DE2132066A1 - PIPETTING DEVICE, ASSOCIATED PIPETTES AND METHOD FOR PIPETTING - Google Patents

Description

Patent attorneys Dipl.-Ing. RWeickmann,

Dipl.-Ing. H.Weickmann, Dipl.-Phys. Dr. K. Fincke Dipl.-Ing. F. A. Weickmann, Dipl.-Chem. B. Huber

8 MUNICH 86, 2132066

n.rri POST BOX 860 820

MÖHLSTRASSE 22, NUMBER 48 39 21/22

<983921/22>

ΒΙΟ-SCIENCE LABORATORIES Van Nuys, Los Angeles, California,

V.StoAo

Pipetting device, associated pipettes and procedures for pipetting «,

The invention "relates to a pipetting device with several interchangeable pipettes can be used, as well as pipettes for this device and a pipetting method.

A large number of pipetting devices are already known. Many of these devices are highly specialized some devices can only pipette a constant, predetermined volume of liquid, whereas others an accurate recalibration of the syringes or the like require when the liquid volume or the liquids to be pipetted change. Lots of pipetting devices are not very adaptable because one and the same device cannot be used for successive pipetting different liquids can be used without each time a different liquid are pipetted all work surfaces should be laboriously washed or cleaned

Many of the common automatic pipettes are suitable for pipetting aqueous fluids and liquids, which have a similar vapor pressure, but cannot be used for low-boiling liquids such as diethyl ether,

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are used under the working conditions of the pipette have high vapor pressures. The portable devices can generally move from one tube to another as desired to be brought; however, many such mobile devices are highly dependent on manual operation On the other hand, the stationary devices cannot be transported during use, many of them but are largely automated and can be operated at the touch of a button »

There is therefore a need for a pipetting device that works simply and accurately, which as well as the volumes of the to be pipetted liquids in use regarding the nature flexible, is transportable or stationary usable and largely automatically ₉ simple and foolproof arbeiteto

The invention has set itself the task of creating such a pipetting device that is interchangeable with several Pipettes can be used

To solve this problem, the invention provides a pipette device which has a pipette holder for optionally holding a pipette in a functional state, which has a sealing insert which detachably grips an end part of a pipette in such a way that a sealing connection is established with the pipette is. In addition, the holder accommodates: a suction line, a pressure line and a valve arrangement that creates an optional connection or shut-off between the suction line and the pressure line and the pipette and between a pull position in which the pipette is connected to the suction line and sealed against the pressure line and a blocking state in which the pipette is blocked from being connected to both lines , with a predetermined volume of fluid

209883/0169

in the pipette is disconnected from the suction line, "and Finally, an emptying state can be switched in which the pipette is shut off from the suction line and connected to the Pressure line is connected

The pipette holder is preferably equipped with a micropipette which is connected to a pipette inserted in the device. which provides the suction force to pull the pipette and the pressure to empty it. The control unit may be movable to the auxiliary device and the latter can the operating device via Schläuohe or other universally movable connection elements with a continuous suction force and a continuous Druok supply "to pipetting device may further comprise a novel pipette or more austausbhbare pipettes include cooperating with the pipetter _e The invention The device is simple in its construction and in operation, it is adaptable in use and offers mobility combined with a largely automatic, precise pipetting of various liquids. The invention also ensures rapid operation while largely eliminating errors

An embodiment of the invention is described in more detail below with reference to the accompanying drawings demonstrate:

Mg «1 is an isometric view of an inventive Pipetting device that allows its use for the pipet «· animals illustratedj

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Mg «, 2 and 3 Schemes of the device according to the invention in two embodiments;

Figo4 is a side view of an embodiment for a pipettor according to the invention, partially broken to the valve assembly, the seal, the To illustrate elements for controlling the valve and the holder and holder for the pipette!

FIG. 5 is a view from above of the pipettor of FIG. 4, partially broken to show the valve and the parts used to operate it ^

Fig. 6 is a side elevation of a second embodiment of the pipettor according to the invention, partially broken, to the valve, its control elements, the sealing means and to illustrate the receiving and holding of the pipette;

3? Igc7 and 8 a view from above and a partially sectioned side view, respectively, of a valve in another embodiment;

Figs. 9f 10 and 11 functional sketches of the valve in the embodiment FIGS. 7 and 8;

Figs. 12, 13, 14 and 15 · Detailed sketches showing the structure and the function of the pipette, the pipette holder, the seal and the pipette holder according to the invention show in one embodiment «,

A pipetting device 30 is shown in FIGS. which has an operating device, namely the so-called pipettor 32. The pipettor 32 includes a Pipette holder 34 which receives one end 35 of a pipette 36 and a part that can be grasped by hand, e.g. a handle 37, which lies well in the hand of a user. The pipettor 32 also houses means for actuating

209883/0159

the pipette 36, for example a suction line 50 and a pressure line 60, which apply negative pressure or pressure for filling and emptying the pipette 36, further an associated valve, here the valve 100, for controlling the negative pressure or pressure for the pipette 36, means in order to optionally functionally connect the end 35 of the pipette 36 to the valve 100, for example a sealing insert 200, then a pipette holder, a fitting 202 to bring the pipette 36 into working contact with the sealing insert 200 and the valve 100, and a lock lever 300. on the pipetter are still further provided: means for operating the valve 100, namely \ lent a knob 38, and for selectively actuating said See "', approximately lever, namely, a trigger 40 · the • pipetting device 30 according to the invention further comprises an auxiliary device 80 for operating the. Pipette. The auxiliary device 80 comprises means for applying suction force and pressure for actuating the pipette to the pipettor 32, for example suction and pressure pumps 82, 84 in Pig. \ 2, or the inlet and outlet openings 86, 87 of a single pump 88 in FIG. 3 and the associated connecting hoses 81, 83, a liquid trap 85, a connection line 79 j for the trap and one or more motors 89 and the like Auxiliary device 80 is preferably accommodated in a housing 28. The housing 28 expediently has a tree 39 for receiving the pipettor 32 when it is not in use, and a removable front panel, accessible from the trap 85, the motor and pumps and whatever else is contained in the housing 28 do. To control the pumps and motors, a conventional circuit, not shown, is provided, which is operated by a switch button 41 on the housing 28. The pipettor 32 and the auxiliary device 80 are functionally connected to one another by means of flexible suction and pressure lines 55, 65. These hoses connect the corresponding lines 50, 60 in the pipettor 32 and the associated pumps (pub »

