Determination of the degree of degradation of specific impurity B contained in the substance of the drug «Lomustine» by high-resolution HPLC–MS/MS method

A high-resolution HPLC–MS/MS method was proposed for the study of solutions of standards of specific impurity B contained in the substance of the drug «Lomustine», which is included in the List of Vital Medicines. A characteristic degradation product of specific impurity B, the content and quantity of which is not regulated by the European Pharmacopoeia, has been found.

Unveiling the impurity-modulated photoluminescence from Mn2+-containing metal chalcogenide semiconductor via Fe2+ doping

Doping impurities into Mn2+-doped semiconductors is an important strategy to tune the photophysical properties toward their potential optoelectronic applications. However, the modulation mechanism of Mn2+-related emission affected by specific impurity...

The Synthesis of YNU-5 Zeolite and Its Application to the Catalysis in the Dimethyl Ether-to-Olefin Reaction

During prior investigations of the synthesis of the novel zeolite YNU-5 (YFI), it was found that a very slight amount of an impurity phase contaminated the desired zeolitic phase. This impurity was very often ZSM-5 (MFI). The phase composition was determined to be sensitive to the water in the synthesis mixture, and it was possible to obtain a pure phase and also to intentionally generate a specific impurity phase. In the present work, trials based on the dimethyl ether-to-olefin (DTO) reaction using a fixed-bed downflow reactor were performed to assess the effect of the purity of YNU-5 on its catalytic performance. Dealuminated pure YNU-5 exhibited rapid deactivation due to coking at time on stream (TOS) values exceeding 5 min. Surprisingly, this deactivation was greatly suppressed when the material contained a trace amount of ZSM-5 consisting of nano-sized particles. The formation of ZSM-5 nanoparticles evidently improved the performance of the catalytic system during the DTO reaction. The product distributions obtained from this reaction using highly dealuminated and very pure YNU-5 resembled those generated by 12-ring rather than 8-ring zeolite catalysts. The high selectivity for desirable C3 and C4 olefins during the DTO reaction over YNU-5 is beneficial.

A Simple and Accurate Method for the Determination of Related Substances in Coenzyme Q10 Soft Capsules

As a new dosage form, coenzyme Q10 (Co-Q10) soft capsules are easily absorbed and utilized by the human body. Co-Q10 soft capsules can effectively improve the bioavailability and reduce medical costs for patients. A main concern about Co-Q10 as an active pharmaceutical ingredient (API) is how to control the total quantity of related substances. In this article, according to the degradation pattern of the API, the most easily degradable impurity (impurity X) in the sample was prepared and its chemical structure was determined. Furthermore, a simple and accurate method was developed for the determination of related substances and to avert the interference of excipient ingredients in Co-Q10 soft capsules. The approach was validated adequately and the primary impurity X was confirmed accurately. The limit of total quantity of related substances (less than 1%) could be revised to the level of specific impurity X being no more than 0.5%, in this effective quality control method of Co-Q10 soft capsules. The revised level is suggested to be included in the corresponding standard of the supplement taken from the Pharmacopoeia of the People’s Republic of China (2015 edition). This can provide a feasible method for the relevant enterprises and regulatory authorities to control the related substances of coenzyme Q10 soft capsules.

Study of Point Defect Concentrations During the Fluorinated Oxidation of Silicon

ABSTRACTSome of our most important and quantitative insights on intrinsic point defects have been established as a result of the study of the influence of oxidation on their “excess” concentrations. From study of the growth and shrinkage of oxidation induced stacking faults (OSF) and from oxidation enhanced or retarded diffusion (OED-ORD) the fractional contribution of self-interstitials and vacancies can be assessed. The dominant influence on relatively thin dry or wet oxides is that of the injection of self-interstitials away from the oxidizing interface into the bulk crystal. These self-interstitials have been variously attributed to the incompleteness of oxidation or interracial stress and relaxation at the Si-SiO2 interface. We have studied the role of fluorine additives (ppm) to the dry oxidation process. This paper will discuss similar oxidation-related phenomena (OSF, OED, and ORD), confirming that under our experimental conditions with normally dry oxidation plus fluorine the active point defect injection consists mainly of “excess” vacancies. OSF anneal at lower temperatures than with nitridation processes and with a lower activation energy (1.7 eV). The study of P,B,As, Sb oxidation enhances-retarded diffusions validates the conclusion, with P,B yielding ORD instead of OED and Sb being enhanced rather than retarded as in normal oxidation. Oxidation-induced diffusion experiments not only explored the role of the specific impurity (P,B,As,Sb) but also utilized specimens with four adjacent active regions (bare Si, oxide covered Si, nitride covered Si, and the normal control oxide covered by nitride). The ratios of Ci/Ci* and Cv/Cv* for fluorine addition will be contrasted with those formed by dry oxidation.