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31.
Validation of chromatographic methods: evaluation of detection and quantification limits in the determination of impurities in omeprazole 总被引:1,自引:0,他引:1
To guarantee that an analytical procedure gives reliable, exact and interpretable information about a sample, it must be validated. Two ambiguous parameters are detection limit and quantification limit. The determination of these limits is still of great concern and there are still a variety of procedures described in the current literature. The fundamental objective of the present work is to apply the different recommendations suggested by official guidelines for the quantitative determination of omeprazole and its impurities (omeprazole sulphone and 5-hydroxy-omeprazole) in capsules and tablets using high performance liquid chromatography with UV detection. The importance of calibration linearity in the context of the quantification limit is considered, since one of the approaches, the estimated concentrations of this limit, are deduced from the regression line. The values of the detection limit and the quantification limit obtained show that, in chromatographic analyses, the best method is that based on the use of the parameters obtained from the analytical curve, which are statistically reliable. It was shown that smaller values of the detection limit and the quantification limit were obtained by the visual approach and by the method using the signal-to-noise ratio. However, these values may reflect a subjective evaluation, prone to error and large variations. This was confirmed by showing that these methods result in values that fall outside the linear range of the method. 相似文献
32.
Takehiko Yamato Carol Pérez-Casas Shofiur Rahman Zeng Xi Mark R. J. Elsegood Carl Redshaw 《Journal of inclusion phenomena and macrocyclic chemistry》2007,58(1-2):193-197
A novel receptor possessing two complexation sites and bearing 1,3-alternate conformation based on thiacalix[4]arene, confirmed by single crystal X-ray analysis, was prepared. The tetrathiacalix[4]arene
diamide shows strong intramolecular hydrogen bonding. The binding behavior towards K+ and halides has been examined by 1H NMR titration experiments. 相似文献
33.
Misra M Banerjee A Davé RN Venanzi CA 《Journal of chemical information and modeling》2005,45(3):610-623
This paper describes a novel clustering methodology for classifying over 700 conformations of a flexible analogue of GBR 12909, a dopamine reuptake inhibitor that has completed phase I clinical trials as a treatment for cocaine abuse. The major aspect of the clustering methodology includes an efficient data-conditioning scheme where a systematic feature extraction procedure based on the structural properties of the molecule was used to reduce the associated feature space. This allowed region-specific clustering that focused on individual pharmacophore elements of the molecule. For clustering of the reduced feature set, the fuzzy clustering partitional method was utilized. Due to the relational nature of the feature data, fuzzy relational clustering was employed, and it successfully detected natural groups defined by rotational minima around N(sp(3))-C(sp(3)), O(sp(3))-C(sp(3)), and C(sp(3))-C(sp(2)) bonds. The proposed clustering methodology also employed several cluster validity measures, which corroborated the partitions produced by the clustering technique and agreed with the results of hierarchical clustering using the XCluster program. Representative structures which exhibited a reasonable spread of energies and showed good spatial coverage of the conformational space were identified for use as putative bioactive conformations in a future Comparative Molecular Field Analysis of GBR 12909 analogues. The clustering methodology developed here is capable of handling other computational chemistry problems, and the feature extraction technique can be easily generalized to other molecules. 相似文献
34.
A straightforward, high-yielding procedure has been developed for the manufacture of substituted vinylphenols from 2- and 4-hydroxybenzaldehydes utilising classical Knoevenagel condensation reaction conditions. 相似文献
35.
David A. Hall Donnis M. Berry Carol J. Schneider 《Journal of Electroanalytical Chemistry》1977,80(1):155-170
The electrochemical behavior of cephalothin has been studied by a.c. and d.c. polarography, cyclic voltammetry, and coulometry in both aqueous and nonaqueous media in order to gain a greater understanding of the reaction pathways involved in cephalosporin reduction. The reductive allylic cleavage of the 3′-acetoxy function has been found to produce Δ3-deacetoxy and 3-exomethylene cephalothin compounds (geometric isomers) and stereochemical isomers of the 3′-exomethylene compound at the 4-position. The ratio of these compounds to one another is dependent on the experimental conditions used, with adsorption playing an important role. The reductive allylic cleavage of the S1?C2 bond is a competitive reaction pathway. Δ3-Deacetoxy cephalothin may undergo further reduction, depending on the electrolysis potential selected. 相似文献
36.
37.
