US 3752651 A
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Description (OCR text may contain errors)
. g- 1973 l. E. BUSH 3,752,651
METHOD AND APPARATUS FOR EXTRACTION OF SOLVENT EXTRACTS Filed April 15, 971 5 Sheets-Sheet 1 wlsnmf FLUID, z; I
' SUCTION SUCTION PUMP PUMP lSAMPLE I if // na-mm 1 HI! /7 4Z4 lllll DISCHARGE I/VVEWTOR IAN E. BUSH his ATTORNEYS Aug. 14, 1973 E. BUSH 3,752,651
METHOD AND APPARATUS FOR EXTRACTION OF SOLVENT EXTRACTS Filed April 15, 1971 5 SheetsSheet 2 IAN El. BUSH mmQuugii Q his: ATTORNEYS Aug.
Filed 1973 E. BUSH METHOD AND APPARATUS FOR EXTRACTION OT" SOLVENT EXTRACTS April 15. 1971 S Sheets-Sheet 5 SUCTION PUMP //V VE/V TOR IAN E. BUSH his ATTORNEYS g- 14, 1973 l. E. BUSH 3,752,651
' Filed April 15,1971
METHOD AND APPARATUS FOR EXTRACTION OF SOLVENT EXTRACTS 5 Sheets-Sheet 4 FIG. 6
INVENTOR IAN E. BUSH BY BMW, GM
his ATTORNEYS I. E. BUSH Aug. 14, 1973 METHOD AND APPARATUS FOR EXTRACTION OI" SOLVENT EXTRACTS 5 Sheets-Sheet Filed April 15. 1971 E4 owmmwcmzoo his ATTORNEYS United States Patent 'ice US. Cl. 23-230 R 11 Claims ABSTRACT OF THE DISCLOSURE Apparatus and method for the extraction of solvent extracts are disclosed. First, a plurality of test tubes mounted on a movable rack are filled sequentially with a prespecified volume of liquid sample from a two-stage sample dispenser. One stage of the dispenser dispenses a sample While the other stage automatically and concurrently is cleaned; then the stages are reversed for the next specimen and the rack is moved on incremental distance to place an empty test tube under the cleaned dispenser. A prespecified volume of extracting solvent is then added to each sample by a second dispenser and the tubes are sealed by a multi-stopper apparatus. After agitation and settling, the solvent layers in each test tube are removed simultaneously by a ganged suction apparatus. For final reduction and extraction, the rack is placed in a ganged multiple-rotary evaporator apparatus wherein the sample is heated, rotated, and evaporated to form a residue. In another embodiment, wherein solid samples or drying agents are utilized, the sample is filtered prior to final reduction by a ganged multifilter apparatus.
BACKGROUND OF THE INVENTION A number of procedures in analytical chemistry involve the purification and extraction of materials to be measured and analyzed. As used herein, the term extraction is meant to include the reduction of liquids to concentrates thereof suitable for analysis. The materials, which may be liquids, such as milk, blood plasma, or urine, or solids, are intimately mixed with an immiscible organic solvent. The two phases are separated and the desired part of the sample material is ultimately reduced to a dry residue or a small volume by evaporation of most of the organic solvent. If the sample material is originally a solid, it is first extracted by grinding or macerating with a liquid such as water and then by filtering the resulting solution to remove the residual solids.
Standard extraction procedures typically consist of many steps of partition of the sample materials between immiscible pairs of liquids. These steps typically are called washes in which the original extract in the organic solvent is purified by mixing and shaking with water or aqueous solutions of acids or bases. In some cases the desired material is back-extracted from the original organic solvent by using an aqueous acid, base, or complexing agent (as with metals), and then reextracted from this aqueous phase with another organic solvent by means of an appropriate change of pH or the like.
