Dissolve this precipitate in sufficient 0.3M hydrochloric acid to yield a final volume of 16 ml. If at this point the solution has even the slightest brown cast (due to basic iron complexes) concentrated hydrochloric acid should be added dropwise followed by stirring, until a clear straw-yellow solution is obtained. If this precaution is not taken, a brown iron species is extracted which causes severe quenching. T o illustrate the applicability of this method for analyzing for iron-55 in biological materials, a blood sample was analyzed in duplicate by both this method and by electrodeposition. The results of these analyses are shown in Table 11. The electrodeposited samples were counted for 400 minutes each in a 2 P windowless proportional counter; 400-minute background counts were taken on each planchet prior to sample preparation. Each sample prepared for liquid scintillation counting was first equilibrated for 1 hour and then counted for 200 minutes. Next, each sample was automatically counted for 1 minute in the presence of the external standard for automatic computation of channels ratio. Background for the liquid scintillation counter had been previously determined for samples in the range of 1 to 15 mg of stable iron. It was found to be 6.07 f 0.17 cpm and independent of stable iron concentration. This procedure is currently being expanded to include the additional determination of iron-59 along with iron-55 and stable iron. Because iron-59 emits fairly energetic beta
particles, these events can be easily resolved in the third channel of a liquid scintillation counter. The ability to measure iron-55, iron-59, and stable iron simultaneously in the same sample would prove to be of great advantage in diagnostic iron function tests (8). It is likely that EHPA is applicable to liquid scintillation measurement of the specific activity of radionuclides other than those of iron, and this is presently under study. ACKNOWLEDGMENT
The authors thank Clifford Strehlow for his measurements of iron recovery, Naomi Harley for providing the calibrated iron-55 standard, and McDonald E. Wrenn for his informative discussions. RECEIVED for review April 12, 1967. Accepted October 6, 1967. This investigation, supported by a project grant from the United States Atomic Energy Commission, contract No. AT (30-1) 3086, is part of a core program supported by the U. S. Public Health Service, Bureau of State Services grant ES00014, and the National Cancer Institute grant CA06989. (8) W. C. Peacock, R. D. Evans, J. W. Irvine, Jr., W. M. Good, A. F. Kip, S. Weiss, and J. G. Gibson, J. Clin. Invest., 25, 605 (1946).
Rapid Gas Chromatographic Separation of Hydrocarbons over 200” C below Their Boiling Points UsingWater as Liquid Phase Barry L. Karger and Arleigh Hartkopf Department of Chemistry, Northeastern University, Boston, Mass.
02115
VOLATILE SOLVENTS have not been used very often as liquid phases in gas-liquid chromatography (GLC) because they seem to contradict the very meaning of the term stationary phase. Even at room temperature, many common solvents such as water, ethanol, and benzene have vapor pressures high enough that they would be gradually removed from the column during chromatographic operation. This change in column characteristics with time need not, however, be an insurmountable problem. Kwantes and Rijnders (1) were the first to presaturate the carrier gas with solvent to overcome this depletion problem. They used a forecolumn containing the same solvent as the column being studied to presaturate the carrier gas. Since then, a number of other workers have utilized this and similar techniques (2-5). The use of volatile solvents as stationary phases in GLC merits further study. In comparison to the ill-defined poly-
meric liquid phases often employed, these simple volatile solvents should offer more controllable and understandable mechanisms of separation. Also, most solution data (including chemical reaction equilibria and kinetics) have been obtained in such solvents. This information can be put to use in separation problems, or, conversely, data obtained by GLC can augment other studies. In this paper we report the use of water as a liquid phase for the separation and rapid elution of high molecular weight n-alkanes at temperatures over 200 O C below their boiling points.
(1) A. Kwantes and G. W. A. Rijnders in “Gas Chromatography
1958,” D. H. Desty, Ed., Butterworths, London, 1959. (2) 0. Grubner and L. Duskova, Collection Czech. Chem. Commun., 26, 3109 (1961). (3) L. H. Phifer and H. K. Plurnmer, ANAL. CHEM.,38, 1652 (1966). (4) R. E. Pecsar and J. J. Martin, Ibid.,p. 1661. (5) P. E. Barker and A. K. Hilmi, J. Gas Chromatog., 5 , 119 (1 967).
EXPERIMENTAL
An F & M Model 810 gas chromatograph equipped for on-column injection and flame-ionization detection was used in this work. T o eliminate the problem of solvent depletion, the carrier gas (He) was presaturated with water by inserting a thermostated fritted glass saturator between the flow controller and the injection port. Copper tubing, 1-meter or 3-meter X 0.25 inch, was packed with uncoated Chromosorb P, nonacid washed, 60/80 mesh (Johns-Manville). Water was added to the column packing by keeping the saturator 10” C above the column temperature. For steady-state operation both sections were kept at the same temperature. (Steady-state was assumed when solute retention times did not vary by more than 3 over a 12-hour period.) Average VOL 40, NO. 1, JANUARY 1968
215
Table I. Comparison of Gas Chromatographic Retention Data for Normal Alkanes on Different Liquid Phases, T = 50" C
Corrected Relative retention time, volatility, t R ' , min. (GO) CY (C1dClo) >io3 ca. 6 > 103 ca. 7
Column solvent bis-2-Ethylhexyl sebacate" Apiezon L grease" 20 5 Polyethylene glycol" Polydiethylene glycol succinate" 80 5
