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Search Results: 1 - 10 of 316550 matches for " Nahla N. Salama and Shudong Wang "
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Quantitative Mass spectrometric Analysis of Ropivacaine and Bupivacaine in Authentic, Pharmaceutical and Spiked Human Plasma without Chromatographic Separation
Nahla N. Salama and Shudong Wang
Analytical Chemistry Insights , 2012,
Abstract: The present study employs time of flight mass spectrometry for quantitative analysis of the local anesthetic drugs ropivacaine and bupivacaine in authentic, pharmaceutical and spiked human plasma as well as in the presence of their impurities 2,6-dimethylaniline and alkaline degradation product. The method is based on time of flight electron spray ionization mass spectrometry technique without preliminary chromatographic separation and makes use of bupivacaine as internal standard for ropivacaine, which is used as internal standard for bupivacaine. A linear relationship between drug concentrations and the peak intensity ratio of ions of the analyzed substances is established. The method is linear from 23.8 to 2380.0 ng mL-1 for both drugs. The correlation coefficient was ≥0.996 in authentic and spiked human plasma. The average percentage recoveries in the ranges of 95.39%–102.75% was obtained. The method is accurate (% RE < 5%) and reproducible with intra- and inter-assay precision (RSD% < 8.0%). The quantification limit is 23.8 ng mL-1 for both drugs. The method is not only highly sensitive and selective, but also simple and effective for determination or identification of both drugs in authentic and biological fluids. The method can be applied in purity testing, quality control and stability monitoring for the studied drugs.
Quantitative Mass spectrometric Analysis of Ropivacaine and Bupivacaine in Authentic, Pharmaceutical and Spiked Human Plasma without Chromatographic Separation
Nahla N. Salama,Shudong Wang
Analytical Chemistry Insights , 2009,
Abstract: The present study employs time of flight mass spectrometry for quantitative analysis of the local anesthetic drugs ropivacaine and bupivacaine in authentic, pharmaceutical and spiked human plasma as well as in the presence of their impurities 2,6-dimethylaniline and alkaline degradation product. The method is based on time of flight electron spray ionization mass spectrometry technique without preliminary chromatographic separation and makes use of bupivacaine as internal standard for ropivacaine, which is used as internal standard for bupivacaine. A linear relationship between drug concentrations and the peak intensity ratio of ions of the analyzed substances is established. The method is linear from 23.8 to 2380.0 ng mL-1 for both drugs. The correlation coefficient was ≥0.996 in authentic and spiked human plasma. The average percentage recoveries in the ranges of 95.39%–102.75% was obtained. The method is accurate (% RE < 5%) and reproducible with intra- and inter-assay precision (RSD% < 8.0%). The quantification limit is 23.8 ng mL-1 for both drugs. The method is not only highly sensitive and selective, but also simple and effective for determination or identification of both drugs in authentic and biological fluids. The method can be applied in purity testing, quality control and stability monitoring for the studied drugs.
Micelle Enhanced Fluorimetric and Thin Layer Chromatography Densitometric Methods for the Determination of (±) Citalopram and its S – Enantiomer Escitalopram
Elham A. Taha, Nahla N. Salama and Shudong Wang
Analytical Chemistry Insights , 2012,
Abstract: Two sensitive and validated methods were developed for determination of a racemic mixture citalopram and its enantiomer S-(+) escitalopram. The first method was based on direct measurement of the intrinsic fluorescence of escitalopram using sodium dodecyl sulfate as micelle enhancer. This was further applied to determine escitalopram in spiked human plasma, as well as in the presence of common and co-administerated drugs. The second method was TLC densitometric based on various chiral selectors was investigated. The optimum TLC conditions were found to be sensitive and selective for identification and quantitative determination of enantiomeric purity of escitalopram in drug substance and drug products. The method can be useful to investigate adulteration of pure isomer with the cheap racemic form.
