Metals graphite furnace atomic absorption

Trace metals in sea water are preconcentrated either by coprecipitating with Ee(OH)3 and recovering by dissolving the precipitate or by ion exchange. The concentrations of several trace metals are determined by standard additions using graphite furnace atomic absorption spectrometry. 

Figure 15-12 is a schematic illustration of a technique known as acid volatile sulfides/ simultaneously extracted metals analysis (AVS/SEM). Briefly, a strong acid is added to a sediment sample to release the sediment-associated sulfides, acid volatile sulfides, which are analyzed by a cold-acid purge-and-trap technique (e.g., Allen et ai, 1993). The assumption shown in Fig. 15-12 is that the sulfides are present in the sediments in the form of either FeS or MeS (a metal sulfide). In a parallel analysis, metals simultaneously released with the sulfides (the simultaneously extracted metals) are also quantified, for example, by graphite furnace atomic absorption spectrometry. Metals released during the acid attack are considered to be associated with the phases operationally defined as "exchangeable," "carbonate," "Fe and Mn oxides," "FeS," and "MeS."... 

In order to derive a quantitative relation between emission Intensity as measured by EMI and actual metal content, cell samples were subjected to graphite furnace atomic absorption (GFAA) analysis (14). Atomic absorption experiments were performed both on cells which had been stained with a fluorescent reagent and on cells not exposed to a lumlnophore. After EMI analysis, 50 fiL of cell suspension were withdrawn from the 0.30 mL of sample used for EMI and were digested In 150 iiL of concentrated HNO3 for 90 minutes at 85° . These solutions were then diluted to 1/10 of their concentration with deionized water, and the 150 liL of these diluted... 

Many of the published methods for the determination of metals in seawater are concerned with the determination of a single element. Single-element methods are discussed firstly in Sects. 5.2-5.73. However, much of the published work is concerned not only with the determination of a single element but with the determination of groups of elements (Sect. 5.74). This is particularly so in the case of techniques such as graphite furnace atomic absorption spectrometry, Zeeman background-corrected atomic absorption spectrometry, and inductively coupled plasma spectrometry. This also applies to other techniques, such as voltammetry, polarography, neutron activation analysis, X-ray fluroescence spectroscopy, and isotope dilution techniques. 

Adsorptive cathodic stripping voltammetry has an advantage over graphite furnace atomic absorption spectrometry in that the metal preconcentration is performed in situ, hence reducing analysis time and risk of contamination. Additional advantages are low cost of instrumentation and maintenance, and the possibility to use adapted instrumentation for online and shipboard monitoring. 

Statham [448] has optimised a procedure based on chelation with ammonium dithiocarbamate and diethylammonium diethyldithiocarbamate for the preconcentration and separation of dissolved manganese from seawater prior to determination by graphite furnace atomic absorption spectrometry. Freon TF was chosen as solvent because it appears to be much less toxic than other commonly used chlorinated solvents, it is virtually odourless, has a very low solubility in seawater, gives a rapid and complete phase separation, and is readily purified. The concentrations of analyte in the back-extracts are determined by graphite furnace atomic absorption spectrometry. This procedure concentrates the trace metals in the seawater by a factor of 67.3. 

Graphite Furnace Atomic Absorption Spectrometry Heavy Metals... 

Cadmium, copper, and silver have been determined by an ammonium pyrrolidine dithiocarbamate chelation, followed by a methyl isobutyl ketone extraction of the metal chelate from the aqueous phase [677], and finally followed by graphite furnace atomic absorption spectrometry. The detection limits of this technique for 1% absorption were 0.03 pmol/1 (copper), 2 nmol/1 (cadmium), and 2 nmol/1 (silver). 

Tominaga et al. [682,683] studied the effect of ascorbic acid on the response of these metals in seawater obtained by graphite-furnace atomic absorption spectrometry from standpoint of variation of peak times and the sensitivity. Matrix interferences from seawater in the determination of lead, magnesium, vanadium, and molybdenum were suppressed by addition of 10% (w/v) ascorbic acid solution to the sample in the furnace. Matrix effects on the determination of cobalt and copper could not be removed in this way. These workers propose a direct method for the determination of lead, manganese, vanadium, and molybdenum in seawater. 

Hayase et al. [684] first extracted the seawater sample with chloroform to remove dissolved organic matter prior to analysis of the aqueous phase by graphite furnace atomic absorption spectrometry. Seawater samples at pH 3 and at pH 8 were extracted with chloroform, evaporated to dryness, and the residue treated with nitric acid. Acid solutions were subjected to metal analyses by graphite furnace atomic absorption spectrometry. 

Table 5.6 compares the ICP-AES results with data generated for the same sample by two other independent methods - isotope dilution spark source mass spectrometry (IDSSMS), and graphite furnace atomic absorption spectrometry (GFAAS). The IDSSMS method also uses 25-fold preconcentration of the metals and matrix separation using the ion exchange procedure, following isotope... 

Mykytiuk et al. [184] have described a stable isotope dilution sparksource mass spectrometric method for the determination of cadmium, zinc, copper, nickel, lead, uranium, and iron in seawater, and have compared results with those obtained by graphite furnace atomic absorption spectrometry and inductively coupled plasma emission spectrometry. These workers found that to achieve the required sensitivity it was necessary to preconcentrate elements in the seawater using Chelex 100 [121] followed by evaporation of the desorbed metal concentrate onto a graphite or silver electrode for isotope dilution mass spectrometry. 

