Device to Control Channeling, Voids, and Disruption of Pressure-Developed Chromatographic Columns Walter G. Jennings, University of California, Davis, Calif.
columns of relaC tively large diameter are widely used in many laboratory procedures.
be better suited to some othcr solvent systems. The adsorbent is placed in the column as a slurry, and settled n i t h suetion applied a t the outlet or pressure a t the top. A disk of filter paper is placed on top. a pad of glass wool is applied, and the plunger assembly is p u t in position. With adsorbents that are column-regenerated and tend to expand-e.g., anion exchange cellulose-sufficient spzce must be maintained to accommodate the expansion. Once the column has been regenerated, the plunger is lowered into firm contact with the packaging. The plunger should not be used to compact the column, but rather should be lowered to maintain contact with the adsorbent as it compacts under gas pressure. This device controls formation of bubbles and voids within the colunin, and effectively eliminates expansion and disruption of the column with changes in pressure.
HROXIATOGRAPHIC
Many established techniques take advantage of the increased speed attained when columns are developed under positive pressure, but the cracks, voids, and channels that not infrequently occur in the column packing are a serious disatlvantnge, particularly when the column pressure must be changed to introduce samples, change influent, etc. Often the adsorbent shifts and the packing may disrupt to such a degree as to ruin an euperinient. A simple device was designcd to ovcrcome these difficulties, and 113s proved successful in this laboratory. All inctal items in contact with the column or solvent are of stainless steelthe upper rubber stopper shown is satisfactory for the aqueous solvent used in this laboratory, but a plug of Teflon or Teflon-shielded metal might
silver solder
Improved Head and Flask for Miniature Distillation A. G. Nerheim, Research and Development Department, Standard Oil Co. (Indiana), Whiting, Ind.
of miniature spinning0 band distillation columns can be improved b y using head and flask assemPERATION
MAGNETIC D R I V E THERMOCOUPLE
BRASS HOUSING
blies of new design. This equipment reduces leaks in the head and simplifies sample charging. The head assembly, shown in Figure 1, features a brass housing machined to fit the standard-taper glass joint of the condenser section. Besides the magnetic drive ( I ) , the housing contains the needle guide and stop, and thermocouple. A solenoid magnetizes the iron stop, which lifts the needle. The thermocouple is encased in hypodermicneedle tubing, which is soldered in place. This compact design eliminates a pressure - hose connection, threaded needle stop, and cement seal for the thermocouple; all mere possible sources of leaks in heads of earlier design
(4).
The flask assembly is shown in Figure 2. The distilling flask is cushioned on a heater and insulated; a twisted length of flexible Nichrome wire, soldered t o the end of the band, serves as a stirrer. The assembly can be rapidly positioned without danger of breaking the flask or column. Depressing the lever of the clamp allows the attached Dewar flask to be pivoted directly under the column. Then the assembly is raised with the flange guided between the slide rod 21 14
0
ANALYTICAL CHEMISTRY
BAND\
Figure 1.
s;; Head assembly
and guide bar. Releasing the lever locks the assembly in position. Both assemblies have greatly reduced maintenance and leaks. Because the drive shaft used with the head design is short, vibration is reduced and higher band speeds can be used to increase column efficiency ( 2 , 3 ) . The new flask assembly has almost eliminated the chief source of trouble in changing distillation flasks-breakage of columns.
Figure 2.
Flask assembly
LITERATURE CITED
(1) Foster,
N. G., Green, L. E.,
Jr., ANAL. CHEM.24, 1869 (1952); U. S. Patent 2,783,401(Feb. 26, 1957). (2) Nerheim, A. G., Ibid., 2,764,534 (Sept. 25, 1956). (3) Nerheim, A. G., Dinerstein, R. A, ANAL.CHEW28, 1029 (1956). (4) Winters, J. C., Dinersteiri, R. A., Ibid., 27, 546 (1955).
