Apparatus For Concentrating Laboratory Specimens By Evaporation

Abstract

Apparatus is disclosed for concentrating chemical and biological specimens which are present in dilute solutions in solvent liquids. By means of a pressure differential and air jet nozzles, the vapor layer which normally appears above the specimens is continuously dispelled. The evaporating areas are maintained under sub-atmospheric pressure both to augment the evaporation process and induce a jet stream of air which impinges on the specimen surface. The specimen containers are heated from a controlled source, such as a thermostatically controlled heat sink.

Description

BACKGROUND OF THE INVENTION

The invention is concerned with apparatus for concentrating chemical and biological specimens which occur in a highly diluted or attenuated form in an evaporatable medium.

Conventionally, laboratory specimens are concentrated by evaporating off the more volatile liquids or solvents by controlled heating of the specimen vials, often under fume hoods which exhaust to the atmosphere in order to prevent the accumulation of vapors in the laboratory. It is also known in the art to augment the evaporation process by the use of a partial vacuum. In such vacuum systems, localized boiling or spattering due, for example, to hot spots, can cause contamination of adjacent specimens by air-borne droplets. The efficiency of conventional evaporating devices is further limited by the presence of vapor layers above the liquid and by poor circulation of the liquid specimen within the vial during evaporation. A further difficulty encountered with conventional devices is solvent vapor contamination of the atmosphere either within the laboratory or, in the cases where fume hoods are used, in the outdoors. It is impractical in most cases to provide adequate filtering and condensing functions in the high volume exhaust fans normally used with fume hoods.

SUMMARY OF THE INVENTION

In accordance with the present invention, a battery of specimen holders is mounted in a common heating source, such as a massive heat sink, temperature-regulated by thermostatic means and formed with a plurality of cavities into which the vials are seated in close proximity with the metal walls. An air-tight chamber is provided above the specimens which is connected to a relatively low volume vacuum pump, preferably through a fume condenser for recovering solvents. Disposed above each of the specimen vials is an air nozzle capable of directing a jet stream of significant velocity directly downward onto the surface of the liquid. The nozzles are connected as through a common manifold to an atmospheric vent so that, when the chamber immediately above the vials is placed under partial vacuum, a jet stream impinges down upon the liquid in the respective vials. The jet stream functions to break down the vapor layer which normally appears above warmed liquids, replacing it with dry air which augments the evaporation process. The dynamic effect of the jet is also felt by the liquid itself and results in a stirring action on the liquid setting up circulation patterns which eliminate localized hot spots in the vials and thus prevent bubbling which causes particles of liquid to become air-borne and hence capable of contaminating other specimens.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view in perspective of an apparatus for evaporating 36 specimens simultaneously;

FIG. 2 is an exploded fragmentary view in vertical section of the apparatus of FIG. 1, taken on the line 2--2 looking in the direction of the arrows; and

FIG. 3 is a view in vertical section of a portion of a specimen-evaporating apparatus showing another embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The invention is illustrated as embodied in a specimen-evaporating apparatus including a housing assembly 10 for holding a plurality of specimens to be evaporated and connected to a vacuum pump 11, preferably through a fume condenser 12. The housing assembly 10, as best seen in FIG. 2, includes a base portion 13 in which is mounted a metal specimen block 14 having a plurality of, say, 36 specimen-receiving chambers 14-1, 14-2 . . . 14-36. The block 14 is heated by electrical resistance heaters 15, and its temperature is sensed by an adjustable thermostat 16 which controls the circuit to the heaters 15.

The block 14 is also formed with slots 17 and 18 at its ends to receive depending legs 19 and 20 respectively of a rack 21 for holding the specimen vials 22-1, 22-2 . . . 22-36. The specimen vials are illustrated in the form of shouldered glass test tubes which rest in holes 23. The holes 23 correspond to the spacing of the heating chambers 14 and are brought into register therewith by the legs 19 and 20 fitting into the slots 17 and 18 of the block 14. In this fashion, the glass vials can be lowered into the heating chambers without bumping the block. The slot 17 and leg 19 are both narrower than the slot 18 and leg 20, thus assuring correct orientation.

The housing assembly 10 is completed by a cover assembly 24 which includes a depending peripheral skirt portion 25 adapted to seat on a sealing gasket 25a on the base 13. The cover assembly 24 is divided into upper and lower chambers 26 and 27 respectively by a transverse barrier plate 28 which includes 36 apertures 29-1, 29-2 . . . 29-36 adapted to be brought into alignment with the respective axes of the specimen vials 22-1, 22-2 . . . 22-36. Seated in the respective apertures are nozzle fittings 30-1, 30-2 . . . 30-36 in sealing relationship with the barrier plate 28, and each including a central bore 31 disposed vertically and connecting the upper and lower chambers 26 and 27.

