as 160 ml. of 1.5M nitric acid being required to recover 99% of the uranium that was loaded initially onto the column. Other solutions that were briefly examined to determine whether the elution rate could be improved were nitric acid solutions of concentrations in the range from 0.3 to 5 M , 21M solutions of sodium carbonate, and sodium carbonate-hydrogen peroxide solutions. None of these proved superior to 1.5M nitric acid. Figure 8 shows a separation of 3 fig. of trivalent plutonium-239 and 5 mg. of sexivalent uranium-235 (93%). The sample volume was 3 ml. Plutonium(111) was easily removed with 60 to 80 ml. of 0.1M sulfuric acid, and the uranium(V1) was then eluted with 160 ml. of 1.511.1 nitric acid. Analysis of consecutive fractions of eluates from similar experiments by a-spectrometry indicated that generally there was no contamination of the uranium by plutonium, although con-
tamination was found occasionally, amounting at most to about 0.7% of the plutonium used. The system was not investigated further because of the prohibitively long elution required to recover uranium. This separation has been made the subject of patent action. ACKNOWLEDGMENT
Acknowledgment is made to the Staff of Chemical Services Department, Windscale Works, who carried out the a-spectrometric measurements, and to Dennis Roscoe, Chemical Services Department, Capenhurst, who supervised the analytical work. LITERATURE CITED
(1) Boscott, R. J., Nature 159,342 (1947). (2) Coleman, C. F., et al., Proc. 2nd
Intern. Conf. Peaceful Uses of Atomic Energy, Geneva, 1958, Pl510, 28, 278 (1959). (3) Currah, J. E., Beamish, F. E., IND.
ENG.CHEM.,ANAL.ED.19, 609 (1947). (4) Ellis, J. F., Iveson, G., “Gas Chromatography,” D. H. Destv, ed., p. 300. Butterworths Scientific Publicatiois, London, 1958. ( 5 ) Francois, C. A,, ANAL. CHEM. 30, 50 (1958). (6) Furman, S . H., ed., “Scotts’ Standard Methods of Chemical Analysis,” Vol. I. D. 1020. Van Nostrand. Sew York, 1939. ( 7 ) Hackl, O., 2. anal. Chem. 119, 321 (1940). (8) Lederer, E., Lederer, L., “Chromatography,” 2nd ed., Elsevier, New York, 1957. (9) Partridge, M. F., Chilton, J., Sature 167, 79-80 (1951). (10) Partridge, S. M., Swain, T., Zbzd., 166, 272 (1950). (11) Peppard, D. F., Mason, G. R., Gergel, 51. V., J . Inorg. & Surlear Chem. 3 , 370-8 (1957). (12) Sato, T., Zbid., 9, 188 (1959). (13) Sekersky, S., Komlinskaya, B., Atomnaya Energ. 7, 160 (1959). RECEIVEDfor review March 15, 1961. Accepted June 29, 1961. Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, Pittsburgh, Pa., February 1961.
Porous Glass Chromatography Used for the Characterization of Water-Soluble inks H. L. MacDONELL and J. P. WILLIAMS Research and Developrnenf Division, Corning Glass Works, Corning, N. Y
b Porous glass has been used as a chromatographic medium for the separation of water-soluble inks. The porous nature of this inert inorganic material, as well as its optical transparency, makes it unique in several respects when compared with paper chromatography. Alternation of the surface character of the silica network by treatment with acidic fluoride solutions or methanol produces changes in the chromatographic separation processes which can be observed b y optical transmittance curves and b y ultraviolet fluorescence.
to the separation of water-soluble dyes used in the manufacture of fountain pen inks and their subsequent characterization through visual observation or direct optical measurements. The necessity for ink characterizations has been discussed in considerable detail by many earlier investigators who also describe a wide variety of chromatographic techniques ( 2 , 3 ) . Without
T
continuity and uniform pore size (about 4 mp), the large void space (about %%), and the large surface area (about 150 sq. meters per gram) of 96% silica porous glass (Corning Glass Works Code 7930 glass), as described by Nordberg (IO), has suggested its use as a chromatographic medium (7). I n addition, the inert, inorganic nature of this matrix coupled with its optical transparency promise certain advantages over conventional chromatographic media. The use of porous glass in electrophoretic separations has also been noted (6): This investigation has been directed HE
1552
ANALYTICAL CHEMISTRY
exception these studies were made using opaque or translucent chromatographic media. For this reason i t was not possible to obtain spectral transmittance curves directly, and all qualitative measurements had to be made by reflectance similar to the work of Bailey and Casey (I). Infrared studies of the nature of silica and porous glass surfaces have indicated shifts in the OH absorption bands caused by adsorption of organic molecules and other reactions (4, 5 , 9, 2 1 ) . This present investigation has established that treatment of the porous glass with acidic fluoride solutions or with boiling methanol, so alters the silica surface character that the chromatograms obtained differ from those of untreated porous glass. EXPERIMENTAL
Wave l e n g t h , mp
Figure 1 . Optical transmittance curves of porous glass chromatograms
(yo)
Bottom, yellow components of Parker No. 5 0 4 3 green ink and Sheaffer No. 7 4 green ink Top, blue constituent of both Nos. 5 0 4 3 and 7 4 and Parker No. 5 0 3 4 blue ink
Untreated Porous Glasses. Porous glass in the form of polished plates I x 4x inches was used to develop the chromatograms. The sample was placed about inch from the end of the plate in the form of a line about inch wide. The plate was then inserted into a 250-nil. electrolytic (tall form) beaker with the sample-containing end downward. Distilled water, dilute acid (such as 1 :20 HCl), or dilute base
400
500
600
Wave Length, mu
Figure 2.
