EP0109416B1

EP0109416B1 - Method and apparatus for dispensing, pipetting and diluting fluids

Info

Publication number: EP0109416B1
Application number: EP19830901609
Authority: EP
Inventors: Gizella Balas; János CSIKOS; Gábor KEMENY; Zsolt Szabo; Ferenc Vadasz
Original assignee: "labor" Mueszeripari Muevek
Current assignee: "labor" Mueszeripari Muevek
Priority date: 1982-05-19
Filing date: 1983-05-19
Publication date: 1988-05-18
Also published as: DE3376680D1; EP0109416A1; HU183961B; EP0109416A4; WO1983004015A1; SU1276257A3

Abstract

Method and apparatus to dispense, pipet and, afterwards, to dilute fluids, primarily for analytical laboratory use. In the method of this invention, a constant stream of the fluid is established and maintained in a part of a tube by means of a peristaltic pump, and a predetermined amount of the fluid is sipped or dispensed by opening a suction or pressure side of the tube for an adequate time. With the apparatus, pressure side tubes of the pump are connected through controlled switch valves to fluid container or to a dispensing tube, and a control unit is attached to the switch valves and is electrically connected to a sensor of a chopper fixed to an axis of the pump.

Description

The invention relates to a method for dispensing, pipetting and consecutively diluting fluids, primarily for analytical laboratory use, wherein a constant stream of the fluid is established and maintained in a part of a tube by means of a pump and a predetermined amount of the fluid is dispensed by opening valve means in said tube on the pressure side of the pump. Furthermore, the invention relates to an apparatus for dispensing and pipetting fluids comprising a pump and controlled valve means in a tube on the pressure side of the pump.
The commercially available numerous automatic laboratory diluter-dispensers utilize almost in all cases piston syringes and servo-motor valves as disclosed in US-A-3 900 289, US-A-3 982 667 and US-A-4141 469.
The rare peristaltic pump type dispensers require a separately operated pump head for each dispensing channel. In order to dispense more than one reagent, precision syringe and displacement mechanism is needed for each additional channel. The cost requirement in this latter case can be multiple compared to the price of the multichannel peristaltic pumps. Furthermore, one of the main difficulties is in the lack of independent control of the channels.
From US-A-3 419 358 a method for diluting a fluid for preparation of automatic analysis is known. Sample liquid to be diluted in a container and sipped therefrom by means of an aspirator vacuum pump. The vacuum pump is operated by a pressure medium being a diluent sipped from another container, by means of a centrifugal pump. Pressure or flow rate, respectively, of the diluent have to be exactly set for maintaining the desired ratio between diluent and sample liquid. This is achieved by two valve means downstream the centrifugal pumps since the centrifugal pump is not capable per se to deliver a predetermined and constant amount of pressure medium.
The main object of this invention is to eliminate the deficiencies of the known solutions and to provide a method and an apparatus with which a fluid can be dispensed, pipetted and diluted in a more convenient and precise way.
According to this invention, this object is solved in such a way that in the method as described in the first paragraph hereinabove, a multichannel peristaltic pump is used, a predetermined amount of the fluid is sipped by opening valve means in the tube on the suction side of the pump for an adequate time, a predetermined amount of the fluid is dispensed by opening said valve means in the tube on the pressure side of the pump, and the control of both valve means is influenced by rotational speed fluctuations of the pump drive and/or by pulsation of the pump.
In a preferable embodiment of the method according to this invention, the fluid delivered by the pump is lead through a controlled two-way switch valve either into a fluid container on the suction side of the pump or, for dispensing, to a dispensing tube. Expediently, the sucking effect of the pump in the dispensing tube may be controlled by a two-way switch valve.
According to this invention, in the apparatus for dispensing and pipetting fluids comprising a pump and controlled valve means in a tube on the pressure side of the pump, the pump is a multichannel peristaltic pump, a pressure side tube of the pump is connected through a controlled switch valve to a fluid container on the suction side of the pump or to a dispensing tube, and a control unit is attached to said switch valve and is electrically connected to a sensor of a chopper fixed to an axis of the pump.
In a preferred embodiment of the apparatus according to this invention, a suction side tube of the pump is connected through an additional controlled switch valve either to said fluid container or to a dispensing and pipetting tube. A further pressure side tube may be connected to the fluid container and a further suction side tube may be connected through the additional controlled switch valve either to the fluid container or to the pipetting and dispensing tube.
The method and the apparatus according to this invention have the advantage that the fluid can be dispensed, pipetted and diluted in a most convenient and precise way. The costs for manufacturing that apparatus and for. proceeding in accordance with that method are relatively low.
Further details of this invention will be described hereinafter with reference to the attached drawing. In the drawing,

Fig. 1 is a schematic block diagram of one embodiment of this invention,
Fig: 2 shows another embodiment, and
Fig. 3 illustrates a further embodiment of the invention.

