I
I3
Part A
B C
D
Table I. List of Materials and Parts for Fluidized Drier (Figure 2) No. 1 Bathroom sink drain pipe (chromium plated brass or SA) 11/4-in.0.d. except at base 0.d. with ll/z which is expanded to 13/~-in. UNF thread. Mfgd by Sterling Tube Co. 1 Kimax fritted disk, 40-mm 0.d. medium porosity, Cat. No. 28280. 1 Pc. alum. tube-ll/$ inch long by 3/~-in.0.d. (for t hermowell). 1 Pc. aluminum round stock or flat plate, 41/2 inch in diameter or square by 3 / 4 inch thick. Bore out to ll/>inch and thread to 12 UNF inside to fit drain tube. 1 Brass fitting male pipe to l/s-in. tube (any appropriate connector to dry nitrogen or air supply).
Parcher and Urone ( 2 ) used a special glass coating and drying type of fluidizer to show that uniform and reproducible coating of the support material could be obtained. The information shown by Kruppa, Henly, and Smead ( I ) , which gave the column efficiencies of the tray-dried packing cs. the fluidized bed-dried packing material, demonstrated the superior performance of the fluidized drying technique. The materials are listed in Table I, and most of them can be obtained from local hardware stores or welding shops. The base plate shown in Figure 1 is the item of major cost. It can be made from any aluminum plate having at least a L/8-inchthickness ( 3/r-inch is recommended). The base plate has to be machined to fit the bathroom sink drain tube which is l1i2inches UNF thread. Figure 2 shows a pictorial view, and the remainder of the parts can be assembled accordingly.
The exact version of the fluidizer described herein has been used consistently in our laboratory for the past three years with much success in duplicating and reproducing G C packing materials, and all for a very modest cost. The use of the fluidizer is as follows. The fluidizer is placed on a hot plate and a source of dry nitrogen or helium is connected to the gas inlet. The fluidizer is heated on a hot plate from 45 to 55 “C; the temperature is measured by a thermometer inserted into the thermowell in the base plate of the fluidizer. The high mass of the base plate allows a sufficient heat transfer to warm the incoming gas which helps dry the packing material. Freshly coated packing material is placed into the fluidizer and the gas flow adjusted to give a low fluidizing effect. As the packing material approaches dryness, the gas flow should be decreased to avoid a high rate of attrition of the particles. The drying time will depend on the solvent used; for dichloromethane, about five minutes is adequate. The packing material after drying, may be used a t once.
(2) J. F. Parcher and P. Urone, J. Gas C/zvomatogr., 2, 184 (1964).
RECEIVED for review June 5, 1972. Accepted July 27, 1972.
Figure 2. Exploded pictorial of fluidized drier
Thin-Film Sorbents for Obtaining Acridine Dye Spectra J. J. Sjoblom 6303 Lake Road West, Ashtabula, Ohio 44004 chloroform and one of 96% ethanol ( I ) . The dipped cover FORTHE PURPOSE of obtaining absorption and luminescence glasses were drained for 2 hours, in a covered jar full of chlorospectra of acridine dyes sorbed by cellulose acetate or silica form vapor, then allowed to dry in a crystallizing dish out of gel, methods were worked out for preparing thin films of these which chloroform had just been poured. After 6 hours of sorbents on glass. A minimum of light scattering was evacuation of these plates at room temperature (elevated temachieved by these matrices. The acridine dye sorbed by and peratures apparently shrink the films so that sorption of dye tested on these films was trypaflavine ( C I I H ~ ~ N I . C H ~ C ~ . H C ~does ) . not take place), they were immersed for 30 minutes in 4 Thin-film preparations and sorption conditions are specified 10-4M trypaflavine solution and rinsed in water. The below. The spectral results in the absence and presence Of cellophane skin was wrinkled while wet, but smooth after oxygen will be indicated briefly. drying. CELLULOSE ACETATE FILMS ON GLASS Dry, clean rectangular cover glasses for microscopic slides were dipped in a 3 % solution of EK cellulose triacetate (tetrachloroethane-soluble) in a solvent made up of 9 volumes of 2416
a
(1) H. N. Holmes, “Laboratory Manual of Colloid Chemistry,” 3rd ed., John Wiley & Sons, New York, N.Y., 1934, p 21.
