Far-ultraviolet excited laser-enhanced ionization spectrometry of As, Se, Cu, and Sb in air/acetylene and Ar/O2/acetylene flames

Laser-enhanced ionization (LEI) measurements of As, Se, Sb, and Cu in air/acetylene and Ar/O-2/acetylene flames are reported. The use of far-UV excitation wavelengths to perform one- and two-step LEI excitation from the ground states of As, Se, and Sb is reported for the first time. Significant ionization background signals are observed for far-UV excitations in the air/acetylene flame, but are reduced by substituting an (80:20) Ar/O-2 mixture for air as the flame oxidant. The sensitivities of the individual LEI techniques are also increased by the Ar/O-2 gas substitution. The limits of detection for As, Se, Sb, and Cu are 30, 0.5, 9 and 2 ng/mL, respectively, and compare favorably with previous LEI reports. Due to the poor atomization characteristics of As and Se, the utility of hydride generation (HG) sample introduction with LEI detection has been explored. Although high sensitivity has been observed for the HG-LEI approach, limits of detection were not evaluated due to nonlinear responses of the signals with respect to analyte concentration.