Micelle Enhanced Fluorimetric and Thin Layer Chromatography Densitometric Methods for the Determination of (±) Citalopram and its S – Enantiomer Escitalopram
Elham A. Taha,Nahla N. Salama,Shudong Wang
Analytical Chemistry Insights , 2009,
Abstract:
Thermoanalytical Investigation of Some Sulfone-Containing Drugs
Nahla N. Salama,Mohammed A. El Ries,Safaa Toubar,Maha Abd El Hamid,Mohammed I. Walash
Journal of Analytical Methods in Chemistry , 2012, DOI: 10.1155/2012/439082
Abstract: The thermal behavior of some sulfone-containing drugs, namely, dapsone (DDS), dimethylsulfone (MSM), and topiramate (TOP) in drug substances, and products were investigated using different thermal techniques. These include thermogravimetry (TGA), derivative thermogravimetry (DTG), differential thermal analysis (DTA), and differential scanning calorimetry (DSC). The thermogravimetric data allowed the determination of the kinetic parameters: activation energy (Ea), frequency factor (A), and reaction order (n). The thermal degradation of dapsone and topiramate was followed a first-order kinetic behavior. The calculated data evidenced a zero-order kinetic for dimethylsulfone. The relative thermal stabilities of the studied drugs have been evaluated and follow the order DDS > TOP > MSM. The purity was determined using DSC for the studied compounds, in drug substances and products. The results were in agreement with the recommended pharmacopoeia and manufacturer methods. DSC curves obtained from the tablets suggest compatibility between the drugs, excipients and/or coformulated drugs. The fragmentation pathway of dapsone with mass spectrometry was taken as example, to correlate the thermal decomposition with the resulted MS-EI. The decomposition modes were investigated, and the possible fragmentation pathways were suggested by mass spectrometry. 1. Introduction Dapsone (DDS) It is antibacterial drug used in the treatment of Mycobacterium leprae infection (leprosy), and malaria [1, 2]. It is official in BP and USP [3, 4]: Dimethyl Sulfone (MSM) It is used as anti-inflammatory agent [5, 6] and in combination with glucosamine and chondroitin to treat or prevent osteoarthritis [7, 8]: Topiramate (TOP) It is antiepileptic drug [9]. It is official in USP [4]: Different analytical methods were reported for the assay of DDS in dosage forms and in biological fluids, including spectroscopy [10–21], electrochemical methods [22, 23], and chromatography [24–28]. In literature two GC methods were reported for determination of dimethyl sulfone [29, 30]. Topiramate has no ultraviolet, visible, or fluorescence absorption, and available methods for analysis of the drug in biological fluids and pharmaceutical dosage formulation consisted of gas chromatography (GC) coupled with flame ionization (FID) or nitrogen phosphorous detection (NPD) [31–33] and fluorescence polarization immunoassay [34]. HPLC methods, including ionic chromatography, or using refractive index (RI), chemiluminescent nitrogen, or MS detector are described [35–37]. Analysis of the drug in human plasma
A Novel Analytical Method for Structural Characteristics of Gene Networks and its Application  [PDF]
Shudong Wang, Yuanyuan Zhang, Kaikai Li, Dazhi Meng
Computational Molecular Bioscience (CMB) , 2012, DOI: 10.4236/cmb.2012.23009
Abstract: Analyzing gene network structure is an important way to discover and understand some unknown relevant functions and regulatory mechanisms of organism at the molecular level. In this work, mutual information networks and Boolean logic networks are constructed using the methods of reverse modeling based on gene expression profiles in lung tissues with and without cancer. The comparison of these network structures shows that average degree, the proportion of non-isolated nodes, average betweenness and average coreness can distinguish the networks corresponding to the lung tissues with and without cancer. According to the difference of degree, betweenness and coreness of each gene in these networks, nine structural key genes are obtained. Seven of them which are related to lung cancer are supported by literatures. The remaining two genes AKT1 and RBL may have important roles in the formation, development and metastasis of lung cancer. Furthermore, the contrast of these logic networks suggests that the distributions of logic types are obviously different. The structural differences can help us to understand the mechanism of formation and development of lung cancer.
Stability-indicating methods for the determination of sertaconazole nitrate by micelle-enhanced spectrofluorimetry and TLC-densitometry
Nahla Nour El-Din Ahmed Salama,Afaf Osman Mohamed
Bulletin of the Chemical Society of Ethiopia , 2009,
Abstract: Two sensitive and selective stability indicating methods were developed for the determination of sertaconazole nitrate (Ser-NO3), in the presence of its acid, alkaline and oxidative degradation products. The first method was based on measuring the fluorescence intensity of the drug at λex/λem = 231 nm/312 nm. The influence of micelle medium on the fluorescence emission was studied. The nonionic surfactant of Triton X 100 showed strong sensitizing effect for the fluorescence. The fluorescence intensity plot was linear over concentrations 0.5 5 μg mL-1 with mean percentage recoveries 100.59 plus or minus 1.49 %. The second method was based on TLC separation of the drug from its degradation products followed by densitometric measurement of the intact drug spot at 302 nm. The developing system used for separation was chloroform acetone 33 % ammonia (14:2:0.1 v/v/v). The linear range was 1 8 μg/spot with mean percentage recoveries 100.07 plus or minus 1.97 %. The methods were validated according to ICH guidelines. Statistical analysis of the results revealed high accuracy and good precision. The suggested procedures could be used for the determination of sertaconazole nitrate in drug substance and drug products as well as in presence of its degradation products.
