Double modulation-optical scanning and mechanical chopping-in atomic absorption spectrometry using a continuum source

Abstract

stoichiometry of the air-acetylene flames between the two portions of the experiment.Interferences in the nitrous oxide-acetylene flames were measured at three stoichiometries: lean, medium, and rich. The curves varied considerably from each other, but not in any identifiable pattern; one stoichiometry did not appear to give "better" results than another. The data in the Figures 2-5 were taken from the medium flame. CONCLUSIONSThe primary conclusion emerging from these experiments is that use of the air-acetylene flame burning on the single slot, flat-top burner produces the fewest interferences when determining copper, manganese, and nickel in acid media. Both the air-acetylene flame burning on a 3-slot head and the nitrous oxide-acetylene flame showed a greater tendency to exhibit interference effects, suggesting that these flames should be chosen with caution. For chromium the choice is not so clear. Both air-acetylene and nitrous oxide-acetylene flames produced roughly equivalent sensitivities and acid interferences. In this case the choice would be dependent on the presence of other possible interferences.The interferences from hydrochloric and nitric acids were smallest indicating that these acids should be used if there is a choice of dissolution methods. However, if high accuracy is required, and the acid medium is other than dilute, standards should be made up in approximately matching concentrations of the same acid or acids.Finally, it is clear that the design of the burner system has an important influence on analytical interferences, even within the general category of premix burners. The interferences found in this work are far smaller and less important than those reported in Reference I , in which a different premix burner system was employed.An atomic absorption flame spectrometer employing chopper modulated continuum radiation and wavelength modulation of radiation transmitted through the flame cell is described. The instrumental system does not respond either to Rayleigh scattering or to molecular absorption and emission processes occurring within theflamegases. Limits of detection of the order of 0.1 bg/ml and analytical curves linear over at least three orders of magnitude in concentration for Ag, Ca, Cd, Cr, Cu, Fe, Mg, and Ni are obtained. Expressions are derived to predict the response of the instrumental system to variation in experimental parameters and are verified experimentally.

Multielement analysis by continuum source atomic absorption spectrometry with the aid of analog data treatment

“…For comparison, the limits of detection obtained by WMAAC (12) and by AAL (4) are also summarized in Table I. The limits of detection obtained in this work were approximately 10-50 times worse than those obtained by WMAAC (12), but they are almost the same as those by others in AAC (14)(15)(16).…”

Continuum source atomic absorption spectrometry and detector technology: A historical perspective

“…Elnser and Winefordner [57] developed a technique combining wavelength and source intensity modulation which in addition caused suppression of flame emission intensities. The most successful development was initiated in 1976 by Zander, O'Haver and Keliher [58], who coupled a refractor plate modulator [59] to a high-resolution echelle spectrometer with an internal prism as order sorter.…”

High-resolution continuum source electrothermal atomic absorption spectrometry — An analytical and diagnostic tool for trace analysis

“…The early publications in this field mainly took advantage of the instability and/or low energy output of the hollow cathode lamps at that time or their unavailability for certain elements [6][7][8][9]. In the following years, several groups investigated wavelength modulation using AC scanning [10], oscillating interferometers [11,12] or a combination of optical scanning and mechanical modulation [13] in order to improve the signal-to-noise ratio (SNR) and the sensitivity of CS AAS.…”