Metals, determination inductively coupled plasma atomic absorption spectrometry

Inductively coupled plasma atomic absorption spectrometry (Sect. 2.55) and neutron activation analysis (Sect. 2.55) have both been applied to the determination of platinum in multi-metal mixtures. 

Analyses for metals in meat and meat products are carried out by atomic spectrometry, generally after dry-ashing and solubilization of the ash in acid. Sodium and potassium, being present at relatively high levels in meats, are determined by atomic emission spectrometry, while other metals, such as cadmium, copper, iron, lead, and zinc, are determined by atomic absorption spectrometry. An alternative method applicable to most metals is inductively coupled plasma atomic emission spectrometry. 

Measurement techniques that can be employed for the determination of trace metals include atomic absorption spectrometry, anodic stripping voltammetry, differential pulse cathodic stripping voltammetry, inductively coupled plasma atomic emission spectrometry, liquid chromatography of the metal chelates with ultraviolet-visible absorption and, more recently, inductively coupled plasma mass spectrometry. 

The determination of chromium is also discussed under Multi-Metal Analysis of Soils in Sect. 2.55 (atomic absorption spectrometry), Sect. 2.55 (inductively coupled plasma atomic emission spectrometry), Sect. 2.55 (emission spectrometry), Sect. 2.55 (photon activation analysis), Sect. 2.55 (neutron activation analysis), and Sect. 2.55 (differential pulse anodic stripping voltammetry). 

The latest study has revealed that CCC has a great potential in the ultratrace determination of metals, because it can concentrate minute amounts of metal prior to the instrumental multielement analysis, such as atomic absorption spectrometry (AAS), inductively coupled plasma-atomic emission spectrometry (ICP-AES), and inductively coupled plasma-mass spectrometry (ICP-MS). 

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. 

An important analysis regarding toxicological and legal requirements of flavourings is the control of heavy metal contaminations. Most of the heavy metals show toxic effects in humans, even in trace quantities. Their determination can only be accomplished using trace analysis techniques. In practice, the different analytical techniques Atomic Absorption Spectrometry (AAS) and Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) have been employed successfully. Both methods require complete dissolution of the sample by decomposition. 

Hence, it is important to have test methods that can determine metals, both at trace levels and at major concentrations. Thus test methods have evolved that are used for the determination of specific metals as well as the multielement methods of determination using techniques such as atomic absorption spectrometry, inductively coupled plasma atomic emission spectrometry, and X-ray fluorescence spectroscopy. 

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. 

Atomic spectrometric techniques such as flame atomic absorption spectrometry (FAAS), electrothermal AAS (ETAAS), inductively coupled plasma atomic emission spectrometry (ICP-AES), and ICP-MS are used for the determination of elements, particularly metals. ICP-MS is the most sensitive, typically with microgram per liter detection limits and multielement capability but it has high start-up and operating costs. UV-visible spectrophotometry is also used for the determination of metal ions and anions such as nitrate and phosphate (usually by selective deriva-tization). It is a low cost and straightforward technique, and portable (handheld) instruments are available for field deployment. Flow injection (FI) provides a highly reproducible means of manipulating solution chemistry in a contamination free environment, and is often used for sample manipulation, e.g., derivatization, dilution, preconcentration and matrix removal, in conjunction with spectrometric detection. Electroanalytical techniques, particularly voltammetry and ion-selective electrodes (ISEs), are... 

If the measurement of individual major ions is required, the metals can readily be determined by atomic absorption spectrometry (AAS) or inductively coupled plasma-atomic emission spectrometry... 

Once the sample is in solution in the acid and the digest made up to a standard volume the determination of metals is completed by standard procedures such as atomic absorption spectrometry or inductively coupled plasma optical emission spectrometry. 

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 determination of trace metal impurities in pharmaceuticals requires a more sensitive methodology. Flame atomic absorption and emission spectroscopy have been the major tools used for this purpose. Metal contaminants such as Pb, Sb, Bi, Ag, Ba, Ni, and Sr have been identified and quantitated by these methods (59,66-68). Specific analysis is necessary for the detection of the presence of palladium in semisynthetic penicillins, where it is used as a catalyst (57), and for silicon in streptomycin (69). Furnace atomic absorption may find a significant role in the determination of known impurities, due to higher sensitivity (Table 2). Atomic absorption is used to detect quantities of known toxic substances in the blood, such as lead (70-72). If the exact impurities are not known, qualitative as well as quantitative analysis is required, and a general multielemental method such as ICP spectrometry with a rapid-scanning monochromator may be utilized. Inductively coupled plasma atomic emission spectroscopy may also be used in the analysis of biological fluids in order to detect contamination by environmental metals such as mercury (73), and to test serum and tissues for the presence of aluminum, lead, cadmium, nickel, and other trace metals (74-77). 

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. 

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. 

If the reference materials are pure substances and can be specified on the microscopic level, then they represent the unit amount of substance. Because there are no absolute pure substances the representation is in all cases an approximation. The degree of approximation is given by the accuracy of the contents of the main component. In case of pure elements, e.g. metals Fe, Cu, Zn the determination of the main component by coulometry is limited by an uncertainty of 0.01%. The determination of all impurities needs completeness and requires a great deal of analytical equipment. However, a combination of inductively coupled plasma-mass spectrometry (ICP-MS), atomic absorption spectrometry (AAS) and isotope dilution mass spectrometry (ID-MS) covering all elements of the periodic table allows a decrease of total uncertainty to 0.0032% (Cu, see Fig. 8). 

Colloid concentrations in the eluent were determined with a Bio-Tek multichannel (optical densitometer with fiber-optics technology Bio-Tek Instruments, Winooski, VT) microplate reader, precalibrated with known concentrations of each colloid at 540 nm. Total metal concentration in the eluents was allocated to solution phase and colloidal phase (colloid-bound contaminant). The eluent samples were centrifuged for 30 min at 3500 rpm (x 2750 g) to separate the soluble contaminant fraction from the colloid-bound contaminant fraction. The absence of colloidal material in the supernatant solution was verified by filtration through a 0.2-pm membrane filter. The soluble metal (Cu, Zn, Pb) fractions were analyzed by atomic absorption (concentrations >0.5 mg/H) or inductively coupled plasma (ICP) spectrometry (concentrations <0.5 mg/H). The colloid fraction was extracted with 1 M HNO3-HCI [32] solution and analyzed with the same methodology used for the soluble fraction. The results for the duplicate soil monoliths and for the two soils were combined for practical purposes, because the reproducibility between soil monoliths was within 15%. 

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