More specifically, known extraction procedures are commonly carried out in one of two ways. The first and most typical way is by use of a separating funnel. The two liquids (sample and solvent) are shaken and finely mixed, allowed to stand so that the immiscible liquids separate into layers, and then the individual layers are removed and separated by means of the tap and stem of the funnel. This first method is described, for example, in Vogel, Textbook of Organic Chemistry (1956). The second method, usually employed for smaller volumes, comprises mixing the liquids in a stoppered test tube or similar vessel, allowing the liquids to stand until they 3,752,651 Patented Aug. 14, 1973 settle into layers, and then removing one or more of the layers by means of a pipette or a similar suction device.
The above methods, however, are extremely costly in labor and usually rather tedious to perform. In many instances, each vessel is worked on by hand, individually or at most in pairs, and the addition of liquids or reagents and the removal of the desired layers is carried out separately on each individual vessel whenever more than one extract has to be prepared.
SUMMARY OF THE INVENTION The invention disclosed herein comprises an apparatus and method for the simultaneous extraction of a plurality of samples. Thus, the apparatus and method of the present invention provide a substantial savings in time, energy and expense and, at the same time, improve reliability and reproducibility.
In particular, a plurality of test tubes positioned in an easily transportable rack are filled one-by-one with a prespecified volume of liquid sample from a unique twostage thistle funnel sampler dispenser. One stage (vessel) of the dispenser dispenses a sample into a test tube while the other stage (vessel) automatically and concurrently is cleaned with washing solution. Serrated discs in each vessel assure effective washing. After each test tube is filled, the rack is moved between specially designed rails and the positions of the two dispenser vessels are reversed so that an adjacent test tube and the cleaned vessel are positioned for dispensing the next specimen.
Once filled with a specimen, the rack is passed under a solvent dispenser whereby a prespecified volume of extracting solvent is added to each test tube. A multistopper apparatus is then fastened onto the rack for sealing the test tubes and, thereafter, the liquids in the test tube are agitated and mixed. After agitation and settling, the multi-stopper apparatus is removed and the top layers (solvent) in the tubes are removed concurrently by a ganged multi-suction apparatus. If necessary, additional extraction solvents can be added to the samples and similarly removed by the multi-suction apparatus.
For final reduction and extraction, the rack is placed in a multiple-rotary evaporator apparatus where the test tubes are immersed in a heated liquid bath and rotated. The heat and agitation causes the samples to evaporate leaving a residue for subsequent analysis. Compressed air is forced through the samples in the test tubes to aid the evaporation.
In another embodiment wherein. solid samples or drying agents are utilized, the sample is filtered, by a multifiltration apparatus, prior to final reduction.
BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:
FIG. 1 illustrates a typical two-stage sample dispenser arranged according to the present .invention;
FIG. 2 illustrates a multi-stopper apparatus for sealing a plurality of test tubes;
FIG. 3 illustrates the multi-stopper apparatus of FIG. 2 in position on a rack and sealing the test tubes therein;
FIG. 4 illustrates a typical suction apparatus for removing the top layers of liquid from a plurality of test tubes;
FIG. 5 illustrates a typical multi-filtration apparatus for filtering liquids from a plurality of test tubes;
FIG. 6 illustrates a typical multiple-rotary evaporator apparatus for heating, rotating and evaporating the specimens; and
FIG. 7 illustrates the suction and compressed-air apparatus for aiding in the evaporation of the specimens.
3 DESCRIPTION OF THE PREFERRED EMBODIMENTS A two-stage (vessel) apparatus arranged according to the present invention and referred to herein as a constant volume sample dispenser, is shown in FIG. 1, A frame consisting of two brackets and 11 is rotatably supported on a vertical rod 12. The bracket 11 is mounted on a circular support flange 12a, while a pair of rods 13 and 13' support the bracket 10 at a fixed distance above the bracket 11. The frame is substantially symmetrical about the vertical axis and holds two vessels 14 and 14' with taps 15 and 16 and spouts 17 and 17, respectively. The vessels 14 and 14' are preferably glass and of the thistle-funnel type. To facilitate the filling of the vessels 14 and 14 from a specimen bottle (not shown), the ves sels are provided with flared tops '18 and 18 in the form of funnels (glass or plastic) with sleeves.
