Showing papers by "Shouzhuo Yao published in 1997"

Detection and analysis of the growth characteristics of Proteus vulgaris with a bulk acoustic wave ammonia sensor.

Abstract: A bulk acoustic wave ammonia sensor to monitor the growth of Proteus vulgaris is described. The corresponding bacterial growth response equation was derived based on the basic growth characteristics of P. vulgaris, and was verified experimentally. The application of the equation to the estimation of kinetic parameters (such as the asymptote, the maximum specific growth rate and the lag time) was accomplished successfully. The generation time is 33.3 min at 37 °C. The influence of temperature on bacterial growth was also investigated and the activation energy of P. vulgaris growth was estimated. Furthermore, the initial bacterial concentrations were determined based on the linear relationship between the inflection time, t i , and the logarithm of the initial bacterial concentration in the range 10 2 –10 7 (cells ml - 1 ). The results were in good agreement with those from the pour plate count method and the precision was better than that of the frequency detection time method.

Determination of iron and copper by spectroelectrochemistry

Abstract: A new spectroelectroanalytical method for the simultaneous determination of iron and copper is presented in terms of the spectroelectrochemical properties of complexes of iron and copper with 2,2'-bipyridine. By using long optical pathlength thin-layer cells, the differences in the absorbance after complete potential-controlled redox reactions of the two complexes (ΔA) were proportional to the investigated concentration over ranges from 2X10 -7 M to 5X10 -5 M for iron and from 4X10 -7 M to 1X10 -4 M for copper, respectively. The proposed method offers a higher selectivity than conventional spectrophotometry. In addition, a preconcentration proceudre for copper was taken in 0.2 M NH 3 .H 2 O-NH 4 Cl for I min; the deposited copper was then dissolved into a solution containing 2,2'-bipyridine as a chromogenic reagent; AA, recorded as before, was used as the analytical signal to determine trace copper. The apparent molar absorptivity obtained was ca. 6 times that without electrodeposition. Iron and copper in aluminum alloys and pig serum were satisfactorily determined by the proposed methods.

Rapid Determination of Dimethoate with a Surface Acoustic Wave Impedance Sensor System

Abstract: Based on the principle of enzyme inhibition, a novel and sensitive lipase biosensor to determine organophosphorus pesticide is presented. Contact of the enzyme with pesticide samples results in specific inhibition of enzyme activity. Sensor calibration was possible by correlating the inhibition of enzyme activity with various concentrations of pesticide compound in a buffer solution. The sensor was successfully used to determine pesticide concentrations ranging from a low of 167ng/ml to 1.34μg/ml, and the detection limit is 81ng/ml. The effects of temperature, pH value, incubation time and solvent were also investigated. The sensor was also applied to the determination of dimethoate residues in the peel and flesh of tomato.

Enzymatic Determination of Organo-Phosphorus Pesticides with a Surface Acoustic Wave Impedance Sensor

Abstract: A novel and sensitive method, based on the inhibition of the lipase-catalyzed hydrolysis by combining hydroxyle groups of lipase with organophosphorous pesticide, is proposed for the enzymatic determination of organophosphorous pesticide. The inhibited enzymatic reaction is monitored with an SAW/impedance enzyme transducer, which is composed of an SAW resonator, oscillating at 61 MHz, and a pair of parallel electrodes. Employing the method described, the frequency response of the transducer is proportional to organophosphorus pesticide concentration over the range of 227ng/mL - 2.27μg/mL; the detection limit is 76ng/mL. The effects of temperature, pH, incubation, and solvent are also investigated. The method was successfully applied to the determination of dichlovors residues in the root, stem, and blade of Chinese cabbage.

Novel surface acoustic wave-interdigitated array electrode gas sensor for dissolved ammonia

Abstract: A novel surface acoustic wave-interdigitated array electrode (SAW-IDA) ammonia gas sensor is proposed A gas-permeable membrane is employed to separate the buffer solution in the inner cell of the gas-sensing probe from the sample solution in the detection cell The response of the IDA conductive electrodes is based on the impedance change of the buffer solution during ammonia adsorption Therefore, this gas sensor overcomes the influence of water vapour in the conventional film-coated SAW gas sensor and can be used for the detection of gases in aqueous solutions The ammonia sensor exhibits a favourable frequency response to 5 × 10−7−1 × 10−3 mol/1 ammonia The optimal buffer composition and probe parameters have been determined Dynamic range, response time, selectivity, and temperature drift are discussed The ammonia sensor was also applied to the determination of serum ammonia Results were in good agreement with those from the conventional enzymatic-spectro-photometric method

The study of diffusion of solvents from the coating films during the curing process by bulk acoustic wave admittance analysis

Abstract: The diffusion of solvents from a coating layer and their evaporation at the surface of the coating film during the curing process of the coating are investigated by bulk acoustic wave (BAW) admittance analysis and can be expressed as change in the relative diffusion rate (J). The porosity and permeability of the coating film are related to the curing degree (η). The changes in J and the values of J s (the relative diffusion rate at the surface dry time, t s , Δt p (the time difference between the surface dry time t s and the turning point time t p when the diffusion behaviour changes), and η can provide much useful information on selecting solvents and optimizing coating ingredients in the preparation of coatings. The effects of the coating film thickness, solvent content of the coating liquid, and the volatility of the solvent on the diffusion of solvent from the film are also discussed.

Bulk Acoustic Wave Technique as a Real-Time Corrosion Probe in Low-Conductivity Solution: In-Situ Corrosion Behavior of Copper in Acetic Acid

Abstract: The possibility of using the bulk acoustic wave (BAW) technique to study metal corrosion in low-conductivity organic solvents was demonstrated in relation to copper corrosion in acetic aci...

SAW enzyme sensor applied to the determination of enzyme kinetic constants with the aid of a non-linear regression algorithm

Abstract: A general program SAWBEH is proposed for the kinetic data evaluation of enzyme-catalysed hydrolysis by using the frequency shift response of an SAW sensor device. The Marquardt-Fletcher algorithm was employed as the minimum basis. The program was validated theoretically and compared with normal linear analysis methods by using synthetic data added with noise at different levels. The standard deviations of results obtained by the latter are about 100 times those obtained by the former. The system trypsin/benzoyl-L-arginine ethyl ester (BAEE) as a test model was studied at pH 7.6–7.8 and 32 °C. The Michaelis constant was estimated to be 6.34 × 10−5 M.

Rapid Detection of GLY, L-ARG, L-ASP Using an Saw-Impedance Sensor

Abstract: The surface acoustic wave (SAW)-impedance sensor, which is composed of a 61 MHz SAW resonator and a pair of parallel platinum electrodes, has been successfully applied to rapid detection of glycine (G1y), L-arginine (L-Arg) and L-aspartic acid (L-Asp) and is reported in this paper. Two methods are described — the calibration curve method and the frequencimetric titration method. The effect of formaldehyde solution on the frequency shift is discussed. For the calibration curve method: in unpretreated formaldehyde medium, the detection limit of G1y, L-Asp, L-Arg is 1.40×10−5M, 1.48×10−6M, 1.04×10−5M and the frequency shift is linear up to 1.83×10−3M, 1.60×10−3M, 1.37×10−3M; in pretreated formaldehyde medium, the above values are 7.85×10−6M, 1.11×10−6M, 2.30×10−6M and 1.53×10−3M, 1.51×10−3M, 0.96×10−3M, respectively. Using the frequencimetric titration method, the lowest titratable concentration of G1y, L-Asp, L-Arg is 1.14×10−5M, 1.07×10−5M, 1.70×10−5M. A comparison study between the SAW method and...