Integrated microfluidic platform based on potentiometric Sonogel-Carbon sensors for the simultaneous determination of Na⁺ and K⁺ in untreated human plasma and serum

Abstract

In the present work, two potentiometric sensors for the simultaneous determination of sodium and potassium ions were successfully developed. A novel functionalized multi-walled carbon nanotube sonogel-based mixture served as ion-to-electron transducer, while sodium and potassium cocktail membranes were employed as ion-selective membranes. Both sensors exhibit a well-defined operational range suitable for the precise quantification of these cations in the biomedical range, the sensors showed linear ranges of 38–4400 and 0.31–314 mM for sodium and potassium, respectively. The LOD and LOQ were 0.28/0.31 mM and 0.38/0.64 mM, respectively while the sensitivities were 58.3 ± 0.5 and 54 ± 0.2 mV/decade. The sensors demonstrate outstanding repeatability, reproducibility, and reversibility, with relative standard deviations (%RSD) below 5%, as well as exceptional selectivity for Na+ and K+ ions in the presence of various interferent substances commonly found in biological matrices. Furthermore, the sensors were applied for the simultaneous determination of sodium and potassium in untreated human plasma and serum samples under continuous flow conditions using a microfluidic cell, whose fabrication is really simple using 3D printing and cost of fabrication is less than 1 euro, and requiring only a minimal sample volume (~300 µL). The analytical results obtained showed an error margin of less than 5% across all tested samples, highlighting the sensor's reliability and potential applicability in clinical diagnostics. Notably, an excellent correlation was observed with the reference technique routinely employed in hospitals, the blood gas analyser, further supporting clinical relevance of the sensors. These findings underscore the practical utility of the developed sensors for rapid and accurate ion monitoring in complex biological fluids.