Article

Paired pulse voltammetry for differentiating complex analytes.

Department of Neurologic Surgery, Mayo Clinic, Rochester, MN 55905, USA.
The Analyst (Impact Factor: 3.91). 02/2012; 137(6):1428-35. DOI: 10.1039/c2an15912k
Source: PubMed

ABSTRACT Although fast-scan cyclic voltammetry (FSCV) has contributed to important advances in neuroscience research, the technique is encumbered by significant analytical challenges. Confounding factors such as pH change and transient effects at the microelectrode surface make it difficult to discern the analytes represented by complex voltammograms. Here we introduce paired-pulse voltammetry (PPV), that mitigates the confounding factors and simplifies the analytical task. PPV consists of a selected binary waveform with a specific time gap between each of its two comprising pulses, such that each binary wave is repeated, while holding the electrode at a negative potential between the waves. This allows two simultaneous yet very different voltammograms (primary and secondary) to be obtained, each corresponding to the two pulses in the binary waveform. PPV was evaluated in the flow cell to characterize three different analytes, (dopamine, adenosine, and pH changes). The peak oxidation current decreased by approximately 50%, 80%, and 4% for dopamine, adenosine, and pH, in the secondary voltammogram compared with the primary voltammogram, respectively. Thus, the influence of pH changes could be virtually eliminated using the difference between the primary and secondary voltammograms in the PPV technique, which discriminates analytes on the basis of their adsorption characteristics to the carbon fiber electrode. These results demonstrate that PPV can be effectively used for differentiating complex analytes.

Download full-text

Full-text

Available from: Kevin Bennet, Jun 20, 2015
0 Followers
 · 
149 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Neurotransmitters are important biological molecules that are essential to many neurophysiological processes including memory, cognition, and behavioral states. The development of analytical methodologies to accurately detect neurotransmitters is of great importance in neurological and biological research. Specifically designed microelectrodes or microbiosensors have demonstrated potential for rapid, real-time measurements with high spatial resolution. Such devices can facilitate study of the role and mechanism of action of neurotransmitters and can find potential uses in biomedicine. This paper reviews the current status and recent advances in the development and application of electrochemical sensors for the detection of neurotransmitters. Measurement challenges and opportunities of electroanalytical methods to advance study and understanding of neurotransmitters in various biological models and disease conditions are discussed.
    Analytical Letters 02/2015; 48(7). DOI:10.1080/00032719.2014.976867 · 0.98 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The oxidation of dopamine (DA) around +0.6V potential in anodic sweep and its reduction around -0.1V in cathodic sweep at a relatively fast scanning rate (300 V/s or greater) have been used for identification of DA oxidation in fast-scan cyclic voltammetry (FSCV). However, compared to the oxidation peak of DA, the reduction peak has not been fully examined in analytical studies, although it has been used as one of the representative features to identify DA. In this study, the reduction process of DA was investigated using paired pulse voltammetry (PPV), which consists of two identical triangle-shaped waveforms, separated by a short interval at the holding potential. Especially, the discrepancies between the magnitude of the oxidation and reduction peaks of DA were investigated based on three factors: (1) the instant desorption of the DA oxidation product (dopamine-o-quinone: DOQ) after production, (2) the effect of the holding potential on the reduction process, and (3) the rate-limited reduction process of DA. For the first test, the triangle waveform FSCV experiment was performed on DA with various scan-rates (from 400 to 1000 V/s) and durations of switching potentials of the triangle waveform (from 0.0 to 6.0 ms) in order to vary the duration between the applied oxidation potential at +0.6V and the reduction potential at -0.2V. As a result, the ratio of reduction over oxidation peak current response decreased as the duration became longer. To evaluate the effect of holding potentials during the reduction process, FSCV experiments were conducted with holding potential from 0.0V to -0.8V. We found that more negative holding potentials lead to larger amount of reduction process. For evaluation of the rate-limited reduction process of DA, PPV with a 1Hz repetition rate and various delays (2, 8, 20, 40 and 80ms) between the paired scans were utilized to determine how much reduction process occurred during the holding potential (-0.4V). These tests showed that relatively large amounts of DOQ are reduced to DA during the holding potential. The rate-limited reduction process was also confirmed with the increase of reduction in a lower pH environment. In addition to the mechanism of the reduction process of DA, we found that the differences between the responses of primary and secondary pulses in PPV were mainly dependent on the rate-limited reduction process during the holding potential. In conclusion, the reduction process may be one of the important factors to be considered in the kinetic analysis of DA and other electroactive species in brain tissue and in the design of new types of waveform in FSCV.
    Journal of electroanalytical chemistry 03/2014; 717-718. DOI:10.1016/j.jelechem.2014.01.020 · 2.87 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In this paper is presented an overview of the technological barriers faced by the in vivo brain analysis with microelectrodes. Numerous microsensors and enzymatic microbiosensors have been developed for the real time monitoring of neurotransmitters, neuromodulators, drugs and diverse other biological relevant substances. A clear understanding of the working principle, advantages and limitations is essential for the acquisition of valid data in neurological investigations. Some of the aspects presented here refer to: microelectrode insertion and positioning related to possibilities to minimize tissue damage, spatial and temporal resolution of the measurements, actual controversies in data interpretation and sensor calibration, simultaneous detection of multiple analytes, interferences and state of the art in the development of wireless devices.
    Current Neuropharmacology 09/2012; 10(3):197-211. DOI:10.2174/157015912803217350 · 2.35 Impact Factor