The last column in Table I gives an indication of the behavior of each compound toward combustion fluid. I n general, compounds of similar constitution exhibit the same reactivity. The ease of oxidation is dependent on the solubility of the sample in the fluid. Compounds soluble at room temperature usually undergo oxidation immediately, although gentle warming is sometimes necessary to increase the rate of decomposition. Less soluble compounds are dissolved and oxidized by more vigorous heating. Initiators behave similarly to the nitroresorcinols from which they are derived; decompositions proceed smoothly at a low temperature. TetraBene fumes and tends to explode in contact with combustion fluid. It seems likely that the analysis of tetrazene by wet or dry combustion is
particularly difficult because of the low ignition temperature of the compound (about 130" C.) compared with those of the lead and barium salts of nitroresorcinols (230" to 250' C.). Low values are obtained for the carbon content of 1,3,5-trinitro-l,3,5triazacyclohexane (RDX) if the usual combustion fluid is used. Attempts to increase the efficiency of oxidation by using finely ground or reprecipitated RDX result in even lower values. Improved results are obtained by heating the reaction mixture rapidly but agreement is still unsatisfactory. These observations confirm earlier work [Farrington, P. S., Niemann, C., Swift, F,.H., ANAL. CREW 21, 1423 (1949)] which showed that compounds capable of forming hydrogen cyanide on decomposition frequently gave low values for carbon by wet combustion. As hydrogen
cyanide is known to undergo hydrolysis in strong sulfuric acid we decided to dilute the usual combustion fluid with water. Entirely satisfactory results are obtained when the wet combustion of RDX and other nitramines and nitrosamines is performed using combustion fluid containing 5% (w./w.) of water. ACKNOWLEDGMENT
The authors are indebted to G. W. C. Taylor and J. R. White for advice and assistance in the analysis of initiators. IVAN DUNSTAN JOHN v. GRIFFITHS
Ex losives Research and Development 8stablishment Ministry of Aviation Waltham Abbey Esaex, England
Partition of Pertechnetate Ion in Nitric Acid with Diethyl Ether One ml. of copper solution (3.0 mg./ml.) was added as a precipitating carrier. (The sulfide of copper is considered to be among one of the best carriers for technetium in sulfide precipitations.) Both were simultaneously heated in a water bavh and H$ waa passed through for the same length of time and cooled for the same length of time before filtering. The samples were filtered on glass fiber filter paper, mounted on stainless steel planchets, and counted. The extraction coefficient is defined as
SIR: In this laboratory it was necessary to obtain information of the partition behavior of tracer quantities of heptavalent technetium as TcOl- in nitric acid concentrations with diethyl ether. Boyd and Larson (1) have completed an excellent survey of the extractibility of technetium into various organic solvents. They reported the distribution coefficient for the pertechnetate ion 1N HnSO4 to be 0.029. Morgan and Sizeland (3) have shown that pertechnetate ion extracts into ether from nitric acid normalities of 0.0 to 4.0, whereas Gerlit (8) reported no extractibility of pertechnetate into ether from 2N H2S0,. EXPERIMENTAL
Apparatus and Reagents. All reagents used in this work were of the highest grade obtainable, usually Reagent ACS purity, which included diethyl ether, hydrogen sulfide, nitric acid, and copper wire. Technetium-99 (TI/? = 2.15 x 106 years) (Oak Ridge National Laboratory, Oak Ridge, Tenn.) in the form of ammonium pertechnetate was used as the radioactive tracer. The purity was about 99.5%. Proper amounts were used to yield solutions containing about 250 d.p.m. per ml. A Tracerlab SC-90 utility scaler equipped with a Tracerlab TGC-2/1B84 Geiger tube housed in a Tracerlab manual sample changer WM used for counting. (Background averaged about 18 c.p.m.) Procedure. Partition of the pertechnetate anion into diethyl ether
E9 =
v.
activity in the organic layer (1) activity in the aqueous layer ' V , Close temperature control was not necessary for the extraction condition Figure 1. Variation of the extraction coefficient of TcO4- with ni':ic acid ~~~
was investigated in the following manner: I n a 125-ml. separatory funnel 4.0 ml. of pertechnetate solution (about 1 X 10s d.p.m.) and a proper amount of nitric acid and distilled water were added to obtain a volume of 10.0 ml. of desired normality of nitric acid. 10.0 ml. of diethyl ether was added, and the two components were vigorously shaken and allowed to equilibrate. After complete separation, the aqueous layer was drawn off into one beaker. The ether layer was backextracted with three portions of 15 ml. of distilled water and all collected into another beaker. Each fraction was made 2N with nitric acid with a total volume of approximately 100 ml.
