Chemistry: analytical and immunological testing – Including sample preparation – Liberation or purification of sample or separation of...
Reexamination Certificate
2000-03-08
2003-08-12
Soderquist, Arlen (Department: 1743)
Chemistry: analytical and immunological testing
Including sample preparation
Liberation or purification of sample or separation of...
C422S072000, C422S064000, C422S067000, C422S091000, C422S105000, C422S105000, C422S082050, C422S082120, C422S082130, C422S062000, C159S006100, C159S044000, C159SDIG006, C159S047100, C202S238000, C202S160000, C034S315000, C034S318000, C034S320000, C034S321000, C436S045000
Reexamination Certificate
active
06605474
ABSTRACT:
This is a 371 application of PCT/GB99/00560 filed Feb. 23,1999.
FIELD OF INVENTION
This application relates to the evaporation of samples comprising solid material dissolved or suspended in a liquid in a vacuum, and to improved methods for determining and controlling the temperature of such samples while they are evaporating. It is particularly applicable to monitoring samples in and control of centrifugal evaporators.
BACKGROUND TO THE INVENTION
In centrifugal evaporators samples are usually held in glass or plastic tubes or, sometimes, in a large number of small wells in plastic blocks. The sample holders are spun so as to arrange for a considerable centrifugal force to be applied to them in a direction which forces the liquid to the lower part of the sample tubes to prevent any frothing or spitting of the liquid out of the sample tubes when a vacuum is applied. The spinning samples are held in a vacuum-tight chamber (referred to henceforth as “chamber”) which is connected to a vacuum pumping device.
Evaporators of this type are well known and many types are available commercially.
They all suffer from the difficulty of providing the latent heat of evaporation to the samples to allow evaporation at reasonably high speed without allowing the samples to reach temperatures which could damage or destroy the samples which are often thermolabile.
No heat can be provided by conduction because the samples are held in a vacuum but microwaves or radiant heat from a high temperature source (500°-3000° C.) can be used to provide the heat required for evaporation. Radiation from a low temperature source, eg the chamber walls at 40° C., is frequently used but it cannot provide sufficient heat for rapid evaporation of anything other than small samples of highly volatile solvents. The use of radiant heat and of microwaves is known. Microwaves can cause damage to some samples and in the known embodiments that use radiant heat, the heat has been applied in a manner in which samples are not heated uniformly so that some samples can be dry whilst others are still liquid. This causes overheating of the dry samples if the heat is maintained long enough to dry the last samples.
SUMMARY OF THE INVENTION
According to one aspect of the invention in a method of evaporating liquid samples contained in at least some of a plurality of individual sample holders which are mounted within a chamber and rotated during the evaporation process so that centrifugal force is exerted on liquid contained therein during the evaporation process, and wherein heat is supplied to the sample holders to heat the liquid therein whilst a pressure below atmospheric is maintained in the chamber in manner known per se, a temperature sensing device is located in or adjacent at least one of the sample holders to sense the temperature therein at least during the evaporation process and to generate an electrical data signal which is proportional to the sensed temperature, and a signal path is provided to convey the temperature data signal to electronic data signal processing means.
Typically the data signal processing means is located at the centre of rotation of the plurality of sample holders.
Conveniently the processing means converts the output of the sensor into a suitable form for transmission to an external receiver.
The processing means may convert the sensor output signals into digital or analogue signals by which a carrier signal is modulated to effect the said transmission.
Conveniently the transmitted signal constitutes a radio signal. This for example may be transmitted to a receiver located externally of the housing by means of an antenna which is located externally of the housing and is connected to the signal processing means by means of a conductor which passes through the housing wall via an insulating seal serving as a lead through.
Where the chamber wall does not readily transmit, or significantly attenuates radio signals, the radio signals from the signal processing means may be received by a stationary radio receiver located within the chamber and conveyed either as radio signals or after demodulation as data signals indicative of the temperature of the sensor, via a conductive path which extends sealingly through and is insulated from the chamber wall. Typically the signals are conveyed through the chamber wall as radio signals, for demodulation to produce the said data signals outside the chamber.
The carrier signal may be a beam of light and the modulation is such as to modulate the intensity of the beam. In this event the light signals may be transmitted through a window which is light transmitting and which forms an integral part of the housing wall, to enable the modulated light beam to pass to a stationary light responsive device located externally of the housing and which is adapted to convert the received light signals into data signals indicative of the temperature of the sensor.
Whatever form the carrier signal and transmission system takes, the data signal may be employed to drive an indicator which is calibrated to indicate sample temperature.
Likewise the data signal may be employed to control the source of heat heating the sample holders in the chamber.
Power for the processing means may be derived from a battery located within a housing within which the processing means is also located. The battery may be connected to the processing means by the closing of a motion sensitive switch which closes when the chamber rotates, and is disconnected therefrom by the opening of the switch when the chamber ceases to rotate.
Alternatively power for the processing means may be transmitted from a source located external to the housing to a receptor located within the housing which is connected to the processing means.
In a further alternative arrangement, power for the processing means may be supplied thereto from an external power source by means of a rotational electrical connection. Such a connection may comprise slip rings and conductive elements in contact therewith.
Preferably any rotational electrical connection is separated from vapours in the chamber by being located outside the chamber, or inside the signal processing means housing, and seals are provided around conductors leading between the signal processing means and the external electrical connection where they pass through the wall of the chamber or the housing.
Typically at least one of the conductors leading between the processing means and any external rotational electrical connection, extends through the hollow interior of a drive shaft which itself extends through a seal in the chamber wall and serves to rotate both the sample holders and the said housing within the chamber.
The drive shaft may itself be electrically conductive and serves as one of the conductive paths for the power to the signal processing means.
Preferably material from which the housing is constructed, is non-conductive as well as being inert in the presence of the vapours given off during the evaporation process.
A preferred material for the housing is polypropylene.
In a further arrangement relating to the supply of power to the signal processing means in the housing, power therefor is generated in a winding which rotates with the housing relative to a stationary magnetic flux.
The winding in or on the housing may be wound on soft magnetic material such as is employed to make transformer laminations. It may be mounted on a central spindle which rotates the sample holder in the chamber.
Typically the magnetic flux is produced by at least one permanent magnet which comes into close proximity with the winding during each rotation of the sample holder, and is located either inside the chamber and the winding is in or on or close to the housing, or is located outside the chamber and the winding is rotated around the interior of the chamber close to the wall thereof.
The sensor may be sheathed in an impervious inert material so that it will not contaminate the sample or suffer corrosion, and may for example comprise a thermocouple.
The sample holders are typically rotated
Genevac Limited
Gordon Brian R.
Lee Mann Smith McWilliams Sweeney & Ohlson
Soderquist Arlen
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