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Of sequential injection valve combined with laboratory electrochemical technology application in the analysis of trace amounts of cadmium

Author: LiuZaiQing
Tutor: WangYang；HuXiaoYa
School: Yangzhou University
Course: Analytical Chemistry
Keywords: sequential injection lab on valve electrochemstry Cadmium
CLC: O614.242
Type: Master's thesis
Year: 2010
Downloads: 32
Quote: 0
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Abstract

Sequential injection lab-on-valve as the third generation flow injection technology, with automatic sample injection, volume size can be flexible to change; equipment simple, easy to use, which achieved determination procee on line. The electrochemical analysis method is with high sensitivity and analysis speed, low cost and so on merit. The sequential injection lab on valve combined with electrochemical analysis methods, retaining the advantages of each method, at the same time which making the conventional electrochemical analysis become simple, greatly increased the frequency of analysis, and achieving a fully automated analysis process. It will have great prospects in the future in the analysis field. In this paper, we used sequential injection lab on valve combined with electrochemical analysis techniques to detect the heavy metals in environmental samples; the main research includes about three parts:Sequential rejection lab-on-valve (LOV) using renewnal mercuy film electrode was first proposed for analyzing Cd coupled with differential pulse anodic stripping voltammetry (DPASV). The electrochemical flow cell including three electrodes was designed as a part of the selection valve of the SIA (sequential injection apparatus). Under the optimal parameters, the response was linear in the concentration range from 5.0 to 75.0μg/L along with a sampling frequency of 30/h, and a detection limit of 0.41μg/L was obtained with a precision of 2.8% RSD at the level of 20μg/L. The total processing was carried out in a closed ehannel system. The established analytical procedure enhanced the repeatability and minimized sample and reagent consumption. The practical applicability was demonstrated by determination of Cd in environmental water samples. This work exploited a sequential injection lab-on-valve (LOV) system for the determination of cadmium by anodic stripping voltammetry (ASV). A miniaturized electrochemical flow cell (EFC) was fabricated in LOV, in which a nafion coated bismuth film electrode was used as working electrode. The cadmium was electrodeposited on the electrode surface with bismuth solution, and measured with the subsequential stripping scan. Under optimal conditions, the proposed system responded linearly to cadmium concentrations in a range 2.0-100.0μg/L. The detection limit of this method was found to be 0.88μg/L. By loading a sample volume of 800μL, a sampling frequency of 25 determinations h-1 was achieved. The repeatability expressed as relative standard derivation (R.S.D.) was 3.65% for 20μg/L cadmium (n= 11). The method was applied to analysis of trace cadmium in environmental water samples and the spiked recoveries were satisfactory. By combining sequential injection lab on valve with anodic stripping voltammetry which increased testing frequency, reducing the conventional dropping mercury electrode as the use of mercury pollution caused by the experimental process. At the same time it achieves full automation.A rapid and sensitive adsorptive stripping voltammetric assay for the determination of trace amount of cadmium was developed in a sequential injection lab-on-valve (SI-LOV) system for the first time. The sample and reagent arrangements were achieved by a syringe pump. The target metal ions were accumulated on the morin modified glassy carbon electrode surface, and the quantification step was performed by subsequent anodic stripping voltammetry. The key experimental variables relevant to the voltammetric measurement procedure were optimized. For a 100 s preconcentration time, a linear calibration curve was obtained in concentration range from 1.0 to 125.0μg/L with a sampling frequency of 27/h. The detection limit was 0.41μg/L and the relative standard deviation was 2.70% at the 25.0μg/L level (n=11). The analytical utility of the established method was applied to the determination of cadmium in real samples, and the results were validated by ICP-OES technique.

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CLC: > Mathematical sciences and chemical > Chemistry > Inorganic Chemistry > Metal elements and their compounds > Section II group metal element and its compounds > The zinc Vice family (Ⅱ B group metal elements ) > Cd Cd
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