V O L U M E 21, NO. 10, O C T O B E R 1 9 4 9 are particularly indebted to S. F. Ravitz for assistance in preparing the manuscript, and offering suggestions. LITERATURE CITED (11 Bambach, K., IND.ENG.CHEar., .%NAL.ED.,11, 401 (1939). 12) &a, F., Collection trau. chim. tche'coslov., 7 , 33, 42 (1935).
(3) Haddock, L. A . , Analyst, 60, 394 (1935). Hollens. W. R. A . a n d Bpencer. J . F., Ibid., 60, Ai3 (1935).
(4)
1273 (5) Kausner, J. L.,and Kassner,.E. 12,655 (1940).
E., IND.ENG.CHKM..ANAL.ED.,
(6) Kolthoff, I. M., and Sandell, E. B., "Textbook of Quantitative Inorganic Analysis," p. 593, New York, hlarmillan Cn., 1938. (7) Proszt, J., Z . anaE. Chem., 73, 403 (1928). (8) Shaw, P. A., IND. ENO.CHEM.,ANAL.ED.,5, 93 (1933). (9) Vosburgh, W. C.. J . Am. Chem. Soc.. 44, 2128 (1922). RECEIVED Janiinrr 5 , 1949
UNIVERSAL MICROAPPARATUS Filtration, Extraction, ReJlux, Distillation, Homogenization, Centrifugation, and Drying in the Same Apparatus CLYDE A. DUBBS' l i n i t w s i t y of Southern California Medical School and Los Angelea County Hospital, Los dngeles, Calij. One simple microapparatus alone can process small amounts of solid makerial through a series of common unit operations without vessel-to-vessel transfer and resulting high percentage loss of material. For radioactive tracer work. the apparatus presents a means of extended proreasinp in a closed system. Other advantages are discussed.
F
OK. riiaiiy years the treiicl in laboratory practice lias been toward the micro scale. Microtechniques are not only t ime-saving and effort-saving, but become indispensable when only very small amounts of material are available for study. A special impetus has been contributed by isotopic tracer studies which demand the ninnipulation of very small amounts. Yet a persistent difficulty a it11 microtechniques has been the perccmtage losses that are necessarily involved when small amounts nf material are transferred from one vessel to mother for different tieatments. Apparently the ideal solution of this difficulty is the elimination of transfer by providing a single apparatus in which all necessary treatments can be carried out conveniently and efficiently. Substantial progress toward this goal has been accomplished by the new universal microapparatus. An original form of this apparatus is shown in Figure 1. An improved form, shown in Figure 2, assumes the general shape of the combustion and cnrhon dioxide volatilizntion apparatus
.
I Present address, G m r r a l Nedical Recrsarcb Lahoratorv, Veterans Administration Center. Loq Angelos, Calif.
d r w i t ~ t dby Allen, Gest, :tnd Kaimri ( 1 ) :uid attriluted to the original design of H. .I.Barker (4). The improved form differs from the Barker apparatus Ly the inclusion of a special disk assembly (Figure 4:)that rffectivcaly ad:ipts the admirdilr Barker design to a univers:il apparatus. To tlatt: this neiv apparatus has been succeisfully tested by processing plant inatrrial without transfer through filtration, extraction, reflux, diatilhtion. homogenization, and centrifugation; and has been so cmployed in the rapid c:irliohydrat>eanalysis of plnnt material and i n the closed em procpsing of radioactive compounds. APPLICATIONS
Centrifugation and Homogenization. Tube 2' (Figures 1 and 2 ) serves as a rugged centrifuge tube which will fit any standard 50-ml. centrifuge cup. It serves as a homogenizing tube when a rotating motor-driven pestle (Figure 3) is inserted after the manner of Potter and Elvehjem ( 7 , 8 ) . Filtration. The disk assembly, detailed in Figure 4, includes the resin disk, D, which is tapered to fit snugly within the standard-taper joint of tube 2'. A disk of filter paper, p , is cemented, c, along its circumference to the resin disk and slightly overlaps the central hole into which it is tightly engaged by the insertion of the tapered inlet tube, I . When the disk assembly is slipped firmly iiito position within the neck of a tube which contains the suspension, slurry, or homogenate to be filtered, and the 100-ml. flask, F (Figure I), or the midpiece, iM, and second tube, Ti (Figure 2 ) , are attached, and the apparatus is inverted t o a position illustrated in Figure 1 or 2, filtration proceeds through the paper disk and the six small holes in the resin disk. The apparatus can frequently siniplify refiltration procedures. In conventional filtrations, the initial filtrate passing through a fresh filter medium may be turbid although subsequent, filtrate comes through clear. Refiltration is required, involving disrmldy of apparatus, filtrate tranrfer, and rinsings. With the new arrangement, i t is necessary merely to invert the apparatus, letting the turbid filtrate return t o tuhe '7 via the inlet tntw, then inverting again for refiltration.
