NMR Spectrometric Analysis of Antazoline

An analytical method is described for the analysis of antazoline [2-(N-benzylanilinomethyl) imidazoline] using pmr. The procedure provides good quantitative results together with a very specific mean for identification of antazoline     

Carbon and proton magnetic resonance studies on the sites of Mn2+ and Ni2+ ion binding with thiamin and thiamin pyrophosphate and on the solution conformation of the coenzyme

Carbon magnetic resonance was employed to determine the Mn²⁺ and Ni²⁺ binding sites on thiamin and thiamin pyrophosphate and to help elucidate the solution conformation of the latter with Mn²⁺. In comparison with previous proton magnetic resonance studies, the results here presented elucidate direct binding to thiamin even without the presence of the pyrophosphate. In thiamin Mn²⁺ is bound to both the pyrimidine ring and to the oxygen of the β-hydroxyethyl chain, albeit more weakly to the former, Ni²⁺, on the other hand is indicated in binding to the pyrimidine ring only. From observation of water relaxation data, potentiometric determination of the pyrimidinium pK_a with metal ions added and carbon magnetic resonance (competition of thiamin and thiamin pyrophosphate for Mn²⁺) we have very strong evidence to indicate that Mn²⁺ is separated from the pyrimidine ring by a solvent molecule. We were able to estimate association constant between the pyrimidine and Mn²⁺ (50 M^?1) and OH and Mn²⁺ (100 M^?1) in thiamin.In thiamin pyrophosphate both Mn²⁺ and Ni²⁺ much prefer the pyrophosphate as binding sites and at least in the former an inner sphere complex is indicated. Also with Mn²⁺ present the dimethylene pyrophosphate is folded back onto the thiazolium ring according to analysis of proton broadening data and relaxation mechanisms.     

PMR Spectrometric Analysis of Chloramphenicol in Pharmaceutical Preparations

A new method is developed using PMR for the assay of chloramphenicol and its pharmaceutical forms. The method is rapid, accurate, precise and helps in confirming the identity and purity of the drug. The principle of the method involves comparing the integral of the well-defined doublet system of chloramphenicol spectrum (positioned at 7.6 δ and 7.5 δ) to that of the sharp singlet (positioned at 6.25 δ) of maleic acid which is used as internal standard.     

Proton Magnetic Resonance Studies of Binary Aqueous Solvent - Dowex 50W Systems

Abstract

Pmr is used to evaluate solvent selectivity and to furnish an indication of water structure in binary aqueous solvent - ion exchange resin systems. The hydrogen form of Dowex 50W-X8 equilibrated with binary aqueous solvents exhibits pmr peaks for internal water which are shifted downfield relative to the water - ion exchanger system. The greater the mole fraction of organic solvent in the system, the greater the downfield shift.