Syringe technique

Syringe techniques have been developed for small volumes, while for large volumes or where much manipulation is required, dryboxes (glove boxes) or dry chambers should be used. 

All manipulations should be carried out in dry flasks under argon. Syringe techniques are best employed. 

Triethoxysilane and especially trimethoxysilane are rather toxic compounds (they may cause blindness if allowed to get into contact with eyes) and therefore care must be taken in their handing. Both need to be manipulated very carefully with suitable gloves, eyes face protection, in a well ventilated fume-hood. However, both can be handled without problems via syringe techniques. 

The different techniques used in solid-phase glycopeptide synthesis, such as the low-cost plastic syringe technique or the multiple column technique, and also one type of fully automated synthesis, have been reviewed by Peters et al.1181... 

All manipulations are performed under an atmosphere of dry nitrogen by using standard Schlenk and syringe techniques. The solvents toluene, benzene, and hexane are dried by reflux over the drying agent sodium and distilled prior to use. Sodium bis(trimethylsilyl)amide is prepared by the literature procedure. W(CO)e is obtained commercially and used without further purification. 

In comparison with syringe techniques, the use of cannulae provides better air exclusion and greater convenience for the transfer of large volumes of solution. However, syringe techniques are much better suited for the quantitative dispensing of liquids, as demonstrated in the following example. 

Brown, H. C., 1973, Organic Syntheses via Boranes. Wiley-Interscience, New York. See Chapter 9, p. 191, Laboratory Operations with Air-Sensitive Substances," by G. W. Kramer, A. B. Levy, and M. M. Midland, which stresses syringe techniques. 

When slight contamination of a gas sample by air is not objectionable, syringe techniques may be used. In order to minimize contamination by air, a syringe... 

Kelly and Brown51 describe a method for the preparation of concentrated solutions of carbocations ( 1 M) in SbFs-S02ClF. This method, which employs a syringe technique, allows quantitative conversion of precursors soluble in SO2CIF at —78°C into the corresponding carbocations. 

An alternative to the syringe technique for the transfer of liquids uses the double-ended needle and is suitable when it is not necessary to know precisely the volume of liquid being transferred, or when the volume is being measured in some other way, e.g. by transfer from a septum-capped measuring cylinder. This... 

If a glove box is not available, Schlenk-type glassware used with medium vacuum and inert gas is a relatively inexpensive and convenient approach. The use of this glassware is described in a general reference.27 Dissolution, recrystallization, solution transfer, and other simple operations can be carried out on the benchtop. Syringe techniques using apparatus closed with rubber septa also have been developed.28... 

The flask is charged through serum cap B with 17 mL (120 mmol) of diisopropyl amine (Note 3) and 200 raL of tetrahydrofuran (THF) (Note 4), using syringe techniques. It is cooled to -75°C 1n a dry-ice bath. With stirring, exactly 100 mmol of butyl lithium (hexane solution) (Note 5) is introduced from the dropping funnel (Note 6) within 10 min, followed after 0.5 hr, by a... 

The dropping funnel was calibrated before use in this procedure. With standard graduated dropping funnels and syringes, the submitters noticed up to 10% deviation from true volumes Syringe techniques were applied the dropping funnel was rinsed with ca. 5 mL of dry THF. 

The procedure used for determination of clotting time is a modification of a Lee-White Clotting Test. Before each test was undertaken, the surface of each sample was thoroughly washed with distilled water and oven dried. Blood used in these tests was obtained from a normal human volunteer and was used as drawn without citration. The twenty cc. of blood used for each test were drawn from an antecubital vein. In order to ensure that the blood which was used in each test was of a low tissue thromboplastin concentration, a two syringe technique was used and only the last 6 cc. of blood taken were used in the test the first 14 cc. were discarded. Time measurement was started as soon as the blood entered the tube and stopped upon the onset of clot formation. Occasionally, when the sample was observed not to have clotted within thirty minutes, a portion of the blood was removed from the tube and placed on a piece of gauze and carefully examined for slight evidence of clot formation. The samples which were used for the above test were as follows ... 

The anionic ring-opening copolymerization of hexamethyl-cyclotrisiloxane (Dj) with 2,4,6-trivinyl-2,4,6-trimethyl-cyclotrisiloxane (Vj) was performed under dry Nj atmosphere in a glass ampoule equipped with a teflon stopcock. All other reactions, except the preparation of Pt(0)-[poly(vinylmethyl-co-dimethyl)siloxane]-carbosilane complexes, were performed using standard Schlenk s or syringe techniques under an atmosphere of argon. 

As Lewis acid activators, weak metal halides such as zinc halides are effective [98,99] too-strong Lewis acids, such as SnCl4 and EtAlCl2, induce uncontrolled polymerization [104]. In some cases, the latter metal halides also initiate polymerization in the presence of a trace of water, which is unavoidable under usual experimental conditions (under dry nitrogen or argon atmosphere, via the syringe technique). Thus, zinc halides [98,99] are used most frequently, but tin(II) halides [99] and some acetyla-cetonate complexes [120] can also be effective. 

Most of the cationic polymerizations and the polymer syntheses thereby, discussed in Chapters 4 and 5, may be carried out conveniently under the dry and inert gas atmosphere (nitrogen or argon) by the so-called syringe technique. Except for highly elaborated kinetic experiments, stringent high-vacuum technique is not required to maintain the control of the polymerizations and polymer architectures. 

Dimethylzinc, prepared and purified by standard methods, is stored in a storage ampul (Fig. 9a), and the required quantity is vacuum-distilled into a similar ampul before reaction ( Caution. Dimethylzinc is very volatile (bp. 46°) and extremely pyrophoric. The transfer of dimethylzinc, even as a dilute hydrocarbon solution, by syringe techniques invariably results in some decomposition.)... 

Syringe techniques for dispensing and transferring chemicals to the apparatus (p. 127). 

The Li[BEtjH] solution (15 mmol in hydride) is prepared by introducing 15mL of the commercial reagent into a 50-mL one-necked side-arm flask through syringe techniques, then evaporating the THF in vacuo at room... 

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