Applications inorganic cations

Examples of the application of ion-exchange chromatography to the analysis of (a) inorganic anions, (b) inorganic cations, (c) antifreeze, and (d) vitamins. (Chromatograms courtesy of Alltech Associates, Inc. Deerfield, IL). 

Since the early 1990s an increasing number of papers has been devoted to the application of CE for the analysis of both inorganic cations [906-915] and low-molecular-mass anions [915-922]. Standard CE methods have been developed and validated for determining inorganic anions (e.g. chloride, sulfate and nitrate), small carboxylic acids and metal ions that all have limited or no UV absorbance. In those situations, short UV wavelengths (190 nm) or indirect UV detection should be used. Such methods might be extended to metallic... 

Zeolites have increasingly found applications as catalysts, adsorbents and ion exchangers [1]. Their microporous properties of the inorganic host-guest systems are based primarily on the structure of the tetrahedral framework built from the TO4 tetrahedral and the possible variation of T atoms (Si, Al, P, Zr, Sn, Ti, 621, B, etc.). The guest species such as organic and/or inorganic cations fill the pore space of the framework to achieve electroneutrality. 

Adsorptive stripping voitammetry has also been applied to the determination of a variety of inorganic cations at very low concentrations. In these applications, the cations are generally complexed with surface active complexing agents, such as dimethylglyoxime, catechol, and bipyridine. Detection limits in the 10 to 10 " M range have been reported. 

Many inorganic cations and anions catalyze indicator reactions—that is, reactions whose rates are readily measured by instmmental methods, such as absorption spectrophotometry, fluorescence spectrometry, or electrochemistry. Conditions are then employed such that the rate is proportional to the concentration of catalyst, and, from the rate data, the concentration of catalyst is determined. Such catalytic methods often allow extremely sensitive detection of the catalyst concentration. Kinetic methods based on catalysis by inorganic analytes are widely applicable. For example, the literature in this area lists more than 40 cations and 15 anions that have been determined by a variety of indicator reactions. Table 29-3 gives catalytic methods for several inorganic species along with the indicator reactions used, the method of detection, and the detection limit. 

Thus, the mechanism of the supporting influence of cationic surfactants on microflotation and flotation can be different. In microflotation the electrostatic barrier can be decreased, in flotation the contact angle can be increased. Naturally, both effects manifest themselves simultaneously. Li Somasundaran (1990, 1992) observed a bubble recharge due to adsorption of multivalent inorganic cations. Thus, their application is recommended in order to increase the contact angle and to stabilise bubble-particle aggregates. Naturally, selective adsorption of multivalent ions at the water-air interface is important. But even in the absence of adsorption selectivity under equilibrium conditions a deviation from equilibrium can happen due to the increase of adsorption within the r.s.c. This is important for the precalculation of increase of the contact angle caused by cation adsorption. 

Experiment 33. Determination of inorganic cations by CE (Adapted with permission, from Dionex Application Note 91)... 

Applications to organic and inorganic substances will be discussed in separate sections. Organic applications will be discussed first since many organic compounds are used to form fluorescent chelates with inorganic cations. The applications will be restricted primarily to fluorescence, which has more analytical uses than phosphorescence at the present time. 

Elektorowicz and Hakimipour (2001,2003a) presented a technology that permitted the simultaneous removal of heavy metals and PAHs from natural soil called Simultaneous Electrokinetic Removal of Inorganic and Organic Pollutants (SEKRIOP). This technology used EDTA for metal mobility and zwitterionic surfactants for hydrocarbon mobility. Furthermore, the application of cationic reactive membranes permitted capturing free metallic ions generated by electrokinetic phenomena before their precipitation in the cathode area. The capture of metal-EDTA complexes was done on anionic reactive membranes. 

---