Elemental analysis, drinking water samples

Elemental Analysis. The elemental analyses are presented in Table IV. The atomic ratios H/C for all drinking water samples (nos. 1-10) were between 1.28 and 1.39. These values were comparable to humic acid derived from lake sediments. However, H/C ratios were much lower when compared to the chlorinated model humic substances (e.g., 1.04-1.08 for CFH-1 and CFH-2). Bromine was present in almost negligible quantities, whereas Cl varied between 0.3 and 2.4, and S varied between 0.9 and 2.7 in the drinking water organic matter. All fractions from drinking water showed similar elemental composition. However, they differed from the elemental composition of the CFH samples in all respects, especially in chlorine content. 

Quantitative analysis by ICP-MS is usually done with external calibration standards and the addition of internal standards to all standards and samples. When a large number of elements across the periodic table are to be determined, it is usual to add Li, Y, In, Tb, and Bi and measure the ions Li, " In, Tb, and ° Bi as internal standards (unless you need to measure one of these elements as an analyte). Not all of the internal standard elements are used to quantitate every analyte. The internal standard that is most closely matched in first ionization potential to the analyte is generally used, since this will compensate for ionization interferences in matrices containing easily ionized elements such as Na. Results obtained using this approach are generally very accurate and precise. Table 10.23 presents typical spike recovery and precision data for ICP-MS determination of 25 elements in a certified reference material (CRM) Trace Elements In Drinking Water from High-Purity Standards, Charleston, SC. 

The determination of elements by atomic absorption in drinking water at the mg/l level or the recording of a mid-infrared spectrum of a pure organic compound are situations rarely encountered. In these cases, the sample is easily prepared. However, these conditions and similarly those under which analyses made by students in a teaching laboratory are not representative of the difficulties encountered when preparing a real sample for analysis. 

The ICP-AES instruments may have different configurations with the torch, which may be positioned either horizontally (axial ICP) or vertically (radial ICP). Because of the longer sample residence time in the axial ICP torch, the axial ICP-AES instruments are more sensitive than the radial ones. The state-of-the-art axial ICP-AES instruments (also called the trace ICP) have the high sensitivity that is required for trace element analysis of drinking water. 

ICP-MS is very promising in the area of environmental studies. Many elements can be determined directly in drinking water. In waste water analysis sample decomposition by treatment with HNO3-H2O2 is often required and the most frequent isobaric interferences have been described [559]. For seawater analysis, the salt contents makes sample pretreatment necessary, which can be done by chelate extraction. Beauchemin et al. [560] obtained a preconcentration of a factor of 50 by sorption of the trace elements onto an SiC>2 column treated with 8-hydroxyquino-line and determined Ni, Cu, Zn, Mo, Cd, Pb and U in seawater. In river water Na, Mg, K, Ca, Al, V, Cr, Mn, Cu, Zn, Sr, Mo, Sb, Ba and U could be determined directly and Co, Ni, Cd and Pb after the above mentioned preconcentration procedure. For As, preconcentration by evaporation of the sample was sufficient. Isotope dilution delivers the highest accuracy [561] and the procedure has been applied to... 

In the field of the determination of environmental samples, one has a wide spectrum of different sample-matrices air and dust, water (drinking water, surface water, waste water etc.), soils, sediments, sludges, plants, animals and their organs. Due to the mostly higher concentrations of relevant elements - dependent of course on the sample material - one can be able to determine more relevant trace and mineral elements by plasma emission spectrometry. Again, it is impossible to discuss here all the possibilities. Therefore some selected examples from the practice of environmental analysis will be given ... 

ETAAS is a very suitable method for analysis of natural waters especially with low total dissolved solids (river, drinking water). About 20 elements may be determined in such samples and after preconcentration the number of elements increases to about 30. In waters with high total solid content (marine, estuarine waters) directly about ten to 12 elements are determined. Of course after appropriate chemical treatment and preconcentration their number increases significantly. 

Environmental applications of ICP-MS are numerous, and include analysis of water, wastewater, soil, sediment, air particulates, and so on. A typical environmental analysis is to determine the leachable metals from soil or sediment the sohd is not dissolved but leached or extracted to determine labile elements. These labile or leachable elements are the ones that might be mobilized from a landfill into a drinking water supply, for example. Figure 10.39 gives an example of determining leachable metals from an NIST Standard Reference Material (SRM) soil sample by ICP-MS. 

AAS are complementary to plasma emission spectrometry. The latter enables determination of a large number of elements per sample, but is more expensive than flame AAS in terms of instrumentation, and less sensitive than furnace AAS. For analysis of drinking water, furnace AAS is very useful, but because of its single-element character, it is increasingly being replaced by plasma mass spectrometry, especially in large laboratories. 

A characteristic example of the performance of IC/ICP-OES is the spedation of chromium [190,191]. Due to it widespread use in industrial applications such as chromium plating, dye manufacturing, and preservation of wood and leather materials, chromium concentrations in environmental samples are monitored on a routine basis. Both the US EPA and the European Union have specified maximum admissible chromium concentrations in their respective drinking water directives. As with many other trace elements, chromium (Cr) is typically found in more than one chemical form, each of which with different chemical properties and behavior, such as bioavailability and toxicity. The spedation analysis of chromium is a challenging task, since the stability of different chromium species is easily affected by conditions during sample collection and treatment. For... 

It means they can now detennine the vast majority of the environmentally significant elements/species by one technique. This capability is very attractive because it means they can typically analyze 5-10 times more samples per day, for a full suite of elements, compared to other approaches that use a combination of flame atomic absorption (FAA), GFAA, CVAA (cold vapor AA for Hg), and ICP-OES. This productivity improvement is exemplified in Table 19.2, which compares the productivity of a drinking water analysis for 12 primary contaminants using three different analytical scenarios. " ... 

ICP-MS is very promising in the area of environmental studies. Many elements can be determined directly in drinking water. In waste water analysis, sample decomposition by treatment with HNO3/H2O2 is often required, and the most fre-... 

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