METHOD AND APPARATUS FOR DISPENSING, PIPETTING AND DILUTING FLUIDS

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: Method and Apparatus for Dispensing, Pipetting and Diluting luids Field of the invention The invention relates to a method and apparatus to dispense, pipet and, afterwards, to dilute fluids, primarily for analytical laboratory use. Background of the invention The commercially available numerous automatic laboratory diluter-dispensers - utilize almost in all cases piston syringes and servo-motor valves. (US. Patent 3 900 289, T7S. Patent 3 982667, US. Patent 4141469) -" * •---. • (Che rare peristaltic pump type dispensers require a separately operated pump head for each dis- pensing channel. In order to dispense more than on 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 pristaltic pumps. One of the main difficulties is in the lack of independent control of the channels. Summary of the invention The main object of this invention is to eliminate the defficiencies 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. In the present invention, a method was sought that enables a multichannel peristaltic pump to carry out labora- tory fluid dispensing, pipetting and diluting by means of its functionally independent channels. According to the 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. Thus, in our method each channel of the peristaltic pump sips one reagent solution and returns it to the adequate container, with a constant flow rate determined by the measurements of the flexible pump tubing and the velocity of the pump rollers. This said handling procedure of the fluid can be carried out by switching these constant streams by con- trolled valves. An essential feature of the invention is in that the timing signal for the control unit is provided by a chopper fastened to the pump drive azis, thus an additional pump motor speed control is no more necessary. Similarly, the pulsation of the peristaltic pump is not a bar, since the pulsation can be synchro¬ nized with the timing signal by appropriate ' selection of the chopper.timing. Thus, the well known recycling of the reagent is here not applied for separating the channels of a peristaltic pump, nor for fluid dispensing through this means. The connection into the sipping side of the recycling ring and the pipetting function by this means are also novel. As the pipetting volume in most cases is smaller by orders of magnitude than the diluent volume, it is necessary to combine the pipetting and diluting functions. Brief description of the drawing Further details of this invention will be. de - scribed hereinafter with reference to the attached drawing. In the drawing, Fig. 1 is a schematic block diagram of one em¬ bodiment in this invention, Fig. 2 shows another embodiment, Fig. 3 illustrates a further embodiment of the invention. Description of the preferred embodiments The apparatus shown in Fig. 1 has a peristaltic pump 1, a fluid container 2, a controlled valve 3a, tubings 4b, 5a, 5b, 6 and a control unit 7. With this system, fluid dispensing can be carried out according to 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 the pump 1, i.e. into tube 4a. In Fig. 3, the embodiment of this invention for pipettin 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 4a, 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 3 is switched over for a certain period of time de- ter ined 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 chooper 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 it 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 cir¬ culating 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 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 -ς { E l OMPI /fa IPO 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 hold in the air. If the sample to be pipetted should be dis- pensed with a larger amount of diluting fluid, the total pipetting cycle time may be too long whtn using the arrangement in Fig.2. For this purpose, the embodiment of Fig. 3, built up in a different manner, while functionally is equiva- lent 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 dif erent 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. OMPI

Claims: CLAIMS: 1. A method for dispensing, pipetting and conse¬ cutively diluting fluids, characterized in that 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. 2. A method as claimed in Claim 1, wherein 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 to the place of dispensing. 3. A method as claimed in Claim 2, wherein the sucking effect of the pump in the dispensing tube is controlled by a two-way switch valve. 4. A method as claimed in Claim 2 or 3, wherein control of the switch valves is influenced by speed fluctuations of the pump drive and/or pulsation of the pump. 5. An apparatus for dispensing fluids, comprising a multichannel, preferably peristaltic pump characterized in that pressure side tubes (5a) of the pump (1) are connected through controlled switch valves (3a) to fluid container (2) or to a dispensing tube (6), and a control unit (7) is attached to the switch valves and is electrically connected to a sensor of a chopper fixed to an axis of the pump. OMPI W °' 6. An apparatus for dispensing and pipetting fluids as claimed in Claim 5 characterized in that the suction side (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). 7- An apparatus for dispensing,pipetting and consecutively diluting fluids as claimed in Claim 6 characterized in that a further channel on the pressure side is connected to the fluid container (2) and on the suction side is connected through an additional controlled switch valve (3b) either to the fluid container (2) or to the pipetting and dispensing tube (6c).

Inventors: BALAS GIZELLA, CSIKOS JANOS, KEMENY GABOR, SZABO ZSOLT, VADASZ FERENC, BALAS, GIZELLA, CSIKOS, JANOS, KEMENY, GABOR, SZABO, ZSOLT, VADASZ, FERENC
Applicants: MUESZERIPARI MUEVEK LAB, LABOR MUESZERIPARI MUEVEK
Application year: 1983
Main classification: B67D5
IPC codes: B01L3, B67D5