Figure 1.
v
Original Universal Microapparatus
Vacuum Filtration. When the apparatus is assembled, there is included the small glass valve, V , which has previously been ground into the top of the inlet tube to permit a tight seal. This valve carries a small Chrome1 wire hook, h, to be hooked over the top of the inlet tube (Figure 2 j when the valve is not in use, and a straight wire, 10, to permit convenient reseating of the valve. The stopcock assembly, 8, is attached to the side arm and vacuum is applied t>hroughthe outlet tube, 0. In practice air leakage mound the valve is frequently great enonKh to require
1274
ANALYTICAL CHEMISTRY
the alternate admission of air to the apparatus to restore the pressure in tube T and re-evacuation-a simple manipulation. (If D is well seated, friction alone can hold it in position despite the stress caused by evacuation of the lower portion of the apparatus.) Extraction. Valve V , if present, is hooked out of the way, and the entire apparatus is evacuated. The glass condenser, C,
Figure 2.
Improved Universal Microapparatus
is slipped over the tube. The flask (Figure 1) is heated with a Glas-Col heating mantle, or tube T 1 (Figure 2) is heated with a special jacket, J ; regulation of temperature is accomplished by a variable transformer. The internal pressure can be checked occasionally by turning the stopcock to connect the system with the small rubber bulb, b, which should remain collapsed. Rarely does difficulty arise due to excess pressure within the system. Extraction roceeds as the extractant boils, passes up through the inlet tug,, condenses in T , and percolates back through the material collected on D. The apparatus permits unobscured observation of the material being extracted. I n the extraction of green leaf material, t h e green color can be seen to pass as a descending cone, simulating an eluting chromatographic column. This feature provides a convenient means for judging completeness of extraction. The apparatus eliminates the need for successive washings of residual material after filtration, a procedure that leads to an undesirably large volume of filtrate plus washings, and often requires subsequent concentration. With the new apparatus it is more convenient to “wash” the residue by simple extraction, whereby no volume increase is involved. For subsequent applications, the improved form of the apparatus (Figure 2) is recommended. Reflux. The application of the apparatus to simple reflux is obvious. However, let it be assumed that a material has just been extracted in the apparatus and it next is required to reflux it in intimate contact with a boiling liquid. The appropriate liquid is admitted, and the apparatus is momentarily inverted to let the liquid run into tube T , then inverted again so as
to entrain the liquid about the inlet tube in T . Gentle swirling, performed while the apparatus is held in hand, serves to loosen up the material collected on the disk and bring it into suspension again. The apparatus is inverted once more, condenser C and heating jacket J are slipped into place, and the apparatus is in h a 1 position for reflux as sketched in C of Figure 5. The apparatus can frequently alleviate bumping problems. Considerable difficulty was initially encountered in attempting, to boil plant homogenates in relatively narrow vessels a t atmospheric pressure, for bumping invariably threw material from the vessels. The new apparatus, after evacuation with a water aspirator, is gradually heated while the lower tube is gently shaken (conveniently done by holding the lead wires to the hesting jacket). Although mild bumping initially occurs, continued shaking and the gradual readmission of a little air into the system through the stopcock readily bring the suspension to a smooth boil; thereafter further manipulation is unnecessary. Should initial bumping be inadvertently allowed to throw some solid material up through the inlet tube, I , advantage is taken of the feature discussed under filtration to wash it back into the lower tube. Distillation. If the apparatus is disposed in the position sketched in D of Figure 5 , simple distillation may take place from one tube to another. I n this application the apparatus becomes essentially that described by Allen, Gest, and Kamen and attributed to Barker. These authors volatilized carbon dioxide under vacuum from one tube, using a gentle heat, and absorbed it in alkali solution contained in the other tube. Under increased heating actual distillation satisfactorily proceeds under vacuum. This arrangement has been applied to concentrate an aqueous solution of C14 glucose to a sirup, the last portion of water condensing on the walls of the tube being driven over by the heat from a flexible heating jacket (Figure 6 ) wrapped about the tube. In this particular case, the stopcock was opened to continuous evacuation in the latter stages. Although distillation is preceded by an application in which the disk aasembly is used, the apparatus need not be taken apart to remove the disk assembly, which will not interfere. Drying. One tube may contain the material to be dried, the other may con; tain a suitable drying agent. After evacuation, the flexible heating jacket (Figure 6) may maintain the material a t a suitable temperature as indicated by a thermometer placed between heater and jacket. In this case the apparatus becomes an efficient Abderhalden drying pistol. In all applications the improved form of the universal microapparatus can be conveniently supported by a single threefingered clamp gripping the midpiece. The tubes and stopcock assembly are held to the midpiece by springs engaging hooks. A metal collar carrying hooks is used with the tubes, in order that permanently attached hooks may not interfere with their application m centrifuge tubes. The condenser is slipped over the upper tube. The end heating jacket is quickly positioned by a long thin spring engaging the two hooks on the jacket and looping over one finger of the clamp, and the flexible heating jacket can be secured about a Figure 4. Disk tube with spring-type clothespins. Thus Assembly the apparatus and its accessories form a comDact svstem which is convenientlv sasembled, disassembled, or’other&se manipulated, either in clamped position or while held in hand.