209883/0159 originally inspected

pen 82, 84 in Figure 2 or inlet and outlet 86, 87 of the pump 88 in Mg.3) via connecting lines 81, 83 in the housing 28, the tubes 55, 65 are flexible so that the pipettor 32 is free from the housing 28 is movable, as is expedient for a typical function, for example for pipetting a predetermined amount of liquid 44 from one beaker 45 into another beaker 46 · -

When the device is in use, for filling and emptying the pipette 36 in the suction line 50 and pressure line 60 located in the pipettor 32, an underpressure or overpressure of a fluid is applied via the flexible hoses 55, 65 with the aid of the overpressure or underpressure generating Components of auxiliary device 80. In this way, negative pressure and positive pressure occur practically continuously at valve 100 in pipettor 32, pressure fluctuations of the fluid in the system primarily resulting from the work required to fill and empty a pipette 36 or from pressure regulators to be described . The pipettor 32 is universally movable in three dimensions relative to the auxiliary device 80. The pipette 36 is filled and emptied. with the aid of lying in the pipetter valve 100, where '35 of the pipette 36 is brought selectively either with the suction line 50 for filling or to the pressure line 60 for emptying in connection, the aggregate in the pipetter end · The used valve also allows the pipette end 35 both to shut off against the suction line as well as against the pressure line 50 or 60 and to seal against the environment, as is appropriate, for example, "to transfer a filled pipette from one beaker 45 to another 46". The pipette device 30! ”Is also worthwhile in that for pipetting a: pipette 36 is completely filled with a liquid 44 to be measured, with an initial part of 4-in dl · with each filling process.

2Q98Ö3 / 0150

Pipette sucked in liquid is used for pre-rinsing. That The valve 100 in the pipettor 32 mechanically separates the measured amount of a filled liquid 44 from a pre-wash part, preferably by separating it from one single point · The pre-rinse part remains in the pipettor 32 and is fed through the suction line 50 and the hose 55 transferred to trap 85 to be finally eliminated The amount of liquid measured in the pipette 36 44 is mechanically and precisely separated from the pre-rinsing part by the valve 100 and is finally emptied by the pipette tip 236 due to the complete filling of the Pipette 36 and the mechanical separation of the measured amount of liquid 44 are many of the curse when pipetting. problems encountered with tiger fluids

The total volume pipetted is equal to the total internal volume the pipette 36 plus the volume of a micropipette 210 associated with the pipette 36 is equal whether the valve 100 is in the blocking position, the filling position or the emptying position »The micropipette 210 is, for example, as shown in FIGS. 8 and 9, of those parts of the valve 100 and the sealing element. Set 200 formed, which include a portion of the amount of liquid 44, which are emptied by the pipette 36 target. So the measurement does not depend on filling up to a meniscus line, as in manual pipetting, or on the calibration of the displacement of a piston, such as when metering with a piston syringe. The volume of the micropipette 210 of the pipettor 32 is small in relation to the volume of the pipette 36 itself. For example, the micropipette volume on the order of 1 microliter or less to 15 microliters, that is 1 percent or less, up to 15 percent or more of the total volume pipetted, depending on the volume of the particular

209883/01 59

th pipette 36 _o The volume of the liquid 44 measured by the micropipette 210 is practical from one pipette to the next, regardless of whether the same pipette or different pipettes with the same or different volumes are used be carried out that one uses a plurality of pipettes 56, each calibrated to a desired volume of liquid, in connection with the micropipette 210. As will be explained in more detail later, through the interaction of the various elements for operating, grasping and securing the pipette in the pipettor 52 with pipettes 56 of different sizes and with the other components of the device 30, a versatile integrated pipetting device that is capable To pipette liquids quickly and accurately over a wide range of volumes.

Further advantages of the invention and additional construction details and details of the function emerge from the following detailed description of exemplary embodiments of the invention. In this description it is useful to the various elements of the pipetting device « device 30 and examples "to explain such elements separately. For the sake of simplicity, the drawings show the same elements in different exemplary embodiments of the invention appear using the same reference numerals

1 ·) Auxiliary device 80, connecting base line 55 * 65 and suction and test line 5Ot60.

The supply of TJnterdruok and Überdruok at valve 100 in Pipettor 32 is practically continuous with no rolcsioht whether the valve 100 is in filling, blocking or emptying

209 883/0159 «m.n * l

position is »It is therefore expedient to explain the means for applying and regulating the negative and positive pressure separately from a detailed description of exemplary embodiments for the valve 100 ₀

As from the I ¹ Ig. 1 to 3, the suction force for filling and the pressure for emptying is provided by a suction and a pressure pump 82 and 84 or from a single pump. 07 - 0.35 kg / cm are designed to be used · The pumps 82, 84 »88 are driven by an electric motor or several electric motors 89 or otherwise. Alternatively, a compressed air cylinder, a jet pump or other means can be used to generate the liquid pressure or negative pressure, and the emptying pressure can also be applied in the form of a liquid that is inert to the substance to be pipetted, although a gas pressure is generally suitable and expedient Trap 85 can be a conventional liquid trap which prevents liquid from penetrating to the pump 82 or 88 and at the same time maintains a negative pressure in the line 50 and the connecting hose 55. The Sohläuohe 79 _t 81, 83, 65, 55 and the suction and pressure lines 50 and 60 are usually flexible hoses made of a polymeric plastic, such as polyethylene, rubber, plasticized polyvinyl chloride or polypropylene. They are preferably elastic and transparent. Flexible hoses with an internal diameter between 1 and 10 mm and an external diameter of 4 to 20 mm are two-fold. So is a for pipetting aqueous solutions

209883/0159

Rubber hose 5j5 useful in the case of repetitive The connection hose 55 carrying negative pressure can carry out pipetting operations in several successive parts of prewash liquid included while the liquid portions The use of a connecting hose 55 is drawn off by the suction into the trap 85 wettable material is used to suck the various portions of pre-rinse liquid from the pipettor 32 down to the trap 85 necessary suction force and contributes to the uniformity of the suction force on the valve 100 during a * Series of pipetting operations in rapid succession beiο The connecting tubes 55, 65 are connected to the corresponding connecting lines 79, 83 in the housing 28 of the auxiliary device and to the lines 50, 60 or parts thereof in the pipettor 32 by a friction fit on tubular couplings 90 or connected by sonatic connection pieces

The fluid circuit connecting valve 100 and pumps 82 and or 88 may have means for controlling overpressure or negative pressure at valve 100. For example low pressure difference at valve 100 is desirable be to provide low flow rates when small volumes (about 100 microliters up to a few

Milliliters). Pur the Rasohe filling and emptying of large volumes (for ₀ B * 25 or 50 milliliters), high pressure differences be desirable. Overpressure and underpressure can be regulated independently of one another by means of an adjustable screw terminal 91 on each connecting hose 55, 65, see FIG. The screw terminals 91 can be fastened in the pipettor 32 "inside the housing 28 or also on the parts of the connecting pieces 55 and 65 running on the outside.

