Method for operating a piston-stroke pipette, piston-stroke pipette, data processing device and system

Abstract

The invention relates to a method, a computer program and a system for operating a hand-held, computer-controlled piston-stroke pipette as well as a corresponding piston-stroke pipette as well a data processing device cooperating with that, wherein a precise pipetting of liquid with a vapor pressure higher than that of water is rendered possible by means of a sequence of prewettings of the pipette tip.

Claims

1. Method (100) for operating a hand-held, computer-controlled piston-stroke pipette (1) used for the computer-controlled execution of a pipetting operation with a fluid sample, in particular for the automatic prewetting of the inside of a pipette tip (10), arranged at the nose cone (11) of the piston-stroke pipette, comprising the computer-controlled steps: Providing a function n_vb (x) specifying a number n_vb of one or more prewetting steps as a function of a variable x characterizing the pipetting operation, (101) Acquiring of the at least one parameter value of the variable x characterizing the pipetting operation; (102) Determining the number n_vb of prewetting step associated to the variable x by means of the function n_vb(x); (103) Executing a sequence of the number n_vb of prewetting steps, (104) in which n_vb>0 and in which the prewetting step in each case comprises that the piston-stroke pipette executes an electrically driven piston movement in order to take up a sample volume into the pipette tip and that subsequently an inverse piston movement is executed in order to release the sample volume contained in the pipette tip from the pipette tip at least partially or completely.

2. Method according to claim 1, wherein the variable x contains the parameter value V of the volume of the pipetting volume V to be aspirated into the pipette tip in the pipetting operation or is formed by this parameter value V.

3. Method according to claim 1, wherein the variable x contains at least one of the parameter values of the following parameters or is formed by it or by parameters that can be determined from the parameters listed in the following: a parameter ID_LM chemically identifying the main liquid component of the fluid sample to be pipetted, a parameter ID_VM identifying a diluent contained in the fluid sample to be pipetted, a parameter ID_GT identifying the type of device of the piston-stroke pipetted executing the pipetting operation, a parameter V_nom identifying the type of device of the piston-stroke pipette executing the pipetting operation by its nominal volume, a parameter ID_ST identifying the type of pipette tip of the pipette tip used in the pipetting operation, a speed v_K of the piston-stroke of the piston-stroke pipette executed during this pipetting operation or during at least one prewetting step, a temperature T of the surroundings of the piston-stroke pipette or the fluid sample to be pipetted in the pipetting operation at the time of pipetting operation, an air pressure or a vapor pressure P of the surroundings of the piston-stroke pipette at the time of the pipetting operation.

4. Method according to claim 1, wherein the function n_vb(x) comprises at least one calculation algorithm in order to assign the number n_vb to the variable x and/or comprises a data assignment table for assigning the number n_vb to the variable x.

5. Method according to claim 1, wherein the function n_vb(x) optimizes a number n_vb of one or several prewetting steps as a function of a variable x characterizing the pipetting operation such that the air pressure in the air cushion between the fluid sample and the motionless piston of the piston-stroke pipette achieved by means of the prewettings is sufficiently constant for avoiding the dripping of the sample aspirated into the pipette tip in the pipetting operation.

6. Method according to claim 1, wherein the variable x contains the parameter value V of the volume of the pipetting volume V to be aspirated into the pipetting tip in the pipetting operation or is formed by this parameter value V, and wherein the function n_vb(V), in particular in function of the solvent of the sample aspirated in the pipetting operation, is described as a linear relation between n_vb and V, thus n_vb=a*V+b, with a and b being real numbers, wherein the range of the volumes V that can be pipetted is preferentially divided in two section, in each of which a characteristic set of parameters a, b is valid, so that the relation n_vb=a1*V+b1 is valid in the range V1 to V2 of the possible volumes and the relation n_vb=a2 * V +b2 is valid in the range V2 to V3 of the possible volumes, and in particular a1<>a2 and b1 <>b2 are valid.

