Atomic spectrometry techniques based

Routine inorganic elemental analysis is carried out nowadays mainly by atomic spectrometric techniques based on the measurement of the energy of photons. The most frequently used photons for analytical atomic spectrometry extend from the ultraviolet (UV 190-390 nm) to the visible (Vis 390-750 nm) regions. Here the analyte must be in the form of atoms in the gas phase so that the photons interact easily with valence electrons. It is worth noting that techniques based on the measurement of X-rays emitted after excitation of the sample with X-rays i.e. X-ray fluorescence, XRF) or with energetic electrons (electron-probe X-ray micro-analysis, EPXMA) yield elemental information directly from solid samples, but they will not be explained here instead, they will be briefly treated in Section 1.5. 

In terms of this group of atomic spectrometric techniques, optical emission spectrometry (OES) is the oldest and most established. Atomic absorption spectrometry (A AS) and atomic fluorescence spectrometry (AES) are two other important types of atomic spectrometry techniques. In this section, AAS and AES will be discnssed only briefly elemental analysis based on ICP spectrometry will be discnssed in more detail, specifically ICP-OES... 

Figure 1.5 Schematics of basic components of analytical techniques based on atomic optical spectrometry, (a) Atomic absorption spectrometry (b) atomic fluorescence spectrometry (c) atomic emission spectrometry.

This section starts with a discussion of selectivity for the most extended analytical atomic techniques based on optical spectrometry. Then, aspects such as detection limits (DLs), linear ranges, precision, versatility and sample throughput will be presented. The section ends with a brief comparison of the... 

Spectrometric techniques based on atomic absorption or the emission of radiation flame atomic absorption spectrometry (FAAS), electrothermal atomic absorption spectrometry (ETAAS), inductively coupled plasma-optical emission spectrometry (ICP-OES), inductively coupled plasma-mass spectrometry (ICP-MS), and cold vapor (CV)/hydride generation (HG), mainly for trace and ultratrace metal determinations. 

The most suitable techniques for the rapid, accurate determination of the elemental content of foods are based on analytical atomic spectrometry, for example, atomic absorption spectrometry (AAS), atomic emission spectrometry (AES), and mass spectrometry, the most popular modes of which are Game (F), electrothermal atomization (ET), and hydride generation (HG) AAS, inductively coupled plasma (ICP), microwave-induced plasma (MIP), direct current plasma (DCP) AES, and ICP-MS. Challenges in the determination of elements in food include a wide range of concentrations, ranging from ng/g to percent levels, in an almost endless combination of analytes with matrix speci be matrices. 

Four techniques based on mass spectrometry are widely used for multi-elemental trace analysis of inorganic compounds in a wide range of sample types. These techniques are thermal ionization (TI), spark source (SS), glow discharge (GD) and inductively coupled plasma (ICP) mass spectrometry. In these techniques, atomization and ionization of the analysed sample are accomplished by volatilization from a heated surface, attack by electrical discharge, rare-gas ion sputtering and vaporization in a hot flame produced by inductive coupling. 

The number of applications of atomic techniques based on solid or slurry sampling is so large that only a comparatively minute fraction is discussed in this section. Interested readers are referred to the biannual reviews of Analytical Chemistry and the atomic spectroscopy update in the Journal of Analytical Atomic Spectrometry, among other sources, for more extensive information. A specific review of the uses of graphite atomizers modified with high-melting carbides has been published by Volynsky that includes virtually all metals determined in this manner [74]. 

Liquid chromatography (LC) has already been described and is an excellent separation technique for compounds that are nonvolatile, thermally unstable and relatively polar in nature. The usual detectors for LC are based on refractive index, conductivity, amperometry, light scattering, UV and fluorescence, all of which have been discussed in Section 3.2. However, sometimes it is desirable to have a more powerful detector attached to an LC instrument and, as such, the following combinations are possible LC-infrared spectrometry, LC-atomic spectrometry, LC-inductively coupled plasma-mass spectrometry, LC-mass spectrometry, LC-UV-mass spectrometry, LC-nuclear magnetic resonance and even LC-nuclear magnetic resonance-mass spectrometry. 

Atomic absorption, plasma atomic emission, and atomic fluorescence spectrometry are all optical atomic spectrometric techniques developed rapidly during the past years. These methods are based on the measurement of absorption, emission, or fluorescence originated from the free, unionized atoms or atomic ions in gas phase. 

The best-known technique based on a combination of methods is ICP-MS. Here, the excited atoms are introduced upon their return to a lower energy level, through an interface into the ion source of a quadru-pole of a mass spectrometer. The ICP thus acts as an ion source and the mass spectrometer as the ion detector. The latest development in atomic spectrometry is the electrothermal evaporation-ICP-MS technique, where a graphite furnace is coupled to an ICP-MS. In this case, use is made of the most remarkable property of a graphite furnace (elimination of matrix interferences) by a graphite tube atomizer and subsequent transport of the atomic phase into the plasma and quadrupole. 

A variety of other techniques based on the reaction of ionizing agents with sample molecules are readily available to the mass spectrometrist. EAB and secondary ion mass spectrometry (SIMS) are used to analyze nonvolatile solids and use respectively energetic atoms and ions to achieve sputtering of the sample including ionization. Laser and PI and ED/EI are also well-established techniques. Inorganic materials may be ionized by arc discharge. 

Atomic spectrometry The use of modem analytical techniques based on atomic absorption and emission spectrometry provides accurate and precise quantitative determination of inorganic species in paints. 

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