Study On Preparation And Application Of Thiadiazole Conducting Polymer Film–Modified Electrode In Electroanalysis

In this paper, two thiadiazole conductive polymer film electrodes were prepared.The preparation method of the film electrodes was studied and optimized, and theirelectrochemical properties were characterized. Based on the responses of filmelectrodes to epinephrine and ascorbic acid, lead （II） and cadmium （II）, anddihydroxybenzene isomers, respectively, three analytical methods, the determinationof epinephrine in the presence of ascorbic acid, simultaneous determination of tracelead （II） and cadmium （II） by differential pulse anodic stripping voltammetry,simultaneous detection of the hydroquinone isomers by differential pulse voltammetrywere established.The completed work in the paper is summarized as following four aspects:1.5-amino-2-mercapto-1,3,4-thiadiazole （AMT） and2,5-dimercapto-1,3,4-thiad-iazole （DMcT） were electropolymerized on the surface of glassy carbon electrode（GCE） to prepare the poly-AMT film electrode （p-AMT/GCE） and poly-DMcT filmelectrode （p-DMcT/GCE）, respectively. The preparation of two film electrodes wasoptimized and the property of film electrodes was characterized by using cyclicvoltammetry （CV）, electrochemical impedance spectroscopy （EIS） and scanningelectron microscopy. The polymerization mechanism of the film electrodes wasdiscussed.2. The electrochemical responses of the p-AMT/GCE to epinephrine （EN） andascorbic acid （AA） were investigated by CV and differential pulse voltammetry （DPV）.The behavior of DPV for the mixture of EN and AA showed that they have a potentialdifference of240mV, and EN presented sensitively current response in the presence ofAA. Under the optimized conditions, the anodic current increased linearly with theconcentration of EN in the range of1.00×10^-71.00×10^-4mol/L, and the detection limitwas estimated to3.80×10^-8mol/L. In the presence of AA, EN was determined in theadrenaline hydrochloride injection with the relative standard deviation of <4.8%（n=5） and the recovery of98.0¹04.6%.3. Using the p-DMcT/GCE as the working electrode, an analytical method forsimultaneous determination of trace lead （Pb（II）） and cadmium （Cd（II）） was developedby differential pulse anodic stripping voltammetry. In0.10mol/L acetate buffersolution at pH5.5, the stripping peak currents after enrichment at–1.20V for300sshowed good linear relationships with Pb（II） and Cd（II） at concentration ranges of1.00²00and0.50²00μg/L, and the detection limits are0.30and0.05μg/L,respectively. The proposed method is applicable to the simultaneous determination oftrace Pb（II） and Cd（II） in actual water samples with the relative standard deviations ofless than5.7%and the recovery rates of97.6%–106%. The findings indicate that theprepared electrode is helpful in monitoring toxic elements in environmental waters.4. As basis of electrochemical responses to hydroquinone, catechol and resorcinolat the p-DMcT/GCE, the feasibility for simultaneous determination ofdihydroxybenzene isomers was investigated. It is found that the DMcT/GCE showedexcellent electrocatalysis and selectivity for the oxidation of dihydroxybenzene fromexperimental result. A linear relationship between peak current and the concentrationsof hydroquinone, catechol and resorcinol were obtained in the range of5.00×10^-71.1×10^-4,5.00×10^-71.2×10^-4, and5.00×10^-61.00×10^-4mol/L. The modifiedelectrode was used for the determination of dihydroxybenzene isomers in commercialhair dye with satisfactory results.