Dissolution techniques

Because of the risk of lead poisoning, the exposure of children to lead-based paint is a significant public health concern. The first step in the quantitative analysis of lead in dried paint chips is to dissolve the sample. Corl evaluated several dissolution techniques. " In this study, samples of paint were collected and pulverized with a Pyrex mortar and pestle. Replicate portions of the powdered paint were then taken for analysis. Results for an unknown paint sample and for a standard reference material, in which dissolution was accomplished by a 4-6-h digestion with HNO3 on a hot plate, are shown in the following table. 

Totland M, Jarvis 1, Jarvis KE (1992) An assessment of dissolution techniques for the analysis of geological samples by plasma spectrometry. Chem Geol 95 35-62... 

The book focuses on the biogeochemistry of trace elements in arid and semiarid zone soils and includes an introductory chapter on the nature and properties of arid zone soils. It presents an updated overview and a comprehensive coverage of the major aspects of trace elements and heavy metals that are of most concern in the world s arid and semi-arid soils. These include the content and distribution of trace elements in arid soils, their solution chemistry, their solid-phase chemistry, selective sequential dissolution techniques for trace elements in arid soils, the bioavailability of trace elements, and the pollution and remediation of contaminated arid soils. A comprehensive and focused case study on transfer fluxes of trace elements in Israeli arid and semi-arid soils is presented. The book concludes with a discussion of a quantitative global perspective on anthropogenic interferences in the natural trace elements distributions. The elements discussed in this book include Cd, Cu, Cr, Ni, Pb, Zn, Hg, As, Se, Co, B, Mo and others. This book is an excellent reference for students and professionals in the environmental, ecological, agricultural and geological sciences. 

Despite these shortcomings, common to any chemical extraction procedure, sequential dissolution techniques still furnish more useful information on metal binding, mobility and availability than can be obtained with only a single extractant. 

The following sections summarize the studies on the dissolution technique for the carbonate fraction from arid and semi-arid soils with different amounts and types of carbonate minerals. In addition, the selectivity and effectivity of the NaOAc-HOAc extraction technique at varying pHs to extract the carbonate phase, and only the carbonate phase, from soils is examined (Han and Banin, 1995). 

Figure 4.1. Removal of carbonate from Israeli arid soils as indicated by the X-ray diffractograms after extraction of the carbonate fraction by NaOAc-HOAc solutions at various pHs for 16 hours. C calcite d = 3.04 A, and D dolomite, d = 2.89 A. Number 1, 2, 3, 4, 5, and 6 indicate non-treated soil (No. 1), treatments (No. 2-6) with NaOAc-HOAc solutions at pH 7.0, 6.0, 5.5, 5.0 and 4.0, respectively (after Han and Banin, 1995. Reprinted from Commun Soil Sci Plant Anal, 26, Han and Banin A., Selective sequential dissolution techniques for trace metals in arid-zone soils The carbonate dissolution step, p 563, Copyright (1995), with permission from Taylor Francis US)...

Figure 4.2. Dissolution of Ca from Israeli arid soils by NaOAc-HOAc solutions at various pHs after the extraction of the exchangeable fraction (after Han and Banin, 1995. Reprinted from Commun Soil Sci Plant Anal, 26, Han and Banin A., Selective sequential dissolution techniques for trace metals in arid-zone soils The carbonate dissolution step, p 568, Copyright (1995), with permission from Taylor Francis US)...

Han F.X., Banin A. Selective sequential dissolution techniques for trace metals in arid-zone soils The carbonate dissolution step, Commun Soil Sci Plant Anal 1995 26 ... 

Reverz, R. and Hasty, E. (1987) Recovery study using an elevated pressure temperature microwave dissolution technique. Paper presented at the Pittsberg Conference and Exposition on Analytical Chemistry and Applied Spectroscopy, March 1987. 

Acebal, S.G. Mijovilovich, A. Rueda, E.H. Aguirre, M.E. Saragovi, C. (2000) Iron-oxide mineralogy of a mollisol from Argentina A study by selective-dissolution techniques, X-ray diffraction, and Mossbauer spectroscopy. Clays Clay Min. 48 322-330 Adams, W.A. Kassim, J.K. (1984) Iron oxy-hydroxides in soils developed from lower palaeozoic sedimentary rocks in mid-Wales and implications for some pedogenetic processes. J. Soil Sd. 35 117-126... 

The amount of bonded surfactant can be determined by simple techniques. A dissolution technique proved to be very convenient for the optimization of non-reactive surface treatment and also for the characterization of the efficiency of the treating technology [74,84]. First the surface of the filler is covered with increasing amounts of surfactant, then the non-bonded part is dissolved with a solvent. The technique is demonstrated in Fig. 11, which presents a dissolution curve of stearic acid on a CaC03 filler. Surface treatment is preferably carried out with the proportionally bonded surfactant (cioo)j this composition the total amount of surfactant used for the treatment is bonded to the filler surface. The filler can adsorb more surfactant (Cjnax)>but during compounding a part of it can be removed from the surface by dissolution or simply by shear and might deteriorate properties. 

Johansson ME, Nicklasson N. Investigation of the film formation of magnesium stearate by applying a flow-through dissolution technique. J Pharm Pharmacol 1986 38 51-54. 

Using dissolution techniques, it was observed that the 10 and 25% 6F-PAI (ODA-based) could be co-dissolved with PBI using DMAc. Solution blends with PBI-PAI ratios ranging from 20/80 to 80/20, in 20% increments, were visually homogeneous and contained no insoluble materials. At 15-20% solids concentration, these blends were processible and showed no sign of polymer precipitation for at least 24 h. Transparent, apparently miscible, blend films were cast from the solution blends of PBI and 10% 6F-PAI. 

The ash is placed in a 100 ml Teflon beaker, containing 5 ml of HF (cone.) and 15 ml of HN03 (cone.). Dissolve the ash by warming, then evaporate just to dryness. Add water and 1 ml of HN03 to dissolve the salts and transfer to a 100 ml volumetric flask. Make to volume with water and mix. Immediately transfer to a plastic bottle and preserve as a stock solution for determining elements which do not require a specialized dissolution technique. 

The Determination of Selenium. The most difficult trace element to determine in coal by wet chemical methods is selenium. Two alternative dissolution techniques can be used—H. L. Rooks combustion method (7) and the oxygen bomb combustion method (4). Also, two alternative analytical methods can be used—the hydride evolution method (5) and the graphite furnace method. 

Siliceous materials—Si, Al, Fe, Ti, Ca, Mg, Na, K, Mn, Ni, Ba, Ag, Au, Ca, Cr, Cu, Ga, In, Mo, Sb and Zn—may be analyzed by a lithium tetraborate fusionr-acid dissolution technique using atomic absorption spectroscopy. Mercury, tin, and lead volatilize by this technique, and gold and silver in concentrations above 0.5 wt% cannot be held in solution. Coal ash is preconcentrated prior to analysis, and there is possible silica interference. Analytical results, where possible, are compared statistically with other reported values. 

Chemical dissolution techniques indicate kaolinite from Cornwall contains 3.1-4.9% of easily soluble Si02 and 1.5-5.9% of easily soluble A1203 (Follett et al., 1965). Most of this material is presumably present as amorphous material. Experiments (by the senior author) with Georgia kaolinite indicate the amount of amorphous material varies as a function of particle size and preparation (Table LX). Amorphous silica and alumina is a common constituent of kaolinite and considerable care must be taken in determining and interpreting the significance of the Si/Al ratio of kaolinites. 

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