Development And Application Of Improved Long Optical Path Thin-layer Spectroelectrochemical Pool

Spectroelectrochemistry is a cross subject of modern spectra technique and electrochemical technique. It is a method that can give much information in an electrochemical cell. It provides very powerful means for studying the electrochemical phenomena, elucidating electrochemical reaction mechanisms, identifying the intermediate compounds or instantaneous state in the reaction process and the properties of products, and determining the kinetic and thermodynamic parameters of electron-transfer processes. It is essential to design high qualitative thin-layer electrochemical cell through utilizing this technique. In this paper, through a modification of a previously reported cell design, an improved long path-length thin-layer spectroelectrochemical cell had been designed and constructed. The optical and electrochemical responses with graphite as the working electrode using ferric/ferrocyanide in KC1 as the test species were evaluated by using cyclic voltammetry, AC Impedance and constant potential control in situ spectrum. The cell's design has the following advantages over conventional spectroelectrochemical cells: (1) long path-length, high sensitivity and good repeatability; (2) simplicity of fabrication; (3) ease of replacing working electrode; (4) small uncompensated solution resistance; (5) small volume of solution; (6) ease of washing cell. Its property is good and reliable. All these indicate that our electrochemical cell is practically usable and suitable for spectroelectrochemical studies.Adrenaline and its oxidative product adrenochrome are widely used in medicine. It is very important to study the electrochemistry properties of them for their applies in medicine, and electroanalytical. In this paper, the electrochemical oxidation of adrenaline in different media was investigated at graphite and platinum plate electrode in home-made long optical path thin-layer spectroelectrochemical cell and gold minigrid electrode in optically transparent thin-layer cell by using electrochemical and UV-Vis spectroelectrochemical technique. The thin-layer cyclic voltammocharacter of adrenaline in different media had been firstly investigated at graphite, platinum plate electrode and gold minigrid electrode by using cyclic voltammetry. On this basis, the formal potentials and electron transfer numbers of the oxidation of adrenaline were determined in different media at room temperatureby means of thin-layer spectroelectrochemical technique. The mechanisms of the electro-oxidation were discussed on the basis of the spectrum recorded in situ during the electrochemical process. The investigation of thin-layer cyclic voltammetry and thin-layer spectroelectro-chemistry revealed that the electrochemical oxidation of adrenaline in the medium of strong acid is a quasi-reversible two-electron transfer process and the final oxidation product is adrenalinequinone. Though the electrochemical oxidation of adrenaline in the organic weak acid is also a quasi-reversible two-electron transfer process, the reversibility of the reaction is worse than that in strong acid. While in the media of pH=3.96 Mcllvaine buffer solution and pH=7.48 KRPB buffer solution, the adrenalinequinone which is the primary electrode product of the adrenaline can take part in a series of the following chemical reactions and the final electrochemical oxidation product is adrenochrome. The adrenochrome can also take part in oxidation-reduction reaction when the potential is about zero volt, consequently, there is another pair of oxidation-reduction peaks correspondingly in the cyclic voltammogram. The deproton step of the protonated adrenalinequinone, viz. the third step, is difficult to proceed in strong acid medium, so a series of subsequent chemical reactions are difficult to occur and the electrolytic product is adrenalinequinone, thus, there is only one pair of oxidation-reduction peaks in the cyclic voltammogram. We can conclude that the deproton step of the protonated adrenalinequinone may be the slowest, that is to say, it is the rate-determining...