Colorimetric screening of elevated urinary mercury levels by a novel Hg2+-selective probe of resorufin phosphinothioate

Abstract

Urinary mercury levels are the most reliable indicators of mercury exposure but identifying them requires complex techniques and heavy instruments. In this research, we reported a simple and convenient urinary mercury analysis method using a readily available office scanner. Probe MP-1 synthesized by the reaction of resorufin and dimethylthiophosphinoyl chloride revealed Hg²⁺-selective chromogenic and fluorescent signaling behavior. Signaling was realized through Hg²⁺-induced deprotection of the phosphinothioate protecting group in the resorufin-based probe MP-1 to yield the parent fluorochrome. A pronounced colorimetric response of color change from light yellow to pink alongside a turn-on type fluorescence enhancement was perceived exclusively toward Hg²⁺ ions over other metal ions and anions. The colorimetry provided a more advantageous ratiometric approach than the simple fluorometric analysis exhibiting an off-on type response, with a detection limit of 12 nM (2.4 ppb). The Hg²⁺ signaling of the MP-1 probe was not disturbed by the presence of coexisting metal ions and anions. The sensitive and convenient diagnosis of clinically important neurological symptoms and fatal inorganic mercury levels in urine was successfully demonstrated using a standard office scanner.