Optical transmittance curves
(70) of porous glass chromatograms
Bottom, dotted curvei reprerent overage curves shown in Figure 1, bottom ond top, which produce solid curve composite of tronminonce of unreporated green inks (Nos. 74 and 50431 TOP, ~pectrol transmittance CUIYCI of vnreporoted inti shown in Figure I INos. 74,5043, and 5034)
(such as 1 : Z O ",OH) were added until its surface was slightly heloiv the sample area of the plate. Finally, the beaker was covered with a watch glass. The entire assembly v a s left undisturbed until development n-as complete (usually about 24 hours). Following development, the chromatogram ,-as removed from the heakcr, .iripcd dry, and placed in a warm (40° to 50" C.) place to dry completely. The completeness of chromatogri;phic separation using porous glass is indicated by the spectral transmittance curr-es shown in Figures 1 and 2. Two porous glass chromatogra.iiis which nere developed with distilled water and with 1:20 HCl are illustrated in Figure 3. PRETREATMENT OF POROUS GLASS
The character of the porous glass surface was changed by boiling the
Wave Length, m p
Figure 3. Spectral transmittance curves Sheaffer No. 14 brown ink
I%)of
porous glass chromatograms of
Developing rolution 11 dirtilled water, 12) I 20 HCI
plates in reagent grade absolute niethanol for 17 hours and, in a second instance, hy soaking plates in an acidic fluoride solution for 1 hour. The fluoride solution was prepared by adding 75 ml. of 28% "&OH followed by 75 ml. of 48% HF to 330 nil. of distilled water and diluting to 1 liter. After each of the above treatments the plates mere rinsed in distilled \rater and then dried at about 50" C. Figure 4 shows a normal photograph of three porous glass chromatograms of Sheaffer No. 14 brown ink. Figure 5 is a photograph of the same chromatograms as viewed under ultraviolet radiation to indicate fluorescent activity. In both illustrations the chromatogram on the left was developed in normal porous glass, the middle chromatograin was produced in methanol-treated porous glass, and the chromatograni on the right resulted in fluoride-treated porous glass. These two illustrations show
that the methanol pretreatment of the porous glass has allowed a more complete migration of the fluorescent component in the sample. The fluoride pretreatment does not result in a separation of the fluorescent substance although its visihle chromatogram is altered. The effect of these two pretreatments on the visihle chromatographic characteristics is shown by the curves in Figure 6. These curves were obtained on the original sample areas of the chromatograms pictured in Figure 4.
EFFECT OF DEVELOPING SOLUTIONS
While porous glass chromatograms of inks were well developed and the hands sharply defined using aqueous solutions, attempts to employ organic solvents were not as successful. Organic liquids of high dielectric constant, such as triethyl phosphate and N,N'-dimethylformamide, required 10 to 20 times as long to develop chromatograms as did distilled water. Treatment of the porous glass, such as fluoride or methanol conditioning, has been necessary before lor\-er dirlectric organic liquids
Figure 4. Normal photograph of poroi matograms of Sheaffer No. 14 brown ink Left, normol porovr gla.. Center, methonol treated Right, fluoride treated
VOL. 33. NO. 1 1 , OCTOBER 1961
1553
Visual Description of Porous Glass Chromatograms of Commercially Available Black Inks
Sample Parker 5035
Sample spot
First Zone Deep violet
Second Zone Violet
Sheaffer 34 Sheaffer 64
Black Light blue
Faint violet Light blue
Faint violet Light blue
Sanford 235 Sanford 236
Green-violet Black
Waterman (new) Waterman (old) Carter 986 Higgins 812 Carter 99
Blue
Blue-green Very faint violet Blue
Blue-green Very faint violet Violet
Purple Blue Purple Violet
Third Zone Violet and yellow Faint violet Red and yellow Violet
Violet and yellow Purple Yellow-violet Blue Red-brown Rose Blue-green Faint purple Faint purple Faint purple Violet Yellow Violet
RESULTS
Table I records the visual comparison of porous glass chromatograms of ten different commercially available fountain pen inks using distilled water as a developing solution. These chromatograms represent a unique and uniformly reproducible characterization of commonly available black inks in the United States. Equally unique chromatograms were obtained for red, green, blue, blue-blacks, and brown inks (8).