209883/0159

hose 83 are regulated, the pressure chamber 92 via an adjustable pressure relief valve 93 to the environment As FIG. 3 shows, the adjustability of the pressure relief valve 93 enables a direct Control of the maximum pressure in the hoses 83 and 60, the connecting hose 65 and the pressure chamber 92β The valve 93 indirectly controls the negative pressure by regulating the outlet pressure of the pump 88. An immediate control The Unterdruokes can with the help of a similar pressure chamber and a pressure relief valve in the vacuum leading line 81 behind the trap 85 can be achieved. The vented pressure chamber 92 can expediently be a short one Have hose piece which is connected to the line 83 or 81 at a T- or Y-shaped fork and is provided with a screw clamp or other adjustable clamp that the hose piece against certain Shuts off pressure differences and thus served as valve 93. To fill a pipette 36, a pre-rinse volume is used Liquid sucked into the suction line 50 through a valve 100 » The line 50 and the pipettor 32 preferably have a transparent piece, a viewing window or the like to enable visual observation of the line 50 In this way, the movement of a column of liquid in conduit 50 gives a visual indication to a user that the filling of the pipette is finished Droseeletelle in the vacuum line, in the form of a Sole connector 90 in Fig.2, provided to the Flow of the liquid column in the suction line. 50 to Trap 85 to throttle and the liquid flow rate in the To reduce line 50 when the filled liquid reaches the Droeeelstelle 95. The reduction in the flow rate makes it possible to observe the end of the filling and reduces the amount of fluid that inadvertently

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tigt can be drawn into the suction line 50, if the filled micropipette 210 is neglected due to the inattentiveness of the user or the like The same flow resistance or a throttle point 95 can be arranged in the pressure line 60 to reduce the volume to limit the pressure gas used for emptying, which flowed into the valve at the beginning of the emptying process in this way, a steady, even flow of compressed gas is obtained regardless of the initial pressure drop between the pressure line 60 and the micropipette 210 when the

* emptying begins. The flow resistance or the throttle portions 95 is preferably disposed in the pressure line 60 so that the inner volume of the conduit 60 behind the throttle point 95 - seen in flow direction - is less than the smallest volume of the pipetting device 32 liquid to be pipetted ₀ The in line The volume of gas for emptying contained downstream of the resistor 95 is preferably sufficiently small in relation to the volume of the pipette to ensure a practically uniform flow during most of the emptying process. to ensure speed from the pipette 36, regardless of the pressure increase in the suction line 60 when the valve 100 closes «,

2o valve 100
a.) First embodiment

As illustrated in FIGS. 2, 4 and 5, a valve 100 a rigid body 124 made of a solid plastic, glass or metal and with the The pipette holder 34 of the pipettor 32 can be formed in one piece. A suction line 50 is located on the body 124 and a pressure line 60 attached, which have a common movable tube wall 126 ", a micropipette 210 extends through body 124 and a hose wall

209883/0159

126 and forms an arm of a three-way fork with the Lines 50 and 60. In the pipettor 32, a double torsion spring 130 is mounted on a pin 134, the End part 131 is firmly anchored in the body 132 of the pipettor · Two movable spring legs 128, 129 of the spring lie across the lines 50 or «. 60 to this normally by holding opposing portions of the hose wall 126 together against the body 124 press. Also on the pin 134 are in the pipettor 32 two levers 136, 137 pivotally supportedj a part of each lever 136, 137 extends under one of the spring struts 128, 129. Two buttons 138, 139 for filling or emptying are held displaceably in the pipettor 32 and extend through its body 132 inside, where they are connected to the first or second lever 136, 137 are in contact. If you press the button 138 for the Föll « operation, then the lever 136 pivots about the pin 134 as a pivot and lifts the strut 128 from the sole wall 126 of the line 50 high, wherein the suction line 50 is opened for the filling process, as shown in Figo2 accordingly the lever pivots when the switch button 139 is pressed 137 around the pin 134, lifts the strut 129 from the hose wall 126 and the body 124 and opens the over « pressure line 60 for the emptying process «If neither of the two Hold buttons 138, 139 depressed, so both press Spring legs 128, 129 against parts of the sole hose wall 126 and press them against the opposite wall parts, the surround the micropipette 210 so that both lines 50, 60 are blocked off from the bore of the micropipette 210 Preload by the spring 130 also lifts the two switch buttons 138, 139 duroh the action of the spring struts 128, 129 on levers 136, 137 and returns them to the normal position.

209883/0159

The valve body 124 preferably has a fixed stop 125 for the spring struts, which is from the valve body stands up, namely by a piece that is greater than the wall thickness 126 and preferably slightly smaller than that double wall thickness., If the struts 128, 129 the Seal hose wall 126 by pressing together, limited the stop 125 their movement in the direction of the valve body 124. The thickness of the stop 125 is chosen so that each Strut 128, 129 can be pressed against the hose wall with a force that is far greater than for sealing of the lines 50, 60 required without unduly deforming or damaging the hose wall «. The attack

125 allows the hose wall 126 to be compressed by the spring legs 128, 129 to a distance of less than two wall thicknesses to strengthen the seal and to deform the hose wall so much that any shortcomings the inner surface are sealed, but at the same time an undesirable squeezing of the lines 50, 60 the fork with the bore of the micropipette 210. derno By using a stop 125, the lines 50 and 60 can also be used much higher Line pressures than usual without damaging the hose wall

126 to be sealed »

The micropipette 210 is cylindrical and the spring legs 128, 129 are preferably arranged so that they _e move in parallel planes tangential to opposing walls of the micropipette 210. This arrangement facilitates precise sealing, because the of the strut or 129 moving part of Sohlauohwand 126 in this case is pressed against an opposing wall piece which is tangential to the micropipette, ie at the center point of the sole wall 126 with one of the opposing walls. i ;. Walls 211, 212 of the micropipette 210. Duron the shut-off

209883/0159

one of the two lines 50, 60 in the manner described above, the three-way bifurcation of the lines 50 and 60 and the bore 210 is converted into a two-way bifurcation of the bore 210 with one of the two lines. When the from the tubular wall 126, Z ₀ as the lines 50, 60, enclosed volume has the same diameter as the bore 210 of the micropipette, .the to this V Zweiweggabelung else formed / has an approximately circular cross-section of substantially the same diameter as the Bore of the micropipette and the open line (50 or 60), and has a smooth wall.This type of construction in valve 100 largely eliminates eddy currents during filling and reduces the amount of pre-rinsing liquid required to drag the liquid from one pipetting process to the next avoid.