7. Method for executing a computer-controlled pipetting operation by means of a hand-held computer-controlled piston-stroke pipette, comprising the method according to claim 1, and comprising the step to automatically execute the following computer-controlled step subsequent to the execution of the sequence of the number n of one or more prewetting steps: Aspirating a sample volume V of the fluid sample into the pipette tip and, in particular, holding that sample volume V of the fluid sample in the pipette tip, in particular for an undetermined period of time or a determined period of time. (205)

8. Method according to claim 1, wherein an external data processing device is provided, which comprises a user interface device (e.g. a touchscreen) and an electronic control device, and wherein the piston-stroke pipette is provided or several piston-stroke pipettes are provided, wherein each piston-stroke pipette comprises an electronic control device, wherein the control devices of the external data processing device and of the piston-stroke pipette are configured to exchange data among each other via a data connection (e.g. a remote data connection, e.g. WLAN), wherein the control device of the external data processing device is configured to acquire at least one or all of the said parameters of the variable x by means of the user interface device, in particular the parameter value V of the volume of the pipetting volume V to be aspirated into the pipette tip in the pipetting operation, a parameter ID_LM identifying the solvent of the fluid sample to be pipetted, a parameter ID_GT identifying the type of device of the piston-stroke pipette that executes the pipetting operation, and/or a parameter ID_ST identifying the type of pipette tip that is used in the pipetting operation.

9. Method according to claim 8, wherein the control device of the external data processing device is configured to determine by means of the function n_vb(x) the value of the number n_vb of prewetting steps from at least one or all of the said parameters of the variable x.

10. Method according to claim 8, wherein the external data processing device and/or the at least one piston-stroke pipette comprises a data storage, in which the function n_vb(x) is stored and/or the value n_vb can be stored.

11. Method according to claim 10, wherein the control device of the at least one piston-stroke pipette acquires the value n_vb via the data connection and stores it in a data storage of the piston-stroke pipette.

12. Hand-held piston-stroke pipette (1) for the computer-controlled execution of a pipetting operation with a fluid sample, comprising an electronic control device, a piston chamber and a piston that can move therein, an electric piston drive for moving the piston, a nose cone, to which a pipette tip can be attached, wherein the control device is configured to control the piston drive and to execute a pipetting program comprising the following steps: Execution of a sequence of the number n_vb of one or several prewetting steps, wherein each prewetting step comprises that an electrically driven piston-stroke is executed by the piston-stroke pipette in order to take up a sample volume into the pipette tip and that subsequently an inverse piston-stroke is executed in order to release the sample volume at least partially or completely from the pipette tip, Subsequent to the at least one prewetting step: Execution of a pipetting operation comprising the aspiration of a sample volume V of the fluid sample into the pipette tip and in particular the holding of that sample volume V of the fluid sample in the pipette tip.

13. (canceled)

14. (canceled)

15. System (200) for the automated prewetting of the inside of a pipette tip arranged at the nose cone of a hand-held, computer-controlled piston-stroke pipette that serves for the computer-controlled execution of a pipetting operation with a fluid sample, comprising at least one hand-held piston-stroke pipette (1) according to one of the claims 12 to 14, an external data processing device (21) comprising a data interface device and an electronic control device, wherein the control devices of the external data processing device and of the piston-stroke pipette are configured to exchange data with each other via a data connection, wherein the control device of the external data processing device is configured to acquire a variable x by means of the data interface device, in particular the parameter value V of the volume of the pipetting volume V that is to be aspirated into the pipette tip in the pipetting operation, a parameter ID_LM that identifies the solvent of the fluid sample to be pipetted, a parameter ID_GT that identifies the type of device of the piston-stroke pipette that performs the pipetting operation, and/or a parameter ID_ST that identifies the type of pipette tip that is used in the pipetting operation, and the system is configured to determine by means of the function n_vb(x) the value of the number n_vb of prewetting steps from at least one or all of the said parameters of the variable x, wherein the control device of the at least one piston-stroke pipette is configured to acquire the number n_vb of prewetting steps via the data connection.

16. Computer program, in particular for operating a hand-held, computer-controlled piston-stroke pipette, that serves for the computer-controlled execution of a pipetting operation with the fluid sample, in particular for the automated prewetting of the inside of a pipette tip that is arranged at the nose cone of the piston-stroke pipette, wherein the computer program comprises commands which, when the computer program is executed by the central processing unit of at least one electrical control device, cause that central processing unit to execute the following steps Acquiring of the at least one parameter value of the variable x characterizing the pipetting operation; Accessing a data storage in which a function n_vb(x) is stored that indicates a number n_vb of one or more prewetting steps as a function of a variable x characterizing the pipetting operation, Determining the number n_vb of prewetting step associated to the variable x by means of the function n_vb(x); Providing at least the value n_vb to the data processing of the control device of the piston-stroke pipette, in particular transferring at least the value n_vb to the control device of the piston-stroke pipette; Optionally: Executing a prewetting step or a sequence of a number n_vb of several prewetting steps, wherein a prewetting step in each case comprises that the piston-stroke pipette executes an electrically driven piston movement in order to take up a sample volume into the pipette tip and that subsequently an inverse piston movement is executed in order to release the sample volume from the pipette tip at least partially or completely; Optionally: subsequent to the at least one prewetting step: Executing a pipetting operation comprising the aspiration of a sample volume V of the fluid sample into the pipette tip and in particular the holding of that sample volume V of the fluid sample in the pipette tip, in particular for an undetermined period of time or a determined period of time of in particular at least 30 seconds.