A third bracket 19 is provided at the top of the vessels 14 and 14' and the rod 12, with the bracket 19 supporting rigid rods 20 and 20" which in turn support a pair of connector blocks 21 and 21'. A pair of tubes 22 and 22' pass through funnels 18 and 18, respectively, and are accurately positioned inside the vessels. The tubes 22 and 22' are firmly attached to the frame and coupled to a pair of corresponding suction pumps 23 and 23' by the connector blocks 21 and 21. The position of each of the tubes 22 and 22 is adjusted in order to withdraw the excess fluid in the vessels 14 and 14' to a desired height corresponding to the desired volume of sample to be dispensed. The height of the tubes 22 and 22' can be easily adjusted to leave any required amount of sample.
Positioned within vessels 14 and 14 are a pair of chemically inert discs 24 and 24, respectively, having serrated edges and central apertures. Preferably, the discs are made of Teflon. The rods 12, 13, 13', 20 and 20' and the brackets 10', 11 and 19 can be of any material with good mechanical strength, such as good, plastic or metal, but preferably the rods are made of aluminum and the brackets are made of a strong plastic, such as Teflon.
The frame is adapted to rotate approximately 180 so that the vessels 14 and 14 can reverse positions. Stops (not shown) prevent the frame from rotating through a full circle and spring-ball indexing means or the like (not shown) maintain the vessels 14 and 14' in position before and after rotation.
The operation of the constant volume sample dispenser is as follows. After initial adjustment and testing, a liquid sample is dispensed into the vessel 14 until the sample reaches a height where it contacts the end of the tube 22. By reason of the action of the pump 23, the excess sample will be drawn off with the result that the sample level within the vessel corresponds to a prescribed volume for the sample. The operator then opens the tap 15 of the vessel 14 and allows the sample to be dispensed into an aligned collection vessel or tube 25. The collection vessels 25 are preferably glass test tubes and are contained in a rack 26. The height of the dispenser is adjusted to accommodate the height of the tubes 25 in the rack 26.
The operator then rotates the frame approximately 180 so that used vessel 14 lies in the rear position and the clean vessel 14 is presented in the front position for repetition of this operation on the next specimen. At about the same time that the vessels 14 and 14' are rotated, the rack 26 is moved an incremental distance to place a new test tube 25 beneath the vessel 14. At this stage, the vessel 14 used in the previous operation of sample dispensing is automatically washed by a conventional tube jet or spray 27. The jet 27 releases washing fluid at a preset rate into the vessel 14. Effective washing (without any need for complex stirring or agitation) is achieved by the spreading action of the serrated disc 24 whose central perforations drain washing fluid around the tip of the suction tube 22. Thus, one cycle of an operation consists of the operator using the funnel in the front position for 4 sample dispensing, while the previously-used funnel is in the rear position being automatically washed without the operators attention being required.
It is understood that any number of dispenser vessels can be attached to the frame and rotated into position for dispensing and then for washing. For example, three or four dispenser vessels could be symmetrically positioned on the frame with corresponding modifications in the funnels, suction tubes, and the like.
The present invention is designed for but not restricted to applications requiring volumetric accuracy in the range of 12%. This accuracy is sufficient for most analytical purposes.
Following the dispensing of the sample, numerous procedures can be followed, but preferably the next step is the addition of a prespecified volume of extracting solvent. While this could be accomplished by a similar constant volume sampler dispenser, it is preferably carried out through the use of one of the commonly available re-pipette or preset syringe pipette units 28, shown schematically in FIG. 1, since the unit 28 does not have to be washed between applications. The solvent is added to the specimen in each test tube and the specimens are subsequently washed by shaking, swirling, or otherwise agitating the rack of test tubes.
The rack 26 shown in FIG. 1 is an improvement over the typical form of laboratory test-tube rack. The rack 26 is designed so as to fit all units of the complete extraction system and is adapted to enable the smooth operation of the system as a whole.
