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Chromatography, Gas: Fractionation of a vaporized sample as a consequence of partition between a mobile gaseous phase and a stationary phase held in a column. Two types are gas-solid chromatography, where the fixed phase is a solid, and gas-liquid, in which the stationary phase is a nonvolatile liquid supported on an inert solid matrix.
 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

 Science Education: Essentials of Analytical Chemistry

Gas Chromatography (GC) with Flame-Ionization Detection

JoVE Science Education

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

Gas chromatography (GC) is used to separate and detect small molecular weight compounds in the gas phase. The sample is either a gas or a liquid that is vaporized in the injection port. Typically, the compounds analyzed are less than 1,000 Da, because it is difficult to vaporize larger compounds. GC is popular for environmental monitoring and industrial applications because it is very reliable and can be run nearly continuously. GC is typically used in applications where small, volatile molecules are detected and with non-aqueous solutions. Liquid chromatography is more popular for measurements in aqueous samples and can be used to study larger molecules, because the molecules do not need to vaporize. GC is favored for nonpolar molecules while LC is more common for separating polar analytes. The mobile phase for gas chromatography is a carrier gas, typically helium because of its low molecular weight and being chemically inert. Pressure is applied and the mobile phase moves the analyte through the column. The separation is accomplished using a column coated with a stationary phase. Open tubular capillary columns are the most popular columns and have the stationary phase coated on the walls of the capillary. Stationary phases a

 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

 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

 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

Measurement of Greenhouse Gas Flux from Agricultural Soils Using Static Chambers

1Office of Sustainability, University of Wisconsin-Madison, 2Department of Soil Science, University of Wisconsin-Madison, 3Department of Agronomy, University of Wisconsin-Madison, 4Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, 5USDA-ARS Dairy Forage Research Center, 6USDA-ARS Pasture Systems Watershed Management Research Unit


JoVE 52110

 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

 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.

 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 Environment

Extraction and Analysis of Microbial Phospholipid Fatty Acids in Soils

1Department of Renewable Resources, University of Alberta, 2Department of Science, Augustana Faculty, University of Alberta, 3Laboratoire Génie Civil et géo-Environnement, Université de Lille, 4Department of Earth and Environmental Sciences, Mount Royal University, 5Forest Ecology & Production, Great Lakes Forestry Centre, Natural Resources Canada


JoVE 54360

 JoVE In-Press

Synthesis of Cationized Magnetoferritin for Ultra-fast Magnetization of Cells

1Bristol Centre for Functional Nanomaterials, University of Bristol, 2Department of Materials, Imperial College London, 3Self Assembly Group, CIC nanoGUNE, 4Ikebasque, Basque Foundation for Science, 5School of Cellular and Molecular Medicine, University of Bristol, 6H.H. Wills Physics Laboratory, University of Bristol

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JoVE 54785

 JoVE Chemistry

From Constructs to Crystals – Towards Structure Determination of β-barrel Outer Membrane Proteins

1Department of Biological Sciences, Markey Center for Structural Biology, Purdue University, 2National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health, 3National Institute of General Medical Sciences (NIGMS), National Institutes of Health


JoVE 53245

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