Signal-to-Noise Ratio Comparison for Dispersive and Non-Dispersive Flame Atomic Fluorescence Measurements

Abstract

Signal-to-noise ratios achievable with dispersive and nondispersive atomic fluorescence systems are compared. In this comparison particular attention has been devoted to considerations affecting optimization of the dispersive system with low and high background flames. Relative signal and noise values are reported for Hg and Fe atomic fluorescence with dispersive, solar-blind nondispersive, and filter nondispersive systems with C2H2-air, separated C2H2-air, H2-air, and H2-O2-Ar flames. It is concluded that, when due consideration is given to optimization of the dispersive system for atomic fluorescence measurements, use of a nondispersive system will not generally provide an improvement in the measurement signal-to-noise ratio and may result in a decreased signal-to-noise ratio with an atomizer of even moderate background emission, such as the separated C2H2-air flame.

Wavelength-modulated continuum source atomic fluorescence spectrometer

“…As pointed out by Vickers (11), flame background emission or fluorescence can be a serious limitation in nondispersive AFS. A sloping or changing background in the modulation interval will produce both f0 and 2/0 signal components.…”

“…Vickers (11) in a recent review has shown that there are some drawbacks to the use of a nondispersive system. Among these include the relatively low transmission of interference filters below 300 nm and the relatively low sensitivity of the R166 solar-blind photomultiplier tube compared to the more commonly used 1P28 photomultiplier tube.…”

“…Among these include the relatively low transmission of interference filters below 300 nm and the relatively low sensitivity of the R166 solar-blind photomultiplier tube compared to the more commonly used 1P28 photomultiplier tube. Also, since most nondispersive systems are flicker noise limited (11) due to flame background emission or fluorescence (12), the S/N ratio may decrease in comparison to dispersive systems for elements which have resonance lines in a region of high flame background (e.g., Fe). At extremely low wavelengths (near 200 nm) where both flame background and monochromator efficiency are low, the S/N ratio may increase for a nondispersive system.…”

Determination of nickel by non-dispersive atomic fluorescence spectrometry using a graphite furnace atomizer and a high frequency discharge lamp.

“…Detec tion limits for about twenty elements including nickel were described by Larkins and Willis.6) The advantages and disadvantages of nondispersive atomic fluorescence spectrometry have been discussed by many workers. [5][6][7][8][9][10][11] According to the best of our knowledge, however, there has been no paper on the non dispersive atomic fluorescence spectrometric measurement of nickel using electrothermal atomization as well as on nickel determination in practical samples for either dispersive or non-dispersive modes. The difficulities seem to be that the high dissociation energy of nickel monoxide (4.2 eV) requires a high atomization temperature, which causes an significant increase of background noise level.…”