a
RAI’II) CARBOHYDRATE ANALYSIS
Figure 3. llomogenizing Pestle
The following brief wrnrn:try illustrates how the apparatus has been employed IU an tclrtual procedure. In conjunction with the
V O L U M E 21, NO. 10, O C T O B E R 1 9 4 9
1275 when high temperature treatments such as extraction, reflux, and distillation are involved. When the apparatus is cooled after such a treatment, any volatile material residual in the apparatus may be removed before disassembly by evacuation of the apparatus through suitable traps (dry ice and carbon dioxide absorptioD traps).
HOMOGENIZATION FILTRATION €%TRACTION
Figure 5 .
REFLUX
DISTILLATION DRYING
Positions of A p p a r a t u s for Different Applications
150 MM. Figure 6.
~
--
Flexible H e a t i n g Pad
extraction scheme of Hassid, McCready, and Rosenfels ( 3 ) ,and a modification of the colorimetric method of Morris (6) using Dreywood’s anthrone reagent ( 2 ) ,the apparatus permits a rapid means of carbohydrate analysis. Rapid disintegration of a fresh sweet potato leaf (weight 300 to 500 mg.) is accomplished by homogenizing it with 1 ml. of 80% alcohol in tube T, using a special pestle (Figure 31, t’o the end of which sharp silicon carbide teeth have been cemented. The pestle is rinsed down with 4 ml. more of 80% alcohol. Homogenization and rinsings require only 5 minutes. The universal apparatus is t,hen assembled, and the leaf residue is filtered and extracted therein €or 1 hour. The tube of alcohol extract is removed. A second tube, containing 5 ml. of acid alcohol (4 ml. of concentrated sulfuric acid stirred into 500 ml. of 9570 alcohol), is attached, and the residue is brought into suspension again as previously described, and boiled for 15 minutes (to “solubilize” the starch), followed by inversion of the apparatus and extraction for 15 minut,es. The efficiency of this extraction, which replaces the repeated alcohol washings required by the conventional procedure, is proved by the inability of t’he extracted residue to redden litmus. A third tube, containing 5 ml. of water, is substituted for the acid alcohol tube, and boiling (1hour) and extraction (15minutes) are repeated. The tube of aqucous starch extract is removed. Finally, the acid alcohol and xater treatments are repeated. (Slow water extractions are sometimes encountered due to the gelatinous nature of the acid-treated plant residue.) For analysis, appropriate aliquots of the 80% alcohol extract (soluble sugars), the water extract (starch), and standard glucose solutions are directly pipetted into separate tubes, to each of which are added 5 ml. of anthrone reagent (1 gram of anthrone dissolved in 1 liter of concentrated sulfuric acid, stirred into 50 ml. of water, and cooled). The mixtures are heated in a boiling water bath for 10 minutes, cooled, and read in a KlettSummerson colorimeter using a 540-mp filter. Vnder the conditions described, a straight-line plot of Klett reading against weight of standard glucose was obtained up t o a t least 200 micrograms of glucose (corresponding to a N e t t reading of a p roximately 450). $he plant material is processed without transfer from the original tube. followed by DromDt determination of the total carvbohydrate contents of -thk solible sugar and starch extracts without “clearing” and hydrolysis treatments. PROCESSING OF RADIOACTIVE COMPOUhDS
The apparatus has been employed to isolate C14 glucose from a photosynthesizing leaf. By providing a means of processing radioactive material through a series of treatments in a closed system, the apparatus minimizes contamination of the atmosphere with radioactivity. It thereby diminishes the health hazard and aids in maintaining a satisfactorily low background count in the laboratory. The closed system feature is especially advantageous
CONSTRUCTION DETAILS
Sufficient details are given in the figures and text to clarify t h e construction of the glass portions of the apparatus. The ground zones of the inner 29/42 standard-taper joints are cut off to an a p proximate length of 30 mm., so that the disk assembly may be accommodated; the bulges around the necks of the tubes should be small enough to permit insertion into centrifuge cups. Further details are required for some of the accessories. Disk Assembly (Figure 4). The resin disk, D, is molded inside the ground zone of an outer 29/42 standard-taper joint which has been packed with firm clay, and the clay surface is flattened down to a level approximately 35 mm. below the lip of the joint. A glass tube (9 mm. in diameter), centered inside t,he tube, is inserted into the clay; and six smaller tubes (3 mm. in diameter) are inserted symmetrically about the central tube. Tubes, clay, and joint are lubricated with silicone grease. A thick mass of asbestos fiber and thermosetting resin is packed in about, the tubes to a thickness of about 4 mm.; the flat unrounded end of a glass rod serves to tamp the upper surface flat,. (The resin employed is Plastitool, manufactured by Calresin Corporation, Culver City, Calif., and is a thick sirup into which a small amount of catalyst solution is stirred before use.) The assembly is baked in an oven a t 50’ to 60’ C. for 0.5 to 1 hour, which treatment sets the resin mixture to a hard mass, resistant to most solvents and chemical agents. The upper and loxer surfacee of the disk are sanded and, for greater durability, varnished with resin and baked again.
