A Macro Spinning-Band Distillation Column Freeman S. Jones and A. Glenn Neheim, Research and Development Department, Standard Oil Co. (Indiana), Whiting, Ind.
distillation columns S have low holdup and low pressure drop, but have the disadvantage of a PINNING-BAND
greater height equivalent to a theoretical plate (KETP) than many packed columns of corresponding size (6,6). The efficiency of miniature spinningband columns fractionating 15 to 50 ml. has been increased by using bands made of Teflon (4). The same approach has now been applied to increase the efficiency of macrocolumns fractionating charges of 1 to 5 liters. Teflon bands were con-
structed with cross sections of two designs : Lengths of Teflon with serrated edges were machined and connected to form bands to fit a column 120 cm. long and 1.3 cm. in diameter. The procedure was that used in the construction of Teflon bands for miniature columns (4). Each band was plate-tested a t atmospheric pressure and total reflux with a mixture of n-heptane and 2,2.4-trimethylpentane (I). Because Teflon would deposit on a dry column wall and reduce efficiency, reflux was established before spinning the band. Optimum efficiency of both bands was attained at speeds of 2500 to 3500 r.p.m.
A comparison of the performance of these macro spinning-band columns with those reported in the literature gave the results in Table I. The columns with Teflon bands have lower HETP values than those with metal
bands. Lowest H E T P values were obtained with the four-bladed Teflon band, even at high throughput. Although the columns differed somewhat in dimensions, the observed differences in performance check earlier experience ( 4 ) with miniature columns of identical dimensions. Both band design and the use of Teflon increase efficiency of macro spinning-band colurnns. I n contrast to metal bands with two blades, the Teflon bands feature large band core and more points of contact with the reflux on the column wall Although the six-bladed band has more points of contact, the four-bladed one has the larger core and higher efficiency. Fur$her improvement may be possible through modifications of these band designs. LITERATURE CITED
Table 1.
Dimensions, Cm. 145 X 1.5 183 X 1.5 120 X 1.3 120 X 1.3 120 X 1.3
Performance of Spinning-Band Columns
Band Construction Pbladed, metal Pbladed, metal Cbladed, Teflon Cbladed, Teflon &bladed, Teflon
Throughput, Ml./Hr. 100 400 100 1500 100
HETP, Cm. 2.1 (3) 3.3 ( 2 ) 1.2 1.6 1.6
(1) Griswold, J., Z n d . Eng. Chem. 35, 247 (1943). (2) Hoffsommer, R. B., Jr., M.S. thesis, Pennsylvania State University, 1956. (3) Murray, K. E., J. Am. Oil Chemists' SOC.28, 1 (1951). (4) Nerheim, A.G., ANAL.CHEW29,1546 (1957). (5) Nerheim, A. G.,Dinerstein, R . h., Ibid., 28, 1029 (1956). (6) Winters, J. C.,Dinerstein, R. .4., Ibid., 27,546 (1955).
Detection and Differentiation of Sugars and Polyols on Single Paper Chromatograms Ross C. Bean and G. G. Porter, Department of Plant Biochemistry, University of California, Riverside, Calif.
procedures have been devised M for the detection of sugars and sugar alcohols on paper chromatograms. ANY
It is nonnally rather difficult t o distinguish between these two classes of compounds on a single chromatogram when they are p a n t in mixtures. Procedures have been published that make i t possible t o differentiate between the sugars and polyols on single chromatograms (I, a), but these are not entirely satisfactory, because they require rather close control of conditions and frequently do not distinguish between overlapping sugars and polyols. The normal procedure of detecting sugars on chromatograms with panisidine hydrochloride (3) can be followed with a periodate treatment which depresses the sugar color and gives rise to a highly sensitive reaction with polyols, permitting their detection even where extensive overlap occurs.
The chromatogram is dipped in a 1% solution of panisidine hydrochloride in butanol (3) or in a saturated solution of benzidine hydrochloride in ethanol and heated by any accepted procedure to produce the normal sugar colors. Heating ovens, hot plates, or infrared lamps have been used successfully. Temperatures should be greater than 100' C. with the panisidine and 120' C. for the benzidine treatment. The chromatogram is heated long enough (3 to 10 minutes) to develop maximal sugar color without excessive background. The sugar spots should be outlined with the pencil or photographed for future reference, because the subsequent step for detection of the polyols results in loss of most of the color due to sugars in many cases. The paper is dipped in a solution freshly mixed from 1 volume of saturated aqueous potassium metaperiodate and 4 volumes of acetone. A s the solvent dries, the polyols appear as white or
yellow spots on a purple (anisidine) or blue (benzidine) background. Maximum sensitivit,y is found soon after development of the color, although the spots with the benzidine treatment may be stable with levels of polyol above 25 y. The spots with panisidin(%tend to fade rather rapidly, although the, initial srnsitivity with this rcagcnt is about the same as with hnzidinc.. Where overlap occurs, the whit'? alcohol spot may suppress the sugar color conipletely unless the sugar is in high cowcentration relative to the polyol and then only a white edge to the spot may indicate the presence of the polyol. The sugar color rcagrnts should prepared fresh daily for maximum sensitivity. The saturated metapcriodatc,. prepared by shaking for a while with itn excess of crystals, may he storcd for VOL. 31, NO. 1 1 , NOVEMBER 1959
1929