Jaffe, R., C.A. Fernandez, and J. Alvarado. 1992. Trace metal analyses in octocorals by microwave acid digestion and graphite furnace atomic-absorption spectrometry. Talanta 39 113-117. 

The major anions and cations in seawater have a significant influence on most analytical protocols used to determine trace metals at low concentrations, so production of reference materials in seawater is absolutely essential. The major ions interfere strongly with metal analysis using graphite furnace atomic absorption spectroscopy (GFAAS) and inductively coupled plasma mass spectroscopy (ICP-MS) and must be eliminated. Consequently, preconcentration techniques used to lower detection limits must also exclude these elements. Techniques based on solvent extraction of hydrophobic chelates and column preconcentration using Chelex 100 achieve these objectives and have been widely used with GFAAS. 

Other applications of supported liquid membranes have been related to metal speciation. For example, recently a system for chromium speciation has been developed based on the selective extraction and enrichment of anionic Cr(VI) and cationic Cr(III) species in two SLM units connected in series. Aliquat 336 and DEHPA were used respectively as carriers for the two species and graphite furnace atomic absorption spectrometry used for final metal determination. With this process, it was possible to determine chromium in its different oxidation states [103]. 

Both flame and graphite furnace atomic absorption spectrometry are two of the commonest techniques used for the determination of metals and metalloids. Various authors " have discussed the application of both to the analysis of trace elements in biological materials. 

The recommended procedure for the determination of arsenic and antimony involves the addition of 1 g of potassium iodide and 1 g of ascorbic acid to a sample of 20 ml of concentrated hydrochloric acid. This solution should be kept at room temperature for at least five hours before initiation of the programmed MH 5-1 hydride generation system, i.e., before addition of ice-cold 10% sodium borohydride and 5% sodium hydroxide. In the hydride generation technique the evolved metal hydrides are decomposed in a heated quartz cell prior to determination by atomic absorption spectrometry. The hydride method offers improved sensitivity and lower detection limits compared to graphite furnace atomic absorption spectrometry. However, the most important advantage of hydride-generating techniques is the prevention of matrix interference, which is usually very important in the 200 nm area. 

De Jonghe, W., Chakraborti, D. and Adams, F. (1980) Graphite furnace atomic absorption as a metal specific detection system for tetraalkyllead compounds separated by gas-liquid chromatography. Anal. Chim. Acta, 115, 89-105. 

Sturgeon, R.E., Siu, K.W.M., Willie, S.N. and Berman, S.S. (1989) Quantification of arsenic species in a river water reference material for trace metals by graphite furnace atomic absorption spectrometric techniques. Analyst, 114, 1393-1396. 

Wang, G., J. Yuan, B. Gong, et al. 2001. Immunoassay by graphite furnace atomic absorption spectrometry using a metal chelate as a label. Anal. Chim. Acta 448 165-172. 

Several biologically important metals can be determined directly in body fluids, especially urine, by atomic absorption. In the simplest cases, the urine is diluted with water or acid and a portion analyzed directly by graphite furnace atomic absorption, taking advantage of the very high sensitivity of that technique for some metals. Metals that can be determined directly in urine by this approach include chromium, copper, lead, lithium, and zinc. Very low levels of metals can be... 

Many metal analyses are carried out using atomic spectroscopic methods such as flame or graphite furnace atomic absorption or inductively coupled plasma atomic emission spectroscopy (ICP-AES). These methods commonly require the sample to be presented as a dilute aqueous solution, usually in acid. ICP-mass spectrometry requires similar preparation. Other samples may be analyzed in solid form. For x-ray fluorescence, the solid sample may require dilution with a solid buffer material to produce less variation between samples and standards, reducing matrix effects. A solid sample is also preferred for neutron activation analyses and may be obtained from dilute aqueous samples by precipitation methods. 

B. Welz, Application of Graphite Furnace Atomic Absorption to the Analysis of Heavy Metals in Biological Materials, a Paper presented to CEC Course on Analytical Technology for Heavy Metals in Biological Fluids, Ispra, Italy, December 1978. 

Maintaining the quality of food is a far more complex problem than the quality assurance of non-food products. Analytical methods are an indispensable monitoring tool for controlling levels of substances essential for health and also of toxic substances, including heavy metals. The usual techniques for detecting elements in food are flame atomic absorption spectroscopy (FAAS), graphite furnace atomic absorption spectrometry (GF AAS), hydride generation atomic absorption spectrometry (HG AAS), cold vapour atomic absorption spectrometry (CV AAS), inductively coupled plasma atomic emission spectrometry (ICP AES), inductively coupled plasma mass spectrometry (ICP MS) and neutron activation analysis (NAA). 

Inorganic extractables/leachables would include metals and other trace elements such as silica, sodium, potassium, aluminum, calcium, and zinc associated with glass packaging systems. Analytical techniques for the trace analysis of these elements are well established and include inductively coupled plasma—atomic emission spectroscopy (ICP-AES), ICP-MS, graphite furnace atomic absorption spectroscopy (GFAAS), electron microprobe, and X-ray fluorescence. Applications of these techniques have been reviewed by Jenke. " An example of an extractables study for certain glass containers is presented by Borchert et al. ". ... 

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