The Structure of Background-error Covariance in a Four-dimensional Variational Data Assimilation System: Single-point Experiment

Juanjuan Liu,Bin Wang,Shudong Wang,

大气科学进展 , 2010,
Abstract: A four dimensional variational data assimilation (4DVar) based on a dimension-reduced projection (DRP-4DVar) has been developed as a hybrid of the 4DVar and Ensemble Kalman filter (EnKF) concepts. Its good flow-dependent features are demonstrated in single-point experiments through comparisons with adjoint-based 4DVar and three-dimensional variational data (3DVar) assimilations using the fifth-generation Pennsylvania State University-National Center for Atmospheric Research Mesoscale Model (MM5). The results reveal that DRP-4DVar can reasonably generate a background error covariance matrix (simply B-matrix) during the assimilation window from an initial estimation using a number of initial condition dependent historical forecast samples. In contrast, flow-dependence in the B-matrix of MM5 4DVar is barely detectable. It is argued that use of diagonal estimation in the B-matrix of the MM5 4DVar method at the initial time leads to this failure. The experiments also show that the increments produced by DRP-4DVar are anisotropic and no longer symmetric with respect to observation location due to the effects of the weather trends captured in its B-matrix. This differs from the MM5 3DVar which does not consider the influence of heterogeneous forcing on the correlation structure of the B-matrix, a condition that is realistic for many situations. Thus, the MM5 3DVar assimilation could only present an isotropic and homogeneous structure in its increments.
A modified surgical technique in the management of eyelid burns: a case series
Haiying Liu, Kun Wang, Qigang Wang, Shudong Sun, Youxin Ji
Journal of Medical Case Reports , 2011, DOI: 10.1186/1752-1947-5-373
Abstract: We present the cases of eight patients, two Chinese women and six Chinese men. The first Chinese woman was 36 years old, with 70% body surface area second or third degree flame burn injuries involving her eyelids on both sides. The other Chinese woman was 28 years old, with sulfuric acid burns on her face and third degree burn on her eyelids. The six Chinese men were aged 21, 31, 38, 42, 44, and 55 years, respectively. The 38-year-old patient was transferred from the ER with 80% body surface area second or third degree flame burn injuries and third degree burn injuries to his eyelids. The other five men were all patients with flame burn injuries, with 7% to 10% body surface area third degree burns and eyelids involved. All patients were treated with a modified surgical procedure consisting of separation and loosening of the musculus orbicularis oculi between tarsal plate and septum orbital, followed by grafting a large full-thickness skin graft in three days after burn injury. The use of our modified surgical procedure resulted in 100% successful eyelid grafting on first attempt, and all our patients were in good condition at six-month follow-up.This new surgical technique is highly successful in treating eyelid burn injuries, especially flame burn injuries of the eyelid.Eyelid involvement is common in facial burns. Treatment of eyelid burn injuries requires great care for the protection of the cornea. Burns damage tissues primarily by denaturing and coagulating cellular proteins and through vascular ischemic damage [1]. The most common etiologic agents of eyelid burns include local thermal and chemical burns and systemic burns [1,2]. Patients with burns involving the face often also have burns to the eyelids. Approximately 15% to 20% of patients with facial burns exhibit ocular injury. Most eyelid burns are the result of exposure to fire. In developing countries, 80% of chemical burns were due to industrial and/or occupational exposure. Approximately 60% of eyelid
Coupling catalytic hydrolysis and oxidation for CS2 removal

WANG Li,WU Diyong,WANG Shudong,YUAN Quan,

环境科学学报(英文版) , 2008,
Abstract: CS2 removal was Obtained by coupling catalytic hyidation on bi-functional catalyst.On the hydrolysis active sites,CS2 is hydrolyzed to H2S,while on the oxidation active sites,H2S is oxidized to elemental S or sulfuric acid deposited on the porous support.The above process can be expressed as follows:CS2→H2O COS →H2O H2S→O2 S/SO2- 4.H2S oxidation eliminates its prohibition on CS2 hydrolysis so that the rate of coupling removal CS2 is 5 times higher than that of CS2 hydrolysis.The same active energy of hydrolysis and coupling reaction also indicates that H2S oxidation does not change the reaction mechanism of CS2 hydrolysis.Temperature has obvious effect on the process while the mole ratio of O2 concentration to CS2 concentration (O/S) does not,especially in excess of 2.5.The formation of sulfuric acid on the catalyst surface poisons hydrolysis active sites and causes the decrease of left OH-1 concentration on the catalysts surface.Lower temperature is suggested for this bi-functional catalyst owing to the low yield ratio of S/SO4 2-.
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