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
(1) Bailey, C. F., Casey, R. S., IND. ENG. CHEM., ANAL. ED. 19, -1020 (1947). (2) Brackett, J. W., Bradford, L. W.,
(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 (8) MadDonell, € L., I. unpublished data.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):
(1958). (4) Folman, M., Yates. D. J. C., Trans. Faraday SOC.54, 1684 (1958).
RECEIVEDfor review May 1.5,. 1961. Accepted July 11, 1961. Division of Analytical Chemistry, 140th Meeting, ACS, Chicago, Ill., September 1961.
Chromatograms of other water-soluble dye combinations can be obtained easily. LITERATURE CITED
J . Criminal Law, Criminol. Police Sci. 43, 530 (1952). (3) Doud, D., J . Forensic Sci. 3, 364
e.,
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 that 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
. .
rous glass wliich has been previously dried. The very slow rate of liquid flow through porous glass virtually eliminates both staining and drying distortion of the final pattern. CONCLUSION
Figure 2. Porous gloss electrophoresis pottern of omino acid separation Buffer, pH 8.6 veional; potential, 1 6 0 volk; current Row, 2.6 ma; time, 2 hours Stained without drying in 2% ~-dimethyl.minobenroldehyde in 1 :1 HCI for 1 0 min. Migration wof toward the cothode (right1 Top, inddacetic acid Bottom, tryptophan
Electrophoresis separations have been achieved using porous glass as a support medium. The physical properties of this rigid, self-supporting, high silica, skeleton network predict still further applications. Continuous electrophoresis may well utilize the rigid structure and uniform flow rate of solutions through this material.
the buffer solution and the surface wiped dry with a clean soft cloth. The slide should immediately be placed into an electrophoresis cell similar to that shown in Figure 1 to nrevent surface drvine. drying. The ajjaws b; of the spring clips are lined with platinum foil to prevent corrosion. Filter paper wicks extend downward into additional buffer maintaining the porous glass in a saturated condition. Each of these strips should dip into separate beakers to prevent unnecessary current flow. Finally, water is added to the hottom of the outside container to maintain a high humidity within the cell retarding evaporation from the surface of the porous glass. After the above conditions have been satisfied, the cover of the cell may be secured and a potential applied to effect separation of the sample. A simple half-wave rectified circuit consisting of an isolation transformer, a 500-ma. silicone diode rectifier, and an electrolytic capacitor was employed. All separations were conducted a t 160 to 180 volts with an average current flow of about 2 to 3 ma. for a 1-inch strip and about 3 to 4 ma. for a 2-inch plate. I
Separations achieved from porous glass electrophoresis are rapid, distinct, and do not develop distortion during drying. Figure 2 illustrates a typical amino acid separation. Additional examples are shown in Figures 3 and 4 illustrating ink and food dye separations, respectively. Visible dyes such as those present in writing inks and food dyes require no additional staining. Porous glass ionograms of these substances are removed from the apparatus a t the conclusion of their separation, wiped dry, and placed in a warm (40' to 50" C.) place t o dry throughout. Drying will be complete in a few hours. In the case of amino acids or other colorless suhstmces the glass is dried, submerged into a staining solution, wiped dry, and thoroughly dried again, When the staining reagent has an appreciable color of its own, it is best to stain the glass as soon as it is removed from the electrophoresiscell without preliminary drying. This procedure limits
tigure 4. Porous glass electrophoresis pattern Ot UaKer I Blue Food Color Buffer, pH 8.6 verond; potential, 1 8 0 volts; current flow 1.6 ma.; time 2112 hours Migration wmi toward the anode (right)
penetration of the staining reagent into the glass and greatly reduces background coloration. Since staining is essentially a surface effect it does not reduce the resulting intensity of the stained components. Staining distortion due to Chromatographic effects is negligible even on PO-
LITERATURE
MacDonell,
