摘要:

A bienzymatic sensing layer containing two enzymes able to work sequentially, choline oxidase (ChOD) and phospholipase D (PLaseD), was used to design an electrochemical biosensor for the detection of either a water-soluble (choline) or insoluble (phosphatidylcholine) substrate. A photocrosslinkable polymer, poly(vinyl alcohol) bearing styrylpyridinium groups (PVA-SbQ), was used as host-matrix for enzyme immobilization. Controlled amounts of PVA-SbQ and of the two enzymes were directly coated on a platinum disk, then photopolymerized. The compatibility of working conditions for choline and phosphatidylcholine detection in the presence of Triton X-100 and CaCl2was investigated. The effect of the activity ratio PLaseD / ChOD on the sensor performance was determined. The sensitivities to choline and to phosphatidylcholine were 18 mA.1mol−1and 0.66 mA.1.mol−1respectively, the detection limit being 1.5.10−8M for choline and 1.5.10−6M for phosphatidylcholine. The linear range extended up toca. 10−4M for choline andca. 2.10−5M for phosphatidylcholine and the response time was close to 30 seconds for choline andca. 2 min for phosphatidylcholine.

ISSN:0003-2719    

DOI:10.1080/00032719608001774

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

An indicator phase for a flow-through chemiluminescence (CL) sensor composed of ordered surfactant assemblies, a polymer and a catalyst was evaluated by measuring adrenaline. The method is based on use of Mn (III)-porphyrin immobilized on a bilayer membrane contained in a blended film, prepared by incorporating dioctadecyl-dimethylammonium chloride into polyvinyl chloride. The sensor consisted of a Pyrex glass tube (30 mm × 5 mm i.d.) packed with silica glass wool, on which the indicator phase was coated, and a photomultiplier tube. The blend film functioned as a favorable reaction medium for the adrenaline CL, and further enhanced CL was observed with the immobilized catalyst. This indicator phase permitted adrenaline to be detected down to 3 × 10−6M with a 20 μl injection into a 0.3 M NaOH carrier solution. The relative standard deviation (n = 10) was 1.0% for 5 × 10−5M adrenaline. For 80 successive injections of 5 × 10−5M adrenaline, the variation of the CL signal was within the relative standard deviation. Almost the same sensitivity and precision were observed with the indicator phase stored in water for at least 3 days. The sensor was successfully applied to determine adrenaline in drug samples.

ISSN:0003-2719    

DOI:10.1080/00032719608001775

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

In solutions containing some urea or thiourea derivatives and alkali metal hydroxides at pH 6 to 10, the pH value measured with glass electrodes changes with time. The degree of change varies between 0.1 and 1.0 pH units and depends on the structure of the urea derivative, its initial concentration, and the glass electrode used, but not on the cation of the alkali metal hydroxide added. In contrast, pH measured in the same solution with a quinhydrone electrode or the UV spectra remain time-independent. It is proposed that urea derivatives are adsorbed in the gel at the surface of the glass electrode and there affect the ion-exchange process.

ISSN:0003-2719    

DOI:10.1080/00032719608001776

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A simplified enzyme based fiber optic uric acid biosensor is reported. It is constructed by coimmobilizing uricase and horseradish peroxidase [HRP] to bovine albumin via glutaraldehyde. A new fluorimetric substrate, thiamine, is used to indicate the sensing process. Under optimized conditions, the linear range of uric acid concentration is 0.5 to 5.0 ug/mL with a correlation coefficient of 0.997, and the detection limit is 0.15 ug/mL with excellent reversibility and stability. The sensor can be used at least two months at room temperature. It is possibly to determine uric acid directly in serum and urine samples with satisfactory results.

