BACKGROUNDThe detection of trace mercury in rocks typically provides biased and non-reliable results because of the complex internal unit cell structure, incomplete hot water bath acid hydrolysis extraction, volatilization loss, and contact pollution.

OBJECTIVESTo establish a more effective method for the determination of trace mercury concentrations in rocks.

METHODSDual-channel atomic fluorescence spectrometry (AFS) and domestic solid sampling-cold atomic absorption spectrometry (AAS) were used to detect the total concentration of trace mercury in rocks.

RESULTSUnder the optimized conditions of dual-channel AFS, the samples were extracted in a boiling water bath with 80% aqua regia solution for 50min. The current was 30mA, the negative high voltage was 280V, the carrier gas flow was 600mL/min, and the shielding gas flow was 1000mL/min. The concentration range was 0.05-2μg/L, and the linear correlation coefficient was greater than 0.999. The sample weight was 0.2g, method detection limit was 0.285μg/kg, and relative standard deviation was 7.3%-15.3%. For domestic solid sampling-cold AAS, the sample was determined by direct injection without chemical digestion. The carrier gas flow was 180mL/min, pyrolysis process was conducted for 60s at 700℃. The concentration range was determined to be 0.05-5ng, and the linear correlation coefficient was greater than 0.999. The sample weight was 0.1g, method detection limit was 0.046μg/kg, and relative standard deviation was 1.3%-4.2%.

CONCLUSIONSThe solid sampling-cold AAS was found to be more effective than dual-channel AFS in terms of operation, detection limit, and stability. It is more suitable for the determination of trace mercury in rocks.