Pihel K, Walker Q D, Wightman R M
Department of Chemistry, University of North Carolina at Chapel Hill 27599-3290, USA.
Anal Chem. 1996 Jul 1;68(13):2084-9. doi: 10.1021/ac960153y.
Thin films of overoxidized polypyrrole have been electro-chemically coated onto carbon fiber microelectrodes and used for dopamine measurements with background-substracted, fast-scan cyclic voltammetry at a scan rate of 300 V/s. The films were stable on the electrode surface only when the electrodes were scanned to high potentials (1400 mV vs SSCE) in pH 7.4 aqueous buffer. Dopamine sensitivity and ascorbate and dihydroxyphenylacetic acid (DOPAC) rejection at the overoxidized polypyrrole-coated electrode were compared to those at carbon fiber electrodes coated with Nafion, a perfluorinated ion-exchange material. At 300 V/s, the overoxidized polypyrrole-coated electrode was almost 3 times more sensitive to dopamine than an uncoated disk electrode. Furthermore, the films were as effective as Nafion in the attenuation of the response to ascorbate and DOPAC, common interferences of dopamine in vivo. Overoxidized polypyrrole-coated electrodes maintained a stable response to dopamine for several hours when implanted in the rat brain. The electrochemical deposition procedure was effective at both elliptical and cylindrical electrodes. This is in contrast to the dip-coating procedures employed with Nafion films that lead to nonuniform coatings at cylindrical electrodes.
过氧化聚吡咯薄膜已通过电化学方法涂覆在碳纤维微电极上，并用于多巴胺测量，采用背景扣除的快速扫描循环伏安法，扫描速率为300V/s。只有当电极在pH 7.4的水性缓冲液中扫描至高电位（相对于饱和甘汞电极1400mV）时，薄膜才在电极表面稳定。将过氧化聚吡咯涂覆电极上的多巴胺灵敏度以及对抗坏血酸和二羟基苯乙酸（DOPAC）的排斥能力与涂覆有全氟离子交换材料Nafion的碳纤维电极进行了比较。在300V/s时，过氧化聚吡咯涂覆电极对多巴胺的灵敏度几乎是未涂覆圆盘电极的3倍。此外，这些薄膜在减弱对多巴胺体内常见干扰物抗坏血酸和DOPAC的响应方面与Nafion一样有效。当植入大鼠大脑时，过氧化聚吡咯涂覆电极对多巴胺保持了数小时的稳定响应能力。电化学沉积过程在椭圆形和圆柱形电极上均有效。这与用于Nafion薄膜的浸涂过程形成对比，浸涂过程会导致圆柱形电极上的涂层不均匀。
