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Search Results: 1 - 10 of 198512 matches for " Nahla N. Salama "
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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
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.
An Approach to a Universal System of Units  [PDF]
Salama Abdelhady
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2010, DOI: 10.4236/jemaa.2010.29071
Abstract: According to many scientists, there are some redundancies in the SI system of units. Through an entropy approach that depends on a previous analogy between the electrical, mechanical and thermal fields; it was possible to introduce a system of units that removes such redundancies. According to the second law of thermodynamics, the temperature was defined as a quality of heat. Following a proved analogy, the electrical and magnetic potentials may represent also the qualities of electric and magnetic fluxes. According to published experimental results, the electric and the magnetic potentials generates also electromotive forces, EMF, that were measured by Al-Fe thermocouples. The chemical potential or the concentration gradient generates also an EMF, as in the concentration cells, which is measured here by the same Al-Fe thermocouple. Such measurement-results are introduced to define a unique scale for measuring the potentials or qualities of the thermal, chemical, electric, and magnetic fields. The mentioned qualities are not defined by directly measurable quantities, as length and time, but they are found as functions of dimensionless concentrations of mass or energy fluxes. Hence, the volt, as a unit of the introduced EMF scale for potentials measurement, is postulated as a dimensionless unit. Finally, a universal system of units that is based only on three dimensions; L, T, and E, and four fundamental units; meter, second, Joule and volt is introduced in this paper to delete the SI redundancies. The energy replaces the mass as a fundamental unit in the introduced US as it plays a dominant role in most of the scientific and engineering fields. The ampere is not included as a fundamental unit since the charge is considered as a form of energy that is measured in one of the US fundamental units, Joule. The candela and the mole were also not considered as fundamental units as they can be related to the selected fundamental units by appropriate numbers. The limited number of dimensions in the introduced US simplifies the application of the “π” dimensional theorem to find plausible relations between the main parameters that characterize many physical phenomena and the energy conversions and interactions.
Comments Concerning Measurements and Equations in Electromagnetism  [PDF]
Salama Abdelhady
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2010, DOI: 10.4236/jemaa.2010.212089
Abstract: The previously introduced US of units has raised many comments. Such comments were the claims of how to measure the electric current and magnetic flux. Other comments were concerned by violating the fundamental laws of electro-magnetism. Such violation is not the concern of the introduced system of units. But it is related to the previous mess in the available SI system of units.
An Entropy-Approach to the Duality Property  [PDF]
Salama Abdelhady
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2011, DOI: 10.4236/jemaa.2011.36036
Abstract: According to a previously introduced entropy approach, it is possible to clarify the confusions of the duality concept that electrons and light may behave as waves or particles. In other words, the electron is clearly defined in this paper as a particle and the light is neatly defined as waves. Such an approach considered the flow of electric charges as a flow of ionized waves and the magnetic flux as electromagnetic waves of magnetic potential. By a similar entropy approach, the particle’s kinetic energy is defined also as electromagnetic waves. So, the electron can be defined as an energized particle whose electric charge, magnetic energy and kinetic energy are forms of electromagnetic waves. According to these definitions and similarity of the mechanisms and laws characterizing the flow of mass and energy in general, the flow of electrons can be postulated as a simultaneous flow of two energy-components; particulized energy and wave energy. Hence, the electron doesn’t have a dual nature. Rather, its behavior as a particle or as waves depends on the relative contributions of such components in the electron’s flow. Reviewing the results of de-Broglie’s experiments, it is possible to consider the flow of any particles as a simultaneous flow of waves and particles. Introducing the definition of the flow of electric charges as ionized waves, the photoelectric-effect can be postulated as an ionization process of the incident radiation during its reflection into an electric field. Similarly, the photovoltaic phenomena are postulated as a result of a photorefractive effect that may induce an electric potential into the incident radiation when crossing the electrically biased p-n junctions of photocells. Such postulates eliminate the confusing particle-property of light and prove that light has a wave-nature only. The truth of the introduced postulates is proven through finding plausible explanation of the sintering phenomena and thermoelectricity. Finally, this paper succeeded in introducing plausible explanations of results of Thompson’s experiment and other phenomena that end the confusions in defining the true nature of light and electrons as waves and particles.
An Entropy Approach to Tesla’s Discovery of Wireless Power Transmission  [PDF]
Salama Abdelhady
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2013, DOI: 10.4236/jemaa.2013.54025
Abstract:

Following an entropy approach, the electric current can be postulated as a flow of electromagnetic waves that has an electric potential. Such postulate is verified in this article by results of experimental measurement then it is applied to review Tesla’s discovery of wireless power transmission. Tesla discovered the wireless transmission of electric power during his operation in an entirely new domain of physics based on abrupt discharging of electrostatic charges. He realized that electrons were not responsible for such discovered phenomena. So, he called the new energy as “Radiant Electricity”. He didn’t identify that the true nature of electric current was a flow of electromagnetic waves that can be normally radiated through air. So, he proposed the term “Aether gas” to describe the discovered transfer of the electric charges by radiation from his designed tower, though air, to specified receivers. Following an entropy approach, the nature of the discovered radiated energy can be identified as electromagnetic waves that have an electric potential. So, the followed approach succeeds in eliminating the confusing observations of Tesla’s measurements in his famous experiment and the confusions found in modern literature that deals with such energy as an “Ambiguous Radiant Energy”.

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