Ultra-sensitive determination of mercury in flue gas by atmospheric pressure glow discharge atomic emission spectrometry coupled with gold amalgam enrichment

In this work, a highly sensitive procedure for the determination of mercury in flue gas was developed, based on direct-current atmospheric pressure glow discharge in hydrogen and helium (H₂–He) atomic emission spectroscopy (APGD-AES) coupled with gold amalgam enrichment (GA). Calibration mercury vapors generated by the cold vapor generation (CVG) system were sent to the GA system for enrichment. Subsequently, mercury was thermally desorbed and transmitted to APGD for excitation, and at the same time, the signal at 253.6 nm was recorded using a micro-spectrometer. The parameters of GA and APGD systems were optimized, including the type and flow rate of the carrier gas, discharge current and discharge gap. Under the optimum operating conditions, when the sampling volume of the flue gas was 10 L, the detection limit (DL) of Hg was 0.1 μg m⁻³, which met the actual measurement requirements, and the relative standard deviation (RSD) was 2% (n = 11), the linear correlation coefficient was better than 0.999. The accuracy and practicality of GA-APGD-AES were verified by the analysis of flue gas. The results were consistent with those of a direct mercury analysis (DMA) system (n = 3, relative deviation was less than 3%).