Author(s): Rosario La Cognata; Stefania Piazza; Gabriele Freni
Linked Author(s): Gabriele Freni
Keywords: Sensor calibration; Colourimetry; Lab-on-chip; Low-cost; Microcontroller; Contaminants of emerging concern (CECs)
Abstract: This work presents the development and calibration of a portable system for in-situ measurement of nitrites, nitrates, and ammoniacal nitrogen in water samples, using optical sensors. The device consists of a colour sensor (e.g., TCS34725) or photodiode with selective light source, integrated into an Arduino platform managing the analytical process. The calibration procedure uses certified standard solutions following steps: 1) determination of blank and background compensation; 2) signal acquisition for known concentrations; 3) construction of calibration curves through linear regression; 4) verification of linearity, sensitivity, and repeatability. Results compared with reference measurements using a benchtop spectrophotometer showed excellent overlap (R² > 0.999) and detection limits below 0.005 mg/L. The validated method proved that calibrated low-cost sensors can achieve accuracy comparable to professional systems, enabling distributed environmental monitoring.
Year: 2026