| Papers [1-5] of 5 | Search results on "CHROMATOGRAPHY": |
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Chromatography, 2004.
An overview of chromatography and outline of its history.
803 words (approx. 3.2 pages), 3 sources, MLA, $ 28.95
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Abstract
This paper looks at chromatography, an analytical technique based on the principle of selective adsorption that is used for the chemical separation of mixtures and substances. It examines how it is an important field of chemistry, which deals with the separation of pure substances from complex mixtures, and is widely used in the analysis of foods, drugs, blood, petroleum products, and radioactive-fission products. It also examines how variants of ?column? chromatography have been developed since its discovery in 1906, including partition, liquid, paper, thin-layer, and gas-liquid chromatography.
From the Paper
"Chromatography was discovered in 1906 by the Russian botanist Mikhail Tswett who first coined the term (derived from the Latin for ?color writing?). The technique used by Tswett for separating the pigments (chlorophyll) of plants consisted of pouring petroleum-ether extract of green leaves over a column of powdered calcium carbonate in a vertical glass tube. As the solution seeped through the column the individual components of the mixture moved downward at different rates of speed, and the column became marked with horizontal bands of colors. Tswett did not enjoy a happy relationship with fellow scientists of his time, as they derided his results, and his technique, with Tswett responding in kind. As a result, it wasn?t until the 1930s that his methods were accepted as a breakthrough in chromatography."
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An Explanation of the Principles and Uses of Supercritical Fluid Chromatography, 2001.
A look at the many advantages of this technique, and in what applications it can be used.
2,310 words (approx. 9.2 pages), 3 sources, $ 71.95
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From the Paper
"Although the properties of supercritical fluids were know, it was not until 1958 when Lovelock suggested that a supercritical fluid can be used as a mobile phase in chromatography. Now, supercritical fluid chromatography (SFC) is widely used in extraction, fraction, and chromatography. SFC has many advantages over other chromatography methods. It allows one to separate many substances that cannot be analyzed by gas chromatography. Its applicability is limited by volatility and thermal properties of many organic compounds. Although less volatile compounds can be analyzed by high performance liquid chromatography, very long analysis time and very small column diameters are needed in order to achieve good separations due to the limitations of solute diffusion in the mobile phase. SFC is able to overcome these difficulties and allows high-resolution separation at low temperatures with short analysis times."
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Gas Chromatography, 2000.
A definition, general principles, apparatus used, sampling, types and conductivity detectors.
1,350 words (approx. 5.4 pages), 2 sources, $ 47.95
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From the Paper
"Gas chromatography is a method for the separation and analysis of complex mixtures of volatile organic and inorganic compounds (1:666). Most compounds with boiling points less than 250oC (480oF) can be analyzed using this technique. This paper will describe the apparatus used for gas chromatography, the principles on which it works, how a thermal conductivity detector works in gas chromatography, and whether or not it can be used with a sample of potassium t-butoxide.
General Principles of Gas Chromatography
There are two types of gas chromatography: gas-liquid chromatography, where the sorbent is a nonvolatile liquid called the stationary liquid phase, coated as a thin layer on an inert, granular solid support; and gas-solid chromatography, where the sorbent is a granular solid of large surface area (1:666). The..."
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Biologically-Active Natural Products, 2002.
This paper discusses the isolation and structural determination of biologically-active natural products by using various chromatographic techniques.
8,750 words (approx. 35.0 pages), 35 sources, APA, $ 183.95
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Abstract
This paper explains that nature acts as a pharmacy, offering us products, from the forest pharmacy and the pharmacy below water, with which we can heal ourselves: For example, aspirin, quinine, cyclosporins, and penicillin. This paper details the techniques that are available to researchers, to collect samples of natural products from the wild in a systematic manner, to extract compounds from these samples, to isolate the biologically-active compounds within these extracts, to characterize the biologically-active compounds chemically in terms of their structure, to evaluate the biologically-active compounds biologically, to determine potentially useful therapeutic effects and finally the methodology necessary to take these compounds to clinical trial. The author stresses the importance of finding new and more effective drugs to fight against bacterial infections and cancer. Outline.
Table of Contents
Introduction
Nature?s Pharmacopeia.
The Isolation of Biologically-Active Compounds and their Extraction Identification: Techniques
Introduction
Chemical Extraction
Biological Evaluation
Chemical Analysis
Chromatography
Solid Phase Extraction
Paper Chromatography
Thin Layer Chromatography
Flash Chromatography
High Performance Liquid Chromatography
Central Counter Current Chromatography
Determining the Chemical Structure of Compounds Isolated by Chromatography
Nuclear Magnetic Resonance
Mass Spectrometry
Drug Development
Examples of the Isolation and Identification
An Example of Extraction, Isolation and Chemical Characterization of Biologically-Active Compounds from Larch Wood
Biologically-active Compounds from Marine Organisms
What Compounds Have Been Isolated From Marine Organisms?
Biologically-Active Anti-Cancer Compounds ? Testing for Human Safety
Conclusion
From the Paper
"Chromatography is the process whereby two or more compounds or ions are separated through the distribution of the compound or ion between two phases, one that is mobile and the other which is stationary. These two phases can be of any combination: liquid-liquid, solid-solid, solid-liquid or gas-liquid, gas-gas, or gas-solid. There are many specific techniques for chromatography, some of which will be described below, and all follow the same basic principles. All forms of chromatography involve a rapid and dynamic equilibrium of molecules between the two phases, either free ? mobile - or absorbed ? stationary. Molecules will constantly move back and forth between the free and absorbed states, with millions of molecules absorbing and desorbing every second. The equilibrium between these states depends on three factors: the polarity and size of the molecule, the polarity of the stationary phase, and the polarity of the solvent. Thus, three different variables can be changed in chromatography, which can change the equilibrium between the stationary and mobile phases: this allows one to choose mobile and stationary phases that will separate just about any combination of compounds."
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Isolation and Purification of Lysozyme, 2007.
This paper looks at an experiment in an enzyme purification lab for the purification of lysozyme.
2,117 words (approx. 8.5 pages), 5 sources, APA, $ 66.95
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Abstract
The writer explains that in this experiment, lysozyme was purified from egg white solution into 24 fractions using gel column chromatography. The writer points out that the odd-numbered fractions were then assayed in order to determine the enzymatic activity of lysozyme, while the even-numbered fractions were assayed for total protein content, using the Bradford protein assay procedure. The writer notes that lysozyme is one of the most well-known enzymes, being abundant in mucus, tears, and albumen (commonly known as egg white).
The writer concludes that the purification of lysozyme from egg white was only somewhat successful since the estimated value of the molecular weight, 14.25 kDa, is practically the same as the known weight of 14.3 kDa. However, the specific activity, calculated at 400 units/mg, was significantly less than the expected specific activity of 25 000 units/mg of protein.
Outline:
Abstract
Introduction
Materials and Methods
Results
Calculations
Discussion
Conclusion
From the Paper
"Lysozyme is itself composed of 129 amino acids, including four disulfide bridges and three sets of alpha helices. The enzyme's active site consists of a long groove that can hold as many as six polysaccharides. According to past experiments, specific activity of lysozyme from egg white is approximately 25 000 units/mg. This is the expected result for this experiment. However, one factor that influences the specific activity is the actual column and type of chromatography being used, since accuracy differs among the different types of chromatographies. Therefore, some are able to purify enzymes better than others, giving a more accurate specific activity. In addition to obtaining the specific activity, molecular weight of the enzyme can be determined by comparing the fraction in which most of the enzyme eluted with the fractionation range."
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