Sensors

170 KiB

Open AccessArticle

Catalytic Oxidation of Thiourea at Alumina Modified Pt Electrode

by Davood Nematollahi and Mohammad Rafiee

Sensors 2003, 3(11), 534-543; https://doi.org/10.3390/s31100534 - 05 Dec 2003

Cited by 18 | Viewed by 8302

Catalytic oxidation of thiourea has been studied at alumina modified Pt electrode using cyclic voltammetry. The results indicate the suitability of alumina modified Pt electrode for voltammetric determination of thiourea. The catalytic peak currents are linearly dependent on the thiourea concentration in the range 2.5 x 10^-5 – 7.0 x 10^-3 M. The usefulness of the method was tested in determination of thiourea in real samples. Moreover, in this work the heterogeneous electron transfer rate constants of thiourea at the surface of modified and unmodified Pt electrodes were estimated by comparing the experimental cyclic voltammetric responses with the digital simulated results. Full article

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194 KiB

Open AccessArticle

Voltammetric Determination of Prochlorperazine and Ethopropazine Using a Gold Electrode Modified with Decanethiol SAM

by Yuxia Yang, Yan Peng, Faqiong Zhao and Baizhao Zeng

Sensors 2003, 3(11), 524-533; https://doi.org/10.3390/s31100524 - 05 Dec 2003

Cited by 5 | Viewed by 10211

Abstract

The voltammetric behavior of prochlorperazine and ethopropazine at a decanethiol (DEC) self-assembled monolayer (SAM) modified gold electrode (DEC/Au) has been studied. It was observed that prochlorperazine exhibited an anodic peak at about 0.60 V (vs SCE), while ethopropazine exhibited two anodic peaks at about 0.49 V and 0.58 V on DEC/Au in pH 10 sodium carbonate buffer. This was due to their different electrochemical oxidation mechanisms. In this case, the oxidation of prochlorperazine and ethopropazine included one 2e step and two 1e steps, respectively. In the presence of some reductants such as ascorbic acid, the oxidation products of them can catalyze the oxidation of the reductants and thus make the peaks grow. In addition, it was found that the SAM structure became not so compact when prochlorperazine and ethopropazine were present, resulting from their permeating in the SAM. Various conditions were optimized for their determination. Under the selected conditions (i.e. 0.080 M pH 10 sodium carbonate buffer; scan rate: 100 mV/s; accumulation potential: –0.4 V or 0 V; accumulation time: 60 s), the peak currents were linear to prochlorperazine concentration in the ranges of 0.1~2.0 μM and 5.0~50 μM, and linear with ethopropazine in the ranges of 10 nM~0.1 μM and 0.5~20 μM. The RSD was 4.28% for 8 successive measurements of 1.0 μM prochlorperazine. The influence of some coexistents was examined. Full article

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163 KiB

Open AccessArticle

Iodide Selective Electrodes Based on Bis(2-mercaptobenzothiazolato) Mercury(II) and Bis(4-chlorothiophenolato) Mercury(II) Carriers

by Mohammad K. Amini, Mehrorang Ghaedi, Ali Rafi, Mohammad. H. Habibi and Morteza M. Zohory

Sensors 2003, 3(11), 509-523; https://doi.org/10.3390/s31100509 - 05 Dec 2003

Cited by 31 | Viewed by 8919

Abstract

New iodide-selective electrodes based on bis(2-mercaptobenzothiazolato) mercury(II) [Hg(MBT)₂] and bis(4-chlorothiophenolato) mercury(II) [Hg(CTP)₂] carriers are described. The electrodes were prepared by incorporating the ionophores into plasticized PVC membranes, which were directly coated on the surface of graphite disk electrodes. The electrodes displayed high selectivity for iodide with respect to a number of inorganic and organic anions. The influence of the membrane composition and pH, and the effect of lipophilic cationic and anionic additives on the response properties of the electrodes were investigated. The electrodes exhibited near-Nernstian slopes of -57.6 ± 0.8 and -58.4 ± 1.4 mV/decade of iodide concentration over the range 1 × 10^-6 – 1 × 10^-1 M, with detection limits of ~4 × 10^-7 and 6 × 10^-7 M for the electrodes based on [Hg(MBT)₂] and [Hg(CTP)₂], respectively. They have relatively fast response times (≤ 10 s), satisfactory reproducibility, and life times of at least two months. The potentiometric responses of the electrodes are independent of pH of the test solution over the range 3.5 – 11.5. Full article

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85 KiB

Open AccessArticle

Semiconductor Sensors Application for Definition of Factor of Ozone Heterogeneous Destruction on Teflon Surface

by Ludmila A. Obvintseva, Fatima Kh. Chibirova, Serge A. Kazakov, Alexander K. Avetisov, Marina V. Strobkova and Nataliya V. Finogenova

Sensors 2003, 3(11), 504-508; https://doi.org/10.3390/s3110504 - 05 Dec 2003

Cited by 6 | Viewed by 8254

Abstract

In our paper we present the results of our research, which was carried out by means of semiconductor sensor techniques (SCS), which allowed evaluating heterogeneous death-rate of ozone (γ) Teflon surface. When ozone concentration is near to Ambient Air Standard value, γ is assessed to be equal to 6,57*10^-7. High technique response provide possibility to determine ozone contents in the air media and the percentage of ozone, decomposed on the communication surfaces and on the surfaces of installation in the low concentration range (1–100 ppb). Full article

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Sensors, Volume 3, Issue 11 (November 2003) – 4 articles , Pages 504-543

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