Direct detection of vacuum ultraviolet radiation through an optical sampling orifice: analytical figures of merit for the nonmetals, metalloids, and selected metals by inductively coupled plasma atomic emission spectrometry

Abstract

and thereby produce a nonlinear interference. Also, because iodide is a much more effective quencher than other ions, the interference effect might be negligible a t high Iconcentrations, especially if interferent concentrations are below the 1.0 M level used in this study.Fluorophore molecules immobilized on the surface of Teflon tape produced better figures of merit than immobilization on resin even though the resin-bound rhodamine 6G has a fluorescence lifetime which is twice as long. Thus, accessibility has proven to be a more important factor in optrode performance than the fluorescence lifetime of an immobilized fluorophore. Resin immobilization does provide an effective solid support, but for optimal optrode performance, surface adsorption or chemical bonding directly to the fiber's surface should be the method of choice.Vacuum ultraviolet (vacuum UV) radiatlon can be readily observed through a sampling orlflce Inserted dlrectly Into an Ar lnducttvely coupled plasma. Limits of detectlon are 50 ng mL-' for the resonance ilnes of Br and Ci during InJectlon Into the plasma of aerosols of aqueous solutions generated by pneumatlc nebulkatlon. With ultrasonic nebulization, the detection limits Improve to 8 ng mL-' for Br and 15 ng mL-' for CI. Analytlcal callbratlon curves are llnear over a range of 3.5-4 orders of magnltude In concentratlon. Each of the group I I I B (group 13 in 1985 notation) elements (AI, Ga, and In) possesses at least one intense line in the vacuum UV region that yields better lknlts of detectlon than the conventional ultraviolet llnes typically observed. Emission signals from Br, CI, and AI are not strongly affected by high concentratlons of Na. The Interference induced by Ca on AI emission (and vice versa) In the vacuum UV region Is sknllar under this mode of observation to that descrlbed In the ilterature for observation of the normal UV llnes elther axially or conventionally (Le., from the slde). l Present address: Dow Chemical Co., Midland, MI 48640.In a recent communication we described the direct optical viewing of an argon inductively coupled plasma (ICP) through a sampling orifice inserted directly into the plasma and the utility of this approach for plasma diagnostic studies (1). Because this optical viewing system does not use any lenses, mirrors, or windows, vacuum ultraviolet (vacuum UV) radiation can be detected down to 78.7 nm, the wavelength corresponding to the ionization energy of Ar. In the present paper, we evaluate the analytical figures of merit of the direct optical viewing approach.

Application of prominent spectral lines in the 125–180 nm range for inductively coupled plasma optical emission spectrometry

“…Especially for Au, B, Bi, Ga, Ge, In, Sn, Pb, Te, and Tl, VUV lines are often useful to overcome spectral interferences from transition elements for wavelengths above 180 nm. Additional lines in the 120-200 nm range which can be used to avoid spectral interferences in the UV range are described elsewhere [6,7,16,17]. Limits of detection have been calculated for similar equipment using a cross-flow nebulizer for sample introduction [15].…”

“…However, a major difficulty for wavelengths below 180 nm is that radiation is absorbed by components of air, such as oxygen or water vapor. Approaches to overcome this problem are to flush the spectrometer with an inert gas or to evacuate the optical system [1,2,3,4,5,6,7,8,9,10]. Kirkbright et al [1,2], who were first to propose VUV spectral lines, purged the monochromator and the optical path between the plasma torch and the entrance slit with nitrogen.…”

“…Kirkbright et al [1,2], who were first to propose VUV spectral lines, purged the monochromator and the optical path between the plasma torch and the entrance slit with nitrogen. Later, other authors [3,4,5,6,7,8,9,10] purged the spectrometer with helium, nitrogen or argon or evacuated the spectrometer in order to study VUV spectral lines. La Freniere et al [7] used a helium purged monochromator and published a list of atom and ion lines for ICP-OES in the range from 115 to 295 nm, detected through an optical sampling orifice inserted directly into the ICP.…”

“…Later, other authors [3,4,5,6,7,8,9,10] purged the spectrometer with helium, nitrogen or argon or evacuated the spectrometer in order to study VUV spectral lines. La Freniere et al [7] used a helium purged monochromator and published a list of atom and ion lines for ICP-OES in the range from 115 to 295 nm, detected through an optical sampling orifice inserted directly into the ICP. The VUV ion lines of the halogens and the chalcogens were studied by Uehiro et al [5] with a nitrogen-purged monochromator.…”

Quadrupole ICP‐MS: Introduction to Instrumentation, Measurement Techniques and Analytical Capabilities

“…The lens stack also removes neutral species and photons from the ion beam that would otherwise be registered as additional ion counts by the detector (Lafreniere et al 1987). A circular disk, or photon stop, may be incorporated into the lens stack in the direct line of the ion beam.…”