ANALYTICAL CHEMISTRY, VOL. 44, NO. 14, DECEMBER 1972
DEPOSITS AND COATINGS OF SILICA GEL ON GLASS The method used to obtain silica gel films was the dehydration of silica sols. Silica sol preparations were of three types, and the silica gel films on glass were obtained by two methods. Sodium Silicate Preparation. The stock silica, a gel, was made by acid-catalyzed hydrolysis of redistilled tetraethyl orthosilicate ( 2 ) . This method yields silica gel immediately free of iron impurities, a desirable feature not found in customary preparations using commercial sodium silicate solution and strong acid. This pure silica gel was dried in an oven at 140 “C before storage. As the first step toward silica sol preparation, it was convenient to prepare by wet fusion a sodium silicate solution in which the molar ratio of NazO to SiOzis 1 :2. Pure silica gel was powdered, then vacuum-dried at 100 “C. The dehydrated silica gel powder (15 grams) and 40% sodium hydroxide solution (25 grams) in a platinum vessel were heated in the following apparatus: oil-bath heating (160 “C) of an 800-ml beaker in which there was a layer of sand providing thermal contact to the embedded platinum vessel. The 800ml beaker was covered with a 500-111 round-bottom flask through which was circulated cold tap water to return condensate to the contents of the platinum vessel. After 1 or 2 hours of heating, these contents resulted in a viscous sodium silicate solution. During this heating, cotton wadding was wedged at the rim of the beaker in contact with the roundbottom flask. A persistent crust at the edge of the wet fusion was easily dissolved toward the end by adding 15 ml of water and concluding the heating. After some cooling, the condenser was lifted off and the platinum vessel lifted out. The sodium silicate solution therein was stirred with 15 ml additional of water, filtered through an asbestos mat in a Gooch crucible, and stored in a tightly stoppered vessel. It was used to make all the following silica sols. Silica Sol Preparation. The author used a column of acid ion-exchange resin (Amberlite IR-120 or IR-112, or Nalcite HCR) through which the sodium silicate solution flowed at a rather slow rate (3). The column apparatus consisted of a wide (35-mm i.d.) Pyrex (Corning) tube (130 mm long) with a coarse fritted glass bottom. A constant level device of glass capillary tubing was connected to the bottom opening of the column by a one-holed rubber stopper. Solutions were led into the column from a dropping funnel attached to the top of the column by a one-holed rubber stopper. Backwashing of resin fines, air bubbles, or any given solution entrained in the resin was readily accomplished by replacing the funnel with a trap and applying suction there while the outlet of the apparatus was connected to a reservoir of distilled water. To change the resin into its hydrogen form, 250 ml of 20% sulfuric acid was allowed to flow rapidly through the column. After rinsing of the dropping funnel and backwashing the resin with about 200 ml of water, 250 ml of water from the funnel was allowed to flow through the column. The acid-conditioned column was used as follows for the preparation of silica sol A. Sodium silicate solution was diluted to 2 % in respect to Si02. The 2 solution (100 ml) was allowed to run through the column at a rate of 5 to 6 ml per minute. [An Ascarite (Arthur H. Thomas) tube was used to exclude carbon dioxide from the sodium silicate.] The first 50 ml of eMuent was discarded, the second 50 ml or more of effluent was retained as silica sol A. The column was washed immediately to rid it of entrained silica sol and have it ready for another run or reconditioning as the case may be. The silica sol A is water-clear when fresh, but becomes opalescent on standing for a day. In a few days it becomes a poorly coherent jelly; finally it becomes a coherent gel. A (2) H. D. Cogan and C . A. Setterstrom, h d . Etig. Chern., 39, 1364 ( 1 947). ( 3 ) H. Walton, “Inorganic Preparations,” Prentice-Hall, New York, N.Y., 1948, p 117.
position o f glass plate
\
1, ,of
salvaged piece glass coffee-maker
-I-’-
Figure 1. Spin-dryer
percentage of SiO.?greater than 2 cannot be handled conveniently in sol A. Silica sol B was made by sending sodium silicate solution ( 5 % in respect to S O 2 )through an ammoniated ion-exchange resin. This resin was formed by passing 250 ml of 1N ,ammonia through a column of Amberlite IR-112, and washing, and then conditioning with 50 ml of 0.01N sulfuric acid. .A weighed portion of the ammoniacal sol B was evaporated to dryness and the residue ignited to show that the sol was 5 % S O n . The ignited residue left a neutral reaction when mixed with water ; hence the sodium ions had been completely exchanged. Silica sol C was made in a pint Mason jar by combining acidic resin and sodium silicate in portions as follows : For every 10 ml (14 grams) of the undiluted sodium silicate solution, four 10-gram portions of moist-dry IR-112 resin in the hydrogen form were used. The first portion, together with 45 ml of water and a Teflon (DuPont)-covered stirring bar, was stirred magnetically as the sodium silicate solution was added from a buret. When the first portion of resin was exhausted, the addition of sodium silicate was interrupted, the exhausted resin filtered off by suction, and the filtrate with a fresh portion of resin returned to the Mason jar, silicate added, and so on. The fourth and last portion of the resin, which was an excess for the remaining volume of silicate solution, was filtered off and one drop of 4Ox NaOH solution was added to the filtrate to prevent gelling. The above proportions oi materials gave a 4 to 5 % silica sol which is very slightly c8austic. Silica Gel Deposition. Silica sol A which is about 2 days old seems best adapted for the method of placing silica gel deposits on glass. Small glass plates for mounting 35-mm photographic transparencies were used as bases for the deposits. Inside a large desiccator, these plates were supported on small glass funnels that were fitted into the holes of the desiccator plate, horizontal adjustment being arranged carefully. A dish of 80% sulfuric acid in the desiccator was found best far removing water not too rapidly from drops of silica sol A