As shown in FIGS. 4 and 5, the lines 50, 60 extend to beyond the valve 100 and the pipettor 52 and are enclosed in the handle 37 in order to finally connect to the connection loop leading to negative pressure or positive pressure. chen 55 or 65 to be connected. The pipette holder 34 of the pipettor 32 has a sealing insert 200 Rubber, silicone rubber or the like, which rests against the valve body 124, and a fitting 202, which for receiving of one end 35 of a pipette 36 is formed «one received in the holder 202 and pressed against the sealing element. A set of 200 squeezed pipettes 36 can, if desired, be supplied by a Si «~ oherungshebel 300 are held in the manner of a trigger. The securing lever 300 has a contact piece 302 made of rubber or the like, with which it grips the pipette, and a trigger 40. The safety lever 300 is pivotally mounted on the pipettor 32, including conventional fasteners, e.g. a flange 306 and a pin 308 can serve. A torsion spring 310 that rests on pin 308 sits, holds the safety lever 300 normally in a

209883/0159

Pre-tensioned locking position, which is shown in Fig.4 and in which the contact piece 302 is pressed against the socket 202 ο between the contact piece 302 and the opposite one A pipette 36 is clamped in the wall of the fitting 202 of the pipette holder 34 of the pipettor 32

"When a pipette 36 is inserted in this way and the Suction or pressure lines 50, 60 to the corresponding Suction or pressure pump 82, 84 are connected, presses you press the button 138 ', whereupon the strut 128 of the

"Hose wall 126 lifts off and line 50 opens _o A column of liquid to be pipetted is sucked into the pipette 36, the ^ micropipette 210 and the suction line 50 and separates an amount of pre-wash liquid in the suction line 50 from the measured volume of liquid in the pipette 36 and the micropipette 210 ₀ The pre-wash amount is continuously subject to the suction force in the line 50 regardless of the further function of the valve 100 and is finally sucked off through the suction line 50 and the connecting hose 55 »The button is used for emptying

j | 139 depressed so-that the lever arm 137 pivots and the strut 129 lifts off the hose wall 126 to the Open pressure line 60. The suction line 50 remains tightly closed tangentially to the bore of the micropipette 210, while the gas pressure applied through line 60 is measured Amount of liquid emptied from the micropipette 210 and the pipette 36 »

b.) Second embodiment

In the embodiment of FIGS. 6-11, the valve 100 a valve body 150, which is in the body 132 of the pipettor with conventional fastening means, for example Screws 151 attached. A seal insert

$ 209 883/015

200 is placed in the fit 202 and on the valve body 150. Through the sealing insert 200 and the valve body 150 extends a cylindrical bore, namely the micropipette 210. Two cylindrical pins 154 protrude from the top 153 of the valve body a short distance, about 0.1 to 2 mm, upwards. A hollow peg 155 protrudes further over the top 153 of the valve body 150 and surrounds the micropipette 210. The hollow pin 155 ends in a Sealing surface 152, which is preferably a planar, sealable surface perpendicular to the axis of the micropipette 210 Is plane and extends radially outward from the micropipette 210 by a distance, which is preferably the one-piece Twice the diameter of the micropipette 210 is.

The valve 100 has a block 160, which encloses the parts of the suction and pressure line 50 or _E 60 in the valve 100 and is rotatably supported on the valve body 150 by means of a pivot pin 164 which in the valve body in a conventional manner, for _o example, is attached by a locking pin 165 ». Means for rotating it are provided on block 160, including a radial arm 168 protruding outwardly from block 160 and pivot 164 and a connecting rod 170 connected to arm 168 by a pin 169. In another part, the connecting rod 170 is connected to a shift lever 172 and a shift button, such that a linear reciprocating movement of the shift button 38 and the shift lever 172 via the connecting rod 170, the pin 169 and the arm 168 in a reciprocating manner reciprocating oscillatory motion of the block is implemented around the pivot 164 160 ·

The block 160 has a surface 162 with which it slides on the pin 154 and the sealing surface 152 of the hollow pin 155, so that surface 162 is constantly in sealing sliding contact with surface 162 of hollow pin 155. The block becomes

209 8 83/0159

Pressed sealingly against the hollow pin 155 with conventional tensioning means, for example with the aid of a spring plate 166 on the pivot pin 164, the resilient pressure being distributed to the pin 154 and the hollow pin 155. A suction line piece .53 and a pressure line piece 63, both with flexible walls, are attached to the block 160 with the aid of pipe couplings 52,62 and are connected to the corresponding lines 50 and 60, which run through the block 160 and face 162 extend in communication. The pressure line 60 and the suction line 50, which are formed by the block 160 have the same cross-section in terms of shape and size as the bore of the micropipette 210o the parts of the lines 50, 60 in the area of the surface 162 have cylindrical bores in the block 160 through its surface 162, whose axes are parallel to the axis of the micropipette, so that when one of the lines 50, 60 is in alignment with the bore of the micropipette 210, as shown in FIGS is, a continuous, smooth-walled, tubular bore is created, which extends through the valve 100 from the valve insert 200 through the valve body 150, the hollow pin 155 extending into the block 160

The body 150 and the block 160 can be made of a solid material that is inert to the liquids to be pipetted. For example, glass, high-density polyethylene, acrylic resins, polytetrafluoroethylene, or stainless steel can be used. The valve body 150 must be made of a material that is strong enough to prevent any noticeable deformation of the volumetric deformation in the micropipette 210 during use. In addition, it must be resistant and inert to the liquids to be pipetted. The surface 162 of the block 160 also comes into contact with the pipetted liquid and serves to seal and limit the measured liquid.

