Rapid detection of trace heavy metals using laser breakdown time-of- flight mass spectrometry

摘要

It has been highly recognized heavy metals pollution concerns the environment, as well as human health. Mercury (Hg) pollution has greatly increased and been considered as a global pollutant because of its long residence time in surrounding. This paper describes the rapid detection of mercury using laser breakdown time-of-flight mass spectrometry at high sensitivity without fragmentation interference from other species. Two irradiation wavelengths 1064nm and 532nm were employed under various experimental conditions. The second harmonic 532nm performs excellent measurement results. The influence of pressure on mercury signal intensity displays a liner growth when increasing the pressure. These results also show as the laser power increased, nitrogen signal intensity increased, but mercury signal intensity increased first and then decreased. Experiment with different buffer gases clarified the recombination of Hg ions and electrons when increasing the laser power, resulting in the decrease of mercury signal intensity. According to these measurement results, the method of enlarging focus area and reducing laser power by tilting the focus lens was applied to decrease the recombination rate to enhance the detection limit. It is demonstrated that the detection limit with lppb can be acquired facilely.