Simple, Selective and Sensitive Determination of CH₃Hg⁺ Using Gold Nanocluster

Mercury is a potent neurotoxin, which causes serious and permanent damage to biota including human beings. Nanomaterials like gold have been used to detect mercury, especially the mercuric ions in recent years, but few have been done on the determination of methylmercury (CH₃Hg⁺). In this study, we present a simple, selective and sensitive method for the determination of CH₃Hg⁺ co-existing with Hg²⁺ based on the fluorescence quenching of bovine serum albumin (BSA) stabilized gold nanoclusters (BSA-Au NCs). It was found that the fluorescence quenching of BSA-Au NCs by Hg²⁺ is stronger than CH₃Hg⁺ at the same concentration. Hg²⁺ can be masked by EDTA while CH₃Hg⁺ is less affected. Therefore, the determination of CH₃Hg⁺ was achieved through EDTA masking. The detection limit for CH₃Hg⁺ is 35 nmol/L after masking Hg²⁺ with EDTA. This method has been successfully applied to quantify CH₃Hg⁺ in rice paddy water from Qingzhen, Guizhou and tap water from Beijing.