17. Data processing device, which is in particular the said external data processing device, comprising: a data interface device, in particular a user interface device, and an electronic control device, wherein the control device of the data processing device is configured to exchange data with the control device of a piston-stroke pipette via a data connection, in particular of the hand-held piston-stroke pipette according to one of the claims 12 to 14, which serves for the computer-controlled execution of a pipetting operation with a fluid sample, wherein the control device of the data processing device is configured to acquire at least one parameter of a variable x by means of the data interface device, and wherein the control device of the data processing device is configured to determine the value of the number n_vb of the prewetting steps from the at least one or all of the said parameters of the variable x and to provide it to the data processing of the control device of the piston-stroke pipette and/or to transfer it to the piston-stroke pipette via the data connection.

Description

[0097] FIG. 1 depicts the hand-held electric piston-stroke pipette 1 in a perspective view. With the pipette 1, the stroke of the piston is electrically driven. The activation of the stroke in the different operating modes of the pipette is electrically controlled by an electrical control device 17 with a connected storage device 18, inside the pipette 1. The control device 17 can comprise a radio module in order to exchange data with an external data processing device 2.1 (see FIG. 2).

[0098] The operating parameter and other setting of the pipette can be controlled by the user via the user interface device, resp. the operational control device and the display of the pipette. In the pipette, several electrically controlled pipetting programs are stored, in which a pipetting program is assigned preferentially to each operating mode. A pipetting program can be uniquely defined by a set of operating parameters. Once defined, the pipetting program can be triggered by the user and is started automatically by the pipette. The pipetting program comprises in particular that the method 100 according to the present invention for the prewetting of the pipette tip 10 is executed. If the relation parameter ID_LM<>0 is true at least one step for the prewetting is executed, if the relation parameter ID_LM=0 is true no step for the prewetting is executed. Instead of the value 0 also any other default value can be declared. The value ID_LM=0 could identify in particular water as main liquid component the sample to be pipetted.

[0099] The pipette 1 comprises a base body 2 which comprises a lower shaft section 3 and an upper section 4, which comprises in particular the display 5 and the control elements. The control section 3 extends parallel to the long axis A of the pipetting apparatus, whereas the upper section 4 is inclined to the axis A and extends parallel to the axis B. By the inclined arrangement of the upper section 4, it is possible to use the display in a very ergonomic way.

[0100] The pipette 1 comprises a handle section 7 with the holding flap 6 that rests on the index of the user when the pipette 1 is held by the user as intended, whereas the handle section 7 rests in the palm of the user. The thumb can reach in particular the eject button 8, which, when pressed down along the axis A, moves the spring-loaded ejection sleeve 9 downwards and ejects the pipette tip 10 from the nose cone 11 of the pipetting apparatus onto which it is clipped. The ejection mechanism can also be electronically driven. The pipette 1 comprises a metallic contact protrusion 19 on each side of the upper section 4, which serves for the charging of the integrated battery, which constitutes the energy storage of the electric pipette.

[0101] The operational control device (12; 13; 14a; 14b) comprises a dial 12, a rocker switch 13 and a first control button 14a and a second control button 14b.

[0102] The disk-like dial 12 is rotatably mounted on the base body 2, in particular parallel to the essentially flat front face of the upper section 4. A device recognizing the position of the dial 12 is provided that comprises in the present case a Hall sensor with which the relative position of the dial 12 is measured contactlessly with respect to the base body. The dial 12 comprises a number of detents that corresponds to the number of selectable positions of the dial. In particular, the detents are such that a mark 12a for designating the set position of the dial 12 can be aligned with the mark 15, which is fixed to the base body 2 on the front of the upper section 4.

[0103] The color display 5 serves as the central information element for the user. In particular, the various operating modes of the pipette 1 are displayed there and the parameter values of the operating parameter are displayed. In each of the two areas 5a and 5b, information is displayed that tells the user which function is associated to the first control button 14a resp. the second control button 14b on the currently displayed display page if a function is associated to it also on the respective display page. Every control button is thus designed as a control element with variable functionality and is termed as a “softkey” in combination with the displayed function. This will be explained below.