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liquid volume in the micropipette 210. It must therefore also be resistant to the pipetted liquid and be inert and, in use, are dimensionally stable glass or stainless steel and polytetrafluoroethylene polymers convenient base materials for the manufacture of block 160. As further found, one obtains one better precision and. a good puncture ability, if of the block 160 at least the surface 162 and of the valve body 150 at least the hollow pin 155 made of one material of different compressive strength are o The difference in the compressive strength should be such that by compression of the hollow pin 155 against the surface 162 of the Blocks under the force of the spring divider 166 despite any small surface irregularities a tight seal is made and when the block 160 slides on the valve body 150 a wiping effect occurs to manufacture the valve body 150 from a material that is compatible with the liquids in question for pipetting is not wetted · For general use offers a valve body 150 made from a polytetrafluoroethylene polymer and a block 160 made of stainless steel, glass, or a composite polytetrafluoroethylene plastic the desired difference in hardness and the correct wetting properties.

The Fig. 9, 10 and 11 illustrate the filling, locking « and emptying phase of a typical pipetting process with the described embodiment of the valve 100. When a pipette 36 is inserted so that it rests against the sealing insert 200, and when the suction line 50 and the Pressure line 60 via suitable couplings and connecting lines to the suction pump 82 and the pressure pump 84 or to the suction or pressure opening 86, 87 of a single pump 88 connected to it, becomes constant in the suction line 50 a negative pressure is applied and in the line 60 always

$ 209883/015

an overpressure.

For filling, the switch button 38 and the switch lever 172 are pushed by hand towards the valve 100, with the block 160 rotating about the pivot 164 and the suction line 50 coming into congruence with the micropipette 210, as illustrated in FIG 60, which in block 160 has a greater distance than the wall thickness of the hollow pin 155 corresponds to, is vented to the atmosphere. When the filling is finished, doi. When a column of liquid 44 has been sucked into the suction line 50 by the pipette 36 and the micropipette 210, the switch button 38 and the switch lever 172 are moved further so that the block 160 rotates into the position in FIG. 10. During this rotation, the block 160 closes the micropipette 210 and thus holds back the calibrated volume of liquid 44. When the block 160 is moved to the valve body 150, to the hollow pin 155 and to the micropipette 210, the valve 100 first separates a pre-rinse liquid quantity 47 from the calibrated liquid quantity 44 when a part of the surface 162 of the block 160 that surrounds the suction line 50 , slides over the sealing surface of the hollow pin 155, while the micropipette · 210 is sealingly closed with another part of the surface 162 Upon further sliding of the block 160, the suction pipe 50 _s open to the environment during the pre-rinsing liquid 47 through the line 50 sucked is and Line 50 is still flushed with air during the blocking and emptying phase o

If you want to empty the pipette, the switch button 38 and the switch lever 172 are pulled back from the valve 100 by hand, with block 160 rotating counterclockwise in Figure 7. The pressure line 60 is thereby connected to the micropipette 210 brought into congruence, while the suction line remains open to the environment, as illustrated in FIG.

209383/01! 5 9

light is o

In each of the examples described above, the Y-valve 100 enables an optional connection of the micropipette 210 to one or the other line 50 or 60, or a shut-off of the micropipette 210. The selective connection and shut-off is done by moving certain wall parts of the suction line 50 or the pressure line 60 to block these lines, preferably by moving the wall parts in a plane perpendicular to the axis of the line or lines _e the block 160 represents a movable wall of both the suction and the pressure line 50 and 60 and the optional blocking of the lines 50, 60 takes place by moving the wall parts of these lines, doio of the block 160 to the wall parts of the micropipette 210, di des Hollow pin 155 and valve body 150

The valve 100 used in the pipetting device 30 obviously gives the possibility of the area of the optional to keep the sealing points produced as small as possible. For example, in a valve 100 according to FIG Embodiment of fig.9-11 the lines 50,60 and the Micropipette 210 may have a diameter of approximately one millimeter and the cylindrical hollow pin 155 may have an outer diameter of just over three millimeters; the resulting area of sealing contact between the hollow pin 155 and the sliding surface 162 is then less than ten square millimeters. Such a small sealing surface, which is achieved by the valve construction according to the invention becomes possible, offers low frictional resistance during operation and facilitates rapid puncture of the valve «, In addition, the requirements with regard to precisely machined

20 9 883/015 9

reduced or abraded valve surfaces «,

The valve 100 offers further advantages, which are that the switchover between the operating state for pulling, blocking and emptying only requires a few moving parts and the required movement of these moving parts takes place in a single plane. In the examples described above, the movement of the struts 128, 129 or of the block 160 takes place in a transverse plane and preferably perpendicular to the plane of the lines 50, 60. The necessary movement can easily be limited to short distances, for example to a distance between the simple and six times the diameter of the micropipette 210 or the lines 50, 60. In contrast to the method of metering using piston syringes, the extent of the movement in the valve 100 is independent of the pipetted liquid volume the interface between the hollow pin 155 and the sliding surface 162 _O

From the above description it is apparent that the valve 100 is able to produce a drawn up liquid by mechanical separation of the liquid at a single point to divide into two continuous quantities «The valve 100 can be modified so that it is the liquid on divided into multiple locations, but provides mechanical segregation at a single location in the fluid flow significant advantages when pipetting volatile liquids. Since the pre-flushing quantity 47 continues the suction effect is exposed, generates the evaporation of the amount of pre-wash liquid 47 no backward pressure against a detachable seal in valve 100. The mechanical

209883/0159

Separation of the pipetted liquid 44 in the valve 100 ″ eliminates the sealing gap in the pipette 36 and the micropipette 210, which reduces the risk of premature emptying due to the vapor pressure of the pipetted liquid. The pipetting device 30 according to the invention can be used for pipetting volatile liquids such as ether , the automatic in many conventional pipettes can not be pipetted _o

3o pipette holder and pipettes

The pipette holder 34 of the pipettor 32 forms the socket 202 for receiving the pipette, which is in the pipettor to be used end 35 receives a pipette 36 and led it to the sealing contact on the sealing insert 200 In the embodiment of FIG. 4, the socket 202 has the The shape of a cylindrical bore in the pipette holder 34 which is adapted to the cylindrical end 35 of a pipette 36. A safety lever 300 similar to a trigger is pivotably mounted on the pipettor 32 and resiliently into a Biased position in which he has a pipette 36 between a contact piece 302 belonging to it and an opposing wall of the cylindrical socket 202, jammed pipettes 36 with the same volume or with different volumes can be exchanged in the pipettor 32, by exerting a pressure on the trigger 40 which separates the contact piece 302 of the safety lever 300 from the socket The pipette 36 can then be pulled out of the holder 202 by hand or it can also be pulled through her Own weight slide out of the holder in order to be replaced by another pipette 36 «,

