Exchangeable cations method

Physico-chemical parameters investigated included pH, electrical conductivity (1 2.5, soilr O), TOM (Walkley-Black Method), and silt and clay content (Stake s method). Exchangeable cations, K, Na, Mg, Ca, Fe and Mn, were determined by extraction with 0.1M BaC and subsequent... 

Thomas, G. W., Exchangeable cations, in Methods of Soil Analysis, Part 2, Chemical and Microbiological properties, ed. A. L. Page, Agronomy Monograph 9, ASA-SSSA, Madison, WI, 1982, pp. 159-165. ASIN 0891180729. 

In soil analysis, the sample pretreatment varies depending on whether a total elemental analysis or an exchangeable cation analysis is required. In the former, a silicate analysis method (see below) is appropriate. In the latter, the soil is shaken with an extractant solution, e.g. 1 M ammonium acetate, ammonium chloride or disodium EDTA. After filtration, the extractant solution is analysed. Fertilizers and crops can be treated as chemical and food samples, respectively. 

Extraction of soils for analysis of die readily available nutrients include replacement of exchangeable cations by salt solutions, dilute acids, and dilute alkalies such as NaHCCh. Fluoride solutions ate employed to repress iron, aluminum, and calcium activity during the extraction of phosphorus. Extraction of the soil solution is effected by displacement in a soil column, often through the application of pressure across a pressure membrane. The soil solution is analyzed by conductance and elemental analysis methods. Also, the total elemental analysis of soils is made by Na2CC>3 fusion of the soil followed by classical geochemical analysis methods. 

Ming, D. W., and Dixon, D. B. (1987). Quantitative determination of clinoptilolite in soils by a cation-exchange capacity method. Clays Clay Min., 35,463-468. 

An ion exchange chromatographic method has been described [16] for the determination of the various forms of vanadium in fresh water. These include tetravalent cationic, pentavalent anionic and neutral complexed forms of vanadium. Separation is achieved on two columns in series involving the absorption of the sample on Chelex 100 and Dowex 1x8 columns followed by the selective elution of the different vanadium species and their assay by neutron activation analysis. Experiments were carried out using vanadium-48... 

The most powerful methods for the study of adsorption mechanism of nitroaromatic compounds on clay minerals have become in situ spectroscopic investigations. Handerlein et al. [152, 153] and Weissmahr et al. [154-156] have investigated the adsorption of NACs particularly on illites, montmorillonites and homoionic kaolinites. The substituted nitrobenzenes on the surface of smectites were investigated by Boyd et al. [157, 158], The main focus in the experimental study of adsorption of NACs on the surface of clay minerals is the influence of the type of clay mineral, the effect of exchangeable cation of the mineral, the effect of the structure and the kind of substituents of NAC compound on the position and orientation of NACs to the surface of mineral, the character of interaction between NACs and the surface of mineral, the adsorption energy. 

The author of this book has been permanently active during his career in the held of materials science, studying diffusion, adsorption, ion exchange, cationic conduction, catalysis and permeation in metals, zeolites, silica, and perovskites. From his experience, the author considers that during the last years, a new held in materials science, that he calls the physical chemistry of materials, which emphasizes the study of materials for chemical, sustainable energy, and pollution abatement applications, has been developed. With regard to this development, the aim of this book is to teach the methods of syntheses and characterization of adsorbents, ion exchangers, cationic conductors, catalysts, and permeable porous and dense materials and their properties and applications. 

Stein reported the separation of choline and acetylcholine by a cation-exchange chromatographic method [198]. Four columns were compared by Salamoun et al. for the separation of choline and acetylcholine by cation exchange liquid chromatography [178]. The mobile phase used was... 

Hendershot, W. H. and M. Duquette. 1986. A simple barium chloride method for determining cation exchange capacity and exchangeable cations. Soil Sci. Soc. Am. J. 50 605-608. 

This rather unexpected result stimulated a number of other investigations, including the present one, with the conclusion that the 4 0 ordering scheme is correct.(13) In addition, the NMR and neutron diffraction data reported in referenced) have been re-interpreted in favor of 4 0 rather than 3 1 order,(14, 15) and it is concluded that the rhombohedral distrotion observed in the neutron pattern is strongly dependent upon the identity of the exchangeable cations. However, in an independent neutron study of Na-A zeolite(16), Adams and Haselden reported no evidence for such a distortion, and conclude that the symmetry must depend subtly upon the method of preparation. 

Another way to get around the problem is complex formation that is, a positively charged complex of the exchanging cation (Mez+) is formed at a pH where the degradation of the clay mineral is avoided. The disadvantage of this method is that the size of the complex is greater than that of the hydrated cations, and they cannot, or can only very slowly, introduce into the interlayer space. As a result, the exchanging cations (Me 1) may get sorbed on the external surfaces. An example of... 

Singh, H., Moorad-Doctor, D., Ratcliffe, R.H., Wachtel, K., Castillo, A., Garcia, G.E. (2007). A rapid cation-exchange HPLC method for detection and quantification of pyridinium oximes in plasma and tissue. J. Anal. Toxicol. 31 69-74. 

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