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V O L U M E 2 4 , NO. 6, J U N E 1 9 5 2 Table IV.
Recoveries of Acids Cc to C, on Column I and Cj to GOon Column I1
Mixture A, Column I Calcd.. Found, Recovery, Arids
mg.
2.93 2.93 2.93 2.93 1.95 1.95 1.95 1.95
mg. 2.77 2.80 2.98 2.91 1.81 1.84 2.05 1.96
%
94.5 93.0 101.7 99.3 92.8 94.3 105.2 101 0
Acids CIO Ce Cs CI CIO Cs
Cs C,
Mixture B, Column I1 Calcd., Found, Recovery, mg. mg. % 2.03 91.1 2.23 2.22 99.4 2.23 2.61 97.0 2.69 2.28 102.2 2.23 2.04 91.5 2.23 2.22 99.4 2.23 2.61 97.0 2.69 2.12 96.1 2.23
c'; band from column I1 and a t the end of the C, band from column I. If, however, 1 drop of 1% alcoholic phenolphthalein solution is added a t that point, the pink coloration of the top layer reappears if alkali is still present. To allow this check to be made, an eye dropper containing the extra indicator is fitted, from the beginning of the operation, in the cork stopper placed inside tube Q of the adapter.
Experimental. REAGEXTSSilicic acid, Mallinckrodt KO. 2844 or 2847. Distilled water 1 M sodium hydroxide. CB6, CBIo. Chloroform (U.S.P. or c.P.), purified by passing through B column of aluminum oxide to ensure a low blank (0.06 ml. of 0.01 A- sodium hydroxide for 20 ml.). Butanol, Eastman Kodak, white label. Sodium hydroxide solution, 0.01 N (titration). Acetone, alcohol, acid-free, redistilled. Dicarboxylic acids. .\I1 yere Eastman Kodak white label without purification except suberic acid, which was synthesized ( l o ) ,and glutaric acid, recrystallized from hot benzene. The acid values were within 1% of theory Melting points were correct, but the range was 3' for sebacic acid. -4CID MIXTURES ASALYZED, COIJJMNUSED. Duplicate analyses of two mixtures, A and B, were made. Mixture A (Cd, C6, Cg, and C,) was analyzed on column I (3 3 ml. of water, 10.1 grams of sllicic acid, Mallinckrodt No. 2844). The powder mixture was made of 5 ml. of acetone solution containing 25 mg. of each acid and 12.8 grams of silicic acid, The first analysis was made using 1.50 grams of the powder mixture, the duplicate with 1 gram. Mixture €3 was analyzed on column I1 (10 ml. of water,
3 drops of 1 N sodium hydroxide, 30.5 grams of silicic acid No. 2844). The powder mixture was made of 5 ml. of acetone solution containing Clo., Cs, and C, (25 mg. eFch) and CS (30 mg.); 16.8 grams of silicic acid were mixed with this solution. In each duplicate analysis 1.5 grams of the powder mixture were used. RESULTS, DISCUSSION, AND CONCLUSIOK
Table IV shows that recoveries are about 95% or better, except for sebacic acid. Impurities in sebacic acid were no doubt partly responsible for the discrepancy observed: When purified sebacic acid was used, the recovery was always higher, although consistently 3 to 5% too low; this suggested that some other cause was involved. I t is suspected that the blsnk correction, as obtained, is systematically too high in that region. Quantities of acids as low as 0.5 mg. and as high as 7.5 mg. have been estimated successfully. The separations of Clo from Cp and of Ca from C, are not as sharp as the others, a consequence of the even-odd solubilities alternation which is not entirely compensated for by the solvent combination used. Other results indicate that hendecadioic acid would be separated very satisfactorily on column I1 and that the acids up to brassylic could be separated on a somewhat higher column (15 ml. of water). LITERATURE CITED
(1) Rergmann, P. I%.,Keppler. J. G., and Boekenoogen, H. A., Rec. trav. chim., 69, 439 (1950). (2) Cassidy, H. G., and Nestler, F. H. >I., Discussions Faraday SOC., 7, 259 (1949). (3) (4) (5)
Fairbairn, D., and Harpur, R. P., Can. J . C h a . , 8 , 633 (1951). Fairbairn, D., and Harpur, R. P., N a t u r e , 166, 789 (1950). .Marvel, C. S.,and Rand, R. D., J . Am. Ch,em. Soc., 72, 2642
(1950). (6) Matthew, F. JV., Warren, G. G., and Uichell, J. H., ANAL. CHEM.,22, 514 (1950). (7) Neish, A. C., Can. J . Research, 27B, 1 (1949). (8) Ramsey, L. L., and Patterson, W. I., J . Assoc. O f i c . Aur. Chemists, 28, 744 (1945). (9) Ibid., 31, 139 (1948). (10) Walker, J., J . C h e m Soc., 1940, 1304.
