Refine your search:

Containing Text
- - -
+
Filter by author or institution
GO
Filter by publication date
From:
October, 2006
Until:
Today
Filter by section
 
 
Chromatography, Liquid: Chromatographic techniques in which the mobile phase is a liquid.
 Science Education: Essentials of Analytical Chemistry

High-Performance Liquid Chromatography (HPLC)

JoVE Science Education

Source: Dr. Paul Bower - Purdue University

High-performance liquid chromatography (HPLC) is an important analytical method commonly used to separate and quantify components of liquid samples. In this technique, a solution (first phase) is pumped through a column that contains a packing of small porous particles with a second phase bound to the surface. The different solubilities of the sample components in the two phases cause the components to move through the column with different average velocities, thus creating a separation of these components. The pumped solution is called the mobile phase, while the phase in the column is called the stationary phase. There are several modes of liquid chromatography, depending upon the type of stationary and/or mobile phase employed. This experiment uses reversed-phase chromatography, where the stationary phase is non-polar, and the mobile phase is polar. The stationary phase to be employed is C18 hydrocarbon groups bonded to 3-µm silica particles, while the mobile phase is an aqueous buffer with a polar organic modifier (acetonitrile) added to vary its eluting strength. In this form, the silica can be used for samples that are water-soluble, providing a broad range of applications. In this experiment, the mixtures of three components frequently found

 JoVE Chemistry

Isolation and Preparation of Bacterial Cell Walls for Compositional Analysis by Ultra Performance Liquid Chromatography

1Department of Bioengineering, Stanford University, 2Department of Molecular Biology and Laboratory for Molecular Infection Medicine Sweden, Umeå Centre for Microbial Research, Umeå University, 3Campus de Cantoblanco, Universidad Autonoma de Madrid, 4Department of Microbiology and Immunology, Stanford University School of Medicine


JoVE 51183

 JoVE Medicine

Quantification of the Immunosuppressant Tacrolimus on Dried Blood Spots Using LC-MS/MS

1iC42 Clinical Research and Development, University of Colorado, Anschutz Medical Campus, 2Division of Clinical Pharmacology, Cincinnati Children's Hospital Medical Center, 3Food and Drug Administration (FDA), Center of Drug Evaluation Research - Office of Generic Drugs, 4Transplant Clinical Research, University of Cincinnati


JoVE 52424

 JoVE Chemistry

Quantitative Detection of Trace Explosive Vapors by Programmed Temperature Desorption Gas Chromatography-Electron Capture Detector

1Chemical Sensing & Fuel Technology, Chemistry Division, U.S. Naval Research Laboratory, 2NOVA Research, Inc., 3Bio/Analytical Chemistry, Chemistry Division, U.S. Naval Research Laboratory, 4Navy Technology Center for Safety and Survivability, Chemistry Division, U.S. Naval Research Laboratory


JoVE 51938

 JoVE Chemistry

Construction of Models for Nondestructive Prediction of Ingredient Contents in Blueberries by Near-infrared Spectroscopy Based on HPLC Measurements

1United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology, 2Faculty of Agriculture, Tokyo University of Agriculture and Technology, 3Institute of Agriculture, Tokyo University of Agriculture and Technology


JoVE 53981

 Science Education: Essentials of Analytical Chemistry

Ion-Exchange Chromatography

JoVE Science Education

Source: Laboratory of Dr. B. Jill Venton - University of Virginia

Ion-exchange chromatography is a type of chromatography that separates analytes based on charge. A column is used that is filled with a charged stationary phase on a solid support, called an ion-exchange resin. Strong cation-exchange chromatography preferentially separates out cations by using a negatively-charged resin while strong anion-exchange chromatography preferentially selects out anions by using a positively-charged resin. This type of chromatography is popular for sample preparation, for example in the cleanup of proteins or nucleic acid samples. Ion-exchange chromatography is a two-step process. In the first step, the sample is loaded onto the column in a loading buffer. The binding of the charged sample to the column resin is based on ionic interactions of the resin to attract the sample of the opposite charge. Thus, charged samples of opposite polarity to the resin are strongly bound. Other molecules that are not charged or are of the opposite charge are not bound and are washed through the column. The second step is to elute the analyte that is bound to the resin. This is accomplished with a salt gradient, where the amount of salt in the buffer is slowly increased. Fractions are collected at the end of the column as