ISSN:0003-2719    

DOI:10.1080/00032719608001777

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A flow injection potentiometric procedure is proposed for the determination of acidity of several samples using an antimony/ antimony oxide electrode. The ΔE/pH curve in phosphate buffer solutions in the pH range from 1.58 to 12.00 showed a linear sub-Nernstian behavior with an operational slope S =-42.1mV/pHcand a conditional standard potential of 264.8mV. This flow potentiometric electrode responds linearly to low acidity variations of dilute acetic acid solutions from 3.16 to 100mM with a slope of 30.1mV/dec and analytical frequency of 23 results/h. Good reproducibility and an average standard deviation of ±0.5% was obtained. The application of this sensor for the determination of coke acidity and acetic acid in vinegar is reported.

ISSN:0003-2719    

DOI:10.1080/00032719608001778

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The potentiometric and impedance characteristics of various selective Ca2+polymeric membranes are described and interpreted by theory and experiments for Ca2+microfabricated sensor arrays. These are designed for further biomedical applications with an emphasis on potentialin situapplications. The polymeric materials used in the present studies consist of either carboxylated PVC or aliphatic polyurethane. Both materials showed good adherence properties to the polyimide-coated Kapton substrate used in planar sensor fabrication. The impedance analysis, performed in the frequency range from 65,000 Hz to 0.1 Hz, revealed the bulk geometrical response at high frequencies. Measured Rbulkcorresponds to the unperturbed bulk resistance. That, in turn, depends on mobilities and concentrations of Ca2+complex and mobile sites. Decreases in Rbulkcorrelated well with sensor behavior during the preconditioning (hydration) period. Studies of blood interactions with these sensors proved that the main sensor characteristics (E0, slope of the calibration curve, and reproducibility of response) are not significantly affected after 14 days of whole blood contact.

ISSN:0003-2719    

DOI:10.1080/00032719608001779

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

We describe here a fast procedure to identify, by Pulsed Field Gel Electrophoresis (PFGE), circular DNA molecules, displaying shift mobility dependent on ethidium bromide (EtBr) concentration. Several identical DNA samples were coelectrophoresed in a multilane gel with different EtBr concentrations in each lane. Samples were run in a Contour Clamped Homogeneous Electric Field (CHEF) or in a small CHEF (miniCHEF) equipment for 15 or 4 h, respectively. Circular DNA molecules from the protozoan parasiteEntamoeba histolyticawere detected in a single running. The circles were isolated from the gels and then their structure was confirmed by transmission electron microscopy. By hybridization it was shown that the circles obtained corresponded to the ribosomal DNA episome.

ISSN:0003-2719    

DOI:10.1080/00032719608001780

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

This research reports the application of derivative spectrophotometry to the determination of timolol maleate in ophthalmic solutions. A systematic approach developed for optimisation of the derivative order, graphical measurements and instrumental conditions led to the adoption of first-order spectrophotometry as a method with suitable precision and selectivity for the determination of timolol maleate in ophthalmic solutions without previous treatment.

ISSN:0003-2719    

DOI:10.1080/00032719608001781

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A new method is described for analyzing a binary mixture of analgin and adamon using extractive and derivative spectrophotometry. In the method, analgin and adamon both were extracted into chloroform as an ion-pair with thymol blue from their aqueous solution buffered to pH 3.6. Determination of these drugs was performed by reading the dA/dλ values at 600.0 nm and 310.5 nm in the first derivative spectra of the chloroform layer. Relative standard deviations of the method are 0.10% for analgin and 0.81% for adamon. The method was successfully applied to an injection solution containing these two active ingredients.

ISSN:0003-2719    

DOI:10.1080/00032719608001782

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A high performance liquid chromatographic (HPLC) assay was developed for the determination of pimethixene in plasma and urine. Pimethixene was extracted by a rapid and simple liquid-liquid procedure using n-pentane:isopropyl alcohol (50:1), and a reversed phase HPLC separation technique with UV spectrophotometric detection at 254 nm. Determination was possible for pimethixene in the concentration range 53–530 ng ml with the limit of detection at 20 ng/ml for both plasma and urine. The overall recoveries of pimethixene added to plasma and urine samples by an external standard method were 95.6 and 98.5%, with coefficients of variation of 0.9993 and 0.9997, respectively.

ISSN:0003-2719    

DOI:10.1080/00032719608001783

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor