Atomic absorption spectrometry quantitative analysis

Quantitative analysis Atomic absorption spectrometry is a very accurate and sensitive method for the quantitative determination of metals and metalloids down to absolute amounts as low as picograms for some elements. It cannot be used directly for the determination of nonmetals. 

Mercury vapour in air Diffusive samplers with qualitative onsite colorimetric analysis and quantitative cold vapour atomic absorption spectrometry in the laboratory 59... 

One of the advantages of the isotope dilution technique is that the quantitative recovery of the analytes is not required. Since it is only their isotope ratios that are being measured, it is necessary only to recover sufficient analyte to make an adequate measurement. Therefore, when this technique is used in conjunction with graphite furnace atomic absorption spectrometry, it is possible to determine the efficiency of the preconcentration step. This is particularly important in the analysis of seawater, where the recovery is very difficult to determine by other techniques, since the concentration of the unrecovered analyte is so low. In using this technique, one must assume that isotopic equilibrium has been achieved with the analyte, regardless of the species in which it may exist. 

Only arc/spark, plasma emission, plasma mass spectrometry and X-ray emission spectrometry are suitable techniques for qualitative analysis as in each case the relevant spectral ranges can be scanned and studied simply and quickly. Quantitative methods based on the emission of electromagnetic radiation rely on the direct proportionality between emitted intensity and the concentration of the analyte. The exact nature of the relation is complex and varies with the technique it will be discussed more fully in the appropriate sections. Quantitative measurements by atomic absorption spectrometry depend upon a relation which closely resembles the Beer-Lambert law relating to molecular absorption in solution (p. 357 etal.). 

Atomic Absorption Spectrometry. Principles of Quantitative Analysis... 

Carbon Monoxide. Methods for determining carbon monoxide include detection by conversion to mercury vapor, gas filter correlation spectrometry, TDLAS, and grab sampling followed by gas chromatograph (GC) analysis. The quantitative liberation of mercury vapor from mercury oxide by CO has been used to measure CO (73). The mercury vapor concentration is then measured by flameless atomic absorption spectrometry. A detection limit of 0.1 ppbv was reported for a 30-s response time. Accuracy was reported to be 3% at tropospheric mixing ratios. A commercial instrument providing similar performance is available. 

H. J. Salacinski, P. G. Riby, S. J. Haswell, Coupled flow-injection analysis-flame atomic absorption spectrometry for the quantitative determination of aluminum in beverages and waters incorporating on-line cation exchange, Anal. Chim. Acta, 269 (1992), 1-7. 

The application of atomic absorption spectrometry to quantitative analysis is illustrated in Figure 2.2. The incident radiation at resonance wavelength with intensity /q is focused on the flame containing the atoms in their fundamental state and is transmitted with a reduced intensity I determined by the concentration of the atoms in the flame. The radiation is directed to the detector where the intensity is measured. The quantity of absorbed light is determined by comparing / to /q. 

A second extended function of the liquid column chromatography is to preseparate trace amounts of several substances for subsequent quantitative analysis by a selective determination method such as atomic absorption spectrometry (Table 2.3). Here often only a particular degree of separation is achieved. Non separated elements are to be determined with high-selective methods. In most cases an enrichment is combined with these chromatographic methods (Chap. 4). 

The range of off-line instruments available for water analysis Is wide. In fact, any analyser with optical or electrochemical detection can be adapted for this purpose. The use of liquid chromatography for the detection and quantitation of detergents or non-volatile organic compounds, of atomic absorption spectrometry for the analysis for heavy metal traces and of UV spectrophotometry for the determination of phosphates, nitrates and nitrites are representative examples of the potential utilization of conventional analysers for water analysis. 

Methods for quantitative analysis of Co indude flame and graphite-furnace atomic absorption spectrometry (AAS e.g., Welz and Sperling 1999), inductively coupled plasma emission spectrometry (ICP-AES e.g., Schramel 1994), neutron activation analysis (NAA e.g., Versieck etal. 1978), ion chromatography (e.g., Haerdi 1989), and electrochemical methods such as adsorption differential pulse voltammetry (ADPV e.g., Ostapczuk etal. 1983, Wang 1994). Older photometric methods are described in the literature (e.g.. Burger 1973). For a comparative study of the most commonly employed methods in the analysis of biological materials, see Miller-Ihli and Wolf (1986) and Angerer and Schaller... 

Absorption of UV /VIS radiation Atomic absorption spectrometry Quantitative elemental analysis... 

Atomic absorption spectrometry (AAS) is nowadays one of the most important instrumental techniques for quantitative analysis of metals (and some few metalloids) in various types of samples and matrices. The history of atomic absorption spectrometry dates back to the discovery of dark lines in the continuous emission spectrum of the sun by WoUaston in 1802. The lines are caused by the absorption of the elements in the atmosphere of the sun. His work was taken up and further pursued by Fraunhofer in 1814. In 1860, Kirchhoff and Bunsen demonstrated that the yellow hne emitted by sodium salts when introduced into a flame is identical with the so-caUed D-Hne in the emission spectrum of the sun. However, it took nearly one century before this important discovery was transferred into a viable analytical technique. In 1955, Alan Walsh published the first paper on atomic absorption spectroscopy [4]. At the same time, and independently of Walsh, AUce-made and Wilatz pubhshed the results of their fundamental AAS experiments [5, 6]. But it was the vision of Walsh and his indefatigable efforts that eventually led to the general acceptance and commercialisation of AAS instrumentation in the mid-1960s. Further instrumental achievements, such as the introduction of the graphite furnace and the hydride generation technique, in the second half of the 1960s further promoted the popularity and applicability of the technique. 

Due to its principle and instrumental realisation, atomic absorption spectrometry is a technique for quantitative analysis and is practically unsuitable for qualitative analysis. Quantitative response is governed by the law of Lambert and Beer, i. e. the absorption A is proportional to the optical pathlength I, the absorption coefficient k at the observed wavelength, and the concentration c of the species. 

Spectrophotometric techniques have been the basis of many coal analysis methods. One of the most widely used techniques for analysis of trace elements is atomic absorption spectrometry, in which the standards and samples are aspirated into a flame. A hollow cathode lamp provides a source of radiation that is characteristic of the element of interest and the absorption of characteristic energy by the atoms of a particular element. X-ray fluorescence is also employed as a quantitative technique for trace element determination and depends on election of orbital electrons from atoms of the element when the sample is irradiated by an x-ray source. 

Atomic absorption spectrometry (AAS) is one of the most commonly used instrumental techniques of analysis for the quantitative determination of metals and metalloids particularly in water samples, including those from wastewater, refuse seepage water, sludges and wastes. (See preceding... 

The first quantitative analytical fields to be developed were for quantitative elemental analysis, which revealed how much of each element was present in a sample. These early techniques were not instrumental methods, for the most part, but relied on chemical reactions, physical separations, and weighing of products (gravimetry), titrations (titrimetry or volumetric analysis), or production of colored products with visual estimation of the amount of color produced (colorimetry). Using these methods, it was found, for example, that dry sodium chloride, NaCl, always contained 39.33% Na and 60.67% Cl. The atomic theory was founded on early quantitative results such as this, as were the concept of valence and the determination of atomic weights. Today, quantitative inorganic elemental analysis is performed by atomic absorption spectrometry (AAS), AES of many sorts, inorganic MS (snch as ICP-MS), XRF, ion chromatography (1C), and other techniques discussed in detail in later chapters. 

Nickel release may be analysed by a quantitative but complicated method (Menne and Solgaard 1979 Morgan and Flint 1989 European Committee for Standardization (CEN) 1998b Flint 1998). Items are stored in artificial sweat at 30 °C for 1 week. Analysis of nickel in the solution at the end of the period may be carried out with atomic absorption spectrometry or with inductively coupled plasma detection (ICP). Nickel release of 0.5 pg/cm per week is the limit of the Nickel Directive (Table 5). The majority of nickel-sensitive persons do not react during patch testing to materials with nickel release below this limit (Liden et al. 1996). 

---