Detection limits atomic emission

Atomic Emission Detection Limits for Selected Elements... 

Table A1 Flame Atomic Emission Detection Limits...

Organotin compounds enriched from a diethylether extract of a snow sample collected from the city of Gdansk, Poland and analyzed are shown in Fig. 22 b, c [286]. Gas chromatography with atomic emission detection (GC-AED) run in the chlorine and tin channels, respectively, revealed the presence of tributyltin chloride and this was subsequently confirmed by GC-MS and GC-AED analyses of an internal standard solution (e.g., 1-chlorooctane) of that compound. Quantification was based on the response to chlorine (wavelength 479 nm) in the AED system, and a detection limit of 0.5-1 ng/1 was achieved for all the reference substances. 

In recent years plasma MS has become very popular, especially where the ion source for the mass spectrometer is an ICP. These systems, which are available commercially, offer detection limits two to three orders of magnitude better than those for atomic emission detection (i.e. subpicogram levels for some elements)... 

There have been several reports [6-10] that describe the speciation of chromium. Many of these reports described the use of DC plasma atomic emission (DCPAE), ICP-AE, and atomic absorption (AA) selective-type detection. UV/VIS detection has also been extensively used. Atomic emission detection has been found to be very promising due to its selectivity and low detection limits. 

Gas chromatography with either sulfur chemiluminescence detection or atomic emission detection has been used for sulfur-selective detection. Selective sulfur and nitrogen gas chromatographic detectors, exemplified by the flame photometric detector (FPD) and the nitrogen-phosphorus detector (NPD), have been available for many years. However, these detectors have limited selectivity for the element over carbon, exhibit nonuniform response, and have other problems that limit their usefulness. 

Ref. [41] describes a procedure developed for the determination of eight organophosphoms insecticides in natural waters using SBSE combined with thermal desorption-GC-atomic emission detection (AED). Optimization of the extraction and thermal desorption conditions showed that an extraction time of 50 min and a desorption time of 6 min were sufficient. Addition of salt and adjustment of the pH were not necessary. Recoveries of seven of the compounds studied between 62 and 88%. For fenamiphos, which is highly water-soluble, recovery was only 15%. The very low detection limits, between 0.8 ng/1 (ethion) and 15.4 ng/1 (fenamiphos), indicate that the SBSE-GC-AED procedure is suitable for sensitive detection of OPPs in natural waters. 

Furnace atomizers have conversion efficiencies much higher than do flame atomizers absolute detection limits are typically 100 to 1000 times improved over flame-aspiration methods. Our discussion will center on atomizers heated by electrical resistance. Although these are not generally useful for emission measurements, they are well suited for atomic-absorption and atomic-fluorescence measurements [3]. 

A comparison of the detection limits for the rare earth elements in flame atomic emission and absorption spectrometry (table 37D.3 in section 2.2.5) allows certain conclusions to be made. The fuel-rich oxyacetylene and nitrous oxide-acetylene flames are very effective in producing free atoms of these elements and are the flames of choice for both atomic emission and absorption analysis. The emission detection limits are equal to or better than those obtained by absorption techniques, and thus flame atomic emission methods are generally superior. Future improvements in hollow cathode discharge tubes (or development of other primary sources) may lower the atomic absorption detection limits and thereby make the two techniques more complementary. However, Kinnunen and Lindsjo (1967) have emphasized that locating the proper rare earth ab-... 

The detection limits in the table correspond generally to the concentration of an element required to give a net signal equal to three times the standard deviation of the noise (background) in accordance with lUPAC recommendations. Detection limits can be confusing when steady-state techniques such as flame atomic emission or absorption, and plasma atomic emission or fluorescence, which... 

The section on Spectroscopy has been retained but with some revisions and expansion. The section includes ultraviolet-visible spectroscopy, fluorescence, infrared and Raman spectroscopy, and X-ray spectrometry. Detection limits are listed for the elements when using flame emission, flame atomic absorption, electrothermal atomic absorption, argon induction coupled plasma, and flame atomic fluorescence. Nuclear magnetic resonance embraces tables for the nuclear properties of the elements, proton chemical shifts and coupling constants, and similar material for carbon-13, boron-11, nitrogen-15, fluorine-19, silicon-19, and phosphoms-31. 

Choice of Atomization and Excitation Source Except for the alkali metals, detection limits when using an ICP are significantly better than those obtained with flame emission (Table 10.14). Plasmas also are subject to fewer spectral and chemical interferences. For these reasons a plasma emission source is usually the better choice. 

Highly sensitive iastmmental techniques, such as x-ray fluorescence, atomic absorption spectrometry, and iaductively coupled plasma optical emission spectrometry, have wide appHcation for the analysis of silver ia a multitude of materials. In order to minimize the effects of various matrices ia which silver may exist, samples are treated with perchloric or nitric acid. Direct-aspiration atomic absorption (25) and iaductively coupled plasma (26) have silver detection limits of 10 and 7 l-lg/L, respectively. The use of a graphic furnace ia an atomic absorption spectrograph lowers the silver detection limit to 0.2 l-ig/L. 

Atomic Absorption/Emission Spectrometry. Atomic absorption or emission spectrometric methods are commonly used for inorganic elements in a variety of matrices. The general principles and appHcations have been reviewed (43). Flame-emission spectrometry allows detection at low levels (10 g). It has been claimed that flame methods give better reproducibiHty than electrical excitation methods, owing to better control of several variables involved in flame excitation. Detection limits for selected elements by flame-emission spectrometry given in Table 4. Inductively coupled plasma emission spectrometry may also be employed. 

Since 1970, new analytical techniques, eg, ion chromatography, have been developed, and others, eg, atomic absorption and emission, have been improved (1—5). Detection limits for many chemicals have been dramatically lowered. Many wet chemical methods have been automated and are controlled by microprocessors which allow greater data output in a shorter time. Perhaps the best known continuous-flow analy2er for water analysis is the Autoanaly2er system manufactured by Technicon Instmments Corp. (Tarrytown, N.Y.) (6). Isolation of samples is maintained by pumping air bubbles into the flow line. Recently, flow-injection analysis has also become popular, and a theoretical comparison of it with the segmented flow analy2er has been made (7—9). 

M + e + hv). The structured background is produced by partially or completely overlapping atomic, ionic, or in some cases, molecular emission. To obtain precision better than 10% the concentration of an element must be at least 5 times the detection limit. 

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