 ml. Using the fixed-time method reduces the procedure to that of an ordinary photometric determination. The method shows reasonable precision and accuracy and is suitable for routine serial analyses in clinical practice.

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Zusammenfassung Eine neue katalytische Methode wurde für die Bestimmung des Kupfers in Blutserum vorgeschlagen. Sie beruht auf der durch Cu(II) katalysierten Oxydation der Sulfanilsäure mit H₂O₂. Infolge ihrer großen Sensitivität genügt für diese Methode eine Serumprobe von nur 0,10 ml. Infolge Ablesung nach Ablauf einer bestimmten Zeit verlangt das Verfahren nicht mehr Zeit als eine gewöhnliche photometrische Methode. Es zeigt gute Genauigkeit und eignet sich für Serienanalysen in der klinischen Praxis.

     

Potentiometric method for determination of kinetic characteristics of radical reactions in aqueous media

Kinetic features of the reactions of K₄[Fe(CN)₆] with radicals initiated by water-soluble azo-initiator 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH) at 37 °C were studied using the potentiometric method. Potassium ferrocyanide was shown to be a radical acceptor, whereas K₃[Fe(CN)₆] formed by the oxidation with the radicals in combination with K₄[Fe(CN)₆] is an electrochemical system, the study of which makes it possible to determine kinetic characteristics of radical reactions. The rate constants for the reactions of peroxide radicals RO₂ · with K₄[Fe(CN)₆] were calculated.     

Gas-chromatographic method for the determination of thiopental in serum

Conclusion The procedure presented is a practical and reliable method for the determination of thiopental in barbiturate loading therapy that can be run on every gas-chromatograph equipped with a flame ionization detector. The sample clean-up is easy and no derivatisation is necessary. Pentobarbital — a metabolite of thiopental — can be determined quantitatively at the same time under the gas-chromatographic conditions described. This is especially advantageous in the case of small clearance rates, which can lead to an accumulation of barbiturates. The use of the method may be expanded to pharmacokinetic studies, where very low concentrations are to be measured by use of an alkali flame ionization detector.

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Gas-chromatographische Methode zur Bestimmung von Thiopental im Serum

     

Potentiometric sensors for the determination of water-soluble polyelectrolytes

Potentiometric sensors for the analysis of water-soluble polyelectrolytes with different molecular masses were proposed. The surface morphology of polyvinyl chloride sensor membranes and chemical analytical characteristics of ready devices were studied. Selectivity coefficients of the sensors were calculated.     

An indirect spectrophotometric method for the determination of silicon in serum, whole blood and erythrocytes.

An indirect method for the determination of silicon in blood samples has been developed. The proposed method overcame interference from a large amount of salts and phosphate in blood samples, and enabled us to determine the silicon contents in serum and whole blood by the same operation. After blood samples were digested by microwave heating, silicon, present as silicate in the sample solution, was reacted with molybdate to form a silicomolybdate complex. The complex was then separated from unreacted molybdate by a cation-exchange resin column. The molybdate liberated from the complex was spectrophotometrically determined in place of silicon. Since the method is not affected the composition of matrices between serum and whole blood, it could achieve good precision and accuracy, and could also estimate the silicon contents in erythrocytes from those in serum and whole blood. The sensitivity of the method was almost equal to that of the conventional silicomolybdenum blue method, and the calibration curve was linear up to 50 micromol l(-1) of silicon with a detection limit of 1.1 micromol l(-1) in whole blood. The mean concentrations of silicon in five healthy subjects were 11 micromol l(-1) for serum, 28 micromol l(-1) for whole blood and 50 micromol l(-1) for erythrocytes. Thus, the obtained distribution ratio between serum and erythrocytes was in the range of 0.15-0.39, and was found to be included in a narrow range.     

Immobilized enzyme electrode for the determination of salicylate in blood serum

This determination of salicylate in blood serum is based on application of an immobilized enzyme electrode. Salicylate hydroxylase (E.C.1.14.13.1) is chemically immobilized onto a pig intestine mounted on an oxygen electrode. The signals are monitored amperometrically and the resulting output voltage is read using a simple adapter. The experimental parameters and possible interferences are discussed. Samples containing 1.0 × 10^?5?1.87 × 10^?3 M (1.6–300 μg ml^?1) salicylate were assayed with relative standard deviations between 1.3% and 6% and recoveries between 98.7 and 103%. Results obtained by the proposed method and by the established clinical method for randomly spiked pooled serum samples correlated well (r = 0.99).     

A simple and sensitive catalytic method for determination of the total iron-binding capacity of blood serum

Summary A catalytic method is proposed for determination of the total iron-binding capacity of blood serum, based on the iron-catalysed oxidation ofp-phenetidine by hydrogen peroxide. Only 0.05 ml of serum is necessary for a single determination. The results obtained by the catalytic method show good correlation with those obtained by a photometric method (with bathophenanthroline) and by atomic-absorption spectrometry.