Fourth Zone Violet
I
I
I
500
400
1
I
600
Wave Length, m p
Red-brown Blue Blue
Figure 6. Spectral transmittance (%) of corresponding sample areas of porous glass chromatograms of Sheaffer No. 14 brown ink 1. 2. 3.
Normal porous g h 5 5 Methanol treated Fluoride treated
Faint purple Violet
Chromatograms of other water-soluble dye combinations can be obtained easily. LITERATURE CITED
(1) Bailey, C. F., Casey, R. S., IND. ENG. CHEM., ANAL. ED. 19, -1020 (1947). (2) Brackett, J. W., Bradford, L. W., J . Criminal Law, Criminol. Police Sci. 43, 530 (1952). (3) Doud, D., J . Forensic Sci. 3, 364 (1958). (4) Folman, M., Yates. D. J. C., Trans. Faraday SOC.54, 1684 (1958).
(5)iLittle, L. H., Klauser, H. E., Amberg, C. H., Can. J . Chem. 3 9 , 4 2 (1961). (6) _MacDonell, H. L., ANAL.CHEM.33, la54 (1961). (7) MacDonell, H. L., Suture 189, 302 (1961). (8) MadDonell, € L., I. unpublished data. (9) McDonald, R . S., J . Am. Chem. SOC. 79,850 (1957). (IO) Nordberg, M . E., J . Am. Ceram. SOC. 27,299 (1944). (11) Sheoard. N.. Mathieu. M.-V.. Yates. ' D. J. X: Electrochem. 64, 734'( 1960):
e.,
RECEIVEDfor review May 1.5,. 1961. Accepted July 11, 1961. Division of Analytical Chemistry, 140th Meeting, ACS, Chicago, Ill., September 1961.
Porous Glass Electrophoresis H. L. MacDONEtL Research laboratory, Corning Glass Works, Corning, N.Y.
b Preliminary experiments using porous glass as a medium for electrophoresis separations are described. The porous nature of this inert inorganic material, in addition to its optical transparency, suggested this usage. Conditions for the separation of amino acids, water-soluble inks, and food dyes are given. A comparison between porous glass chromatography and porous glass electrophoresis is shown.
I
was suggested earlier t h a t porous glass (C-orning Code 7930 glass) should be investigated as a possible medium upon which to conduct electrophoretic separations (1). A preliminary investigation has confirmed that this medium is well suited for such separations. Amino acids, food colors, and fountain pen inks have produced electrophoresis patterns which offer the inherent properties of the original porous glass. Specifically, the optical transparency of this inorganic medium allows T
1554
ANALYTICAL CHEMISTRY
off center and running perpendicular to
mbc m
W r/ n
Figure 1.
\ adrm
Electrophoresis cell
absorption spectrophotometric measurements t o be made directly on the separated bands producing excellent transmission or absorption curves. PROCEDURE
For observing the separation of constituents in a single sample, a 1 X 3 inch or 1 X 5 inch porous glass slide was most convenient. Comparisons between two or more samples were made on larger pieces up to 2 or 3 inches wide. In all cases, polished glass 1.5 mm. in thickness was used. Single samples were superimposed on the reverse side of a pencil line located well
the long dimension of the slide. When two or more samples were run at the same time they were also placed on the reverse side of the pencil line but in the form of small spots rather than a line. Sample size will depend upon whether a line or spot. is placed on the glass. In either case the sample range was between 1 and 5 pl. As a result of the very high surface area of porous glass (ea. 150 to 200 sq. meters per gram), a small sample dries instantaneously upon application to the surface of the glass. The entire slide (or plate) is then submerged into a buffer and allowed to become completely saturated. This operation requires only 2 or 3 minutes at most. Complete saturation is easily observed by watching the buffer penetration from the edge of the glass. When saturated] the menisci meet in the center of the glass and disappear. The extremely small pore diameter of the glass does not allow a chromatographic effect to interfere and distort the sample during the saturation procedure. After the glass has become completely saturated, it is withdrawn from