Atomic absorption electrothermal, detection limits

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. 

Electrothermal vaporization can be used for 5-100 )iL sample solution volumes or for small amounts of some solids. A graphite furnace similar to those used for graphite-furnace atomic absorption spectrometry can be used to vaporize the sample. Other devices including boats, ribbons, rods, and filaments, also can be used. The chosen device is heated in a series of steps to temperatures as high as 3000 K to produce a dry vapor and an aerosol, which are transported into the center of the plasma. A transient signal is produced due to matrix and element-dependent volatilization, so the detection system must be capable of time resolution better than 0.25 s. Concentration detection limits are typically 1-2 orders of magnitude better than those obtained via nebulization. Mass detection limits are typically in the range of tens of pg to ng, with a precision of 10% to 15%. 

Electrothermal atomic absorption spectrophotometry with Zeeman background correction was used by Zhang et al. [141] for the determination of cadmium in seawater. Citric acid was used as an organic matrix modifier and was found to be more effective than EDTA or ascorbic acid. The organic matrix modifier reduced the interferences from salts and other trace metals and gave a linear calibration curve for cadmium at concentrations < 1.6 pg/1. The method has a limit of detection of 0.019 pg/1 of cadmium and recoveries of 95-105% at the 0.2 pg of cadmium level. 

Nishioka et al. [525] coprecipitated nickel from seawater with sodium di-ethyldithiocarbamate, filtered, and redissolved the precipitate with nitric acid followed by electrothermal atomic absorption spectrophotography determination of the nickel. The detection limit was 0.5 p,g/l and the relative standard deviation was 13.2% at the 2 ig/l level. 

Chang et al. [952] used a miniature column packed with a chelating resin and an automatic online preconcentration system for electrothermal atomic absorption spectrometry to determine cadmium, cobalt, and nickel in seawater. Detection limits of 0.12,7 and 35 ng/1 were achieved for cadmium, cobalt, and nickel, respectively, with very small sample volume required (400-1800 xl). 

Chemistry (Brown et al. 1981). Direct aspiration into a flame and atomization in an electrically heated graphite furnace or carbon rod are the two variants of atomic absorption. The latter is sometimes referred to as electrothermal AAS. Typical detection limits for electrothermal AAS are <0.3 pg/L, while the limit for flame AAS and ICP-AES is 3. 0 pg/L (Stoeppler 1984). The precision of analytical techniques for elemental determinations in blood, muscles, and various biological materials has been investigated (Iyengar 1989). Good precision was obtained with flame AAS after preconcentration and separation, electrothermal AAS, and ICP-AES. 

Flameless atomic absorption using an electrothermal atomiser is essentially a non-routine technique requiring specialist expertise. It is slower than flame analysis only 10—20 samples can be analysed in an hour furthermore, the precision is poorer (1—10%) than that for conventional flame atomic absorption (1%). The main advantage of the method, however, is its superior sensitivity for any metal the sensitivity is 100—1000 times greater when measured by the flameless as opposed to the flame technique. For this reason flameless atomic absorption is employed in the analysis of water samples where the flame techniques have insufficient sensitivity. An example of this is with the elements barium, beryllium, chromium, cobalt, copper, manganese, nickel and vanadium, all of which are required for public health reasons to be measured in raw and potable waters (section I.B). Because these elements are generally at the lOOjugl-1 level and less in water, their concentration is below the detection limit when determined by flame atomic absorption as a result, an electrothermal atomisation (ETA) technique is often employed for their determination. 

Traditional flame atomization methods have been preferred for atomic absorption analysis of ceramics. Very little mention has been made of electrothermal atomization (ETAA) in the literature. Although ETAA offers increased sensitivity with lower detection limits and smaller sample sizes, the problems of matrix interference (22-25) have resulted in the development of sample-specific methods for ETAA. 

Persson and Irgum determined sub-p.p.m. concentrations of DMAA in seawater by electrothermal atomic absorption spectrometry. Graphite-furnace atomic absorption spectrometry was used as a sensitive and specific detector for arsenic. The technique allowed DMAA to be determined in a sample (20 ml) containing a 10 -fold excess of inorganic arsenic with a detection limit of 0.02ng As ml ... 

Values taken from V. A. Fassel and R. N. Knisely, Anal. Chem., 1974,46, 111 A J. D. Ingle, Jr., and S. R. Crouch, SpectrochemicalAnalysis. Upper Saddle River, NJ Prentice-Hall, 1988 C. W. Fuller, Electrothermal Atomization for Atomic Absorption Spectroscopy. London The Chemical Society, 1977 Uhrapure Water Specifications. Quantitative ICP-MS Detection Limits. Fremont, CA, Balazs Analytical Services, 1993. With permission. 

