Rubber septa

Injector The sample, typically 5-200 )J,L, is placed in the carrier stream by injection. Although syringe injections through a rubber septum are used, a more common means of injection is the rotary, or loop, injector used in ITPLC and shown in Figure 12.28 of Chapter 12. This type of injector provides reproducible injection volumes and is easily adaptable to automation, a feature that is particularly important when high sampling rates are desired. 

For GC, the injector is most frequently a small heated space attached to the start of the column. A sample of the mixture to be analyzed is injected into this space by use of a syringe, which pierces a rubber septum. The injector needs to be hot enough to immediately vaporize the sample, which is then swept onto the head of the column by the mobile gas phase. Generally, the injector is kept at a temperature 50 C higher than is the column oven. Variants on this principle are in use, in particular the split/splitless injector. This injector can be used in a splitless mode, in which the entire injected sample goes onto the column, or in a split mode, in which only part of the sample goes onto the column, the remainder vented to atmosphere. For other less usual forms of injector, a specialist book on GC should be consulted. 

S. Pvepavation of a solution of lithium di(Z-hexenyl)auprate. A needle connected to an acetylene supply (Note 6) is introduced through the rubber septum of the flask, with its end at least 1 cm below the surface of the cuprate solution. The stopcock is fully opened towards the balloon, the... 

A. E)-(2-Methyl-l,3-butadienyl)dimethylalane. An oven-dried, 1-L, twonecked, round-bottomed flask equipped with a magnetic stirring bar, a rubber septum, and an outlet connected to a mercury bubbler is charged with 7.01 g (24 mmol) of dichlorob1s(n -cyclopentadienyl)z1rconium (Note 2) and flushed with nitrogen. To this are added sequentially at 0 C 100 mL of 1,2-d1chloro-ethane (Note 3), 12.48 g (120 mtiol) of a 5016 solution of l-buten-3-yne in... 

The funnel is capped with a rubber septum. For ease of operation, volume markings, corresponding to the amounts of reagents to be added, are put on the addition funnel. 

The checkers used a home-made, glass-jacketed funnel sealed with a rubber septum. The submitters cut one side and part of the bottom of a styrofoam cup and with tape held this in place around the lower part of the addition funnel. 

B. -Butyl- a-methyl- >-2-octalone. A 250-ml., three-necked flask equipped with a magnetic stirring bar, a reflux condenser, a 50-ml., pressure-equalizing funnel, and a rubber septum is charged with 1.4 g. (0.032-0.036 mole) of 55-60% sodium hydride dispersion in mineral oil... 

Continuous porous polymer rods have been prepared by an in situ polymerization within the confines of a chromatographic column. The column is filled with glycidyl methacrylate and ethylene dimethacrylate monomer mixtures, cyclo-hexanol and dodecanol diluents, and AIBN initiator. They are then purged with nitrogen, stopped, and closed with a silicon rubber septum. The polymerization is allowed to proceed for 6 hr at 70°C with the column acting as a mold (47). 

Catalytic hydrogenation. Aqueous solution of FMN (50 pM) containing a small amount of platinized asbestos is babbled with hydrogen gas for 10-20 minutes, until the yellow color and green fluorescence of FMN completely disappear. A suitable setup for this purpose can easily be constructed using a small flask, a rubber septum and two syringe needles (used as the inlet and outlet of H2 gas). 

To a three-necked 100-mL flask equipped with mechanical stirrer, jacketed dropping funnel and rubber septum, under argon, are added 3.52 g (15 mmol) of (-)-sparteine, 20 mL of anhvd pentane, 3 mL of cyclohexane and 2.99 g (15 mmol) of ( )-2-bulenyl diisopropylcarbamate. The mixture is chilled to below -70 C in a dry ice/acetone bath. 10 mL of 1.6 N butyllithium in hexane are slowly added with rapid... 

Via the Z-enolate an oven dried Schlenk tube equipped with a rubber septum is flushed with argon and charged with 0.66 mL (1.0 mmol) of butyllithium (1.5 N in hexane). The Schlenk tube is cooled to 0°C (icc/salt) and 0.12 g (1.1 mmol) of diisopropylaminc are added slowly by a syringe. This mixture is stirred for 15 min and the rubber septum is replaced by a glass stopper. The hexane and the excess diisopropyl-amine are removed under reduced pressure. After the flask is filled with argon the stopper is replaced with a septum and 0.47 g (4.3 mmol) of HMPA and 2.5 mL of THF are added. This solution is immediately cooled to — 78 °C and 0.14 g (1.1 mmol) of tert-butyl propanoate arc added quickly by syringe. After stirring for... 

A dry, 250-ml., three-necked, round-bottomed flask is equipped with a sealed mechanical stirrer (Note 5), a glass stopper, and a rubber septum through which are inserted hypodermic needles with which to evacuate the flask and to admit nitrogen. After the apparatus has been... 

B. (E)-4-(2-Phenylethenyl)benzonitrile (2). An oven-dried, 250-mL, three-necked, round-bottomed flask equipped with an argon inlet adapter, rubber septum, glass stopper, and a teflon-coated magnetic stir bar is cooled to room temperature under a flow of argon. The flask is charged successively with bis (tri-tert-butylphosphinc)palladium [(Pd(P(t-Bu)3)2] (0.238 g, 0.466 mmol, 1.5 mol% Pd) (Notes 1, 2), tris(dibenzylideneacetone)dipalladium(0) (Pd2(dba)3) (0.213 g, 0.233 mmol, 1.5 mol% Pd) (Note 3), and... 

B. N-(tert-Butoxycarbonyl)-fi-iodoalanine methyl ester (3). A one-necked, 250-mL, round-bottomed flask equipped with a rubber septum and magnetic stirbar is charged with 27.8 g (74.0 mmol) of N-(terC... 

B. 2-Cyclopentylacetophenone (2). A 500-mL, two-necked, round-bottomed flask (Note 11) equipped with an egg-shaped magnetic stir bar (4 cm x 1.5 cm), argon inlet adapter, and a rubber septum is flame-dried and allowed to cool to room temperature under a positive pressure of argon. A thermometer is inserted through the septum (Note 12) and the flask is charged with 114 mL of dry,... 

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