A Green Method Based on Cloud Point Extraction-Atomic Fluorescence Spectrometry for Trace Mercury in Water: Preconcentration, Separation, and Determination

A method for the preconcentration of trace mercury in water has been proposed, utilizing ammonium pyrrolidinedithiocarbamate (APDC) as the chelating agent and the non-ionic surfactant Triton X-114 as the extractant. The trace mercury present in the water is concentrated into the surfactant phase via cloud point extraction (CPE), and is determined by hydride generation atomic fluorescence spectrometry (HGAFS). The optimal determination conditions were successfully obtained by optimizing the cloud point extraction conditions and atomic fluorescence test conditions, such as pH, chelating agent dosage, extractant dosage, equilibrium temperature and time, carrier solution (HCl), and reducing solution (KBH4). Under the optimal extraction conditions, it was demonstrated that the detection limits of the APDC-CPE-HGAFS method can reach 0.002 μg/L, which is one order of magnitude lower than that of the current standard method. The standard addition method was employed for recovery experiments, with recovery rates ranging from 92.5 to 98.5%. The relative standard deviation of the measured values (n = 6) ranged from 4.2 to 8.1%. This indicates that the method possesses the advantages of a low detection limit, good precision, and high accuracy.