A simple isocratic reversed phase high performance liquid chromatography was used to separate three impurities present in the sample of 8-chlorotheophylline. LC-MS was used for the characterization of impurities. Based on mass spectral data, the structures of these impurities were characterized as 3,7-dihydro-1,3-dimethyl-1H-purine-2,6-dione (impurity I), 3,7-dihydro-1,3,7-trimethyl-1H-purine-2...

We calculate the plasmon dispersion in quasi-one-dimensional quantum wires, in the presence of non-magnetic impurities, taking into consideration the memory function formalism and the role of the forward scattering. The plasma frequency is reduced by the presence of impurities. We also calculate, analytically, the plasmon dispersion in the Born approximation, for the scattering of the electrons...

To be administered to patients, therapeutic monoclonal antibodies must have very high purity, with process related impurities like host-cell proteins (HCPs) and DNA reduced to <100 ppm and <10 ppb, respectively, relative to desired product. Traditionally, Protein-A chromatography as a capture step has been the work horse for clearing a large proportion of these impurities. However, remaining le...

Impurity profiling of seized methamphetamine can provide very useful information in criminal investigations and, specifically, on drug trafficking routes, sources of supply, and relationships between seizures. Particularly important is the identification of "route specific" impurities or those which indicate the synthetic method used for manufacture in illicit laboratories. Previous researchers...

The electrochemical properties of graphene are highly sensitive to residual metallic impurities that persist despite various purification efforts. To accurately evaluate the electrochemical performance of graphene, highly purified materials free of metallic impurities are required. In this study, the partial purification of chemically reduced graphene oxides prepared via Hummers (CRGO-HU) and S...

Operando UV/Vis spectroscopy with on-line mass spectrometry was used to study the effect of different types of impurities on the hydrocarbon pool species and the activity of H-SAPO-34 as a methanol-to-olefins (MTO) catalyst. Successive reaction cycles with different purity feedstocks were studied, with an intermittent regeneration step. The combined study of two distinct impurity types (i.e., f...

Atomic impurities are critical for many technologies. They are used to engineer the optical and electronic properties of semiconductors for applications such as transistors, solar cells, lightemitting diodes (LEDs), and lasers, as well as to store energy for applications such as batteries and electrochemical cells. While the characterization and understanding of impurities in bulk semiconductor...

Gas purity is a key factor in optimizr ing excirner and carbon dioxide laser performance. Gas impurities in these laser systems degrade beam profiles, reduce output powers, and shorten laser lifetimes. Much has already been done to reduce impurities-cleaner supply gases are now available, and laser systems are being conshucted of materials that produce significantly lower amounts of gas impurit...

The degradation products of Cefepime dihydrochloride that emerged throughout stress stability studies have been determined, identified and characterized. The two new impurities were detected by gradient reverse-phase high performance liquid chromatography (HPLC), and Impurity-I was formed in the range from 0.2 to 11.0% and Impurity-II range from 0.2 to 3.5%. These impurities have been identifie...

We study how quenched impurities affect the surface diffusion and ordering of strongly interacting adsorbate atoms on surfaces. To this end, we carry out Monte Carlo simulations for a lattice-gas model of O/W~110!, including small concentrations of immobile impurities which block their adsorption sites. We examine the behavior of the diffusion coefficients and order parameters as a function of ...