Fiber-Optic pH Sensor

The new enhancement in the determination of pH using optical fiber system is described here. This work uses the membrane made of cellulose acetate membrane for reagent immobilization and congo red (pK_a 3.7) and neutral red (pK_a 7.2) as pH indicators. An effective covalent chemical binding procedure is used to immobilize the indicators. The response time, reversibility, linear range, reproducibility, and long-term stability of fiber optic sensor with congo red as well as neutral red have been determined. The linear range measured for the sensor based on the congo red and neutral red is 4.2-6.3 and 4.1-9.0, respectively. The response time of sensor membrane is measured by varying the substance pH values between 11.0 and 2.0.     

一种新颖的涂层光纤传感器

作者提出一种新型的涂层光纤传感器,传感头是在裸光纤外周涂以SnO₂薄层。理论推知,它对还原性液体敏感。对甲醇溶液浓度进行测量的结果与理论预期相符。测量范围为0～90%体积浓度。分辨率为1.3%体积浓度。     

Enzymatic Determination of Glucose by Optical-Fiber Sensor Sequential Injection Renewable Surface Spectrophotometry

Introduction Determinationofglucoseisrequiredinmedicine industry,foodindustry,clinicaldiagnosisaswellas variousresearchfields.Therefore,intensiveefforts havebeendirectedtothedevelopmentofanalytical methodsfordeterminationofglucose,suchasthose basedonbiose…     

模糊传感器训练算法

本文提出了模糊传感器的一种分段式训练调参方法。对温度模糊传感器的仿真结果表明，该方法能在不同的测量结构下，较好地解决人类感知温度的模糊语言描述问题。     

Electrochemical sensor for the detection and presumptive identification of quinolone and tetracycline residues in milk

A novel application of an electrochemical biosensor is here employed as analytical method for the detection and presumptive identification of antimicrobial drug residues in milk. The measurement was based on carbon dioxide production rate in relation to inhibition of microbial grow (Escherichia coli ATCC 11303). In this pilot study quinolone and tetracycline residues have been taken into consideration because use of these last in livestock production has been identified as area of particular concern. The experimental approach and analytical method developed appear adequate for the purpose, and compared to older screening methods as, for example, the microbial inhibition assays and immunoassays, offers the advantages of (i) very short analysis time (about 120 min); (ii) smaller sample amount (approximately 0.5 mL); (iii) no sample treatment (iv) good precision; and (v) the possibility of following, in a continuous manner, the inhibition process. Moreover, sensitivity of electrochemical biosensor system is resulted very high considering that for all quinolones and tetracyclines investigated it has been possible detect a residue concentration below or equal to 25 μg L⁻¹. Under this point of view, it must be considered that the maximum residue limits fixed by UE for quinolones and tetracyclines in milk are, at present, all higher of this concentration.     

An Electrochemical Robotic System for Routine Cathodic Adsorptive Stripping Analysis of Ni2+ Ion Release from Corroding NiTi Shape Memory Alloys

Cathodic adsorptive stripping voltammetry (AdSV) as highly sensitive and selective method for quantifying trace amounts of dissolved Ni²⁺‐ions has been integrated into an electrochemical robotic device using the wells of microtiter plates as low‐volume electrochemical cells. A three‐electrode assembly integrating a Bismuth film‐modified glassy carbon electrode as working electrode and a glass capillary for delivering Ni²⁺ standard solution in conjunction with an adapted software allowed multiple AdSV measuring cycles to be performed one after the other in the individual compartments of a 24‐well microtiter plate. Of advantage for the automation was the possibility of an in‐well electrochemical removal of used and a replating of fresh Bi films in between distinct measuring cycles. With optimized parameters for the accumulation of the complex between Ni²⁺‐ions and dimethylglyoxime onto the surface of the Bi film electrode and the subsequent stripping procedure, automated adsorptive stripping voltammetry in the established system offered a linear dynamic range of up to 170 nM, a sensitivity of 12 nA/nM Ni²⁺ and a limit of of detection of 2.1 nM (N=16) for the detection of trace levels of Ni²⁺‐ions. Automated AdSV certainly is of convenience for studying larger number of samples due to the high‐throughput capability of the robotic apparatus. As example, the automatic quantification of Ni²⁺‐ion release from electropolished surfaces of NiTi shape memory alloys during corrosion in NaCl solutions is described.     

Influence of Aprotic Solvent on Selectivity of an Amperometric Sensor with Nafion Membrane

This paper presents the results of investigation on selectivity of the sulfur dioxide amperometric sensor with Nafion membrane in the presence of carbon monoxide and nitrogen dioxide as the interferents. There have been compared selectivity coefficients, for the sensors containing the following internal electrolytes: solution of sulfuric acid (concentration 5 mol dm^?3) in pure water (A) and solution of sulfuric acid (concentration 5 mol dm^?3) in mixed solvent dimethylsulfoxide‐water with an DMSO: H₂O mole ratio of 1 : 2 (B). Values of the selectivity coefficients have been calculated based on the calibration curves. Analysis of both calibration curves and selectivity coefficients plays a significant role in optimization of a working point of a particular sensor. The investigated sensor operates in a three‐electrode system, where the working and counter electrodes are vacuum sublimation deposited on the membrane surface.     

用硅双结型色敏器件测量色温

提出了一种用硅双结型色敏器件测量色温的方法．在合理的测控电路下，硅双结型色敏器件的电流对数比与实验灯泡的色温值呈良好的单值对应，经单片机处理后可以得到分段线性关系．通过对电流对数比与波长随线的数据拟合，结果表明，用硅双结型色敏器件测量色温，其测量温度可以到10^4K以上，精度可以达到10K．本文的方法与传统方法相比减少了工作量，降低了费用，具有通用性和实用价值．     

Electrochemical Reduction of Oxygen on Multi-walled Carbon Nanotubes Electrode in Alkaline Solution

The multi-walled carbon nanotubes (MWNTs) electrode was constructed using polytetrafluoroethylene as binder, and the electrochemical reductive behavior of oxygen in alkaline solution was first examined on this electrode. Compared with other carbon materials, MWNTs show higher electrocatalytic activity, and the reversibility of O2 reduction reaction is greatly improved. The experiments reveal that the electrochemical reduction of O2 to HO2 is controlled by adsorption. The preliminary results illustrate the potential application of MWNTs in fuel cells.     

Fast characterization of foodstuff by headspace mass spectrometry (HS-MS)

The field of the rapid characterization of products by HS-MS is reviewed. The general principle of HS-MS systems consists of introducing volatile components present in the HS of a sample without prior chromatographic separation into the ionization chamber of a mass spectrometer. The spectrum resulting from simultaneous ionization and fragmentation of the mixture of molecules introduced constitutes a “fingerprint” that is characteristic of the product being analyzed. Exploitation of this spectral information allows one determine the composition of the sample.