Graphite furnace atomic absorption spectroscopy , measurement

A technique is any chemical or physical principle that can be used to study an analyte. Many techniques have been used to determine lead levels. For example, in graphite furnace atomic absorption spectroscopy lead is atomized, and the ability of the free atoms to absorb light is measured thus, both a chemical principle (atomization) and a physical principle (absorption of light) are used in this technique. Chapters 8-13 of this text cover techniques commonly used to analyze samples. 

GPC (total radioactive strontium) = beta gas proportional counter Bq = Becquerel dpm = disintegrations per minute EDTA = ethylenediamine tetraacetic acid GFAAS (total strontium) = graphite furnace atomic absorption spectroscopy ICP-AES (total strontium) = inductively coupled plasma atomic emission spectroscopy ICP-MS (isotopic strontium composition) = inductively coupled plasma-mass spectrometry LSC (isotopic quanitification of 89Srand 90Sr) = liquid scintillation counting pCi = pico curies (10-12 curies) PIXE (total strontium) = proton induced x-ray emission TMAH = tetramethylammonium hydroxide TNA (total strontium) = thermal neutron activation and radiometric measurement TRXF (total strontium) = total-reflection x-ray fluorescence... 

Wet chemical methods involve sophisticated sample preparation and standardization with National Bureau of Standards reference materials but are not difficult for the analytical chemist nor necessarily time consuming (Figure 1). The time from sample preparation to final results for various analytical methods, such as GFAA (graphite furnace atomic absorption), ICP (inductively coupled plasma spectroscopy), ICP-MS (ICP-mass spectrometry), and colorimetry, ranges from 0.5 to 5.0 h, depending on the technique used. Colorimetry is the method of choice because of its extreme accuracy. Typical results of the colorimetric analysis of doped oxides are shown in Tables I and II, which show the accuracy and precision of the measurements. 

The GECE sensors were used for lead determination in real water samples suspected to be contaminated with lead obtained from water suppliers. The same samples were previously measured by three other methods a potentiometric FIA system with a lead ion-selective-electrode as detector (Pb-ISE) graphite furnace atomic absorption spectrophotometry (AAS) inductively coupled plasma spectroscopy (ICP). The results obtained for lead determination are presented in Table 7.1. The accumulation times are given for each measured sample in the case of DPASV. Calibration plots were used to determine the lead concentration. GEC electrode results were compared with each of the above methods by using paired -Test. The results obtained show that the differences between the results of GECE compared to other methods were not significant. The improvement of the reproducibility of the methods is one of the most important issues in the future research of these materials. 

The method to be employed for measurement of the analytical signal largely determines the form of the sub-sample and, consequently, the extent and type of sample preparation required. Nuclear activation methods, x-ray fluorescence techniques, graphite furnace atomic absorption, classical emission spectroscopy and many mass spectrome-... 

Frost, M.R., Harrington, W.L., Downey, D.F., Walther, S.R. (1996) Surface metal contamination during ion implantation comparison of measurements by secondary ion mass spectroscopy, total reflection x-ray fluorescence spectrometry, and vapor phase decomposition used in conjunction with graphite furnace atomic absorption spectrometry and inductively coupled plasma mass spectrometry. Journal of Vacuum Science Technology B Microelectronics and Nanometer Structures, 14, 329— 335. 

Two colorimetric methods are recommended for boron analysis. One is the curcumin method, where the sample is acidified and evaporated after addition of curcumin reagent. A red product called rosocyanine remains it is dissolved in 95 wt % ethanol and measured photometrically. Nitrate concentrations >20 mg/L interfere with this method. Another colorimetric method is based upon the reaction between boron and carminic acid in concentrated sulfuric acid to form a bluish-red or blue product. Boron concentrations can also be deterrnined by atomic absorption spectroscopy with a nitrous oxide—acetjiene flame or graphite furnace. Atomic emission with an argon plasma source can also be used for boron measurement. 

Atomic absorption spectroscopy is an alternative to the colorimetric method. Arsine is stiU generated but is purged into a heated open-end tube furnace or an argon—hydrogen flame for atomi2ation of the arsenic and measurement. Arsenic can also be measured by direct sample injection into the graphite furnace. The detection limit with the air—acetylene flame is too high to be useful for most water analysis. 

The methods of atomic spectroscopy, important in the first decades of the twentieth century, again played a significant role in the 1960s as a result of new inventions (Table 1.3). Development of atomic absorption, in particular with graphite furnace atomization, resulted in new procedures that could measure down to the 10 % level. Somewhat lower concentrations could be determined with generation of volatile compounds, in particular hydrides however, this was restricted to only a few elements. The development of atomization and excitation in... 

In 1955, A. Walsh recognized this and showed how the absorption from the great preponderance of unexcited molecules could be exploited analytically. " Thus, in atomic absorption spectroscopy (AAS) the light from a (usually modulated) source emitting the spectrum of the desired analyte element is passed through a sample atomization cell (such as a flame or graphite tube furnace), a monochromator (to isolate the desired source emission line) and finally into a detector to allow measurement of the change in source line... 

Routinely, dissolved Mo in soil solutions is measured using atomic-absorption spectroscopy (AAS) coupled with a graphite furnace (GF). The GF-AAS method is capable of measuring low concentrations of dissolved Mo in soil solutions (micrograms per liter). However, this method determines the concentration (C) of all possible dissolved Mo species together ... 

The most common analytical procedures for measuring cadmium concentrations in biological samples use the methods of atomic absorption spectroscopy (AAS) and atomic emission spectroscopy (AES). Methods of AAS commonly used for cadmium measurement are flame atomic absorption spectroscopy (FAAS) and graphite furnace (or electrothermal) atomic absorption spectroscopy (GFAAS or ETAAS). A method for the direct determination of cadmium in solid biological matrices by slurry sampling ETAAS has been described (Taylor et al., 2000). 

Wizemann HD and Niemax K (2000) Measurement of Li-7/Li-6 isotope ratios by resonant Doppler-free two-photon diode laser atomic absorption spectroscopy in a low-pressure graphite furnace. Spectrochimica Acta B 55 637-650. 

This method describes the colledion of airborne elemental cadmium and cadmium compounds on 0.8- m mixed cellulose ester membrane filters and their subsequent analysis by either flame atomic absorption spectroscopy (AAS) or flameless atomic absorption spectroscopy using a heated graphite furnace atomizer (AAS-HGA). It is applicable for both TWA and Action Level TWA Permissible Exposure Level (PEL) measurements. The two atomic absorption analytical techniques included in the method do not differentiate between cadmium fume and cadmium dust samples. They also do not differentiate between elemental cadmium and its compounds. 

All analyses of lead were measured by atomic absorption spectroscopy using a Perkin Elmer mod. 5000 instrument equipped with a graphite furnace system mod. 400. 

Besides flame AA and graphite furnace AA, there is a third atomic spectroscopic technique that enjoys widespread use. It is called inductively coupled plasma spectroscopy. Unlike flame AA and graphite furnace AA, the ICP technique measures the emissions from an atomization/ionization/excitation source rather than the absorption of a light beam passing through an atomizer. 

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