The lower chamber 27 includes an evacuating fitting 32 adapted to be connected to the vacuum pump 11 and fume dispenser 12. The upper chamber 26 is vented to the atmosphere. With the system assembled with the specimen vials in place in their respective chambers and the cover assembly 24 seated in air-tight relationship on the base 13, evaporation of the specimens is commenced under the controlled heat of the block 14. With the vacuum pump in operation, air will flow from the atmosphere in the chamber 26 which serves as a manifold for all of the 36 nozzle fittings, with the result that an individual jet air stream will be directed downwardly into each of the specimen vials as a result of the sub-atmospheric pressure in the lower chamber which functions as an exhaust manifold. From this chamber both the vapors which arise from the specimens and the air which enters through the nozzle fittings will be exhausted to the atmosphere, preferably externally of the laboratory. The downwardly directed air jets will impinge dynamically on the liquid surfaces in each of the specimen vials and will perform the dual functions of gently stirring the liquid (and thus tending to prevent localized hot spots which might cause bubbling) and of blowing away or dispelling the vapors which continuously rise from the specimen liquid. With the evaporation action already augmented by the sub-atmospheric pressure in the chamber 27 and with the vapor layer being continuously dispelled, an accelerated evaporation rate occurs without the necessity of resorting to higher evaporating temperatures which might be harmful to the specimens or which might cause boiling or spattering which would cause particles of the specimens from rising into the chamber 27 to fall into other specimen vials to cause contamination.

Referring to FIG. 3, there is illustrated a modification of the invention in which the cover assembly 24' includes nozzle tubes 33 (which can correspond in number to the number of rows of specimen vials) supported by the end walls of the cover assembly 24'. The nozzle tubes 33 are vented at their ends to the atmosphere and include at equally spaced points along their lengths radial bores 34-1, 34-2 . . . 34-36 directed downwardly to the respective specimen holders. In this modification, the entire inside chamber 35 of the cover assembly defines the exhaust manifold and the spaces within the nozzle tubes 33 define the intake manifold. With the chamber 35 placed under sub-atmospheric pressure, the system functions identically with that described above having reference to FIG. 2.

While the invention has been described having reference to the preferred embodiments thereof, it will be understood that it can take various other forms and arrangements within the scope of the invention. It should not, therefore, be regarded as limited except as defined in the following claims.

Claims

We claim:

1. Apparatus for concentrating laboratory specimens by evaporation comprising a base receptacle for a plurality of specimen vessels and including a heat sink having a plurality of individual chambers adapted to have seated therein open vessels containing laboratory specimens, a heat source for the heat sink including means to regulate the temperature thereof, a detachable cover assembly adapted to be seated in substantially air-tight relationship on the base over the chambers, said cover assembly comprising depending side walls including opposing end portions to engage the base in air-tight relationship, at least one rigid horizontal tube member carried by and joined to the opposing side walls and open to the atmosphere through at least one side wall, the tube member passing horizontally over a plurality of said chambers in close proximity thereto and carrying a plurality of downwardly directed air orifices aligned respectively with the plurality of chambers below, and means to establish sub-atmospheric pressure in the closed space whereby air is drawn into the tube member and discharged downwardly in a plurality of jet streams into the respective vessels disposed in the chambers.

2. Apparatus as set forth in claim 1, including a common rack for supporting said plurality of specimen vessels in positions in vertical alignment with the respective chambers in the heat sink, said rack having downwardly extending legs to carry the respective specimen vessels above a supporting surface, and means forming guide slots in the receptacle to receive the legs and to cause the respective vessels to be lowered into their corresponding chambers.

3. Apparatus for concentrating laboratory specimens by evaporation comprising a base for receiving a plurality of specimen vessels, a heat source for the vessels including means to regulate the temperature thereof, a detachable cover assembly adapted to be seated in substantially air-tight relationship on the base over the vessels, said cover assembly comprising depending side walls to engage the base and a substantially flat, horizontally disposed top surface, manifold means carried by the side walls between the top surface and the chambers and defining an air conduit both to the underside of the top surface and to the respective vessels below, the air path to the chambers including a plurality of downwardly directed openings defining air nozzles above the respective chambers, inlet means connecting the manifold to the atmosphere, and means to establish sub-atmospheric pressure in the closed space whereby air is drawn into the conduit and caused to impinge both on the underside of the top surface and downwardly in a plurality of jet streams directed into the respective vessels.