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Zusammenfassung Eine katalytische Methode zur Bestimmung der Eisenbindungskapazität von Blutserum wurde vorgeschlagen. Sie beruht auf der Fe-katalysierten Oxydation vonp-Phenetidin durch Wasserstoffperoxid. Für eine Bestimmung werden nur 0,05 ml Serum benötigt. Die mit dieser Methode erhaltenen Ergebnisse korrelieren sehr gut mit Werten, die mittels Atomabsorption und Spectralphotometrie (Bathophenanthrolinmethode) erhalten wurden.

     

Potentiometric determination of cephalothin

The composition of a pseudo-liquid potential-determining phase for the cephalothin-selective electrode has been determined and the following basic electrode parameters were examined: measurement range, slope, limit of detection, selectivity and lifetime. This paper discusses the effect of side-chain substituents on the electrode properties, the electrode having been used for cephalothin determination in the range 43-436.5 mg l-1 (standard deviation, 0.64-4.5 mg l-1).     

Solid contact ion sensor with conducting polymer layer copolymerized with the ion-selective membrane for determination of calcium in blood serum

A new solid contact ion selective electrode with intermediate conducting polymer (CP) layer formed by electropolymerization on a gold electrode of a bifunctional monomer, n-phenyl-ethylenediamine-methacrylamide (NPEDMA), which contains a methacrylamide group attached to aniline, is presented. The conducting polymer was studied by means of optical spectroscopy, cyclic voltammetry and potentiometric measurements. Ca²⁺-ion-selective membrane based on acrylated urethane polymer was shown to co-polymerize with the CP forming highly adhesive boundary that prevents formation of water layers between the CP and membrane, thus enhancing the stability and life-time of the sensor. The designed ion-selective electrode was successfully used for determination of total calcium ion concentration in blood serum samples.     

Flame spectrometric determination of sodium,potassium and calcium in blood serum by measurement of microsamples

Summary The discrete sampling flame atomic emission method described previously by Sarbeck, St. John, and Winefordner¹ has been applied to the determination of K, Na, and Ca in serum controls and in several blood serum samples (10 to 100l of blood serum per element needed). The results compare well with the control values and serum values obtained by clinically accepted methods. The percent relative standard deviation of all measurements was better than 4 %. The present method consists simply of injecting the blood serum sample (in some cases diluted with appropriate chemicals) directly into a suitable carrier solution which transported the serum plug into a H₂/N₂O flame. The resulting integrated emission signal is corrected for a blank emission signal and the amount of K, Na, or Ca in the blood serum sample is read directly on a suitable analytical curve.

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Zusammenfassung Die kürzlich von Sarbeck, St. John und Winefordner beschriebene flammenphotometrische Atomaremissionsmethode wurde für die Bestimmung von K, Na und Ca in Kontrollseren und einigen Blutserumproben herangezogen. Pro Element werden 10 bis 100l Serum benötigt. Die Resultate stimmen mit den Kontrollwerten und mit den Ergebnissen anerkannter klinischer Methoden gut überein. Die relative Standardabweichung aller Messungen war besser als 4%. Das Verfahren besteht einfach darin, daß die Serumproben (gegebenenfalls mit geeigneten Reagenzien verdünnt) direkt in eine Trägerflüssigkeit injiziert und so in eine H₂/N₂O-Flamme eingeführt werden. Das integrierte Emissionsignal wird um einen Blindwert korrigiert und die Menge K, Na bzw. Ca in der Serumprobe direkt aus einer Eichkurve abgelesen.

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This work supported by AF-AFOSR-70-1880 H.     

PIXE determination of calcium in red blood cells

The determination of calcium in erythrocytes by the method PIXE requires the preliminary elimination of large amounts of potassium. The best results, with regard to potassium removal and calcium yield, were obtained by carrying out a coprecipitation of calcium and strontium in 80% nitric acid. The development of the method has shown the importance of the total elimination of leucocytes and platelets from the serum in order to avoid erroneously high values for erythrocyte calcium.     

Highly specific HPLC method for the determination of theophylline in serum

Conclusion Because of its high specifity, accuracy and precision the described HPLC method appears to be very useful for establishing the accuracy of other procedures in comparative studies or as confirmation analysis in cases of suspected interference. For routine monitoring of serum theophylline concentrations this procedure is less suitable due to the relatively short life time of the column. Further studies are in progress to develop a candidate reference method for the determination of theophylline based on this procedure.

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Hochspezifische HPLC-Methode zur Bestimmung von Theophyllin im Serum