The pipettes 36 used with the pipettor 32 in the example of Figure 4 are generally tubes also a transparent, dimensionally stable and chemically inert

20 9 «ß3 / Q159

Material, such as glass, with a tapered tip 236 through which liquids are drawn up and emptied. They have a generally circular cross-section, as is customary with pipettes a smooth, flat sealing surface 235 which seals against the sealing insert 200 around the micropipette 210. The erfindungsge- ψ MAESSEN pipettes 36 are calibrated to a certain volume, which is contained between the tip 236 and the sealing surface 235, and have a label 238 in standard volume units on which the light emitted from the pipette total volume when used in conjunction with Pipettor 32 indicates the label 238 can thus indicate a volume that differs from the volume of the pipette 36 between the tip 236 and the sealing surface 235, the difference between the specified volume and the pipette volume corresponding to the volume of the micropipette 210 of the pipettor 32 o

How in particular'from the troublesome. 13-15, a suitable pipette 36 has an inscription 238, a tip 236, a sealing surface 235 and an end 35 for insertion into the pipettor, as already described above. The end 35 of the pipette 36 also points on its circumference in a predetermined distance from the sealing surface 235 an outwardly projecting collar 240, as well as a conically tapering end 242 surrounding the sealing surface 235 at ₀ attached to the pipette 36. » In the case of a pipette 36 with a large volume, which has an enlarged part with a larger diameter, this bulge is located between

209383/0159

see the collar 240 and the tip 236 _O

The pipette holder 34 of a pipettor 36 has a fitting 202 and a sealing insert 200 which surrounds the micropipette 210. The fitting 202 has an inner cylindrical part 248 which receives an end 242 and the sealing surface 235 of a pipette 36 and the pipette 36 up to sealing engagement of the sealing surface 235 leads to the sealing insert 202, so that the micropipette 210 with the interior of the pipette 36 _e communicates Further, the fitting 202 is a conically flared piece 250 having a funnel-shaped flared extension of the inner cylindrical Fitting part 248 isto At the periphery of the funnel-shaped part 250, the pipette holder 34 has a narrow edge 252 The edge 252 can slide under the sealing surface 235 of a pipette 36 and lie horizontally on a flat surface so that the edge 252 is at the beveled end 242 and insert the end portion 35 of the pipette into the funnel 250 of the fitting e In this way, the pipette 36 and the pipette holder 34 of a pipettor 32 cooperate to give a user the ability to pick up a pipette 36 lying horizontally on a table or in a drawer with one hand, the pipette holder 34 as a kind of shovel is used

Also on the pipettor 32 are a securing lever 300, which is articulated around a pivot 306, and one with the hand-detectable trigger 40 attached, the latter is hinged to the pipettor with a pivot 307. The safety lever 300 and the trigger 40 are mechanically rerbunden with a rod 308 and pin 309. The safety lever 300 has two fork arms 310 which input the cylindrical end piece 35 of a pipette, and a partially conical pocket 312 into which the collar 240 of a pipette fits

209883/0159

36 embeds "so that the pipette is carried by its collar 240 will. The safety lever 300 is normally in the direction of the position holding the pipette in place, see Pig 15, biased by conventional spring means, for example a spring 314. In this position, the fork arms 310 extend at least partially across the funnel-shaped Part 250 of fit 202 and pocket 312 is centered on the axis of fit 202 opposite the seal insert 200 and the micropipette 210. The distance between the safety lever 300 and the sealing insert 200 is preferably slight smaller than the predetermined length of the pipettes 36 from the collar 240 to the sealing surface 235, so that the sealing surface 235 of the pipette 36 is pressed into tight sealing contact with the sealing insert 200 by the seated collar 240 in the pocket 312 »The pressure exerted by the spring 314, the trigger 40 and the rod 308 are sufficient to press the sealing surface 235 against the sealing surface. insert 200 regardless of the orientation of the device, the volume and weight of the pipette 36 and its fill " to achieve the degree of efficiency with liquid «. The inner edge 252 of the funnel-shaped fitting part 250 can be a solid Have stop 320, which limits the movement of the safety lever into the plague holding position. The stop 320 prevents excessive movement of the safety lever 300 and a pipette 36 grasped by it into a position. ge, in which an undesired deformation of the sealing insert occurs under the pressure of the sealing surface of a pipette but allows sufficient movement toward the seal insert 200 and sufficient deformation of the sealing insert in order to ensure that the pipette 36 is sealed against the sealing insert 200 · As the stop 320 prevents deformation of the sealing insert 200 beyond a predetermined maximum amount, the spring force can the peder 314 can be made larger than required to seal a heavy pipette 36, if desired.

209883/0159

When used, the pipettes are sufficiently similar in weight and the sealing insert 200 has sufficient dimensions, so that the precise placement of the stop 320 is not critical. The stop 320 can possibly can also be omitted

The safety lever 300 is (for example, by finger pressure on the trigger 40) between the holding position of Figei5 and an insertion position of Figo "! 3 pivotable ο The fork arms 310 and the Pocket 312 moved away from the funnel-shaped extension 250 of the holder enough to allow a pipette 36 to be unobstructed between the fork arms 310 and to be able to insert the collar 240 into the pocket 312, or around a pipette 36 to be able to remove it from the safety lever 300 if it is to be replaced by another pipette 36 ««

In use, finger pressure is applied to the trigger 40 to move the safety lever 300 into the deployed position 13 to be transferred. Then a pipette 36 placed between the fork arms 310 in such a way that their collar 240 nestles in the pocket 312. This can be, for example by inserting the pipette 36 by hand or by bringing the pipettor 32 up to a pipette 36 which is vertical is in a pipette stand, not shown, so that the The pipette is caught between the fork arms 310. When the trigger 40 is released, the safety lever rotates 300 around the pin 306 towards the socket 202 and guides the end part 35 of the pipette 36 into the socket 202 a. As Figo14 shows, the beveled end 242 slide the pipette along the wall of the extension 250 into the cylindrical socket part 248 while the safety lever moves. The collar 240 can tilt freely in the pocket 312, while the sealing surface 235 through the Slide along the pipette end piece 35 and the beveled

209383/015 9

th end 242 on the walls of the fitting 202 to the seal insert 200 is led there. When the safety lever 300 has reached its holding position shown in Fig. 15, prevents the sealing contact of the sealing surface 235 with the sealing insert 200 around the micropipette or if used, the stop 320 provides further movement. The cylindrical socket portion 248 does not need the same To have a diameter like the pipette 36, as long as it only has the sealing surface properly for sealing contact Sealing insert 200 can lead so that the micropipette 210 is in communication with the interior of the pipette 36

Pipettors 32 and pipettes 36 according to the invention can thus cooperate in order to receive the pipettes 36, to hold and release without having to manually handle the pipettes, the freedom of movement of the pipettor 32 and the interacting structural elements the pipette holder 34, the securing lever 300 and the pipettes 36 themselves allow picking up and holding and sealing the pipettes 36 from the two most common positions in laboratory operation, namely a horizontal position of the Pipettes on a table or in a drawer and the vertical position of a pipette 36 in a pipette stand.