A
Figure 7.
I3 M e t a l Disk Assemblies
The grade of paper chosen for the disk assembly will vary with the nature of the material being filtered. For leaf homogenates the rather thick porous paper used in extraction thimbles haa proved very satisfactory, and clear green filtrates have been consistently obtained. Each paper disk, p , is given a preliminary coat of resin over an approximate 2-mm. zone about its circumference and baked. A second coat is applied, the paper disk is pressed firmly against the resin disk (a glass slide employed with spring-type clothespins is convenient for this purpose), and the assembly is baked again. A metal disk similar to those sketched in Figure 7 might be superior to the resin disk. In A there is shown a metal disk with an outer flange, f i , to fit into the standard-taper joint and an inner flange, fi., to take the inlet tube, I . In order not t o entrain liquid about the disk rrhen the apparatus is inverted, f2 should contain a slot or hole. The disk presents the sieve area, s. The paper disk, p , is cemented on as before. In B is shown a disk with a double outer flange, f3, and an inner upwardly disposed flange, fi. If cut large enough, p can fit snugly between the flanges, eliminating the need for cementing. Linch ( 5 ) has suggested that D be made of sintered 1ms and sealed inside the inner 29/42 standard-taper member o f adapter (midpiece) M flush with the top, and tube I be either fitted as shown (Figure 2) or sealed directly to the porous disk to make a rigid assembly. Although the author believes the use of separate disks favors flexibility in choice of filters for different filtration and extraction requirements, the suggested modification provides convenient and positive means of seating and removing the disk. End Heating Jacket (J,Figure 2). A jacket of asbestos cloth is sewed tightly about the end of a tube using glass thread, and the free edges of the cloth are whipped with the thread. A p proximately 40 em. of No. 20 Chromel wire are wrapped about the asbestos and securely sewed on with glass thread, and the whole is coated with a thick paste of asbestos fiber and water glass (sodium silicate solution), and allowed to dry. This jacket will usually operate a t 10 volts or less. Flexible Heating Jacket (Figure 6 ) . About 90 cm. of S o . 20 Chromel wire are sewed onto a piece of asbestos cloth in the
ANALYTICAL CHEMISTRY
1276
nianner illustrated. A similar piece of asbestos cloth is overlaid and the jacket is sewed together. Homogenizing Pestle (Figure 3). The end of the pestle is roughened with emery aper, coated with a layer of phenolic thermosett,ing resin, a n a dipped into sharp silicon carbide particles, 6/30 grit. o n e half hour in an oven at 50” to 60” c. firmly sets the part,icles in place. ACKNOWLEDGMENT
This hark was aided by a grant from the National Foundation For lnfaiitile Paralvsiq. LITERATURE CITED (1)
t l h , 11. B
Gwt.H.. and Kamen, M. D.. Arch. Bwchem., 14,
xx5 (1947)
(2) Dreywood, R., IND.ENG.CHEM.,ANAL.ED., 18,499 (1946’. (3) Hassid, W. Z., McCready, R. M., and Rosenfels, R. S., Itid., 12, 142 (1940). (4) Kamen, M. D., in “Isotopes in Biology and Medicine.” pp. I 51-2,
Madison, University of Wisconsin Press, 1948. (5) Linch, 8.L., private c o m m u n ~ c a t ~ o n ~ (6) Morris, D. L., Science, 107,254 (1948). (7) Potter, V. R., and Elvehjem, C. A., J. B k l . Chew., 114, 195 (1936). (8) Potter, V. R., in Umbreit, W. W., Burris, R . H., and Stauffer, J. F., “IManometric Techniques and Related Methods for the Study of Tissue Metaholisni,” pp. 92-9,Minneapolis, Burgess Publishing Co., 1945 EECEIVED December 21, 1948. Presented before the Division of .-inalyti~al and Micro Chemistry a t the 115th Meeting of the A U E R I C ~ VC H F I I I ~ ~ L S O C I ~ San Y . Francisco, Calif
Organic Onium Compounds as Inorganic Analytical Reagents Detection of Bismuth and Cobalt HERBERT A. POTRATZ’AND JEKOME M. ROSEK* University of Colorado, Boulder, Colo. The action of various organic ammonium, phosphonium, arsonium, stibonium, oxonium, sulfonium, selenonium, telluronium, and iodonium ions on iodide and thiocyanate complexes of a number of metals was investigated. On the basis of the reactions observed new- tests are praposed for the detection of hisrnuth and cobalt.
