Instrumentation flameless atomic absorption

Analysis of the samples for elemental constituents was performed using instrumented neutron activation analysis (NAA) and spark source mass spectrometry (SSMS) (2). In addition, the many mercury determinations were made by flameless atomic absorption (AA). 

Carbon Monoxide. Methods for determining carbon monoxide include detection by conversion to mercury vapor, gas filter correlation spectrometry, TDLAS, and grab sampling followed by gas chromatograph (GC) analysis. The quantitative liberation of mercury vapor from mercury oxide by CO has been used to measure CO (73). The mercury vapor concentration is then measured by flameless atomic absorption spectrometry. A detection limit of 0.1 ppbv was reported for a 30-s response time. Accuracy was reported to be 3% at tropospheric mixing ratios. A commercial instrument providing similar performance is available. 

Neutron activation analysis (NAA) with a rapid radiochemical separation has been the method generally used in recent years, but requires substantial investment, has high operating cost and limited availability. Modem flameless atomic absorption (AAS) instruments provide sensitivity approaching that of NAA and offer a viable alternative for the detection of firearms discharge residue. 

C. Flameless Atomic Absorption Spectroscopy. A Jarrell-Ash Model 810 Dual Monochromator Atomic Absorption Spectrophotometer was used for this work. The instrument was equipped with the Bames Instrument s tantalum ribbon flameless atomizer and a two-... 

Both chemical and instrumental means have been developed for overcoming interferences in flameless atomic absorption and these are discussed below. 

Numerous procedures, by a variety of different instruments, are available to quantify the amount of thallium present in hair, blood, tissue, saliva, and urine (for reviews, see [9,81]). Instrumentation used includes emission spectrography, flame and flameless atomic absorption spectroscopy (AAS), voltammetry, neutron activation analysis, and field desorption mass spectroscopy [13,17,82-90]. Field desorption mass spectroscopy when combined with stable isotope dilution can detect fentomole quantities and has value in that no tissue preparation (other than homogenization) is required [65,82,89], The use of these two methods, however, is restricted to specialized laboratories. 

Atomic Absorption Spectroscopy. One of the more sensitive instruments used to detect metal-containing toxicants is the AA spectrophotometer. Samples are vaporized either by aspiration into an acetylene flame or by carbon rod atomization in a graphite cup or tube (flameless AA). The atomic vapor formed contains free atoms of an element in their ground state, and when illuminated by a light source that radiates light of a... 

Liquid or digested samples are atomized by direct aspiration in a flame atomic absorption (FLAA) instrument or in an electrically heated flameless furnace in a GFAA instrument. 

The multielement detection limits with the echelle/image dissector are comparable to, or better than, single element detection limits reported for a silicon vidicon and conventional optics. Detection limits for Cr, Cu, and Mn with the echelle/ image dissector compare favorably with single element data reported for a conventional atomic absorption instrument with a photomultiplier detector, but detection limits obtained here for Ni and Co are higher by factors of 10 or more than for the conventional instrument. The echelle/image dissector system should be adaptable to a so-called flameless atomizer and be subject to the same improvements in sensitivities and detection limits as conventional detector systems. 

Instrumentation Laboratory Inc. Atomic Absorption Methods Manual, Vol. 2, Flameless Operations, Wilmington, MA, 1976. 

New flameless methods for sample presentation to the instrument, like the graphite rod and the. tantalum boat, are expanding the use and applications of atomic absorption spectrometry. In the first technique the burner is replaced by a graphite rod with a small well where a few microliters of sample are deposited and electrically heated by means of controlled power supply. Important advantages of this procedure are that a very small sample is needed and the dilution of viscous samples is not required. 

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