4o actuating means for the valve 10 0

The second embodiment of the valve described above is controlled by a rod 170 which is a rotatable Element of the valve 100 connects to a switch lever 172 and a switch button 38, which are movably attached to the pipettor 32. The shift lever 172 is, as in Fig. 6 shown, mounted pivotably about an axis 190 in the pipettor, which is fixed in the pipettor and passes through a slot in the switch lever. For holding the gearshift lever 172 on the axis .does also have a device.

209883 / 0-159

part to push the switch lever outward away from the axis, for example one every 176 _O. The other end of the switch lever exits through a slot 191 in the housing 132 of the pipettor and ends in a switch button 38 along the inside surface of the pipettor body Sides of the slot 191 form a guideway 175. The shift lever 172 has an outwardly protruding pin 174 on each side which slides along the guideway 175 and is normally urged by the spring 176 into sliding contact with the guideway. The slot 191 is at both ends of a front stop

177 for the filling position and a rear stop 179 for the emptying position. The stops 177 and 179 represent parts of the body 132 of the pipetter on the front or _o rear end of the slot 191. They correspond to the positions of the rod 174 and the shift lever 172, when the valve or in its filling position ₀ is in its emptying position 100th The guide track 175 has a groove between the two stops 177 and 179

178, which receives the pin 174 when the switch lever 172 and the pin 174 the locking function of the valve 100 take the appropriate position. With the help of the groove there is an inevitable locking of the 'shift lever in the position corresponding to the blocking function of the valve in that the pin 174 slides along in the guide track 175, until it engages in groove 178 under the pressure of spring 176. This inevitable locking of the shift lever 172 provides a safeguard against unintentional filling or emptying and also indicates to the user when the switch button 38 has been moved far enough to bring the valve 100 into the blocking position »The switch button 38 and the shift lever 172 can be shifted by hand to either the suction line 50 or the pressure line 60 in valve 100 can be partially opened if an immediate

209883/0159

Bare manual control of the speed when filling or emptying ■ is desired. An unintended move of the valve 100 beyond the filling or emptying position, the stops 177,179 prevent

How the entire device works

For pipetting with the device 30 according to the invention, the auxiliary device 80 is used, for example, by producing the corresponding Connections to an energy source and closing the switch 41 put into operation in order to reduce negative pressure or over-

"pressure on the connection hoses 65,55 and the suction or» To apply pressure line 60, 50 in the pipettor 32. The user grasps the pipettor 32 with his hand 25 Handle 37, lifts it out of its storage space 39 in the housing 28 and brings it into a favorable position, wherein it is only limited by the length of the tubes 55,65. Then a pipette 36 of the desired volume is selected, the trigger 40 is depressed by hand and the end piece 35 of the pipette 36 is inserted into the socket 202. The trigger 40 is now released and the pipette 36 is secured with the aid of the safety lever 300 and the sealing insert 200 ready for operation in the pipettor

fc put The pipette tip 236 is placed in the to be pipetted Immersed liquid 44, which is to be taken, for example, from a beaker 45, and the switch button 38 is pushed into the filling position (in the example of FIGS. 4 and 5, the switch button 138 is depressed) and now is the pipette 36 is filled. Since the pipette 36 generally contains air prior to filling, in the initial stage of the Filling the micropipette 210, the valve 100 and the suction line 50 washed with air

When the filling is finished, the switching elements are actuated, to move the valve 100 into the blocking position

209 8 8 3/0159

Ren, and the filled pipette 36, liquid 44 and pipettor 32 are moved as desired to place the pipette tip 236 in or over another beaker 46, tube or the like into which the pipetted liquid is to be emptied · The appropriate controls, d _o i. Either the button 38 or the button 139 for emptying are actuated to move the valve into its emptying position, whereupon the liquid is emptied. When the pressure medium causing the emptying (gas or inert liquid) flows into the pipette 36, the valve 100 and the micropipette washed out of the print medium. When the emptying is complete, the process can be repeated using the device as a repeat dispenser. Or the valve 100 can be brought into the blocking position again and the pipette 36 can be removed from the pipettor 32 and replaced by another pipette 36. In normal use, it is useful to provide several standardized pipettes 36 with the same sealing surfaces 235, beveled ends 242 and collars 240, but with different volumes, for example 0.1; 1j 2 "5;10; 15 milliliters and so on, the number of pipettes of each volume being chosen according to the needs of the user. In a typical analytical procedure, a single pipetting device 30 can be used with several identical pipettes 36 in succession To pipette 0.1 milliliter quantities of various serum samples into a number of test tubes, and then the device can be used directly in conjunction with a single larger pipette 36 to pipette 5 milliliters of the biuret reagent into each tube for the analysis of protein by the biuret reaction “In most cases, washing the micropipette 210 and valve 100 while pipetting is sufficient to handle several different liquids

209H83 / 0159

to be able to pipette one after the other, with hardly any impairment of the liquid samples occurs. The mutual interference can be further reduced if one a clean pipette is used for each liquid sample. The pipettor 32 can also be cleaned very quickly or washed, if necessary, without having to disassemble the valve 100. In the course a series of pipetting operations, the trap 85 is emptied from time to time as necessary to prevent overflow pd.er to prevent the accumulation of incompatible substances in the trap 85

Various modifications can be made to the pipetting device 30. For example, the The trigger 40, the fork arms 310 and the pocket 312 of the holder can all be combined in a safety lever 300, such as The walls of the cylindrical part 248 shown in FIG and the funnel-shaped extension 250 of the socket 202 can be made of glass or a transparent plastic, for example made of polystyrene or an acrylic resinj or they can have a transparent part, a viewing opening or the like in order to allow visual observation of the seat of a To allow pipette 36 on sealing insert 200. In another In a modified form, each pipette 36 can be of its own Have sealing insert 200. Various means can be used in the auxiliary device 80 to measure the liquid level to perceive in the case 85 and to automatically interrupt the operation of the suction and pressure pump when the The liquid level in the trap 85 has reached a certain level. The device for sensing the liquid level in the trap 85 it can also be coupled to a signal lamp, a buzzer or the like, in order to indicate to the user: show that trap 85 must be emptied * If on the Mobility can be dispensed with, the pipettor 32 and the auxiliary device 80 can be fastened with suitable