In order to simplify the location of the rack 26 under the constant-volume sample dispenser and the solvent dispenser, the rack 26 includes a base plate 29 which is designed to slide between a pair of guide rails 30 and 30 fixed to a supporting surface. The base plate 29 has notches (not shown) corresponding with each tube position which enable the rack 26 to be moved incrementally and located accurately by a spring-ball indexing means, a ratchet unit or the like (not shown) so that each tube 25 comes automatically and reliably under the spouts 17 and 17 of the dispensers 14 and 14', respectively. The rails and spring-ball indexing means make the extraction process faster and more reliable.
The rack 26 also is designed to allow firm and reliable contact with the driving belts in the multiple-rotary evaporator apparatus (discussed below).
The rack 26 can be made of any material with good mechanical strength and resistance to corrosion and further comprises a pair of longitudinal members 31 and 32 which are preferably constructed of a material with a low coefiicient of friction. The aligned holes in the members 31 and 32 act as bearings for the vessels 25 when they are rotated in the multiple-rotary evaporator unit. Delrin is one type of plastic that has been found to achieve excellent results in this regard; Delrin has satisfactory resistance to moisture during immersion in hot fluids, good mechanical strength, is lightweight for manual handling, and has a very low coeflicient of friction. Many other materials also are adequate for members 31 and 32, as well as the rack 26, for example, Teflon, stainless steel, polypropylene, various metals suitably protected against rust or chemical corrosion, or numerous combinations of metal and plastic.
It is preferable to modify the holes in members 31 and 32 with a 45 bevel to reduce to a minimum the cylindrical surfaces bearing on the tubes 25. This modification is not necessary, however, if the multiple-rotary evaporator unit is fitted with a series of rollers positioned to support the tubes 25 during rotation.
The rack 26 also includes side members 33 and 33' which have generally rectangular notches at the tops thereof. A pair of retaining clasp mechanisms 34 and 34 are secured to the exterior surfaces of the side members. The clasp mechanisms 34 and 34' enable the rapid detachment or attachment of various apparatus (discussed below) to be used with the rack 25.
The base plate 29 of the rack 26 is equipped with leaf springs 36 to provide an elastic pressure pad on which the tubes rest. The leaf springs can be secured to base plate 29 by screws (not shown) or any other similar means. The springs 36 preferably are bent metal leaf springs of beryllium copper, but individual coiled springs, a strip of foam rubber, or other elastic devices also could be used.
When the tubes 25 are placed in the rack 26 prior to being placed into position adjacent the sample dispenser, it is preferable to slip an O-ring 38 (FIG. 3) over each tube and position the O-ring 38 slightly below one or the other of the perforated longitudinal members (31 and 32). The O-rings 38 fix the tubes 25 in the rack and enable the rack to be inverted without the tubes falling out, for example, whenever it is necessary to decant liquid from the tubes or to invert them over a simple spray washing unit. For many purposes it is adequate to clean the tubes 25 between periods of use with simple sequences of washing fluids which are not corrosive to the rack or the O-rings. In some cases, however, cleaning with highly corrosive fluids such as concentrated sulfuric acid is required. In such cases, the rack and O-rings should be made of Teflon or polypropylene.
A rack containing s'ix test tubes 25 is shown in FIG. 1, but it is understood that any size rack capable of holding any number of tubes may be utilized. For example, a twelve-tubed rack is illustrated in FIG. 6.
For further process, a ganged stopper apparatus (multistopper) 45, as shown in FIG. 2, is utilized. The multistopper 45 has an elongated plate 46 having a series of holes of a diameter slightly less than the maximum diameter of stoppers 47 which are frictionally received within the holes. The positions of the holes match the positions of the tubes 25 in the rack 26 (FIG. 1). The stoppers 47 are pushed into the holes so that portions thereof lie above the bottom strip and holes grip them firmly. A second elongated plate 48 is secured to plate 46 by screws (not shown) at frequent intervals. The second plate 48 holds the stoppers in position.
The stoppers 47 can be of any type and material, but preferably are Teflon-coated neoprene stoppers in order to provide optimum flexibility and firmness for ganged operation and, at the same time, adequate resistance to chemical attack. Further, the combination of slight elasticity in the neoprene and the elastic cushion under the tubes 25 in the rack (provided by springs 36) enables secure closure of the tubes 25 when using commercially available glass test tubes with small flanges.
