Over-oxidized polypyrrole-modified carbon fibre ultramicroelectrode with an integrated silver/silver chloride reference electrode for the selective voltammetric measurement of dopamine in extremely small sample volumes

The fabrication and characterization of carbon fibre cone nanometre-sized ultramicroelectrodes (nanoelectrodes, CFCNEs), modified with an over-oxidized polypyrrole (OPPY) film and equipped with an integrated micro Ag/AgCl reference electrode, is reported. The OPPY-modified CFCNEs are suitable for the anodic stripping voltammetric determination of a neurotransmitter, dopamine (DA), in extremely small sample volumes in the presence of ascorbic acid (AA). The observed high selectivity for DA and the ability for its accumulation were found to be a consequence of the exclusion of anionic species by the negative charges in the OPPY film. The OPPY film was prepared via electropolymerization by cycling the potential between –0.2 and 0.7 V versus Ag/AgCl, which also allowed control over its thickness. The permselectivity of the OPPY membrane was thoroughly evaluated. The anodic stripping voltammetric response for DA was found to be dependent on the film thickness, accumulation time and potential and on the pH of the measurement medium. A good linear relationship between the anodic stripping peak current and DA concentration was obtained over the range 2.5 × 10–6–5.0 × 10–4 mol l–1, using a CFCNE modified with 15 OPPY coatings and a 2 min preconcentration time. The reproducibility of the measurement cycles (accumulation–detection–regeneration) was satisfactory, with an RSD of 5.6%(n= 10), and the limit of detection achieved with a 2 min preconcentration time was 1.0 × 10–7 mol l–1 of DA in phosphate buffer solution (pH 7.1). Owing to their ultra small size, and the integrated micro reference electrodes, the proposed OPPY-modified CFCNEs permitted the detection of DA in remarkably small sample volumes (as small as 10 nl), and in the presence of high concentrations of AA.

[1]  A. Hillman,et al.  An Ellipsometric Study of the Nucleation and Growth of Polythiophene Films , 1988 .

[2]  L W Jelinski,et al.  Nuclear magnetic resonance spectroscopy. , 1995, Academic radiology.

[3]  T. Kuwana,et al.  Oxidative mechanism of ascorbic acid at glassy carbon electrodes , 1986 .

[4]  C. R. Martin,et al.  Ionomer Film-Coated Electrodes as Electrochemical Sensors , 1988 .

[5]  R. Wightman,et al.  Heterogeneous mechanisms of the oxidation of catechols and ascorbic acid at carbon electrodes. , 1986, Analytical chemistry.

[6]  A. Bond.  Past, present and future contributions of microelectrodes to analytical studies employing voltammetric detection. A review , 1994 .

[7]  R. Wightman,et al.  Electrochemical detection of histamine and 5-hydroxytryptamine at isolated mast cells. , 1995, Analytical chemistry.

[8]  J. Wang,et al.  Selectivity and sensitivity improvements at perfluorinated ionomer/cellulose acetate bilayer electrodes. , 1986, Analytical chemistry.

[9]  R. Mark Wightman,et al.  Hyperlocomotion and indifference to cocaine and amphetamine in mice lacking the dopamine transporter , 1996, Nature.

[10]  J. M. Fernández,et al.  Release of secretory products during transient vesicle fusion , 1993, Nature.

[11]  Xingyao Zhou,et al.  Voltammetry of dihydroxyphenylalanine (l-DOPA) using a Nafion-coated carbon fibre ultramicroelectrode array , 1992 .

[12]  R. Wightman,et al.  Fast-scan cyclic voltammetry of 5-hydroxytryptamine. , 1995, Analytical chemistry.

[13]  R. Wightman,et al.  Response of microvoltammetric electrodes to homogeneous catalytic and slow heterogeneous charge-transfer reactions , 1980 .

[14]  A. Burewicz,et al.  Measurements of nitric oxide in biological materials using a porphyrinic microsensor , 1993 .

[15]  H. Abruña,et al.  Electroanalysis with chemically modified electrodes , 1985 .

[16]  Kazuko Tanaka,et al.  In vivo voltammetry with an ultramicroelectrode , 1989 .

[17]  J. Heinze.  Ultramicroelectrodes in Electrochemistry , 1993 .

[18]  Z. Gao,et al.  Voltammetric determination of dopamine in the presence of ascorbic acid at over-oxidized polypyrrole-indigo carmine film-coated electrodes. , 1994, The Analyst.

[19]  W. Zhang,et al.  Fabrication, characterization, and potential application of carbon fiber cone nanometer-size electrodes. , 1996, Analytical chemistry.

[20]  Robert H. Chow,et al.  Delay in vesicle fusion revealed by electrochemical monitoring of single secretory events in adrenal chromaffin cells , 1992, Nature.

[21]  T. Malinski,et al.  Nitric oxide release from a single cell measured in situ by a porphyrinic-based microsensor , 1992, Nature.

[22]  R. M. Wightman,et al.  Rapid and Selective Cyclic Voltammetric Measurements of Epinephrine and Norepinephrine as a Method To Measure Secretion from Single Bovine Adrenal Medullary Cells , 1994 .

[23]  C. Hsueh,et al.  Electrochemical Preparation and Analytical Applications of Ultrathin Overoxidized Polypyrrole Films , 1994 .

[24]  A. Brajter-toth,et al.  Overoxidized polypyrrole films: a model for the design of permselective electrodes. , 1992, Analytical chemistry.