摘要:

Sequential Simplex Optimization was popularized by Deming and coworkers at Emory University and the University of Houston in the 1980's. A text, Sequential Simplex Optimization was published by CRC Press in 1991.1This article provides an updated bibliography from 1992 to present.

ISSN:0003-2719    

DOI:10.1080/00032719908542815

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Clark type oxygen microsensors were developed for measurement of photosynthetic light response in cyanobacteria isolated from epilithic microbial communities colonizing Roman hypogea. Microelectrodes were built using polyester or teflon insulated platinum wires as working electrodes and silver wires as reference electrodes, then inserted in glass capillaries previously coated at one end with a silicon gas-permeable membrane. Platinum was polarized at −750 mVvsAg/AgCl, and 0.1 M KCl was used as supporting electrolyte. Stability, sensitivity and reproducibility of the probes were tested. These cost effective sensors exhibited comparable behaviour with those commercially available. Photosynthesis of selected cyanobacterial species was followed by monitoring the oxygen evolution at increasing irradiances (P/I curves).

ISSN:0003-2719    

DOI:10.1080/00032719908542816

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The electrochemical behavior of uric acid at a cysteine modified glassy electrode has been studied by cyclic voltammetry(CV) and differential pulse voltammetry (DPV). The results indicated that the modified electrode exhibited efficient electrocatalytic oxidation for uric acid. The anodic overpotential was reduced nearly 200mV compared with the result obtained at a bare electrode. The diffusion coefficient of uric acid in solution and the rate constant for the catalytic reaction were calculated by a Koutecky-Levich plot. A good linear response to uric acid in the range of 7.0x10−7to 3.0x10−4mol/L was obtained. The detection limit was 3.7x10−7mol/L. High stability and good selectivity made possible applications to in-vivo measurements.

ISSN:0003-2719    

DOI:10.1080/00032719908542817

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The catalytic properties and stability of soluble and immobilised in nylon-6,6 mesh tyrosinase were studied with the help of an oxygen sensor. A variety of methods were examined for the immobilisation of tyrosinase, although active immobilised enzyme was obtained only with the help of benzidine and dicyclohexylcarbodiimide. The immobilisation caused an increase in the Kmvalue for catechol almost 2 times in comparison with that found for soluble enzyme (0.39 and 0.22 mM, respectively). The immobilised tyrosinase retained sufficient activity for several months. Due to its characteristic suicide inactivation induced by catechol, it is only of single use for analytical purposes.

ISSN:0003-2719    

DOI:10.1080/00032719908542818

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The biosensors based on the enzyme electrode in a flow injection analysis suffer an interference from hemacyte, macromolecules and some lower molecular weight species in whole blood, plasma, serum or urine, besides endogenous electroactive species such as ascorbate. This often results in an increasingly serious tailing phenomenon in the response current peak of substrates. A unique method used daily is to cover the outer enzyme membrane with a porous ultrafilter film to isolate it from hemacyte and macromolecules but not from some smaller molecules. In the present paper, we first introduce a tailing inhibitor-ion pair reagent into the flowing buffer system for eliminating the tailing phenomenon from the complex matrices on biosensors. When 0.25 or 0.5% tetrabutylammonium chloride (V/V) was added to 0.02 M phosphate buffer, serious lags of whole blood, plasma, serum and urine on the two biosensors for uric acid and glucose disappeared entirely so that their response time was shortened to about 50 seconds; their base lines also became more smooth and stable. Thus, the resulting two biosensors were capable of detecting over 60 biosamples per hour. The reported experiment shows that the tailing inhibitor has effects on the response current and response time of various biosamples and on the concentration of the dissolved oxygen in buffer, with no evident effect on the recoveries of glucose and urate in biosamples with both sensors. The finding confirmed that some lower molecular weight species with negative charge result in the serious tailing phenomenon in the response current peaks of various biosamples on the glucose and urate biosensors in a flow injection system.

ISSN:0003-2719    

DOI:10.1080/00032719908542819

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The potentiometric performance characteristics of microelectronically fabricated solid-state planar ethylmorphine sensors based on silicon/silicon nitride substrate and a mixture of ethylmorphine-tetraphenylborate and potassium tetrakis(p-chlorophenyl)borate as ion exchangers in a plasticized PVC matrix are described. Sensors incorporating dibutylsebacate and dioctylphthalate plasticizers display linear and stable near-Nernstian responses for ethylmorphine concentrations over the range 1x10−2- 4.5x10−5M and 1x10−2- 2.5x10−5M with calibration slopes of 53.1±0.8 and 57.1±0.8 mV/decade, respectively. The lower limit of detection is 1 μg/ml. The working pH range is 2.5-6:5 and the selectivity of the sensors for ethylmorphine is substantially higher with respect to a large number of opiate derivatives, amines, amides, amino acids and inorganic cations. The sensors are used for direct potentiometry and potentiotitrimetry of ethylmorphine in aqueous solutions and in pharmaceutical preparations. Results with an average recovery of 98.2% and a mean standard deviation of 1.2% are obtained.