The plate 48 also includes a pair of flanged ends 49 and 49' which are adapted to be located in the rectangular notches on the tops of the end members 33 and 33' of the rack 25 and to be secured in position by the latches 34 and 34. FIG. 3 shows a ganged multi-stopper apparatus 45 fastened securely in place on a rack 26.
If the test tubes have standard-taper, ground-glass sockets, ground glass stoppers should be used in the multi-stopper 45. Such tubes with stoppers, however, are much more expensive than plain glass test tubes and, unless grease is used, make it difficult to avoid one or two stoppers from binding so that smooth removal of the multi-stopper apparatus becomes ditficult or impossible.
With the inventive rack 26 and stopper apparatus 45, a set of tubes simultaneously can be stoppered for subsequent processes, such as washing with solvents, and then be simultaneously opened smoothly by a single action. The present invention overcomes many practical difliculties provided by known materials and methods and substantially reduces the time required for this operation over the typical method wherein individual stoppers are used.
Once securely stoppered, the rack 26 can then be lifted up and rotated with an oscillating movement about its longitudinal axis to ensure gentle but complete mixing of the liquid sample and extracting solvent as is conventionally done with single stopped tubes or separating funnels. On completion of the operation, the latches 34 and 34' are released, the multi-stopper apparatus 45 is removed and the liquids are allowed to settle and separate. A ganged suction apparatus 50 as shown in FIG. 4 can then be placed in a similar position on the tubes 22 and used to simultaneously remove the top layers of liquids.
Referring to FIG. 4, the ganged suction apparatus preferably comprises a series of stainless steel tubes 51 attached to a manifold 52. The tubes 51 are relatively small in diameter, are arranged in a substantially parallel manner, and are adjusted to protrude within test tubes 25 when the unit is positioned in the manner shown in FIG. 4. The number of stainless steel suction tubes 51 corresponds to the number of test tubes 25 in the rack 26.
For any given extraction procedure the heights of the suction tubes 51 are adjusted so that when the ganged suction apparatus is located in the appropriate notches of the rack 26 the tips of the tubes lies a few millimeters above the interface between the sample or washing liquid (top layer) and the extract (bottom layer). The manifold 52 is connected to a conventional vacuum or suction pump 53 and the top layers of liquids concurrently are removed as the tips of the suction tubes pass down through the liquids in the test tubes.
The suction operation simultaneously removes substantially all of the top layer of liquid from each tube. The fraction of the top layers remaining can be removed in any conventional manner. For example, distilled water can be lightly squirted into the tops of the tubes 25 from a wash bottle (not shown) in order to dilute and mix with the residual top layers without serious disturbance of the bottom layers. These layers can then be quickly subjected to a second suction operation. Another procedure for removing the residual layers of washing liquid comprises drying the extracts and adding a small portion of a solid drying agent, for example, sodium sulphate, to the residues. Commonly, several washing and suction steps are carried out with each sample and therefore, only the last washing step concerns the removal of the remaining fraction of the top layers.
In some instances, the sample liquid is more dense than the extracting solvents and bottom layer instead of the top layer must be removed. The accurate removal of such bottom layers requires individual operations on each tube and units for this purpose are commercially available. In most extraction procedures, however, a suitable combination of extracting solvents which are denser than the usual aqueous sample can be found to obviate the bottom layer removal problem. Thus, for every extraction procedure using a top layer solvent, for example, diethyl ether, it is usually possible to find in the literature, or to develop, an equivalent method using solvents denser than water, such as carbon. tetrachloride, chloroform, mixtures thereof, and the like.
It is often desirable to add a solid drying agent such as sodium sulfate or a filter aid or adsorbent to the extract after washing, but the solution then must be filtered. For filtering, a ganged filtration apparatus (multi filter) 60, as shown in FIG. 5, is utilized. A metal block 61, preferably made of stainless steel, Teflon, or polypropylene, is machined with a series of frusto-conically shaped holes 62, the number of holes 62 corresponding to the number of test tubes in the sample rack. A stainless steel wire mesh filter disc 63 is positioned at the bottom of each hole 62. The disc 63 can be held in position by a flat C- spring 66 or any other appropriate means. Insert 67 is provided to assure passage of the specimen into the test tubes.
