Design of a portable RGB colorimetric detection device using nano-optodes and a Raspberry Pi platform for the reversible quantification of potassium in Peruvian agricultural soil samples

Villanueva M.; Vega-Chacón J.; Picasso G. · Microchemical Journal (2025) · DOI: 10.1016/j.microc.2025.114205

Resumen

This paper focuses on the quantification of potassium in soil. This nutrient is essential for the growth of plants. It presents a colorimetric device based on selective nano-optodes for ion potassium (K+). The nano-optodes (NOde) were characterized using scanning electron microscopy (SEM) and dynamic light scattering (DLS). These nano-optodes are nanometer-sized micelles that utilize valinomycin and chromoionophore I (CHI) for K+ quantification. A Raspberry Pi single-board computer facilitates color measurement. This study evaluates the sensor's analytical capabilities, including sensitivity, precision, and accuracy under varying illumination conditions. The system achieves high linearity across a concentration range of 10−5 to 10−1 M (mol/L) using red–green–blue (RGB) corrected color. Statistical analysis reveals results comparable to those obtained with ultraviolet–visible (UV–Vis), atomic absorption (AA), and electrode selective for ions (ISE) for agricultural soils, confirming the reliability of the colorimetric method. Sensitivity, assessed by the limit of detection (LOD = 1.03 × 10−5 M) and the limit of quantification (LOQ = 3.42 × 10−5 M), aligns with the proposed concentration range. The reversibility of nano-optodes is demonstrated through K+ ion extraction and precipitation, as evidenced by consistent calibration curves after two cycles of use. Overall, this study highlights the potential of this colorimetric device for accurate and cost-effective environmental monitoring of potassium in soil.

Instituciones: Universidad Nacional de Ingeniería