Abstract: A quartz acousto-optic tunable filter (AOTF) is utilized as a wavelength selection device for inductively coupled plasma atomic emission spectrometry (ICP-AES). System design is detailed. Fundamental characterizations indicate that the useful spectral range exceeds the 206 to 405 nm range. Wavelength calibration is extremely accurate with the correlation coefficient of the ICP atomic emission wavelength/inverse frequency plot exceeding 0.999999. Bandpasses were measured as 0.06 nm at 226 nm and 0.36 nm at 405 nm. These values are comparable to those of a moderate-resolution monochromator. The system was characterized with 12 metals: Ag, Ba, Ca, Cd, Cr, Cu, Eu, Fe, Hg, Mg, Mn, and Ph. Detection limits are in the single to tens of ng/mL range for many metals. Linearity is demonstrated from lower concentration ranges near the detection limit.

Abstract: The sample solution is introduced directly or in 0.5 mL increments into a CETAC (Ames, IA) ultrasonic nebulizer, which supplies the He microwave-induced plasma (modified TM010 cavity; demountable silica torch; 500-W microwave generator at 2.45 GHz). The F emission is measured at the 685.6-nm (I) line. Although detection limits are 36 and 4 ppm for flow injection and direct nebulization, respectively, of test solution containing 1% of HNO3, flow injection is preferred because extended direct nebulization of aqueous F- causes memory effects. The calibration graph is curvilinear. The highest signals are obtained at pH~0.7. The F- signal is enhanced in the presence of Cu, Zn, K, Li and Na, and suppressed by Al; reasons for the effects are suggested. The determination of aqueous fluoride by flow injection analysis (FIA) with a helium microwave-induced plasma (He-MIP) is described. This system operates at 500 W and utilizes a modified TM010 resonator cavity with a demountable plasma torch. Both direct nebulization and FIA in conjunction with ultrasonic nebulization (USN) were investigated. FIA was found to be the most reliable method because extended nebulization of aqueous fluoride was found to cause memory effects. Detection limits for aqueous fluoride of 35 and 4 ppm were observed for FIA and direct USN, respectively. The interference effects of pH and selected elements were also studied.