Acid-base buffer systems

There are compatibility issues for chromatographic methods and NMR. Protic solvents such as water or methanol are usually replaced with deuterated solvents although solvent suppression algorithms can be used with shallow gradient methods. Organic modifiers such as ion-pair reagents must be avoided, and mineral acid based buffer systems are preferred (the opposite of the LC-MS situation).34... 

Diagrammatic representation of the production of stomach acid. Carbon dioxide from metabolic processes is converted to carbonic acid under the influence of carbonic anhydrase. Carbonic acid and sodium chloride dissociate, hydrogen ion is actively pumped across the parietal cell membrane and associates with free chloride ion. The remaining sodium and bicarbonate ions combine and remain in the plasma to be utilized in the acid-base buffering system. 

Despite general acceptance of the catalytic mechanism, the order of the microscopic steps through which the acid-base catalysis occurs remains arguable. An acid-base buffer system, with or without zinc ion, that promotes the chemical catalysis of cyclization and cleavage of phosphodiester bonds provides some insight into the mechanism. In this nonenzymatic system, acidic imidazolium (Im+) ion initiates the conversion to a pentacoordinate phosphorane intermediate then the basic imidazole (Im) catalyzes the decomposition of this intermediate to a... 

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