tili organic reagents used most frequently in the detection and determination of metals are compounds that contain in the molecule acidic groups, the hydrogen atoms of which may be replaced by metal atoms. Such reagents ionize to give organic anions m-hich react with metal ions to form simple or inner-complex salts. Compounds that ionize to give organic cations have been used less frequent,ly as analytical reagents. Because many metals readily form complex anions, the possibility of employing organic cations for the detection and determination of these metals through salt format’ion is evident. The particular organic cations which have come into use a8 reagents for metals are predominantly nitrogen compounds. Tetraphr:n~larsoniumion stands out as an important exception. Willard and Smith (21) have shown that this cation may be used for tho determination of mercury, tin, cadmium, zinc, and rhenium. Smith (18) has recently employed this same cation for the d d erinination of thallium. Dwyer, Gibson, and Nyholm (9) have reporkd t,he use of methyl aryl arsonium compounds in the dekction of bismuth and cadmium and in the detection and estiinat,ion .of cobalt. Possible analytical applications of onium compounds of elements ot,her than nitrogen and arsenic have not thus f w r been report,ed. IBETECTION OF BISMUTH
Alkyl ltiiiniuiiiuin salts, aniline, pyridine, quinoline, certain alkaloids, and a large number of other nitrogen bases are known to react with bismuth in the presence of iodide to give colored, insolublr: reaction products (20). That this type of reaction is not, limited t,o nitrogen compounds is indicated by the fact that 1
Present addreis. I k p a r t irirnt of Clirinistry, Washington University,
tit. Louis, hlo.
*
Pre-rnt
adrlrvsr, Sa\-al Orduance Laboratory, Whitn Oak, hfd.
alkyl sulfonium iodides react with bismuth in a similar maimer (2, IS). The observations cited are perhaps best interpreted b> assuming that in each case reaction has occurred between an organic cation and a bismuth-containing anion or anions. I n beginning a survey of the reactions of onium ions, varioue organic onium compounds of nitrogen, phosphorus, arsenic, antimony, oxygen, sulfur, selenium, tellurium, and iodine were tested with respect to their reartivitv toward BiIa-. (The reactions here described are attributed to BiL-, which is taken as the probable formula of the predominant bismuth anion present in a bismuth solution containing excess iodide. No evidence is prestwted to support this formula.) The fourteen potential reagents which ssere investigated are listed in Table I. Optimum conditions for reaction, limits of sensitivity, and interfering effects of foreign ions were determined for each of the compounds tested. Cinchoninc was included because i t is a spot test reagent commonly used in bismuth detection (10) and could therefore serve as a convenient standard of reference. Tetramethylammonium bromide (IS), triinethylsulfoniuin iodidt, (Z), and triethylsulfonium iodide (13) had been observed to react nith bismuth, but no study had been made of the possible analytical applications of the reactions. The limits of sensitivity given in Table I are in terms of mioiograms of bibmuth per drop (0.05 ml.) of test solution. The reactions were carried out on spot test paper (Schleicher and Schuli No. 601), following the technique recommended by Feigl ( I O ) The compounds tested were found to be remarkably similar 111 their behavior toward Bi14- in that all reacted to give insolublc: orange or red-orange products. Preliminary studies indicated that froin considerations of specificity and sensitivity the aryl sulfoniuni, triphenylselenoniuni, tetraphenylphosphonium, tetraphenylarsonium, and tetraphenylstibonium compounds were the best of the reagents tested Iu
