Spectrophotometric bioanalytical flow-injection system for control of hemodialysis treatment.

A spectrophotometric flow-injection analysis (FIA) system for monitoring clinical hemodialysis is demonstrated. The role of a dialysate urea detector incorporated in this bioanalytical system is played by an optical flow-through biosensor based on Prussian Blue film with chemically linked urease forming a monomolecular layer of the enzyme. This pH-enzyme optode-FIA system is useful for the selective determination of post-dialysate urea in the range of concentration corresponding to its level in real clinical samples (2-16 mmol l(-1)). This bioanalytical system allows the analysis of about 15 samples of spent dialysate per hour. The operational and storage stabilities of the applied biosensor are longer than 2 weeks and 2 months, respectively. Clinical evaluation of the bioanalytical system was performed.

Optical biosensors based on Prussian Blue films.

Optical biosensing schemes based on enzymatically modified inorganic/organic transparent films predominately composed of Prussian Blue are demonstrated. The composite film, which is non-electrochemically deposited on a non-conducting support. is used as an optical transducer for flow-through biosensors based on hydrolases and oxidases. Urease and glucose oxidase are utilized as model enzymes. Action of the urea biosensor is based on optical pH sensitivity of Prussian Blue indicator. The glucose biosensor is acting as first-generation optical biosensor based on in situ generated Prussian White transducer for hydrogen peroxide. These simple, single-pass transmission optical biosensors exhibit sensitivity in the millimolar range of concentration. The biosensors are very stable owing to presence of a poly(pyrrolylbenzoic acid) network in the composite material. This organic polymer plays a dual role as a binding agent for inorganic material and as a functionalized support for strong covalent immobilization of enzyme molecules.

Application of Prussian blue-based optical sensor in pharmaceutical analysis.

Optical flow-through cell-detector with incorporated transparent chemosensitive layer of Prussian blue has been applied in simple, single-channel flow-injection system for pharmaceutical analysis. The reductant analyte converts the Prussian blue based sensing layer to Prussian white form, and the attendant color change is used for sensing. Discoloration of the film is spectrophotometrically detected at 720 nm wavelength. The flow injection system has been successfully used for selective determination of ascorbic acid in simple and complex pharmaceuticals. The method is free from interferences caused by various ions and active ingredients commonly found in pharmaceuticals. The flow-through sensor is useful for spectrophotometric flow-injection analysis of intensively colored and turbid samples. The results of medicine analysis are comparable to those obtained using reference pharmacopeal method. The analytical system could be also used for determination of cysteine and hydrogen peroxide in medicines.

[Evaluation of methicillin-resistance in Staphylococcus aureus by the agar disk diffusion method and PCR]. / Ocena metycylinoopornosci Staphylococcus aureus metoda krazkowo-dyfuzyjna i technika PCR.

Staphylococcus aureus is a widespread human pathogen. One the most striking characteritics of this bacterium is resistance to methicillin and all beta-lactam antibiotics. The agar disk diffusion method is the most widely used in vitro susceptibility test, but recently molecular methods, e.g. Polymerase Chain Reaction, have been also introduced. We compared the detection of methicillin resistant coagulase positive Staphylococcus aureus isolated from clinical materials in Silesian microbiological laboratories by diffusion method and PCR through the detection of nuc and mec A genes. Our results show that PCR used for the detection of mec A gene increases the detection of methicillin-resistant Staphylococcus aureus strains by 10% as compared to the agar disk diffusion method. Among Staphylococcus aureus strains, detected as methicillin-resistant, 17% of organisms showed no presence of mec A gene.

Screen-printed copper ion-selective electrodes.

A simple, low-cost and reproducible method for the mass production of potentiometric ion-selective electrodes for copper ions is presented. These planar, strip sensors were obtained by screen-printing. The application of pastes cured at low temperature allows printing of the sensors on low-cost, plastic substrates. The pastes for printing of ion-sensitive thick-film membranes were based on copper (1) and copper (II) sulfides. The analytical characteristics of the thick-film electrodes were compared. The analytical properties (range of determination, sensitivity, selectivity, response time) of the copper (I) sulfide-based sensors were comparable with those for conventional ion-selective electrodes.

Potentiometric determination of dialysate urea nitrogen.

An enzymatically modified ammonium ion-selective electrode has been applied for the determination of urea in spent dialysate. The biosensor has been used in a simple flow-injection analysis (FIA) system. The system enables one to perform over 25 dialysate urea nitrogen (DUN) determinations per hour. The interferences from other components of posthemodialysis fluid were eliminated by simultaneous measurements with non-modified enzymatically ion-selective electrode. It is possible to use both the sensors in a simplified differential potentiometric system. The results of DUN determination using the biosensor/FIA system and a conventional method of urea determination were comparable. The presented analytical system can potentially find wider biomedical application in the monitoring of hemodialysis progress.

[Puerperal infection of the urinary tract]. / Pologowe zakazenia dróg moczowych.

An urine routine and bacteriological analysis was performed in 100 female patients in third "trimester" of pregnancy and in the second day after delivery. When bacteriuria was detected a next urine bacteriological examination was done in 8-10 and 30-50 days after the delivery. A rate of bacteriuria in female patients before the delivery was 33% and after 56%. The results of routine urine analysis were in normal limits in 31.1% of females with significant bacteriuria. A spontaneous disappearance of bacteriuria between 8 and 50 day after the delivery was observed in 46.6% of patients, but in 53.4% symptoms of urinary tract infection were noticed. Escherichia coli (serotype A and B) was defined in 79.3% of observed urinary tract infections.

Urea sensors based on PVC membrane pH electrode.

