Effects of recording media composition on the responses of Nafion-coated carbon fiber microelectrodes measured using high-speed chronoamperometry

The present study concerns methodological issues of electrochemical recordi ngs using Nafion-coated 30 mum diameter single carbon fiber microelectrodes for high-speed chronoamperometric measurements of biogenic amines. First, the single carbon fiber microelectrodes were coated with Nafion and dried a t 85 vs. 200 degreesC and their recording properties were determined. Secon d, the effects of shifts in solution pH, ionic strength, changes in recordi ng solution levels of Ca2+ or Mg2+ and temperature on the recording charact eristics and sensitivity of Nafion-coated high temperature dried (200 degre esC) single carbon fiber microelectrodes for measures of dopamine were stud ied. These studies showed that the high temperature drying of the Nafion pr oduced a microelectrode with better recording properties: higher selectivit y for cations versus anions, increased differences between the reduction an d oxidation current ratios for the identification of dopamine versus seroto nin, and more rapid response times. In addition, these studies demonstrated that the chronoamperometric recordings were insensitive to small changes i n pH and divalent cations such as Ca2+ or Mg2+. However, increases in ionic strength decreased the sensitivity of the microelectrodes, while increases in temperature produced increases in the sensitivity of the microelectrode s for biogenic amines. These data support that Nafion-coated high temperatu re (200 degreesC) dried microelectrodes have enhanced recording properties as compared to microelectrodes, which are coated with Nafion and dried at 8 5 degreesC. In addition, high-speed chronoamperometric. recordings of bioge nic. amines are not affected by solution changes in divalent cations (Ca2or Mg2+). (C) 2001 Elsevier Science B.V. All rights reserved.