Rapid and accurate detection of urinary iodine by single crystal silver iodide sensor

Iodine deficiency or excess impacts thyroid health, necessitating accurate urinary iodine monitoring. However, existing detection methods face challenges including complicated sample handling, poor anti-interference ability, and the detection range does not cover the range of human urinary iodine concentration. Conventional iodide ion-selective electrode is based on polycrystalline membranes, which has high detection limit and is susceptible to chloride ion interference. It is also not suitable for accurate detection of human urinary iodine. In this study, we introduced a single-crystal AgI electrode for rapid and interference-free detection of urinary iodine. The dense (220) crystal plane of the single-crystal AgI electrode provided excellent selectivity and sensitivity, with a detection limit as low as 59 μg L^-1 and good linearity in the range of 100-1000 μg L^-1. This fully covers the optimal range of urinary iodine concentrations recommended by the World Health Organization (100-500 μg L^-1). Importantly, the single-crystal AgI electrode has excellent resistance to chloride interference, which is a significant improvement over conventional polycrystallaline iodide ion-selective electrodes. Our results show that the electrode has excellent precision, stability and accuracy without interference from common urine ions. This work addresses the limitations of existing methods and provides a rapid, inexpensive and reliable method for urinary iodine testing.