Several procedures of urease immobilization on the surface of the polymeric membrane pH electrode with tri-n-dodecylamine as a neutral carrier were compared. The best results were obtained for the urea sensor with covalently bound urease. The sensor characteristics including the effect of buffer, pH and concentration and the effect of stirring rate are presented. These effects are in good agreement with theoretical expectations.

Coulometric titration in the study of metal ion-ligand equilibria.

The coulometric titration technique is applied to evaluation of stability constants of metal complexes with ligands which have protolytic properties. The validity of the procedure was checked by studying several well-known systems. The proposed method can be used with success when metal ions are not reduced at the working cathode. Constants for calcium and magnesium complexes with components of some biologically important buffers, so-called Good buffers, were evaluated under experimental conditions (ionic strength of 0.16M, 37 degrees ) used in clinical analysis.

Potentiometric study of end-point detection in the coulometric determination of carbon dioxide.

The coulometric determination of carbon dioxide is based on the alkalimetric titration of the product of absorption of carbon dioxide in an organic solution of monoethanolamine. The processes occurring in various solvents have been investigated and optimized for analytical application. The protolytic reactions of 2-hydroxyethylcarbamic acid have been investigated in 2-propanol + 2, 5 and 10% water, dimethylformamide + 2% water, dimethylsulphoxide +5, 10 and 20% water. In coulometric generation of the base, 0.1M solutions of tetraethylammonium bromide in these solvents were used. The course of the titration was followed potentiometrically with glass and antimony indicator electrodes. From the titration curves the autoprotolysis constants of the mixed solvents and protonation constants of monoethanolamine in them were calculated. These constants and the concentration of monoethanolamine influence the size of the end-point break for the titrations. On this basis, optimal conditions for analysis have been selected and the total carbon content in samples of natural waters has been determined.

Determination of protonation constants by coulometric titration.

Application of coulometric titration to the determination of the protonation constants of acids and bases offers several advantages because of its simplicity, precision and accuracy. This procedure is rapid and requires only one calibration solution of strong acid in the same solvent and at the same ionic strength as the solution of acid (or base) being investigated. The procedure seems to be especially advantageous in the case of non-aqueous or mixed solvents having amphiprotic character. The validity of the method has been checked with several substances in water, 95% ethanol and ethylene glycol.

Polycrystalline and monocrystalline antimony, iridium and palladium as electrode material for pH-sensing electrodes.

Different ways of making pH-sensing electrodes from monocrystalline or polycrystalline antimony, iridium and palladium have been investigated. Monocrystalline antimony and iridium are superior to the polycrystalline elements with respect to reproducibility between electrodes and stability of the electrode potential over long periods of time. No good palladium/palladium oxide electrode could be obtained by electrochemical oxidation and the thermal preparation method could not take advantage of the properties of the monocrystalline palladium. Therefore, only polycrystalline palladium was used to study this type of electrodes. The different electrodes were compared with respect to the manner of preparation, the pH-response (reproducibility and time response) and the effect that different complexing ligands present in the measuring solutions may have on the electrode response. Also, the redox-response of the electrodes and the effect of different oxygen pressures on the electrode potentials were studied. The monocrystalline antimony electrodes have the best reproducibility and long-term stability but also respond to complexing ligands and to variations in the oxygen pressure. Monocrystalline iridium electrodes can be obtained by continuously cycling the potential between -0.25 and +1.25 V (SCE) in 0.5M sulphuric acid. They do not respond to the complexing ligands tested, and have fairly good long-term stability, but the reproducibility between electrodes is inferior to that of the monocrystalline antimony electrodes. Polycrystalline antimony and iridium electrodes were inferior to the monocrystalline ones. The properties of the palladium electrodes were similar to those of the iridium ones.

Effects of some complex-forming ligands on the potential of antimony pH-sensors.

The E vs. pH relationship for oriented monocrystalline antimony electrodes was studied in various ionic media, containing no buffer or one of several common buffer substances, and the stability of the electrode potential with time was investigated. Several makes of commercially available polycrystalline antimony electrodes were also studied. The results indicate that tris(hydroxymethyl)aminomethane may be used for calibration of antimony electrodes, but most other commonly used buffer substances, e.g., orthophosphate, yield erroneous results. Monocrystalline antimony electrodes are preferable to polycrystalline ones, especially when measurements are made in unstirred solutions. The long-term stability of monocrystalline electrodes is superior to that of polycrystalline ones.

Autoprotolysis constants by coulometric titration.

A procedure is described for the evaluation of autoprotolysis constants in which a strong acid is titrated with coulometrically generated strong base. A two-compartment cell is used, and the acid may be added as such to the solvent under study, or generated in situ in the cell. When a silver auxiliary electrode can be used, as with solutions containing bromide ion, a single-compartment cell may be used, which seems to give more accurate results because it avoids the errors caused by diffusion of solution through the diaphragm. The results for the constants obtained for ethylene glycol, for methanol and for water are in reasonable agreement with values in the literature.

Dissociation constants of thymolphthalexone.

For the dissociation constants of thymolphthalexone the following values have been found: pK(3) = 7.03 +/- 0.02, pK(4) = 8.05 +/- 0.09 (by potentiometric titration), pK(5) = 10.83 +/- 0.10, pK(6) = 12.99 +/- 0.11 (by spectrophotometry). They were determined at I = 0.4 and at 25 degrees.

Autoprotolysis constants and acid-base properties of propylene glycol mixtures.

The autoprotolysis constants of propylene glycol and its mixtures with water, acetone, propan-2-ol and chloroform have been determined potentiometrically. In the same solvent mixtures the protolysis constants of the phthalic acid-hydrogen phthalate system have been evaluated and indicate that the solvent is more acidic than water, but less acidic than ethylene glycol.