Total elements determination

The possibility of contaminating the sample with the elements under investigation during the various steps is a major risk in trace analysis. The precautions required in order to minimize this problem are similar to those already identified when dealing with biological materials used for total element determinations. Heydom Ver-sieck et al. Stoeppler Behne and Aitio et al. have diam ed the extent... 

The addition of anticoagulents and/or preservatives, a practice that may be tolerated for total element determination, should be avoided for two reasons. First, the compounds used are usually complexing agents. They therefore could bind various trace elements. Second, they could destroy some species. For example, the addition of potassium dichromate to urine in the presence of nitric acid could destroy methylmercury If the use of such compounds is unavoidable, then there should be experimental evidence to show that the speciation of the element imder study has not been adversely affected. 

Metal concentrations are determined using molecular spectrophotometric, atomic spectrometric, and electrochemical techniques. All of these require samples to be homogenous, or at least to contain the smallest possible amounts of organic matter that could interfere with the metal determination by interacting with the metal ions and the analytical reagents. Traditionally, decomposition of the sample in elemental analysis requires it to be mineralized in order to remove the organic content.1 Sample decomposition for total element determination therefore appears to be the recommended procedure on every occasion. 

These analytical problems regarding total element determination in human milk are magnified in milk speciation analysis as this requires a series of carefully planned steps of which chemical and/or physical pretreatments of the sample are almost always mandatory. In this context, both sampling and sample preparation... 

In principle, the applications of ICP-MS resemble those listed for OES. This technique however is required for samples containing sub-part per billion concentrations of elements. Quantitative information of nonmetals such as P, S, I, B, Br can be obtained. Since atomic mass spectra are much simpler and easier to interpret compared to optical emission spectra, ICP-MS affords superior resolution in the determination of rare earth elements. It is widely used for the control of high-purity materials in semiconductor and electronics industries. The applications also cover the analysis of clinical samples, the use of stable isotopes for metabolic studies, and the determination of radioactive and transuranic elements. In addition to outstanding analytical features for one or a few elements, this technique provides quantitative information on more than 70 elements present from low part-per-trillion to part-per-million concentration range in a single run and within less than 3 min (after sample preparation and calibration). Comprehensive reviews on ICP-MS applications in total element determinations are available. " ... 

Before performing the voltammetric/polaro-graphic determination, in some cases the analyte must be separated from the matrix and from other interfering components, and converted into a measurable form. For total element determinations, sample digestion is normally required. To separate organic analytes from the matrix, extraction methods and chromatographic separation are mainly used. 

Many of the matrix interference problems found in total element determinations are ehminated because of the chromatographic step. Thus, important interferences in speciation studies originate either from Ar-based molecular ions like Ar2 or °Ar 0, or matrix-based ions, like 02. 

Cost Calculation. The main elements determining production cost are identical for fine chemicals and commodities (see Economic evaluation), a breakdown of production cost is given in Table 2. In multipurpose plants, where different fine chemicals occupying the equipment to different extents are produced during the year, a fair allocation of costs is a more difficult task. The allocation of the product-related costs, such as raw material and utiHties, is relatively easy. It is much more difficult to allocate for capital cost, labor, and maintenance. A simplistic approach is to define a daily rent by dividing the total yearly fixed cost of the plant by the number of production days. But that approach penalizes the simple products using only part of the equipment. 

Releases to Air. In April 1989, you conducted stack tests to determine air releases from the battery facility. The release data provided baseline data for a proposed 1990 air emission reduction program. The tests were performed using EPA Reference Method 12, which determines exhaust concentrations as total elemental lead, and EPA Reference Methods 1-4, which determine total exhaust volumes. Releases from all stacks and vents at the facility were measured, including those from the following release points ... 

In characterizing layered silicate, including layered titanate (HTO), the surface charge density is particularly important because it determines the interlayer structure of the intercalants as well as the cation exchange capacity (CEC). Lagaly proposed a method of calculation consisting of total elemental analysis and the dimensions of the unit cell [15] ... 

ABSTRACT The results of a soil geochemical survey of the Canadian Maritime provinces and the northeast states of the United States are described. The data presented are for the <2-mm fraction of the surface layer (0-5 cm depth) and C horizons of the soil. Elemental determinations were made by ICP-MS following two digestions, aqua regia (partial dissolution) and a strong 4-acid mixture (near-total dissolution). The preliminary results show that Hg and Pb exhibit elevated abundances in the surface layer, while As and Ni exhibit abundances that can be attributed to the geological provenance of the soil parent materials. 

Holmes, L.J., Robinson, V. J., Makinson, P. R. and Livens, F. R. (1995). Multi-element determination in complex matrices by inductively coupled plasma-mass spectrometry (ICP-MS). Science of the Total Environment 173 345-350. 

Available commercial instrumentation for the determination of the following total element is discussed below ... 

Acid-digestion is often used with composts derived from municipal wastes, sewage and slurry, where toxic amounts of heavy metals may cause problems on the land to which they are applied. It is probably more convenient to determine total elements in soils by a benchtop X-ray fluorescence spectroscopy (XRF) instrument. This only requires the soil to be ground, and several reference standards of a similar soil. A Reference Materials Catalogue, Issue 5, 1999, is available from LGCs Office of Reference Materials, Queens Road, Teddington, Middlesex TW11 OLY, UK. Tel. -i-44 (0)20 8943 7565 Fax h-44 (0)20 8943 7554. 

An on line dialysis flow system coupled to ICP-MS (VG Plasma Quad PQII, Thermo Elemental, Winsford, Chaeshire, UK) has been employed to determine trace elements in serum samples by IDMS. Isotope dilution was performed on samples incubated with enriched 65Cu, 66Zn, 77Se and 206Pb for 24 h at 36 °C prior to dialysis to quantify total element concentrations.60... 

It has been generally accepted for several years that the determination of total element concentrations in environmental samples does not give an accurate estimation of their potential environmental and biological impact. About 1/3 of all ICP-MS applications in environmental analytical chemistry... 

Of a total of 23 objects for which comparative analyses for different parts are available, seven are matching in all reliable elements determined... 

The method used for correcting the other elements for matrix variations was proposed by Sweatman et al. (4). Total mass absorption was determined by measuring the attenuation of the radiation in question by a thin layer of the sample to be analyzed. The mass absorption coefficient M was calculated by M = A/W (In Cs/Cx) where A = area of sample (cm2), W = weight of sample (g), Cs = intensity of the standard (counts/sec), and Cx = intensity of the standard (counts/sec) attenuated by the thin layer coal elements determined. Using these coefficients, a corrected value was obtained for the elements determined, even when matrix variations were considerable. Great care was taken to press the coals to a uniform thickness so that the mass absorption coefficient was affected only by density (for which compensation was made) and matrix considerations. 

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