Selective and sensitive colorimetric detection of p-aminophenol in human urine and paracetamol drugs based on seed-mediated growth of silver nanoparticles

p-aminophenol (pAP), which is a well-known nephrotoxicant, has been widely used in diverse industries as a versatile intermediate material for the synthesis of chemical products. The concentration of pAP in urine is one of the markers for exposure assessment of carcinogenic aniline compounds, and pAP is also the main impurity in paracetamol-based pain-relieving drugs. Herein, we developed a colorimetric sensor for selective and sensitive assay of pAP in human urine and paracetamol drugs. Silver nanoparticles were used as a colorimetric indicator that changes color upon its growth because of the reducing power of pAP. The developed pAP sensor provides a dynamic linear range of 0–85 μM with a low limit of detection of 0.32 μM through an ultraviolet (UV)–visible (Vis) spectrometer. A clear color change was observed at 15 μM, making the proposed colorimetric sensor suitable for a point-of-care diagnosis by naked eyes. Our pAP assay is highly accurate for the standard addition method for both urine and paracetamol samples, with a recovery rate above 94%, proving the feasibility of using the sensor in daily applications.