Impurities structure

The future holds the promise that GC/MS and LC/ MS experiments (with accurate mass measured MS/ MS fragmentation maps) in combination with LC/ NMR (in spite of its current limitations) will be in routine use for trace level impurity structure elucidation in the pharmaceutical industry. 

The ability of modern analytical chemistry to identify and quantify impurities in pharmaceutical products is staggering. It is now routine to elucidate organic impurity structures below the 0.1 %o level, which has led to an increased ability to detect and identify those chemical entities of potential concern for the safety and efficacy of pharmaceuticals. New developments, such as hybrid MS systems and LC/NMR when fully integrated into the MS-based paradigm, hold the promise of increased efficiency for trace impurity identification with resulting efficiency increases in the overall pharmaceutical development process. 

Low-molecular povidone can be polymerized in 2-propanol and in such case it contains the radical 2-propanol-vinylpyrrolidone adduct (hydroxy-methyl)-butylpyrrolidone as impurity (structure and determination see Section 2.3.3.8). The level of this impurity depends on the average molecular weight. 

Identify impurities (structural elucidation, or comparison to known compounds). 

Impurities, added or unintentional, can have a major effect on rates of nucleation and crystal growth. Table 4-1 shows the effect of an impurity, structurally similar to the crystallizing solute, added to an all-growth crystallization (separation of stereoisomers. Examples 7-6 and 11-6). The data for a continuous stirred tank (CSTR) operation show a sevenfold decrease in the first order growth rate constant as a result of addition of this impurity to prevent nucleation of the undesired isomer. 

Common numerical realizations of the Eq. (1) used in Refs. [12, 15] enable us to calculate the kink structure and dynamics accurate enough to watch the kink pinning and passing through the impurities, structure and properties of the nonlinear waves excited. Yet much higher accuracy is required to study possible resonance effects. So N =10" points were used for approximating the function 0(x,t). Special control of the result errors is carried out. 

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