ANALYTICAL CHEMISTRY, VOL. 44, NO. 14, DECEMBER 1972
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placed on the glass plates. At the end of 4 to 5 hours, the drops had changed completely to hard gel deposits slightly larger in diameter than the original spread liquid drops. The gel deposits were quite uniform in thickness. Under the microscope they were seen to consist of numerous adherent flakes of irregular shape but of roughly uniform size. This reticulated feature is caused by the shrinkage of gel on drying. The deposits readily adsorb trypaflavine from aqueous solution. Aqueous solutions cause some flaking off of the deposits. Hydrocarbon solutions of other dyes, however, do not cause these deposits to flake off. Silica Gel Coating. The second general method of silica gel plate preparation was one of coating glass by use of silica sol A, B, or C. The spin-dryer shown in Figure 1 was effective for the desired coatinp. A clean glass plate dipped in silica sol was placed in the receptacle of the spin-dryer and spun for 10 minutes. A very thin uniform coating of silica gel was spread over almost the entire area of the glass plate, with excessive deposits appearing only at the corners. The more concentrated the sol, the greater should be the spinning speed for uniform coating. Concentrated sols give coatings which adsorb more dye per plate. The pH of aqueous solution has a strong influence on the degree of adsorption from that solution. For example, trypaflavine is not adsorbed from 2.5 x l 0 P M solution with a pH of 4, but is adsorbed from 10WM solution with a pH of 6.
SPECTRAL RESULTS
The t~ypaflavine in cellophane was tested by its carbon-arcexcited phosphorescence in vacuo. Although this phospnorescence was bright, it was not quenched noticeably by oxygen until the oxygen pressure exceeded 1 torr. These plates were considered unsuitable for the intended study (4) of trypaflavine phosphorescence which is sensitively quenched by oxygen. The trypaflavine adsorbate in the silica gel deposits was tested for phosphorescence excited by carbonarc radiation. Under vacuum, the phosphorescence was bright and was quenched by very small pressures of oxygen (millitorrs in magnitude). ACKNOWLEDGMENT
This work toward the author’s Ph.D. thesis was conducted at the University ofMinnesota and Lawrence College. R ~ c ~ ~ v ~ ~ f o r r May e v i e11,1972. w AcceptedJuly28,1972. (4) J. J. Sjoblom, Dim. Abstr., 16(4), No, 15,959 (1956).
A Simple Disposable Teflon-Capped Reaction Vial Robert L: Wolen filly Laboratory for Clinical Research, Marion Counfy General Hospital, Indianapolis, Ind. 46202
WITHTHE INCREASING use of derivatization in gas chromatographic procedures and the increased chemical reactivity of derivatizing reagents, a need arises for an inexpensive simple Teflon (Du Pont fluorocarbon resin) -capped reaction chamber. A number of screw-capped vials with Teflon-lined caps are available, as are special reaction vials with Teflon-lined caps. We have found these useful but relatively expensive, and they exhibit some difficultyin washing because of size and shape. We have devised a method utilizing inexpensive vials and Teflon tape in a manner making the cost per unit low enough to effecta single use of the vial a practical reality. The procedure utilizes ampoules (Kimble Ampoule No. 12012-L) of appropriate volume, that are sealed with a double layer of tightly stretched Teflon sealing tape (Applied Science Laboratories, Inc.), (Figure l), of the type used as a sealant with threaded fittings. The ampoules are well adapted to solvent drying under a nitrogen stream and, following addition of derivatizing reagents, to incubation in a heating block (Figure 1). Their shape facilitates refluxing of volatile reagents during heating, while the Teflon tape serves as an adequate flexible seal which will not permit pressure to build up and create an explosion hazard should the block temperature control fail. In recovery of the derivatized material, the user has the choice of using a Pasteur pipet or long needle syringe to recover material at the bottom of the intact ampoule, or of breaking the ampoule at the constriction and using a syringe equipped with a short needle. The Teflon covering is readily pierced, negating the need for its removal. The technique has been successfully utilized in the derivatization of amines with highly reactive acid anhydrides and other 2418
Figure 1. Illustration of technique described. Front: (left to right) Teflon (DuPont flnorocarbon resin) tape; vial; sealed vial. Rear: Typical incubation setup similar reactions requiring heating of the reaction mixturf during derivatization. The total cost per unit including cost of the tape and am poule varies from 3.5 to 5 cents each, depending on type quantity, etc. This cost is low enough to make disposal afte use practical.
RECEIVED for review July 27, 1972. Accepted September 11 1972.
ANALYTICAL CHEMISTRY, VOL. 44, NO. 14, DECEMBER 1972
