A facile smartphone-based digital image colorimetric sensor for the determination of tetracyclines in water using natural phenolic compounds induced to grow gold nanoparticles.

A cost-effective smartphone-based digital image colorimetric sensor was developed to determine tetracyclines by inducing in situ growth of gold nanoparticles using naturally occurring phenolic compounds derived from para rubber tree bark waste. The green intensity of the purple-red product was measured using smartphone-based digital image analysis. Under optimal conditions, the calibration graph exhibited linearity within the range 0.05 to 0.50 μg mL-1, with a coefficient of determination (R 2) of 0.9940. The limits of detection (LOD) and limits of quantitation (LOQ) were 15 and 50 ng mL-1, respectively, with levels of precision for intraday and interday less than 3.91% and 4.59%, respectively. The proposed method was effectively validated to determine the spiked tetracycline antibiotics in water samples, achieving a high relative recovery rate ranging from 86.4% to 114.4%. Our method is facile, convenient, dependable, and verifiable as an alternate procedure for measuring tetracycline levels in water.