In operation, the unit 60 is positioned in the rectangular notches on a fresh rack 65 of cleantest tubes. After the solid reagent is mixed with the liquid in the sample rack 26 (FIG. 1) and the multi-stopper apparatus 45 is removed, the rack 26 is brought up to the fresh rack 65 so that the rims of all of the test tubes 25 rest on the rims of the funnel-shaped holes 62 and the contents of the tubes are dispensed into the filtration apparatus 60. Vertical brackets 64 and 64' help in locating rack 26 longitudinally and preventing accidental longitudinal displacement of the first rack and spilling or mixing of the samples.
It is understood that other types of filtering and funneling apparatus can be utilized. For example, the filtration apparatus can be a perforated metal plate with a series of suitable funnels in bushings attached thereto. Glass thistle-funnels with stainless steel wire mesh filter discs are satisfactory in this regard.
It is preferable for smooth operation that the funnels be tall enough or the holes 62 be deep enough to hold the entire extracts in test tubes 25 at one time. Also, funnels, if utilized, preferably should be small enough in diameter to allow location on centers matching the positions of test tubes in the standard-size racks 26 or 65; and the rim of each funnel should be at a height and of a diameter sufficient to allow easy location of the mouths of the tubes of one rack over the funnels on the other rack.
For final reduction and evaporation of liquid samples contained in test tubes mounted in a rack, the rack 26 or 65 preferably is placed in a ganged multiple-rotary evaporator apparatus 70, as shown in FIG. 6. The rack 26 is mounted in a metal guide frame 72 and slid down until the bottom portion of the rack 26 and tubes are inserted in a water bath 71. The water bath 71 can be any standard unit, such as the Napco Model 230 manufactured by National Appliance Co. The bath 71 is set and maintained at a prespecified temperature to heat the samples. The apparatus 70 also has a frame 73 which is hinged to the base of the apparatus 70 by pins 74. Se cured to frame 73 is a motor 75 which drives a rubber belt 76 positioned over a series of pulleys 77.
In operation, the rack 26 containing the sample tubes is inserted in the bath 71 within the guide frame 72. The operator then rotates the frame 73 toward the frame 72 so that the rubber belt 76 comes into contact with the tubes. The motor 75 is then switched on to drive the belt 76 which in turn rotates the tubes in the rack 26 at a set angular velocity. For more efficient and reliable rotation of the test tubes, it is preferable to roughen (as by sand blasting) the area of the tubes engaged by the belt 76. The rotation, agitation and heat combine to evaporate the liquid portion of the sample and to leave a residue for subsequent analysis.
Prior to starting the motor 75, a ganged gas-jet apparatus 80, as shown in FIGS. 6 and 7, preferably is positioned on the rack 26 by means of the standard locating notches and latches. The ganged gas-jet apparatus 80 consists of an outer shield 81, preferably made of sheet metal, which forms an envelope around the tops of the tubes in the rack 26 and is connected to a powerful suction pump or fan 84 of any conventional type which discharges into a large capacity waste pipe or fume hood (not shown). Protruding in the center of shield 81 is a set of small diameter gas tubes 82, the number of tubes 82 corresponding to the number of sample tubes in the rack 26. The set of gas tubes 82 is connected to a manifold 83 which in turn is attached to a conventional compressed-air or other gas supply 85. During rotation of the test tubes, compressed air is forced through tubes 82 and preferably onto the surface of the liquid in the test tubes. The vapor exiting from the tubes and accumulating within the area defined by the shield 81 is drawn off by the pump 84 to prevent excessive concentrations of possibly noxious vapors from being discharged into the laboratory. It is understood that the suction shield 81 would not be necessary if the evaporator apparatus 70 were used in a fume hood of sufficient capacity. If it is desired to recover the vapors, the shield 81 can be connected to the suction pump or fan by means of a trap (not shown) which would allow the vapors to condensate and collect.