 Science Education: Essentials of Analytical Chemistry

Internal Standards

JoVE Science Education

Source: Laboratory of Dr. B. Jill Venton - University of Virginia

The goal of many chemical analyses is a quantitative analysis, where the amount of a substance in a sample is determined. In order to accurately calculate the concentration of an unknown from a sample, careful sample preparation is key. Every time a sample is handled or transferred, some of the sample can be lost. There are strategies however, for minimizing sample loss. There are also strategies for coping with sample loss and still making accurate measurements of concentration. To minimize sample loss, the ideal is to minimize the number of sample handling and transfer steps. For example, massing a solid sample directly into a flask that a solution will be made in reduces a transfer step. If it's necessary to transfer from one flask to another and a dilution is being made, then triple rinsing the glassware helps ensure all the sample is transferred. Other strategies are more specific to the sample. For example, samples that adsorb to glass, such as proteins, might better be handled in polypropylene disposable tubes. The tubes are not hydrophilic, so if a small amount of sample is to be pipetted in water, it is best to have already added the water to the tube, so the sample can be pipetted directly into the solve

 Science Education: Essentials of Organic Chemistry

Column Chromatography

JoVE Science Education

Source: Laboratory of Dr. Jimmy Franco - Merrimack College

Column chromatography is one of the most useful techniques for purifying compounds. This technique utilizes a stationary phase, which is packed in a column, and a mobile phase that passes through the column. This technique exploits the differences in polarity between compounds, allowing the molecules to be facilely separated.1 The two most common stationary phases for column chromatography are silica gel (SiO2) and alumina (Al2O3), with the most commonly used mobile phases being organic solvents.2 The solvent(s) chosen for the mobile phase are dependent on the polarity of the molecules being purified. Typically more polar compounds require more polar solvents in order to facilitate the passage of the molecules through the stationary phase. Once the purification process has been completed the solvent can be removed from the collected fractions using a rotary evaporator to yield the isolated material.

 JoVE Chemistry

Characterization, Quantification and Compound-specific Isotopic Analysis of Pyrogenic Carbon Using Benzene Polycarboxylic Acids (BPCA)

1Department of Geography, University of Zurich, 2Department of Earth and Ocean Sciences, University of South Carolina, 3Department of Earth Sciences, ETH Zurich, 4Laboratory of Ion Beam Physics, ETH Zurich, 5Department of Geological Sciences, Stockholm University


JoVE 53922

 JoVE Chemistry

Conducting Miller-Urey Experiments

1School of Chemistry and Biochemistry, Georgia Institute of Technology, 2Earth-Life Science Institute, Tokyo Institute of Technology, 3Institute for Advanced Study, 4Astromaterials Research and Exploration Science Directorate, NASA Johnson Space Center, 5Goddard Center for Astrobiology, NASA Goddard Space Flight Center, 6Geosciences Research Division, Scripps Institution of Oceanography, University of California at San Diego


JoVE 51039

 JoVE Environment

LC-MS Analysis of Human Platelets as a Platform for Studying Mitochondrial Metabolism

1Center for Cancer Pharmacology, University of Pennsylvania, 2Center for Excellence in Environmental Toxicology, University of Pennsylvania, 3Penn SRP and Department of Systems Pharmacology and Translational Therapeutics, University of Pennsylvania, 4Division of Traumatology, Department of Surgery, Critical Care and Acute Care Surgery, University of Pennsylvania, 5A.J. Drexel Autism Institute, Drexel University


JoVE 53941

12345678949
More Results...
Waiting
simple hit counter