Study And Application Of Adsorptive Stripping Voltammetry On Carbon Paste Electrode

This thesis involves two parts: Part one Documents reviewAdsorptive stripping voltammetry (AdSV) based on adsorption and accumulation is a sensitive analytical technique. It is applied to determine trace of metals, organic matters and pharmaceutical. Most procedures of AdSV utilize the hanging mercury drop electrode and mercury film electrode, which restrict their application scope due to their major limits of toxicity and of no use in positive potential. In comparison, carbon paste electrode (CPE) has advantageous of nonpoisonous, easy in preparation and wider potential window. Study on AdSV using CPE instead of mercury electrode extends the application scope of voltammetry. Then, combining AdSV with catalytic technique efficiently improves the analytical sensitivity.Three aspects of the study of CPE, AdSV, and AdSV on CPE are described respectively.Part two Research reportsThe two aspects are mainly performed in this thesis, based on the study of AdSV on CPE and the theory of complex adsorptive wave. On the one hand, study on the metals. The electrochemically inactive calcium ion and electrochemically active copper ion are chosen as research subjects respectively, the reduction characters and electrode processes of their complexs forming by the metals and chelating reagent are investigated on CPE, a AdSV method is established for the determination of free calcium; And the correspoding catalytic adsorptive wave of copper ion in the presence of suitable oxidant is obvered. Thereout, a CAdSV method with higer sensitivity is established for the determination of trace of copper. On the other hand, study on the organic pharmaceutical. Amiodarone Hydrochloridum is chosen as research subject, it is observed that the analytical sensitivity of amiodarone hydrochloridum is remarkably improved in the coexistence of suitable oxidant and surfactant. A novelCAdSV method is developed on CPE for the determination of pharmaceutical based on the increase effects of the oxidant and surfactant. In additional, the polarographic method for quality control of calcium dobesilate is established on mercury electrode in this thesis.The concrete contents are described as follows:Chapter one Adsorptive stripping voltammetric determination of free calcium on carbon paste electrodeIn 1.5 x 10'2 mol L'1 potassium hydroxide solution containing 2.0 x 10'5 mol L"1 alizarin red S (ARS), calcium-ARS complex adsorbed on the CPE surface yields a adsorptive stripping wave with peak potential -0.89 V. the second-order derivative cathodic stripping peak current of the complex is proportion to free calcium concentration in the range of 3.0 x 10"8 ~ 2.0 x 10*6 mol L"1 by single sweep voltammetry. The detection limit is 9.4 x 10"9 mol L"1. With rinsing the CPE in 0.2 mol L"1 HC1 solution for 2min, it shows good reproducibility. The proposed method is applied to the rapid determination of free calcium in serum, milk and tap water. Chapter two Catalytic adsorptive stripping voltammetric determination of copper on carbon paste electrodeIn Britton-Robinson (pH4.56±0.1) buffer solution containing 3.6 x 10"5 mol L"1 ARS and 1.6 x 10"3 mol L'1 K2S2O8, the copper (II)-ARS complex yields a sensitive catalytic adsorptive wave with peak potential -0.68 V on CPE. The experiment confirms that both the electrochemical reduction of Cu(II) ion and subsequent chemical oxidation of the Cu(II) reduction product by persulfate form a catalyzed cycle, resulting into a significant increase of the cathodic stripping current of Cu(II). The second-order derivative peak current of the catalytic adsorptive stripping wave is proportional to copper (II) concentration in the range of 8.0 x 10"10 ~ 3.0 x 10"8 mol L"1, and the detection limit is 1.6 x 10' I0mol L"1. The method is evaluated by analysis of copper in water and soil samples.Chapter three Catalytic adsorptive stripping deconvolution voltammetry determination of amiodarone hydrochloridum on carbon paste electrodeIn 0.2 mol L"1 HAc-NaAc ( pH 5.3) buffer solution containing 2.2 x 10"2 mol L"1K2S2O8 and 0.0020% Triton X-100, amiodarone hydrochloridum yields a catalytic adsorptive stripping wave with peak potential +0.30 V on CPE. The experiment shows that the coexistence of the oxidant K2S2O8 and surfactant Triton X-100 conduces to a significant improvement of the analytical sensitivity of amiodarone hydrochloridum. The catalytic adsorptive stripping wave is rectilinear to amiodarone hydrochloridum concentration in the range of 2.0 x 10"10 ~ 2.3 x 10"8 mol L"1 with a detection limit of 1.5 x 10"10 mol L"1. The proposed method is applied to determine the content of amiodarone hydrochloridum in various pharmaceutical dosage samples.Chapter four Polarographic method for quality control of calcium dobesilateIn 0.1 mol L*1 HC1 supporting electrolyte, the oxidation product p-quinone sulfonate (PQS) of calcium dobesilate (calcium 2,5-dihydroxy benzenesulfonate, CDB) yields a reduction wave with peak potential -0.76 V (vs. Ag/AgCl)on mercury electrode. The second-order derivative peak current of PQS is proportional to CDB concentration in the range of 6.0 x 10" 6~ 4.0 x 10"4 mol L"1, the detection limit is 1.2 x 10"6 mol L'1. Based on this, the content of oxidation product PQS of oxidized CDB can be directly determined. Then, the unoxidized CDB is completely conversed to PQS by Fenton reaction, and the sum of both unoxidized and oxidized CDB is determined. The content of unoxidized CDB is calculated by the difference method. The procedure for quality control of calcium dobesilate is simple and rapid and it is expected to apply for the quality control of calcium dobesilate in Pharmaceuticals.