The detection of ions in low-volume samples presents significant challenges due to their small size, high mobility, and rapid diffusion. Potentiometric ion-selective electrodes (ISEs) have emerged as a reliable method for ion detection due to their cost-effectiveness, ease of use, and potential for miniaturization, making them suitable for microfluidic applications. In the first part of thesis, descirbes the fabrication of microelectrodes (r-ISE) using radially aligned carbon nanotubes (RACNT) grown on glass fibers (GF) via chemical vapor deposition as solid contact materials. The r-ISE fabricated with RACNT-GF as an interface material exhibited a limit of detection (LOD) of 7.5×10⁻⁶ M and a linear response range from 1.0×10⁻⁵ to 1.0×10⁻¹ M. The use of RACNT-GF significantly improved the LOD, and detection selectivity compared to conventional solid-contact materials like graphite. The high surface area and mechanical durability of RACNT-GF enhanced the electrode's performance, providing stable and repeatable potentiometric responses even in confined microfluidic environments., In the second part of the thesis explores a systematic approach to a molecular cage as an synthetic ionophore for nitrate ions. By varying the molecular structure and therefore size of cage molecules, aimed to adjust the interaction between host-cage molecules and the guest-NO3- ions. Six synthetic molecular cage ionophores were evaluated for their nitrate-selective binding capabilities. The optimized CAGE ionophore-based ISE demonstrated a linear response from 1.0×10⁻⁵ to 1.0×10⁻¹ M, with a high coefficient of determination (R² = 0.9971), a slope of -53.1 ± 1.4 mV/decade and LOD of 7.5×10⁻⁶ M for nitrate detection. In the last part of the thesis, the effect of droplet evaporation on the sensitivity in ion detection by screen printed electrode is explored. The results revealed that ion concentration lower than 1.0×10⁻⁵ M does not yield linear response and droplet evaporation methods is not preferable.