The use of furnaces as atomizers for quantitative AAS goes back to the work of L vov and led to the breakthrough of atomic absorption spectrometry towards very low absolute detection limits. In electrothermal AAS graphite or metallic tube or cup furnaces are used, and through resistive heating temperatures are achieved at which samples can be completely atomized. For volatile elements this can be accomplished at temperatures of 1000 K whereas for more refractory elements the temperatures should be up to 3000 K. 

For the homogeneity studies, the extractants (0.05 mol L EDTA, 0.43 mol L" acetic acid and 0.005 mol L DTPA) were prepared as laid out in the certification reports [15, 17], The trace element contents (Cd, Cr, Cu, Ni, Pb and Zn) in the extracts were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) for the CRMs 483/484, flame atomic absorption spectrometry (FAAS) or electrothermal atomic absorption spectrometry with Zeeman background correction (ZETAAS) for the CRM 600. In the case of the CRM 483, little analytical difficulty was experienced as illustrated by the good agreement obtained between the within-bottle and between-bottle CVs for the CRM 484, lower extractable contents, closer to the detection limits and consequent poorer analytical precision was observed in particular for Cr (EDTA extractable contents), Cd and Pb (acetic acid extractable contents). No particular difficulties were experienced for the CRM 600. On the basis of these results, the materials were considered to be homogeneous at a level of 5 g for EDTA- and acetic acid-extractable contents and 10 g for DTPA-extractable contents (as specified in the extraction protocols). 

In-line retention of electro-active chemical species, separation, accumulation at a specific manifold site and further release can be accomplished by taking advantage of electrolytic deposition, as originally demonstrated in the determination of lead in high-purity sodium chloride and sodium sulphate reagents by electrothermal atomic absorption spectrometry [303]. Selectivity was improved because the analyte was electro-deposited inside a 3 iL flow cell, thus separating it from the bulk matrix. By optimising the operation of a potentiostat linked to the flow cell, a deposition efficiency of 70% and analyte dissolution in 40 pLof eluent were reported. With a 3 min in-line concentration, a detection limit of 1.2 ng L-1 was achieved. 

Analytical Methods and Speclatlon Electrothermal atomic absorption spectrophotometry (ETAAS), differential pulse adsorption voltammetry (DPAV), isotope-dilution mass spectrometry (ID-MS), and inductively coupled plasma mass spectrometry (ICP-MS) furnish the requisite sensitivity for measurements of nickel concentrations in biological, technical and environmental samples (Aggarwal et al. 1989, Case et al. 2001, Stoeppler and Ostapczuk 1992, Templeton 1994, Todorovska et al. 2002, Vaughan and Templeton 1990, Welz and Sperling 1999). The detection limits for nickel determinations by ETAAS analysis with Zeeman background correction are approximately 0.45 jg for urine,... 

Extraction systems with following electrothermal atomic absorption spectroscopy (ET-AAS) may be useful in some cases. For example, Zendelovska and Stafilov (2001) used isoamyl acetate extraction with following ET-AAS for thallium analysis in sulfide minerals. Eleischer (1997) reported a detection limit of 0.8 JgL when using ET-AAS with matrix modification (uirmineralized urine, diluted 1 2). 

Detection limits are presented for 61 elements by ten analytical determinative methods FAAS flame atomic absorption spectrometry ETAAS electrothermal atomization atomic absorption spectrometry HGAAS hydride generation atomic absorption spectrometry including CVAAS cold vapor atomic absorption spectrometry for Hg ICPAES(PN) inductively coupled plasma atomic emission spectrometry utilizing a pneumatic nebulizer ICPAES(USN) inductively coupled plasma atomic emission spectrometry utilizing an ultrasonic nebulizer ICPMS inductively coupled plasma mass spectrometry Voltammetry TXRF total reflection X-ray fluorescence spectrometry INAA instrumental activation neutron analysis RNAA radiochemical separation neutron activation analysis also defined in list of acronyms. 

The introduction of atomic absorption spectrometry in 1955 by Walsh has brought about a preferred analytical technique among clinical chemists in the field of element determinations. Flame atomic absorption atomization techniques with solution aspiration is not sufficiently sensitive (detection limits varies from 0,05-3 mg Se/L for most clinical applications where sub-mg/L concentrations are encountered. The sensivity can, however, be improved by generation of volatile selenium hydride and subsequent atomization in argon-hydrogen flames or electrically heated quartz tubes. Electrothermal atomization of solutions in graphite tubes has developed rapidly since the analytical use was first proposed and studied by L vov (1961). For most clinical chemists this technique may be the most appropriate technique to analyze samples for low concentrations of selenium. 

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