Dual screen-printed electrodes with elliptic working electrodes arranged in parallel or perpendicular to the strip

• Two designs (symmetrical and not) of dual screen-printed electrodes were evaluated.
• Two elliptical gold working electrodes replace the traditional circled one.
• Ellipses located parallel and perpendicularly to the strip were working electrodes considered.
• Methylene blue is used as electroactive species in the comparative study of designs.
• Carbon nanotubes were used as modifiers of electrodes for enhancement of the analytical signal.

The number of works based on electrochemical mono-, bi- and multi-sensors is increasing, especially in which multiplexing is concerning. Determination of a panel of analytes in clinical analysis or of different related molecules in environmental or food analysis has increased the efforts for designing appropriate sensors, becoming the design, a very important step in their development. In this paper, two different dual designs for screen-printed electrodes, one of them symmetrical, were electrochemically evaluated with methylene blue as electroactive species. Two elliptic working electrodes substituted the traditional circled and centered working electrodes in the monosensing mode. Ellipses perpendicular to the strip and with the same configuration than conventional for reference and auxiliary electrodes constituted the asymmetrical design. Placing the ellipses in parallel with the strip, surrounding them with a counter electrode and locating the reference at the basis, produces a symmetrical design. Although both could be employed, more precise peak intensities are obtained for the more symmetrical design as well as with the employ of an external reference and auxiliary electrode system. Since a more sensitive detection is increasingly required, comparison is made also after nanostructuration with carbon nanotubes. The symmetrical design appears also to be more appropriate for all the electrochemical techniques tested: cyclic voltammetry, differential pulse voltammetry and square wave voltammetry.