Gas chromatography is a common type of chromatography used in analytical chemistry for separating and analyzing compounds that can be vaporized without decomposition. Typical uses of GC include testing the purity of a particular substance, or separating the different components of a mixture. In some situations, GC may help in identifying a compound. In preparative chromatography, GC can be used to prepare pure compounds from a mixture. In gas chromatography, the mobile phase is a carrier gas an inert gas such as helium or an unreactive gas such as nitrogen. Helium remains the most used carrier gas in about 90% of instruments although hydrogen is preferred for improved separations; the stationary phase is a microscopic layer of liquid or polymer on an inert solid support, inside a piece of glass or metal tubing called a column. The instrument used to perform gas chromatography is called a gas chromatograph; the gaseous compounds being analyzed interact with the walls of the column, coated with a stationary phase.
This causes each compound to elute at a different time, known as the retention time of the compound. The comparison of retention times is. Gas chromatography is in principle similar to column chromatography, but has several notable differences. First, the process of separating the compounds in a mixture is carried out between a liquid stationary phase and a gas mobile phase, whereas in column chromatography the stationary phase is a solid and the mobile phase is a liquid. Second, the column through which the gas phase passes is located in an oven where the temperature of the gas can be controlled, whereas column chromatography has no such temperature control; the concentration of a compound in the gas phase is a function of the vapor pressure of the gas. Gas chromatography is sometimes known as vapor-phase chromatography, or gas–liquid partition chromatography; these alternative names, as well as their respective abbreviations, are used in scientific literature. Speaking, GLPC is the most correct terminology, is thus preferred by many authors.
Chromatography dates to 1903 in the work of the Russian scientist, Mikhail Semenovich Tswett, who separated plant pigments via liquid column chromatography. German physical chemist Erika Cremer in 1947 together with Austrian graduate student Fritz Prior developed the theoretical foundations of GC and built the first liquid-gas chromatograph, but her work was deemed irrelevant and was ignored for a long time. Archer John Porter Martin, awarded the Nobel Prize for his work in developing liquid–liquid and paper chromatography, is therefore credited for the foundation of gas chromatography; the popularity of gas chromatography rose after the development of the flame ionization detector. A gas chromatograph is a chemical analysis instrument for separating chemicals in a complex sample. A gas chromatograph uses a flow-through narrow tube known as the column, through which different chemical constituents of a sample pass in a gas stream at different rates depending on their various chemical and physical properties and their interaction with a specific column filling, called the stationary phase.
As the chemicals exit the end of the column, they are identified electronically. The function of the stationary phase in the column is to separate different components, causing each one to exit the column at a different time. Other parameters that can be used to alter the order or time of retention are the carrier gas flow rate, column length and the temperature. In a GC analysis, a known volume of gaseous or liquid analyte is injected into the "entrance" of the column using a microsyringe; as the carrier gas sweeps the analyte molecules through the column, this motion is inhibited by the adsorption of the analyte molecules either onto the column walls or onto packing materials in the column. The rate at which the molecules progress along the column depends on the strength of adsorption, which in turn depends on the type of molecule and on the stationary phase materials. Since each type of molecule has a different rate of progression, the various components of the analyte mixture are separated as they progress along the column and reach the end of the column at different times.
A detector is used to monitor the outlet stream from the column. Substances are identified by the order in which they emerge from the column and by the retention time of the analyte in the column; the autosampler provides the means to introduce a sample automatically into the inlets. Manual insertion of the sample is no longer common. Automatic insertion provides better time-optimization. Different kinds of autosamplers exist. Autosamplers can be classified in relation to sample capacity, to robotic technologies, or to analysis: Liquid Static head-space by syringe technology Dynamic head-space by transfer-line technology Solid phase microextraction The column inlet
The Brooklyn Bushwicks were an independent, semi-professional baseball team that played its games totally in Dexter Park in Queens from 1913 to 1951. They were unique at their time for fielding multi-ethnic rosters, they played what amounts to exhibition games against barnstorming Negro league teams, minor league baseball teams, other semi-pro teams. The Bushwicks were owned by Max Rosner, who hired many former major league players to play on his club, including Dazzy Vance and others. Many of the famous players of the time came to play exhibitions at Dexter Park including Dizzy Dean, Hank Greenberg, Joe DiMaggio, Babe Ruth, Lou Gehrig, Joe Medwick; until he became friends with Rosner, Ruth demanded upfront payments in cash before agreeing to personal appearances. The DiMaggio picture was taken during his debut year with Yankees; the great black stars, Josh Gibson, Cool Papa Bell and many others opposed the Bushwicks. The team appeared on radio as well; the team's picture appeared in three different Spalding Guides.
The 2000 Currie Cup was the 62nd season of the Currie Cup, South Africa's premier domestic rugby union competition, since it started in 1889. The competition was known as the Bankfin Currie Cup for sponsorship reasons and was contested from 21 July to 28 October 2000; the top eight sides from an initial qualification stage competed for the premier Currie Cup, while the bottom six sides from the qualification stage competed for the secondary Bankfin Cup. The Currie Cup was won by Western Province for the 30th time in their history; the Bankfin Cup was won by the Blue Bulls for the first time. There were fourteen participating teams in the 2000 Currie Cup, all of them starting the season in the 2000 Currie Cup qualification stage. At this stage, the teams were divided into two sections and played all the other teams in their section once, either home or away; the top four teams from both sections qualified to the 2000 Currie Cup Top 8 stage, carrying forward the results they got against their three fellow qualifiers.
In the Top 8, they faced all the teams from the opposite section once, either home and away. The bottom three teams from both qualification sections qualified to the 2000 Bankfin Cup stage, carrying forward the results they got against their two fellow qualifiers. In the Bankfin Cup, they faced all the teams from the opposite section once, either home and away. In all three stages of the competition, teams received four points for a win and two points for a draw. Bonus points were awarded to teams that scored four or more tries in a game, as well as to teams that lost a match by seven points or less. Teams were ranked by log points points difference. At the end of the Top 8 and Bankfin Cup stages, the top four teams qualified for the title play-offs. In the semi-finals, the team that finished first had home advantage against the team that finished fourth, while the team that finished second had home advantage against the team that finished third; the winners of these semi-finals advanced at the home venue of the higher-placed team.
Rather than the single division used in 1999, the 2000 Currie Cup competition was divided into two stages: an initial qualification stage took place, followed by two second-stage competitions: the Currie Cup for the top eight teams from the qualification stage and the Bankfin Cup for the bottom six teams. There was a name change prior to this season: North West were renamed the Leopards The Boland Cavaliers, Free State Cheetahs, Golden Lions and Sharks qualified for the Top 8 stage after finishing in the top four teams in Section X, while Griquas, Pumas, SWD Eagles and Western Province qualified for the Top 8 stage after finishing in the top four teams in Section Y; the Falcons and Mighty Elephants qualified for the Bankfin Cup after finishing in the bottom three in Section X, while the Border Bulldogs, Blue Bulls and Leopards qualified for the Bankfin Cup after finishing in the bottom three in Section Y. The Free State Cheetahs, Golden Lions and Western Province finished in the top four of the Top 8 stage to qualify for the semi-finals.
After winning their respective semi-finals, the Natal Sharks and Western Province played in the final, which Western Province won 25–15 in Durban. The Blue Bulls, Falcons and Mighty Elephants finished in the top four of the Bankfin Cup stage to qualify for the semi-finals. After winning their respective semi-finals, the Blue Bulls and Mighty Elephants played in the final, which the Blue Bulls won 41–20 in Port Elizabeth; the honour roll for the 2000 Currie Cup was