The apparatus shown in Fig. 1 has a peristaltic pump 1, a fluid container 2, a controlled valve 3a, tubes 4b, 5a, 5b, 6 and a control unit 7. With this system, fluid dispensing can be carried out according to the method of this invention.
An apparatus capable to carry out pipetting is shown in Fig. 2, where an additional controlled switch-valve 3b is built into the sipping side of pump 1, i.e. into tube 4a.
In Fig. 3, an embodiment of this invention for pipetting and consecutively diluting is shown. Tubes 4d and 5d are connected to another channel of the peristaltic pump 1.
The realisation of the method in this invention will be described by illuminating the operation of the apparatus. In Fig. 1, the peristaltic pump 1 delivers the contents of container 2 through tubes 4b, 5a towards controlled valve 3a, which is closed towards tube'6 and open towards tube 5b before the dispensing cycle. Thus, a constant rate of recirculation is maintained. If the valve 3a is switched over for a certain period of time determined by the control unit 7 the selected amount of liquid leaves the dispensing tube 6. The timing signal for the control unit 7 is given by a chopper fixed to the axis of the peristaltic pump 1.
The frequency of the impulses is preferably unit multiple of the pulsation frequency of the pump, which is known to emanate from the rollers that lift off from the tubes one after the other. The exact time of the valve switching has to be selected in such a manner that it occurs in all cases at the minimum point of the pulsation.
This can be achieved by delaying the said signal or by fixing the signal chopper in the right phase. In this manner, the minimum dispensable volume for each tube diameter of the pump is given by the distance of the rollers that is the "length" of the pressure pulses. However, with a pump having a negligible pulsation only, the frequency of the signal chopper and, thus, the minimum dispensable volume is limited only by the general technical parameters.
The channels of a multichannel peristaltic pump can independently be equipped with controlled valves as is shown in the figure. Thus, each channel can be used for dispensing independently from each others without disturbing the even rotation of the pump.
The pipetting procedure will be explained with reference to Fig. 2. Auxiliary to Fig. 1, is a switch-valve 3b connected into the suction side of the pump 1. Switch-valve 3b connects the suction side tube 4a either through tube 4b to the fluid container 2 or, in the other setting of the valve 3b, through tube 6b to the pipet and outlet tube 6c. The timing signal arrives from the pump 1 and serves as a basis for the control of both valves. The pipetting cycle of the system filled already with the fluid is as follows:
In the preparatory stage, the pump 1 is circulating the fluid through tubes 4a, 4b, 5a, 5b. The pipet tip 6c, which contains some microliter air gap (see last step of the cycle) is immersed into the fluid sample to be pipetted. At that time, the control unit 7 switches over the valve 3b for a short time, or for an appropriate number of pulses and, thus, the desired amount of sample will flow into tube 6c. The sipping is finished and the pump works through tubes 4b and 5b again. During this time, the pipet tip 6c is placed above the appropriate vessel and dispensing can be started. This occurs by switching over the valve 3a in the same manner as described with Fig. 1. If pipetting is carried out without dilution, the active time of the valves 3a and 3b is equal. In the case, the pipet tip 6c can be flushed by a small amount of fluid from inside. The flush fluid if required serves for the dilution of the sample. At the end of the cycle, a little amount of air can be sucked by switching over valve 3b for a short time, while the tip is held in the air.
If the sample to be pipetted should be dispensed with a larger amount of diluting fluid, the total pipetting cycle time may be too long when using the arrangement in Fig. 2. For this purpose, the embodiment of Fig. 3, built up in a different manner, while functionally is equivalent to that of Fig. 2. The rate of outflow is determined by the cross section of the pump tube 4a, 5a, whereas the inflow sipping rate is determined by the delivery rate of the pump tube 4d, 5d.
The method according to the present invention makes it possible to utilize a multichannel peristaltic pump and more controlled valves to build different systems and establish further additional operational functions. Thus, automatic titration will be possible with the system on Fig. 1 if an end point indicator is connected to the control unit.

Claims

1. A method for dispensing, pipetting and consecutively diluting fluids, wherein a constant stream of the fluid is established and maintained in a part of a tube by means of a pump and a predetermined amount of the fluid is dispensed by opening valve means in said tube on the pressure side of the pump,

characterized by

using a multichannel peristaltic pump;

sipping a predetermined amount of the fluid by opening valve means in the tube on the suction side of the pump for an adequate time;

dispensing a predetermined amount of the fluid by opening said valve means in the tube on the pressure side of the pump;

influencing control of both valve means by rotational speed fluctuations of the pump drive and/or by pulsation of the pump.

2. A method as claimed in claim 1, characterized in that the fluid delivered by the pump is lead through a controlled two-way switch valve either into a fluid container on the suction side of the pump or, for dispensing, to a dispensing tube.

3. A method as claimed in claim 2, characterized in that the sucking effect of the pump in the dispensing tube is controlled by a two-way switch valve.

4. An apparatus for dispensing and pipetting fluids comprising a pump and controlled valve means in a tube on the pressure side of the pump, characterized in that the pump is a multichannel peristaltic pump (1), a pressure side tube (5a) of the pump (1) is connected through controlled switch valve (3a) to a fluid container (2) on the suction side of the pump (1) or to a dispensing tube (6), and a control unit (7) is attached to the switch valve (3a) and is electrically connected to a sensor of a chopper fixed to an axis of the pump (1

5. An apparatus as claimed in claim 4, characterized in that a suction side tube (4a) of the pump (1) is connected through an additional controlled switch valve (3b) either to the fluid container (2) or to a dispensing and pipetting tube (6c).

6. An apparatus as claimed in claim 5, characterized in that a further pressure side tube (5d) is connected to the fluid container (2) and a further suction side tube (4d) is connected through the additional controlled switch valve (3b) either to the fluid container (2) or to the pipetting and dispensing tube (6c).