Objective: We have shown that High-Intensity Focused Ultrasound (HIFU) can effectively control bleeding from injuries to solid organs such as liver, spleen, and lung. Achievement of hemostasis was augmented when a homogenate of tissue and blood was formed. The objective of this study was to investigate quantitatively the effect of homogenate production on HIFU application time for hemostasis. Possible mechanisms involved in homogenate production were also studied.Methods: Ten anesthetized rabbits had laparotomy and liver exposure. Liver incisions, 15-25 mm long and 3-4 mm deep, were made followed immediately by HIFU application. Two electrical powers of 80 and 100 W corresponding to focal acoustic intensities of 2264 and 2829 W/cm2, respectively were used. Tissue and homogenate temperatures were measured. Smear and histological tissue sample analysis using light microscopy were performed.Results: In treatments with homogenate formation, hemostasis was achieved in 76 ± 1.3 s (Mean ± Standard Error Mean: SEM) at 80 W. In treatments without homogenate formation (at 80 W), hemostasis was achieved in 106 ± 0.87 s. At 100 W, hemostasis was achieved in 46 ± 0.3 s. The time required for homogenate formation, at 80 and 100 W were 60 ± 2.5 and 23 ± 0.3 s, respectively. The homogenate temperature was 83 °C (SEM 0.6 °C), and the non-homogenate tissue temperature at the treatment site was 60 °C (SEM 0.4 °C). The smear and histological analysis showed significant blood components and cellular debris in the homogenate, with some intact cells.Conclusion: The HIFU-induced homogenate of blood and tissue resulted in a statistically significant shorter HIFU application time for hemostasis. The incisions with homogenate had higher temperatures as compared to incisions without homogenate. Further studies of the correlation between homogenate formation and temperature must be done, as well as studies on the long-term effects of homogenate in achieving hemostasis. 相似文献
38.
McGowan RS Nittrouer S Manning CJ 《The Journal of the Acoustical Society of America》2004,115(2):871-884
Beginning at the age of about 14 months, eight children who lived in a rhotic dialect region of the United States were recorded approximately every 2 months interacting with their parents. All were recorded until at least the age of 26 months, and some until the age of 31 months. Acoustic analyses of speech samples indicated that these young children acquired [inverted r] production ability at different ages for [inverted r]'s in different syllable positions. The children, as a group, had started to produce postvocalic and syllabic [inverted r] in an adult-like manner by the end of the recording sessions, but were not yet showing evidence of having acquired prevocalic [inverted r]. Articulatory limitations of young children are posited as a cause for the difference in development of [inverted r] according to syllable position. Specifically, it is speculated that adult-like prevocalic [inverted r] production requires two lingual constrictions: one in the mouth, and the other in the pharynx, while postvocalic and syllabic [inverted r] requires only one oral constriction. Two lingual constrictions could be difficult for young children to produce. 相似文献
39.
The rust fungus Puccinia spegazzinii (Basidiomycotina: Uredinales) has been identified as a potential classical biological control agent for the invasive weed Mikania micrantha (Asteraceae). Long-term, live storage of this pathogen is required for reference. As biotrophs, almost all rusts species cannot be preserved by traditional cryopreservation protocols, which rely on in vitro culture techniques. In addition, the embedded teliospores and delicate basidiospores of this microcyclic rust are not amenable to direct plunge freezing. Continuous culture of the rust on living plants is both laborious and expensive, so a variety of approaches for cryopreservation and storage were tested. These methods included traditional approaches to fungal cryopreservation such as variation of cooling rate regime and alginate encapsulation techniques. However, an in situ cryopreservation technique was the only method identified as having any potential for the long-term cryopreservation of the 10 isolates tested. Material from either petiole or stem tissue remained viable after cryopreservation, determined by the ability of the material to produce basidiospores. However, despite great progress being made in developing an optimal cryopreservation method, infection of the host plant by basidiospores produced from previously cryopreserved teliospores, embedded in leaf petioles, was not achieved. 相似文献
40.
Deep-ultraviolet resonance Raman (DUVRR) spectra is sensitive to secondary structural motifs but, similar to circular dichroism (CD) and infrared spectroscopy, requires the application of multivariate and advanced statistical analysis methods to resolve the pure secondary structure Raman spectra (PSSRS) for determination of secondary structure composition. Secondary structure motifs are selectively enhanced by different excitation wavelengths, a characteristic that inspired the first methods for quantifying secondary structures by DUVRR. This review traces the evolution of multivariate methods and their application to secondary structure composition analyses of proteins by DUVRR spectroscopy from the first experiments using two-wavelengths, and culminating with recent studies utilizing time-resolved DUVRR measurements. 相似文献