Novel instrumentation of a nondispersive vacuum ultraviolet atomic absorption spectrophotometer for mercury

A nondispersive vacuum ultraviolet atomic absorption spectrophotometer for mercury has been developed. A mercury electrodeless discharge lamp (EDL), which provided a significant radiant flux at both the main resonance line at 185.0 nm and the resonance-intercombination line at 253.7 nm, was utilized with a nitrogen-purged system and a CsI phototube. Because of its spectral response, the CsI phototube allowed it to measure effectively the mercury atomic absorption only at 185.0 nm. The dependence of the atomic absorption sensitivity on the EDL operational power was similar to that in a dispersive system. Since the nondispersive system allowed operation of the EDL with lower power compared with the dispersive system, better sensitivity could be obtained owing to less self-absorption of the resonance line. Furthermore, the low fluctuation noise of the light source led to a lower detection limit. The sensitivity and detection limit were 0.077 and 0.014 ng, respectively, and the relative standard deviation for 0.05 ng mercury was at most about 5.8%.