Atomic absorption spectrometry, flame performance

Five liquid membrane electrodes (Table 13.3) are now commercially available and have found wide application in the testing of electrolytes in biological and technological systems. All five electrodes perform well in the concentration range over which the Nernstian slope is maintained, i.e., from 10 -10 moldm . These electrodes to a certain extent have replaced in both chemical and clinical laboratories the more traditional instrumental methods of analysis, such as flame photometry and atomic absorption spectrometry. There are, of course, many more liquid membrane electrodes, but the availability of satisfactory solid electrodes has greatly restricted their development and practical application. 

An analyte transport efficiency of nearly 100% has been obtained with an interface for flame atomic absorption spectrometry (FAAS) [3]. It has been used for the determination of lead in blood [5] and for coupHng with a high-performance Hquid chromatograph (HPLC) [6]. 

The following blank-corrected readings were obtained for the determination of nickel in steel, using nickel standards dissolved in iron solution (10 g k ). The determination was performed by atomic absorption spectrometry using an air-acetylene flame and the 232 nm nickel line. 

In an interlab oratory study involving 160 accredited hazardous materials laboratories reported by Kimbrough and Wakakuwa [28], each laboratory performed a mineral acid digestion on five soils spiked with arsenic, cadmium, molybdenum, selenium and thallium. Analysis of extracts was carried out by atomic emission spectrometry, inductively-coupled plasma mass spectrometry, flame atomic absorption spectrometry and hydride generation atomic absorption spectrometry. 

Diemer, J. and Heumann, K.G. (1997) Bromide/bromate speciation by NTI-IDMS and ICP-MS coupled with ion exchange chromatography. Fresenius J. Anal. Chem., 357,74-79. Duan, YX., Wu, M., Jin, Q.H. and Hieftje, G.M. (1995) Vapour generation of nonmetals coupled to microwave plasma-torch mass-spectrometry. Spectrochim. Acta B, 50,355-368. Ebdon, L., Hill, S. and Jones, R (1987) Interface system for directly coupled high performance liquid chromatography-flame atomic absorption spectrometry for trace metal determination./. Anal. At. Spectrom., 2, 205-210. 

Hansen, S.H., Larsen, E.H., Pritzi, G. and Cornett, C. (1992) Separation of seven arsenic compounds by high performance liquid chromatography with on-line detection by hydrogen-argon flame atomic absorption spectrometry and inductively coupled plasma mass spectrometry./. Anal. At. Spectrom., 1, 629-634. 

Basic techniques for speciation analysis are typically composed of a succession of analytical steps, e.g. extraction either with organic solvents (e.g. toluene, dichloromethane) or different acids (e.g. acetic or hydrochloric acid), derivatisa-tion procedures (e.g. hydride generation, Grignard reactions), separation (gas chromatography (GC) or high-performance liquid chromatography (HPLC)), and detection by a wide variety of methods, e.g. atomic absorption spectrometry (AAS), mass spectrometry (MS), flame photometric detection (FPD), electron capture detection (ECD), etc. Each of these steps includes specific sources of error which have to be evaluated. 

The most widely used spectrochemical methods are flame atomic absorption spectrometry (FAAS), electrothermal atomization atomic absorption spectrometry (ETA-AAS), and inductively coupled plasma atomic emission spectrometry (ICP-AES). Some work has been performed using inductively coupled plasma mass spectrometry (ICP-MS) and the unique properties of Hg have allowed the use of cold vapor (CV) A AS. It is beyond the scope of this chapter to describe these well-established and well-accepted spectrochemical techniques. The reader is referred to several excellent texts which describe in detail the basic principles, instrumentation, and method development of these analytical techniques [1-4]. The most toxic elements, such as As, Cd, Cr, Pb, and particularly Hg have been the most widely studied. Other metals, such as Ba, Cu, Fe, Mn, V, and Zn, have also been investigated. 

G. Alsing Pedersen, E. H. Larsen, Speciation of four selenium compounds using high performance liquid chromatography with on-line detection by inductively coupled plasma mass spectrometry or flame atomic absorption spectrometry, Fresenius J. Anal. Chem., 358 (1997), 591-598. 

Clinical measurements of lithium may be performed using atomic absorption spectrometry (AAS) or flame emission spectrometry (FES) 64). AAS is regarded as the more reliable of the two techniques for blood lithium. FES is rather more sensitive, but suffers from interference from the high sodium and potassium concentrations in blood. Recent developments include inductively coupled plasma (ICP) emission spectrometry, electrothermal atomization atomic absorption spectrometry (ETAAS), and spectrofluorimetric methods. Spectrofluorime-try and ETAAS offer greater sensitivity than the traditional methods and are useful research tools 65, 66). 