R E C E I Y Efor D re\-ie\v September 8, 1951. Accepted March 25, 1952.
Dielectric Indicator for Column Chromatography DONALD E. LASKOWSKI AND RICHARD E. PUTSCHER Armour Research Foundation of Illinois Znstitute of Technology, Chicago 16, 111. The purpose of this work was to determine the feasibility of using a dielectric constant-sensitive device for detecting colorless components in the effluent stream of a chromatographic column. The instrument chosen for this work was the Thermocap relay. With properly designed dielectric cells this instrument has proved to be a very sensitive detector of small changes in the dielectric propertiesof the eluate. Several examples of separations achieved are described. This instrument should find wide use among chromatographers working w-i th colorless substances.
T
HAT different solvents possess different dielectric constants and that the dielectric constant of a solution varies with the concentration of the solute are well known. As qualitative measurement of changes in the dielectric properties of a subetance is relatively simple, it was felt that this type of measurement should offer a n easy and useful method for detecting the presence of colorless components during a chromatographic separation. Zechmeister (6)and Cassidy (1) refer t o work by Troitskii (4), i n which he detected the presence of colorless bands on the column by means of the dielectric properties of the adsorbed material. A set of earphones was used as an indicator t o locate the bands.
Although this method is a sound one, it leaves much to be desired; its sensitivity is poor and the results are a t times questionable. It was felt that a device that would continuously measure the dielectric properties of the eluate would be more sensitive and useful. An instrument of this type should be sensitive to small changes in dieleceric constant but stable over a n extended period of time, be simple to operate, and require a minimum amount of attention, Preferably, it should require no knowledge of electronics on the part of the operator, and it should be relatively inexpensive and readily available t o the practicing chromatographer, In order t o meet these requirements, two courses were available: t o
ANALYTICAL CHEMISTRY
966
design an instrument with the desired qualifications or select an availsble instrument that already possessed these requirements. The latter course was chosen.
rn
-e33
(D
QUIPMENT AND REAGENTS
._ ..._ ~~
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C.P.
reagent grade, used without further puri-
fieat.ion.
I
C
Satisfactory Cell Designs
Figure 3.
Figure 1. Thermoeap Relay
constant level of liquid between the condenser plates. For liquids of low dielectric constant, it must have the largest plate area consistent with t h e smallest possible hold-up volume. For liquids of high dielectric constant, the plate area should be large enough t o
The equipment used was a Thermacap relay manufactured by ,he Niagara Electron Laboratories, Andover, N. Y. This instrunent is normally used as a. thermal regulator; however, it was 1'onnd to work verv ~" well 8 8 a dielectric indicator for column :hromatography, without modifications. The frequency of os:illation, caleulrtted from the circuit parameters, is roughly 320 ~
~~~~~~
~
~
~~
~
Immeter, B i c a piidt light, C i s a &3ppfd. variable air condenser, D is a D - 7 5 ~ f dvariable . air condenser. Faoh condenser has I scale divided into 100 equal divisions.
Iind
Figure 4.
Calibration Curves for Three Cells
roinfs ohfaincd h) using liquids of known dielectric EO"StP"t
ship of dielectdo cell to ostiIl=tar Eircuit A . To indicator oircnif
-. ~'iowst h,e nortion of the circuit actually concerned r,gure " SL with indicatin g ch?ni condenser sh