~
Table 1. Extraction Coefficients of Tc04- in HNOI Media with Diethyl Ether Initial "0, N Extraction in Aqueous Phase Coefficient 0.0 0.016
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 6.0 8.0 10.0
0,029 0.047 0,068
0.087 0,094 0.244 0,271 0.413 0.408
0.705 0.906 1,267 1.098
VOL. 34, NO. 10, SEPTEMBER 1962
1349
(I) ; thus, all extractions took place a t room temperature (25' + 1' C.). To prove that the back extraction was complete, the ether layer was evaporated on a planchet and counted. Less than 1 c.p.m. was detected which indicated a good back extraction. The average error was about 20%. Experimental results are shown in Table I and Figure 1. DISCUSSION
TCO4- is an example of the MXaclass of complexed metal ions. The presence of donor atoms in the organic liquid enhances the extraction of the pertechnetate ion. Although the pertechnetate anion is poorly extracted into diethyl ether, there is evidence that the partition is significant. In
the region of 0.0 to 6.ON HKOa thr extraction coefficient is significantly dependent upon hydrogcn ion concentration. Increasing thc acidity of the aqueous layer favors protonation of the ether molecule to yield the diethH yloxonium ion, CzHs-0-CzH5+. This might provide an explanation of the increased extractibility of pertechnetate ion with increasing hydrogen ion concentration by the "oxonium" salt
H formation C:H~-0-CC2H5+TcO4-. In the region of 6.0 to 10.ON HNO,, it appears that maximum protonation has been obtained, and the partition of the pertechnetate ion is a t a relative maximum.
ACKNOWLEDGMENT
The author tliniiks P. K. Kuroda for his tlirec*tionof this research and for his cnc~our:igrnietit. LITERATURE CITED
(1) Boyd, G. E., Larson, Q. V., J . Phys. Chem. 64, 988 (1960). (2) Gerlit, J. B., PTOC.Intern. Cmj. Peaceful Uses At. Energy, Geneva, 1966, Vol. 7 , p. 145 (1956). (3) Morgan, F., Sizeland, M. L., U . K .
At. Energy Authority Report AERE C/M 96 (1950). MOSESA'ITREP, JR Department of Chemistry University of Arkansas
Fayetteville, Ark. THISinvestigation waa performed under the auspices of the U. S. Atomic Energy Commission Contract At-(40-1)-1313.
Water Transpiration as an Aid to Quantitative Paper Chromatography of C144abeled Compounds Paul D. Hoeprich and James N. Whitesides, Department of Internal Medicine, University of Utah College of Medicine, and the Salt Lake County General Hospital, Salt Lake City, Utah
ELIABLE
RADIOCARBON
R compounds chromatography
ASSAY
Of
separated by paper requires quantitative recovery of each compound in a form suitable for measurement of radioactivity. The burden of nonsample carbon must be minimal because high efficiency in carbon-14 measurement generally requires combustion to yield the sample carbon as carbon dioxide. Various elution techniques (4, 6, 8) useful to chemical analysis result in relatively large volumes of aqueous solutions. The additional procedure of drying required before combustion can be carried out is tedious and carries with it the risk of loss of some carbon if heating is used to hasten the process (CY) E~risionof the filter paper locus of a separated rompound, followed by comhistion and recovery of the samplr (*arbon,phis tlw rarbon of the supporting paper, should yield quantitativc recovery of the sample carbon. However, the location of the compound must be precisely defined; if this is done by color development, loss of sample carbon is again a hazard. Color development loss of sample carbon can be avoided by cutting the paper chromatogram so as to leave a wide border around a zone known to 1350
ANALYTICAL CHEMISTRY
contain a compound by comparison with a concomitantly irrigated, colordeveloped guide strip. But after combustion, the sample radiocarbon may be so diluted by the large amount of supporting paper stable carbon that counting of radioactivity may be seriously hampered. Glass fiber sheets for chromatography ought to avoid dilution of sample carbon. However, in our hands, such sheets were friable and difficult to handle, even after treatment with monopotassium phosphate (3) or alumina ( 5 ) . In addition, we did not obtain satisfactory chromatographic separation of mixtures of monosaccharides with glass fiber sheets. Transfer of separatrd sugars from filter paper to small fiber glass sheets has been accomplished with 1 0 0 ~ orecovery by chemicnl analysis (7). Our experience, using C"4-labelrd monosaccharides indicated transfer was not romplete. Quantitative recovery of C14-labeled monosaccharides after chromatographic resolution on filter paper has attended concentration by water transpiration. That other water soluble C14-labeled compounds should be amenable to quantitative recovery from paper chromatograms by this technique is sug-
gested both by our radioassay data with monosaccharides (Figure 1) and by the chemical data accumulated by Davis, Dubbs, and Adams with purines and pyrimidines (2). EXPERIMENTAL
Ten- and 5O-pl. aliquots of an aqueous solution containing D-glucuronic acid (-6-C14) (0.40j0),D-glucose (uniformly Clelabeled) (0.8%), and >rhamnose (-l-C14) (0.870) were applied marginally and centrally, respectively, on two 15 X 57 cm. sheets of Whatman No. 2 filter paper (sites A and B of Figure 1). Irrigation a t room temperature, descending, with ethyl acetatepyridine-water (120: 50: 40) was continued for 18 hours. A 2-cm. wide marginal strip bearing the resolved sugars of the 10-11. aliquot (deposited at A , Figure 1) was cut off and sprayed with aniline-salicylate reagent (aniline, 0.93 gram; salicylic acid, 2.76 grams; acetone q.s. 100 ml.) before heating for 5 minutes a t 106' Cy. In descending order from the origin spots appeared representing: 1)-glucuronic acid, Dglucose, Lrliamnose ( G A , G, and R, Figure 1). Guided by the location of the marginal strip spots, the remainder of each sheet was cut into transverse segments, allowing a t least 2 cm. above and below the predicted locus of a separated monosaccharide. Each segment was trimmed to a blunted point a t one
