Ion chromatographic characterization of toxic solutions: analysis and ion chemistry of biological liquids.

The literature on the analysis of biological fluids by ion chromatography is reviewed herein. It has been demonstrated that ion chromatography is the method of choice for the determination of anions such as chloride, nitrite, bromide, phosphate, nitrate, sulfate, oxalate, thiocyanate, thiosulfate, citrate, isocitrate, carbonate, and similar species. Cations such as sodium, ammonium, potassium, magnesium, and calcium in various biological solutions have also been successfully identified and quantified. The technique fulfils several requirements of a reliable microanalytical method by providing sufficient speed, automation, case of use, and accuracy. For many types of analyses, very little or even no sample preparation is required. Because of this, as presented in this review, ion chromatography is widely used not only to obtain reliable clinical data, but also to study ion chemistry. It has been an invaluable tool in nephrolithiasis and dental research. This review should provide a useful reference for analysts and researchers involved in clinical studies. The review is presented in four sections: (1) introduction, (2) methods of analysis, (3) ion chemistry and (4) critical comments and concluding remarks. Section 1, as usual, deals with the general introduction of the subject and objectives. Section 2 includes the review of the literature on ion chromatography (IC) methods developed for routine analysis of various analytes present in biological fluids. Section 3 deals with the applications of IC used in the understanding of ion chemistry of biological fluids. Specifically, it deals with the physical chemistry aspects related to nephrolithiasis and dental research, such as speciation, driving force for crystals formation and crystallization, and pathophysiology. Section 4 contains critical comments and concluding remarks.

Physical chemical studies of calcium oxalate crystallization.

The physical chemical approach to the investigation of the calcium oxalate (CaOx) crystallization and urolith formation is the systematic examination of the various aspects of mineral precipitation and growth in pure solution, in the presence of individual urinary components, and in whole urine media. Recent experimental studies have indicated that while small urinary ions such as citrate, magnesium, and phosphocitrate retard the mineralization rate of CaOx, urinary macromolecules may act either as inhibitors of growth or promoters of nucleation. Some CaOx mineralization inhibitors have also been found to influence the growth mechanism of the phase and its flocculation properties. Therefore, urinary macromolecules that are adsorbed on the mineralizing crystals and incorporated into the developing stone may play a significant role in urolithiasis.

The dual role of polyelectrolytes and proteins as mineralization promoters and inhibitors of calcium oxalate monohydrate.

Polyelectrolytes and protein molecules appear to be able to act not only as crystallization inhibitors when present in solution, but also as promoters of crystal growth when immobilized onto surfaces. Because this is especially relevant for systems in which heterogeneous nucleation can occur, the influence of poly-L-glutamic (PGlu) acid, poly-L-aspartic (PAsp) acid, and human serum albumin (HSA) on the nucleation and growth inhibition of calcium oxalate monohydrate (COM) was studied using the Constant Composition (CC) kinetics technique. The overgrowth of COM on hydroxyapatite (HAP) seed crystals pretreated with HSA was also investigated. Pronounced differences in inhibiting and nucleating potential were found for the various additives. HSA, a relatively poor growth inhibitor when present in solution, was found to nucleate very regular, hexagonal COM crystals when immobilized on a surface and to enhance the overgrowth of COM when adsorbed on HAP surfaces.

The influence of urinary macromolecules on calcium oxalate monohydrate crystal growth.

The Constant Composition (CC) kinetics method has been used for studying the mineralization of calcium oxalate monohydrate (COM) at sustained supersaturations in the presence of pre-bladder urine and macromolecules isolated from normal urine and kidney and bladder stones. The method is especially sensitive for investigating the inhibitory activities of these urinary macromolecular components (UMMC) and matrix macromolecular components (MMMC) with a coefficient of variation in growth rate of approximately 2%. Significant COM mineral inhibition was observed in a wide molecular weight region of urine components. Urine removed directly from the kidney showed appreciable inhibitory activity towards COM crystallization. Normal urinary proteins and the dissolved precipitate resulting from urine centrifugation were fractionated by gel filtration. The resulting solutions were mostly COM mineralization inhibitors. Electrodialysis was utilized to isolate the MMMC (greater than 7000 d) of renal and bladder calculi. While these solutions inhibited COM crystallization, they were also found to be calcium binders as measured by the calcium electrode.