[0104] Preferentially, the pipetting apparatus is designed to switch between the various functionalities of a soft-key if a certain operating mode of the pipette 1 is selected. This can be achieved, for example, by double clicking the soft-key or by holding the soft-key for a minimum amount of time, for example for 2 seconds.

[0105] Preferentially for every operating mode of the pipette 1, a display page that is displayed on the display is provided with the layout specific for the operating mode. Also for the definition of at least one prewetting step, a display page can be provided. If adjustable operating parameter or other mutable entries are provided on the display page, they can be marked using the control rocker switch 13 and, in particular, be selected with the control button 14a. In this case, the control button 14a has the functionality “selection” and the text “select” is shown in the display at the position 5a. Changing the parameter values of an operating parameter or changing the selection or an entry is achieved by the actuation of the rocker switch 13.

[0106] The rocker switch 13 is arranged on the base body so that it can pivot around an axis that is arranged perpendicularly to the long axis A. If the uses presses the upper range 13a a first function of the rocker switch 13 is activated, if the user presses the lower range 13b a second function of the rocker switch 13 is activated. The rocker switch is mounted such that no function is triggered if it is not presses. The rocker switch 13 serves, in particular in a manual operating mode of the pipette, for aspirating the sample to be pipetted into the pipette tip 10 while the user presses the upper range 13a and serves furthermore for releasing the sample from the pipette tip 10 while the user presses the lower range 13b.

[0107] The pipette 1 can be operated in different operating modes that have been explained above in detail. A first number of operating modes can be selected directly via the dial 12, a second number of operating modes can be selected with multiple selectable entries via a display page that is labeled as “special” resp. “Spc”, in which each entry describes an operating mode. Via the dial, also an operating mode can be selected in which the at least one prewetting step is defined, in particular n_vb or x.

[0108] The pipette 1 comprises a storage device with a data storage, in which suitable storage ranges are provided for at least one operating parameter resp. parameter of the variable x and the value n_vb. In other embodiments of the pipette, the data storage can also comprise the complete function n_vb(x) or the data range relevant for the pipette regarding the respective parameter ID_GT.

[0109] FIG. 2 depicts the external data processing device 21 which is a portable, hand-held computer with a touchscreen 22, a network cable connector 23 for operating the computer 21 and a USB port 24. The electric control device 25 comprises a data processing device in order to execute a control program (operating system) that controls the functions of the computer 21, in particular the display of the content of the display e.g. the display page in FIG. 4, the data exchange with the pipette 1 via a radio module contained in the control device, a WLAN adapter. The control device 25 comprises a data storage, in which, in this case, the function n_vb(x) is stored. This function is formed by data assignment table consisting of data and data correlations and at least one data algorithm for interpolating or extrapolating further assignments n_vb(x) from known assignments n_vb(x). The determination of the content of the function n_vb (x) will be explained below in an example. The computer is configured to determine the parameters of the variable x from the user entries, to determine the assigned value n_vb from the parameter values of the variable x via the function n_vb(x), and to wirelessly transfer the value n_vb as well as other parameters x serving as operating parameter via the WLAN adapter to the pipette 1.

[0110] FIG. 3 depicts the system 200 that comprises the pipette 1 and the external data processing device 21, which exchange data via a radio connection 201, 250′, 250″ resp. via a network 250, in particular via WLAN.

[0111] FIG. 4 depicts a display page 40 to be displayed on the touchscreen display 22 of the portable computers 21, which is used as input device for entering parameters of the variable x resp. of operating parameters of the pipette 1:

[0112] Shown in it: [0113] 41 Output and input field for entering the parameter V [0114] 42 Output and input field for entering the parameter v_k [0115] 43 Output and input field for entering the parameter p regarding another property of a pipetting operation [0116] 44 Output and input field for entering the parameter ID_OM for the selection of the operating mode resp. the pipetting mode of the pipette [0117] 45 Output and input field for entering the parameter ID_ST regarding the type of pipette tip [0118] 46 Output and input field for entering the parameter ID_LM regarding the type of liquid of the sample used in the pipetting operation [0119] 47 Display area for displaying in particular the number n_vb determined in function of the other parameters x [0120] 48 Input field for starting the transfer of data, in particular n_vb, to the pipette 1, that has established a data connection with the computer 21 [0121] 49 Input field for canceling the inputs

[0122] FIG. 5 depicts an embodiment example of the method 100 according to the present invention. The method 100 serves for the operation of a hand-held, computer-controlled piston-stroke pipette 1 which serves for the computer-controlled execution of a pipetting operation with a fluid sample, in particular for the automated prewetting of the inside of a pipette tip 10 arranged at the nose cone 11 of the piston-stroke pipette 1, comprising the computer-controlled steps:

[0123] Step 101: Providing a function n_vb(x) in the data storage of the external computer 21 that indicates the number n_vb of one or several prewetting steps n_vb in function of a variable x characterizing the pipetting operation.