ISSN:0003-2719    

DOI:10.1080/00032719908542820

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

An amperometric sol-gel-derived biosensor for the detection of hydrogen peroxide was constructed by immobilizing horseradish peroxidase(HRP) and an osmium redox polymer([Os(bpy)2(PVP)10Cl]Cl; abbreviated Os-polymer) as mediator. Upon addition of hydrogen peroxide to the solution, a bioelectrocatalytic reduction current wave was observed. The steady-state hydrogen peroxide catalytic reduction current reached a plateau at 150 mV vs, Ag/AgCl and hydrogen peroxide could be determined amperometrically with good sensitivity at -50 mV vs. Ag/AgCl. This biosensor exhibits a rapid response(t(95%)=10 s) on addition of 1.0 mM hydrogen peroxide. The linear response range, apparent Michaelis-Menten constant(Km'), and detection limit were 0.01 ∼ 2.7 mM, 5.93 mM, and 0.005 mM, respectively. Uric acid, dopamine, ascorbic acid, paracetamol were found not to interfere at this potentials. The biosensor was found to be stable for 1 month on storage at 4°C.

ISSN:0003-2719    

DOI:10.1080/00032719908542821

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Oxygen insensitive glucose biosensors based on PQQ-dependent glucose dehydrogenase fromErwiniasp. 34-1 and carbon paste have been designed. Without special precautions the sensitivity of the biosensors with the immobilized enzyme was low. Several methods of enzyme immobilization were compared. The enzyme was immobilized in the polylysine-albumin gel and in a paste consisting of water insoluble organic mediator, chemically modified carbon powder, fumed silica and binding material. Chemical modification of carbon with quinonic water insoluble mediators and application of fumed silica in the paste considerably improves the reproducibility, stability and sensitivity of the biosensors. The anodic response current of the biosensor on glucose was recorded at 0-200 mV vs Ag/AgCl reference electrode. Sensitivity can be increased more than 100 times in the presence of soluble mediators, such as phenazine methosulphate. Linearity of the biosensor can be extended by coating the enzymatic layer of the biosensor with a layer of the PVA emulsion. An advantage of the biosensor based on PQQ-glucose dehydrogenase is good linearity at low glucose concentrations due to the elimination of oxygen influence.

ISSN:0003-2719    

DOI:10.1080/00032719908542822

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

In this study, an immunosensor with a piezoelectric quartz crystal was developed. An oscillator system, in order to measure the frequency shifts caused by the increase of mass on the piezoelectric crystal, was used. The surfaces of the quartz crystals were treated by a glow-discharge technique utilizing ethylene diamine monomer to substitute amino groups on the surface of the crystal. These groups were activated by a bifunctional cross-linker, glutaraldehyde, to immobilize an antibody (so called anti-HBs). Optimum conditions for each of the modification steps for application on the quartz crystal surfaces were established and the results were represented for optimum time, pH and concentration. The sensor was calibrated at optimum conditions for HBs-Ag detection.

ISSN:0003-2719    

DOI:10.1080/00032719908542823

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

To attain optimum sensitivity (defined as the minimum detection limit) in an assay, an immuno-chromatographic assay system forSalmonella typhimurium(see Figure 1) were arranged at three different stages of: preparation of the respective system components, integration of the analytical parts, and trial test after fabrication. Primary approaches focused on the manufacture of two major components. In preparing the gold-antibody conjugate as tracer, important steps that may eventually affect the system performance were an appropriate blocking of residual surfaces of gold particles after conjugation and the subsequent separation of excess antibody used. The immobilized antibody on nitrocellulose membrane brought about variable results according to the storage time of the antibody solution before addition and also incubation conditions of the added solution onto the membrane. In the second stage, analytical elements were adapted for the construction of the system. Chemical composition of a medium used for elution as well as for the component production significantly altered the signal intensity. The concentrations of the both antibodies (conjugated and immobilized) as well as the time for antigen-antibody reaction (reflected by the volume of sample absorption pad) were the critical parameters that regulated the relative magnitude of the signal to the background obtained at zero dose of analyte. As the final step of control, the system fabricated was adjusted to a signal-to-noise ratio by two methods. Thermal treatment of the NC membrane with the immobilized antibody was effective to eliminate the background signal, while a detergent addition into the sample solution could be used to increase the signal density within a limited concentration range of analyte. Under the conditions optimized for sensitivity, the chromatographic system detected 2.5x105cells/mL or higher after an assay time of approximately 15 min.

ISSN:0003-2719    

DOI:10.1080/00032719908542824

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor