~
Table I.
N O I5 HYPODERMIC
Performance of Unit
Added, Recovered, Methyl stearate Methyl arachidate
R4g. 24.9 26.1
RTg. 24.9 26.1
,
OETECTiON CELL/ *-- /
BOX
, TEFLON
E X I T TUBE
STOPCOCK
F///,'
, '/ /
/ / , ,
'\ -~ or component could be collected separately without disturbing the pressure in the system. In actual practice a momentary deviation was noted on the recorder as the Teflon stopcock was turned, A knonn mixture of methyl stearate and methyl arachidate was separated and the fractions FTere collected. The unit was operated at a temperature of 225' C., inlet pressure 70 mni. of mercury. outlet pressure 2 nim. of mercury, in a column 3/g inch X 5 feet, packing Cz2 fire brick, 10 to 30 mesh, impregnated rrith silicone grease. Recovery was quantitative as shown in Table I. ISSGED as 90.4897 by the Sational Research Council of Canada.
NEEDLE
INSULATED
SILICON
RUBBER
WASHER
GLASS WOOL-
J
n
lo VACUUM
+-
Figure 1.
4
Collection unit
Upper part. Detailed view of unit Lower left. Collector tube Lower right. Frontal view of assembly
A Simple Ascending Paper-Strip Chromatography Device for Rapid Exploratory Studies
G.J.
Miller and
R. J.
McColloch, Department of Agricultural Research Chemistry, University of Wyoming, Laramie, Wyo.
for paper M chromatography are now available (1-3), but simple, rapid, paper-strip AXT ELEGANT TECHNIQUES
methods can be employed in exploratory work with a minimum of effort and specialized equipment (2, 4, 5 ) . The apparatus described n-as developed for rapid qualitative chromatography in studies of stored-meat flavors. It has all the advantages of speed and simplicity found in the popular test-tube chromatography ( 5 ) , but avoids the difficulties inherent in this technique. Much longer paper strips can be employed, the difficult task of cutting trapezoidal paper strips is unnecessary, and a vapor-proof glass-to-glass seal is provided for the chromatography chamber. The apparatus, shown in Figure 1, consists of a separable vacuum trap used for the chromatography chamber, a thermometer suspension glass stopper from which the paper is suspended, and a special paper-weighting device which makes the use of this system possible. The separable vacuum trap and thermometer suspension stopper are commercially available in chemical glassware having standard taper ground glass joints. The chamber shown in Figure 1 was 200 mm. long and had an outside diameter of 27 mm. below the joint. However, various other sizes are commercially available. The application of this glassnre to paper-strip chromatography is made
320
ANALYTICAL CHEMISTRY
possible only by the special paper weight, which prevents the paper strip contacting the chamber wall after it has become wet with solvent. This weighting device is made from the largest diameter glass tubing which will slide through the mouth of the vacuum trap. The glass tubing is sawed into 0.5- to 1-inch lengths to form the paper weight. The hook arrangement on the weight may be formed from glass rod or with wire-e.g., stainless steel, Nichrome, or platinumwhich is inert to the solvent system used. -4 piece of the wire is woven across the glass ring in the pattern of a figure 8, and another piece of wire is woven across the ring in the same manner a t right angles to the first. This forms a wire intersection a t the center of the glass ring. A wire or a double glass hook can then be used a t this intersection to suspend the weight from the bottom of the paper strip. Holes arc? made at the top and bottom of the paper strip with a paper punch to accommodate the paper and the weight suspension hooks. To ensure even development of the chromatogram, hhe solvent layer in the vacuum trap should be higher than the punched hole at the bottom of the strip. The weighting device has been employed satisfactorily with Whatman Nos. 1,4,and 40 papers in both aqueous and nonaqueous solvent systems. il solid or a hollo-iv (Figure 1) thermometer suspension stopper may be
used. It is easier to hang the paper from the hook of the solid stopper, but the hollow stopper furnishes additional restriction of lateral movement a t the top of the paper strip.
PART S T O P P E R , WITH HOOK
-INNER
1-T
29/42
-
SEPARABLE VAOUUY TRAP
-PAPER
STRIP
€El\/
SPECIAL WEIOHT
Figure 1. Chromatography assembly illustrating paper weight in use
1,
K i t h the system illustrated in Figure developing chromatograms have
been carried in vest pockets without adverse effects. LITERATURE CITED
(1) Block, R. J., Durrum, E. L., Zneig,
G., “-1 Manual of Paper Chromatography and Paper Electrophoresis,” Academic Press, Xew York, 1955. (2) Cas&, H. G., *‘Techniquesof organic Chemistry,” A. Weissberger, ed., Vol. X, p. 135, Interscience, Sew York, 1957. (3) Lederer, E., Lederer, AI, “Chromatography, A Review of Principles and
Applications,” Elsevier, Ken- York, 1957. (4) Mitchell, L. C., J . Assoc. Oflc. Agr. Chemists 40, 999 (1957). ( 5 ) Rockland, L. B , Dunn, M. S., Sczence 109, 539 (1949). APPROVEDfor publication by the director of the Wyoming Agricultural Experiment Station as Journal Paper No. 104.
Potassium Bromide Pellet Technique Alien L. Olsen, Chemistry Division, U. S. Naval Ordnance Test Station, China Lake, Calif.
used t o preN pare potassium bromide disks for solid phase infrared spectroscopy, have U J ~ E R O U SDIE DESIGNS,
been described recently (1, 3, 5 , ’79). The most practical design, from the standpoint of fabrication, produces a circular plate. To eject the pressed specimen, without damage of radial cracking or peripheral shattering, the die is provided with a split-bore chamber, or the plungers press the potassium bromide into steel rings. In the latter case, even with moderate pressing pressures, permanent distortion of thinn-alled rings occurs, restricting the number of presses available from each ring. As an even more serious consequence, this distortion brings about a scoring of die-bore surfaces until the punches no longer pass freely. Measurement of the infrared spectra of fusible solids in a cell at elevated temperatures required a maximum diameter of the pressed halide disk. A simple, evacuable, and easily manipulated die, designed for use in the ARL-
Dietert briquetting press and eniploying a new technique of pressing the ‘/,-inch diameter pellet directly into a 1-inch diameter ring, is described. The pressed disk fits directly into the PerkinElmer demountable cell holder, or by removal of the lead ring, the disk can be inserted in the specimen holder of the high-temperature cell (6) I
APPARATUS
The various parts of the die assembly, designed and fabricated by the Applied Research Laboratories, Glendale, Calif., are shown in Figure 1. The die body was machined from a 3-inch diameter AIS1 440C stainless steel rod and hardened t o a Rockwell C-50. Tungsten carbide cylinders, Kennametal K-96, provided with a 4microinch finish on the pressing faces, become the top and bottom plungers. A 1-inch stainless steel rod serves to insert the seal ring into its O-ring groove ivithout damage and to pack initially the pondered potassium bromide into the lead ring. The filling sleeve provides a means of inTOP CAP
TUNGSTEN CARBIDE
Figure 1 . Die assembly for pressing potassium bromide disks
n -7
TAMPER O-RING GUIDE
O-RING
,/ ,-FILLING SLEEVE UPPER PLUNGER
HOSE ADAPTER
RING LOWER PLUNGER COLLAR LOWER PLUNGER
traducing the powdered potassium bromide into the die body. A constraining sleeve for the upper plunger makes it possible for the pressing surfaces to compress the powder within the lead ring. O-rings within the die body and on the under side of the top cap provide adequate seals for evacuation. Lead rings with 1-inch outside diameter, 7,’s-inch inside diameter, and a length of l/s-inch can either be machined by use of simple jigs or punched out from a sheet of alloyed lead. As the potassium bromide die is now commercially available from the Applied Research Laboratories, details on tolerances are omitted. S n BRL-Dietert briquetting press was employed in the pressing operations. A Perkin-Elmer Model 21 spectrophotometer n-as used to determine transiiiiqsion data. TECHNIQUE
Sample Preparation. For qualitative cleterminations, approximately 2 grams of infrared-quality potassium bromide, and 3 t o 5 mg. of finely divided sample n ere weighed out. The vibrator-grinding technique n as used for the dispersion of the sample in the ponder ( 5 ) . Pressing Operation. The lower plunger, attached to the top of the ram by the retaining ring, and the die are placed a t the top of the recess of the briquetting press. The ram and plunger are lowered to the bottom position and the lead ring and filling sleeve are inserted into the bole. The powder charge is introduced and leveled nith a straight edge of a spatula. The plunger-tamper further flattens and compacts the charge within the lead ring. The top plunger with its retainer sleeve is inserted into the die bore; the bridge of the prms is secured in pressing position, and the die cavity is evacuated for 2 minutes. 4 pressure of 80,000 pounds total force or approxiniately 133,000 p.s.i. is applied for 2 minutes. The pressure is gradually released to zero dial reading and the vacuum line is opened to the atmosphere. The bridge support is swung to the ejection position, holding the die body with one edge of the bridge, n-hile the compressed pellet is ejected by the ram action. If the lead ring adheres to the punch, a simple twist removes ring and pellet. Lead flash, VOL. 31, NO. 2, FEBRUARY 1 9 5 9
321