In known methods of evaporation by heat using a stream of nitrogen or air, the evaporation is normally accomplished by placing tubes individually in suitable racks in a vertical position. The racks typically are linear tube racks or square grills made of wire. One advantage of the present invention is that the sloping position of the test tubes in frame 72 increases the surface area of the liquid approximately two and one-half times and the rotation spreads the film over even a substantially larger area. The rotation also allows higher temperatures to be used in heating the liquids, plus stronger jets of displacing gas without splashing.
Tests have shown that the evaporation of 50 milliliters of chloroform in vertical tubes by known evaporation methods takes approximately fifteen minutes. With the present invention, on the other hand, evaporation was completed in about four minutes.
An important advantage of the present invention is standardization of dimensions and the provision of structure which allow the operations of the extraction procedure, including rotary evaporation, to be carried out without removing the sample tubes from the rack or having to handle the tubes individually. Each rack can be numbered and the identification of samples can be carried out automatically without separate labeling of tubes; this greatly decreases the number of manipulations required and improves the reliability of identification of samples in large batches.
The present invention greatly reduces the processingtime and working-time necessary to extract a group of samples. The mechanization of the process improves the reproducibility and reliability of the extraction procedure, thus reducing errors. Also, the shorter exposure time of the extracts to being heated in concentrated, or nearly dry states, on the walls of the tubes reduces quite considerably the extent to which labile substances are destroyed or chemically altered during this kind of evaporation.
Although the invention has been described with reference to specific embodiments thereof, it is understood that modifications and variations are possible in light of the above teachings. All such modifications and variations are intended to be included within the scope of the invention as defined by the following claims.
1. An apparatus for simultaneously evaporating specimens in a plurality of collection vessels comprising: a liquid bath, means for positioning the collection vessels in the bath and means for rotating the vessels in place.
2. The apparatus according to claim 1 wherein the means for positioning the collection vessels comprises a collection vessel rack and a rigid first frame for holding the collection vessel rack, the first frame being positioned in the liquid bath at an angle to the vertical.
3. The apparatus according to claim 2 wherein the means for rotating the collection vessels comprises a second frame pivotally mounted in the liquid bath to permit the second frame to be selectively positioned adjacent the first frame, a plurality of pulleys rotatively mounted on the second frame, a belt mounted on the pulleys and means for rotating the belt, the belt contacting the vessels and imparting in place rotation to the vessels when the second frame is positioned adjacent the first frame.
4. The apparatus according to claim 1 further comprising means for heating the liquid bath.
5. The apparatus according to claim 1 further comprising means for blowing a gas onto the surface of the specimens. 6
6. The apparatus according to claim 5 wherein the gas blowing means comprises a shield positioned over the collection vessels, a manifold, a plurality of gas tubes attached to the manifold, the manifold being in communication with the shield and the gas tubes protruding through the center of the shield and into the collection vessels, and means for supplying a gas to the manifold.
7. The apparatus according to claim 6 further comprising means connected to the shield for removing the gas.
8. A method of simultaneously evaporating specimens contained in a plurality of collection vessels comprising heating a liquid bath, placing the vessels in the bath and rotating the vessels in place.
9. The method according to claim 8 wherein the step of placing the vessels in the bath includes positioning the vessels at an angle to the vertical.
10. The method according to claim 8 further comprising blowing a gas on to the surfaces of all the specimens in the collection vessels to form vapors.
11. The method according to claim 10 further comprising emoving the vapors resulting from blowing the gas on to the surfaces of the specimens.
10 References Cited UNITED STATES PATENTS 3,511,613 5/1970 Jones 23-259 5 3,549,330 12/1970 Jungner et al 23-259 3,592,605 7/1971 Noma et al. 23-292 3,622,279 11/1971 Moran 23-259 MORRIS O. WOLK, Primary Examiner 10 R. E. SERWIN, Assistant Examiner US. Cl. X.R.