For the analytical determination of metals (Cd, Cu, Fe, Mn, Pb and Zn) in surface sediments, suspended particulate matter and biological matrices, digestion with a 3 1 HNO3-HCIO4 mixture under controlled temperature was used (36). Analysis of sediments and suspended particulate matter were made by Flame Atomic Absorption Spectrometry (FAAS) with air-acetylene flame and deuterium background correction. The analysis of metals in lichens and molluscs were performed by ICP-AES. The operating conditions for FAAS and Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) analysis are shown in Tables 6.1 and 6.2, respectively. 

Atomic absorption spectrometry with flame (AA-F) or electrothermal atomization furnace (AA-ETA), inductively coupled plasma-emission spectroscopy (ICP-ES), inductively coupled plasma-mass spectrometry (ICP-MS), and high-performance liquid chromatography-mass spectrometry (LC-MS) are state-of-the-art analytical techniques used to measure metals in biological fluids. They are specific and sensitive and provide the cfinical laboratory with the capability to measure a broad array of metals at clinically significant concentrations. For example, ICP-MS is used to measure several metals simultaneously. Photometric assays are also available but require large volumes of sample and have limited analytical performance. Spot tests are also... 

Posta J., Berndt H., Luo S. K. and Schaldach G. (1993) High-performance flow flame atomic absorption spectrometry for automated on-line separation and determination of Cr( III)/Cr(VI) and preconcentration of Cr VI, Anal Chem 65 2590-2595. 

Dithiocarbamate fungicides containing cbfferent metal ions such as Zn, Mn " " and Fe were resolved using a C q column that performed better than the conventional RP-C18 sorbent [123]. However, the method did not allow the speciation of dithiocarbamates that contain no metal. Finally, C q—fullerene was reported to be an effective sorbent material for preconcentrating mercury compounds, and to be preferable to RP-C18 on account of its large specific surface area and volume, which endow it with an increased physical sorption capacity [124]. Also recendy, Pereira et al. [125] developed a new alternative for Cd and Pb determinations at low concentrations, using the preconcentration of a Cjio/CyQ mixture coupled to thermospray flame furnace atomic absorption spectrometry. 

L. Ebdon, S.J. Hill and P. Jones, Speciation of tin in natural waters using coupled high-performance liquid chromatography-flame atomic-absorption spectrometry. Analyst, 110,515,1985. 

The choice of an analytical method depends on its performance characteristics (detection limits, accuracy and precision, speed etc). Other conditions to be reached are the concerned element, the concentration in the sample of interest, the variability of their concentration. The concentration of metal ions in studied Seaside Lakes were determined by flame atomic absorption spectrometry (FAAS) (Chirila et al., 2003a), inductively coupled plasma atomic emission spectrometry (ICP-AES) (Chirila et al., 2002), molecular absorption spectrometry in visible (Chirila and Carazeanu, 2001). These investigations were carried out in the biotope (sediment and water) and biocenosis (different plants and fish) from one ecosystem (Tabacarie Lake) and in water samples from the other Seaside lakes. 

The separation of yttrium from the lanthanides is performed by selective oxidation, reduction, fractionated crystallization, or precipitation, ion-exchange and liquid-liquid extraction. Methods for determination include arc spectrography, flame photometry and atomic absorption spectrometry with the nitrous oxide acetylene flame. The latter method improved the detection limits of yttrium in the air, rocks and other components of the natural environment (Deuber and Heim 1991 Welz and Sperling 1999).Other analytical methods useful for sensitive monitoring of trace amounts of yttrium are X-ray emission spectroscopy, mass spectrometry and neutron activation analysis (NAA) the latter method utilizes the large thermal neutron cross-section of yttrium. For high-sensitivity analysis of yttrium, inductively coupled plasma atomic emission spectroscopy (ICP-AES) is especially recommended for solid samples, and inductively coupled plasma mass spectroscopy (ICP-MS) for liquid samples (Reiman and Caritat 1998). 

Atomic absorption spectrometry (AAS) has been widely used to determine biological materials for aluminium content. Flame techniques, even with the hotter nitrous oxide acetylene flame, do not perform as well as the graphite furnace methods. However, flame atomic absorption methods have been used to analyze brain and cerebrospinal fluid (Krishnan et al., 1972), rat tissues (Mayor et al., 1980), food, urine and feces (Clarkson et al., 1972). heart muscle (Chipperfield et al., 1977), and plasma and tissues (Berlyne et al., 1972 Berlyne et al., 1970 Weinberger et al.. 1972). 

The determination of the different forms (e. g. compounds or complexes) in which an element occurs (often referred to as the speciation of an element and speciation analysis, respectively [28]) is in most cases performed by hyphenated techniques. These are the combination of a high-performance separation technique such as gas or liquid chromatography, or electrophoresis, and an element- or compound-specific detector [29]. While the former provides the separation of the different elemental species prevalent in the sample, the latter brings selective and sensitive detection. In the case of AAS, only the hyphenation with gas and Hquid chromatography, respectively, has gained importance. The combination of atomic absorption spectrometry and electrophoresis has never proven successfiil, obviously due to the incompatibility of the extremely low flow rates of electrophoretic separations with the aspiration volumes of flame atomisers and the difficulties of interfacing the two techniques. 

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