Glass, columns surface

Figura 2.9 Dse of th Grob test Mixture to compare tbe activity of various glass surfaces coated with ov-ioi. Surface types A > Untreated pyrex glass, B pyrex glass deactivated by thermal degradation of Ceurbowax 20M, C < SCOT column, prepared with Silanox 101, D pyrex glass column coated with a layer of barium carbonate and deactivated as in (B), and E - untreated fused silica. Components are identified in Table 2.7 with ac - 2-ethylhexanoic acid. (Reproduced with permission from ref. 152. Copyright Elsevier Scientific Publishing Co.)...

Carbon Sulphidoselenide, CSSe, may be prepared by the action of carbon disulphide vapour on ferrous selenide at 650° C. The product, on fractional distillation through a 50-inch head-filled glass column, yields a deep yellow liquid as residue, which on repeated fractionation through the same column yields a middle fraction of the pure sulphidoselenide. It is obtained as a yellow oil of boiling-point 88-90° to 83-95° C. at 749-2 mm., and having a surface tension y =40-44 dynes/cm. at 20° C. 

Increased Surface Area of Walls. If glass columns are used the surface area may be increased by treatment with hot ammonium or sodium hydroxides. If aluminum columns are used a similar treatment can be employed. In the former case a layer of porous silica is formed, in the latter a layer of porous alumina. 

Stainless steel transfer lines leading from the effluent and of the column to the detector should not be used because they will promote derivative decomposition. Glass columns should be used instead. Tyrosine, serine, and threonine are easily decomposed on hot metal surfaces. 

The liquid chromatograph used 1n this study consisted of a Cheminert Model CMP-2K (Laboratory Data Control, Riviera Beach, FI.) which is capable of a maximum flow rate of 2 ml/min at a maximum pressure of 500 PSI. This pump has all liquid contact parts limited to glass, teflon or KEL-F materials to reduce corrosion to a minimum. The Injection valve is a Laboratory Data Control Model SU 8031 slider valve with a 0.5 ml sample loop. The injection valve is located at the top of the column to minimize dead volume. The separating column is a Laboratory Data Control type MB glass column, 30 cm long with a 2 mm bore capable of a maximum pressure of 500 PSI. The column is packed with surface sulfonated cation exchanger resin prepared in this laboratory in the following manner. 

The results presented below from the study of the behaviour of steady-state foams allow to estimate the role of foam films in foam stability. Two types of steady-state foam have been studied 1) wet steady-state foams from aqueous solutions of low surface active surfactants, e.g. normal alcohols [96] and 2) dry steady-state foams [121] from aqueous solutions of micellar surfactants, e.g. NaDoS, in the presence of electrolyte at different concentrations (ensuring different types of foam films). The device employed in this study represents a glass column (of inner diameter 3.4 cm) with a sintered glass filter as a bottom [94-96,121]. The gas volume passing through the column was measured by a rheometer. The total gas volume both in the foam and in the solution was measured when a steady-state was reached, i.e. when the system volume ceases changing. Usually the total gas volume V c as well as the gas rate vc were measured. 

The minimum pressure ensuring a movement of the foam through a tube has been first determined by Siehr [3,32]. He used open glass tubes of length 1.5 m and introduced a foam from a diluted potato juice (n - 100) in the 1 m middle section of the tubes. The pressure was gradually increased from the bottom part of the tube until the upper foam column surface began to advance. The minimum excess pressures were 9.30, 4.90, 2.95 and 2.60 kPa at 4, 8, 12 and 18 mm internal tube diameters, respectively. After keeping the foam for 25 min the minimum excess pressure increased to 9.85, 5.35, 3,35 and 2.65 kPa, respectively. 

For the purification of fullerenes from the fullerene oxides the activated alumina and silica can be used. Fulllerene oxides are adsorbed strongly on such adsorbents from solution and the oxides are removed from fullerene samples. For the preparative separation of fullerenes at present activated carbons and graphite are used [11-14], For this purpose silica with the deposited carbon layer [16] can be used also. In this case it is very easily to regulate the pore diameter and specific surface area of adsorbents as well as particle diameter. Such adsorbents is very important for the decreasing of fullerenes loss. On preparative separation of fullerenes on LiChrosorb SI 60 with deposited carbon layer by modified method [15] on glass column first fractions contained quite pure Csq. 

It is not only possible to force the mobile phase through a capillary or column by means of a pump but also by electroendosmosis. Thereby one utilizes the fact that an electric double layer occurs on all boundary layers. Silica or quartz glass are surfaces covered with fixed negative excess charges and a solution in contact with it forms positive boundary charges. If a potential gradient of approximately 50 kV m is applied the solution flows in the direction of the negative electrode. 

Product Isolation and Analysis. At the conclusion of the run, the reactor was partially filled with benzene and refluxed on a steam bath for two hours. The benzene soluble material from the column was combined with the yellow brown solid which collected in the lower receiver. The insoluble material was swelled by benzene and generally loosened from the glass dielectric surface. This insoluble material was filtered off, washed several times with chloroform and dried overnight at 70 °C. in a vacuum oven. The reactor was cleaned with a 5% hydrofluoric acid solution to remove final traces of polymer after each run. Benzene insoluble polymer—0.7 gram yellow brown color, % C 86.95, %H 7.17, C/H 1.01. 

Surface silylation of solid supports, glass columns, inserts, or even glass-wool spacers and glassware for the sake of surface deactivation remains highly recommended in biochemical GC. An alternative approach to surface deactivation is the method of Aue et al. [93], in which thermal treatment of polymer-coated supports results in a partial linkage of the macromolecule to the surface. This approach has been successfully employed with both packed and capillary columns. 

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