203 f3 83/01 ISO

Teln be attached to each other and to operate the valve 100 can be electrical devices, such as solenoids, electric motors or the like, or else mechanical means served

In short, the device according to the invention represents a very versatile and simple device for pipetting liquids, such as from the above apparent _o Apart from the described embodiments are still a number of other variations possible Thus, the pipette holder can for example be modified such that it comprises a second Contains valve, a second socket and a second sealing insert so that filling and emptying can be carried out through corresponding lines using additional valve shapes. Several pipettes can be used together with several valves and additional lines to fill all pipettes at the same time and then to empty them one after the other at a point of use. When using several valves, lines and pipettes, it is also possible to empty one pipette and fill another pipette _{or similar at the same time}

209883/01 59

Claims (1)

Expectations Pipetting device for use with several interchangeable pipettes, characterized by a pipette holder (34), in which optionally a pipette (36) ready for operation can be detected and the one sealing insert (200) which can be brought into detachable contact with an end piece (35) of the pipette in such a way that that the inserted pipette is in sealed connection with a cavity in the pipette holder, furthermore by a hollow suction line (50), a hollow pressure line (60) and a valve (100) which optionally have a connection or a closure between the suction line and the pressure line and the pipette and that between a filling position in which the pipette is connected to the suction line connected and closed against the pressure line, a blocking position in which the pipette against both Lines is shut off, whereby a predetermined flow « fluid volume in the pipette is separated from the connection with the suction line, and finally one Emptying position can be switched in which the pipette shut off from the suction line and connected to the pressure line P in connection with isto 2e device according to claim 1, characterized in that the pipette holder (34) comprises a micropipette (210) which is operable with an in the device the pipette used Device according to claim 2, characterized in that that the valve (100) a column of liquid, which in the micropipette (210) and the suction line (50) during the Filling process was sucked into a first coherent amount of liquid of a given volume, 209883/01 59 which is enclosed in the micropipette and the inserted pipette, and divided into a second contiguous volume of liquid in the suction line, the valve being constructed in such a way that it undertakes this division of the liquid column at a single point within the valve, _{or the like} 4. Device according to one of claims 1 to 5, characterized by a flow indicator for displaying the Movement of a column of liquid beyond the pipette (36), Device according to Claim 4, characterized in that the flow indicator consists of a transparent wall piece in the suction line (50) there is »which allows visual observation of a column of liquid flowing past, and that a flow resistance (95) in the suction line at a predetermined distance downstream of the valve (100) is provided to reduce the flow rate of such a column of liquid 6ο device according to one of claims 1 to 5 »thereby characterized in that the valve (100) is normally pressed into the blocking position and that a detent is provided to releasably place the valve in the filling position to keep" Device according to one of Claims 2 to 6, characterized characterized in that the valve (100) has a valve body (150) with a through bore, the walls of which are parts of the walls of the micropipette (210), and a block (160) which has separate bores, the these bores surrounding walls partially walls of the 209883/0159 Form suction line (50) and the pressure line (60), and optionally can be brought into sealing contact with the walls of the micropipette, and that the block (160) to the valve body (150) can be moved into positions in which the micropipette with the suction line or with the pressure line is in communication and is blocked from the other line, as well as in a position in which the micropipette through the sealing abutment of the walls of the micropipette on the valve block against both lines (50.60) is closed 8. The device according to claim 7 »characterized in that the valve body (150) on a surface facing the block (153) has a hollow pin (155) which surrounds the micropipette and ends in a sealing surface which extends against part of the surface (162) of the block (160) creates a sealed connection between the micropipette and one of the two lines (50, 60) _o 9β device according to one of claims 1 to 8, characterized in that the suction and pressure line (50, 60) consist of flexible hoses ₀ 10, device according to one of claims 1 to 9 »characterized in that a securing lever is used to hold the pipette (300) is provided which has two fork arms (3i0) that attach a collar (240) to the pipette (36) and which are attached to the device such that they are movable in a direction to and from the sealing insert (200) 11e pipette for the pipetting device according to one of Claims 1 to 10, characterized by a sealing surface (235) at one end which .uich sealingly against the 2 0 9 8 8 3/0159 _ttAD -37- 2132Π66 Pipetting device hugs, and by an outwardly protruding part (240), which in a predetermined Is arranged at a distance from the sealing surface and designed such that it is in a corresponding part (312) of the safety lever fits around the sealing surface of the pipette in operational contact in the pipetting device to keep· 12o pipette according to claim 11, characterized in that the outwardly protruding part is a collar on the circumference of the Pipette is 13 · Method of pipetting using a pipetting device according to claims 1-10, characterized in that a pipette with the tubular Suction line, which has a movable wall, and the tubular pressure line, which also has a movable wall, is coupled that one is optional The three-way connection of the pipette with the lines creates a negative pressure in the suction line is that a positive pressure of a fluid is continuously applied in the pressure line that the pipette is filled is, for which purpose certain wall parts of the pressure line are moved so that this line of the Three-way crossing point is blocked, and certain wall parts of the suction line are moved so that a connection between the suction line and the pipette is established that a liquid to be measured is sucked into the pipette and partially through this into the suction line that then certain Wall parts of the suction line are moved in such a way that the suction line is shut off from the intersection point, whereby the liquid portion drawn into the suction line is separated from the liquid remaining in the pipette ^y '~ "' ^ 209383/01 ^r ) f5 amount is separated, and that by the movement of the wall parts the barrier at a single point in the line is made, and that finally certain wall parts of the pressure line are then moved in such a way that a connection is made between the pressure line and the crossing point. 14o method according to claim 13t, characterized in that the movable wall parts of the suction and pressure lines consist of mutually movable, opposing walls of these lines, and that these opposing wall parts moved in a plane perpendicular to the axis of the line in question will" I5o method according to claim 13 »characterized in that the pipette is coupled to the lines in such a way that it is connected to a micropipette in the form of a tubular Cavity is releasably connected, which optionally einmindeto in the lines 209883/0159 Blank page