[0124] Step 102: Acquiring the at least one parameter value (V; ID_LM) of the variable x characterizing the pipetting operation via the touchscreen 22, on which the user enters resp. selects these values;

[0125] Step 103: Determining the number n_vb of prewetting steps assigned to the variable x from the function n_vb(x) via the control device 25 of the external computer 21; the control device 25 comprises a WLAN adapter and, here, is configured to automatically find the WLAN adapters of suitable piston-stroke pipettes, in particular that of piston-stroke pipette 1, in reach of the radio connection, in particular to determine their identification parameter ID_GT, in particular to determine the correct value—or the values—n_vb in function of ID_GT and of the value of x (V, ID_LM) defined by the user via the function n_vb(x), in which it is considered that only those pipettes are taken in consideration that are suitable for pipetting the desired sample volume V, to establish data connection to those WLAN adapters found, and in particular to transfer the respective values n_vb, in particular also V and other parameters as described for example in FIG. 4, in dependence of ID_GT to each of the respective piston-stroke pipette ID_GT, in particular to the piston-stroke pipette 1. In this case, the computer 21 thus automatically transfers the desired parameters to all pipettes within reach without the user having to select the pipette separately when operating the computer 21. Preferentially, all operating parameters of the pipette 1 required for the desired pipetting operation are determined and transferred to the pipette, so that the user does not have to use the input device of pipette 1 in order to immediately start the pipetting operation plus the upstream prewetting steps.

[0126] Step 104: after the user has started the automated pipetting operation at the pipette 1 by pressing a button resp. entering: Execution of a sequence of a number n_vb of prewetting steps with the pipette 1 that has gathered this value and in particular also V from the computer 21 via WLAN, in which n_vb>0 and in which the prewetting step comprises that the piston-stroke pipette executes an electrically driven piston movement in order to take up a sample volume of the liquid with the ID_LM into the pipette tip and that subsequently an inverse piston movement is executed in order to release the sample volume contained in the pipette tip from the pipette tip completely. By using only the volume V (and not the entire nominal volume of the pipette resp. the pipette tip) for the aspiration during the prewetting steps, it is ensured that the appropriate amount of liquid is available. With the selection of V, the user defines that this amount is available.

[0127] Step 105: Aspiration of the volume V of the fluid sample (ID_LM) into the pipette tip 10 and holding of that amount of liquid V for an appropriate amount of time Δt in the pipette tip 10, in particular for the release of the sample into a target container, resp. for the stepwise release into several target container, resp. for the execution of the respectively desired pipetting operation.

[0128] FIG. 6 depicts an algorithmic function n_vb(V), in which the number n_vb of prewettings (here: “prewetting steps”) is indicated in function of the desired volume V. The function comprises a first straight line section indicating the volume values V between 10% and 50% of the nominal volume V_nom of the respective pipette (ID_GT) for the respective liquid (ID_LM), and a second straight line section indicating the volume values V between 50% and 100% of the nominal volume V_nom of the respective pipette (ID_GT) for the respective liquid (ID_LM). In practice, this interpolation of values n_vb(V) has been proven suitable for determining also the values n_vb(V), which were not determined experimentally before, with sufficient accuracy. The algorithmic function n_vb(V) and other similar functions are a component of the function n_vb(x) resp. complement it.

[0129] Determination of the Function n_vb(x)

[0130] In order to determine the function n_vb(x), the following procedure is suitable.

[0131] To avoid a dripping of organic solvents from the pipette tip 10, the used pipette tip have been prewetted, partially multiple times. It turns out that the required number of prewetting steps (the prewetting time) of a pipette depends on various factors of the variable x: [0132] vapor pressure of the liquid [0133] volume of the air cushion of the used pipette [0134] Percentage filling level of the pipette tip [0135] speed of the prewetting steps

[0136] 100%, 50% and 10% of the nominal volume were tested with each volume variant of the piston-stroke pipette Xplorer® plus, Eppendorf AG, Germany. The required number n_vb of prewetting steps was determined until the pipette did not show dripping behavior for Δt=30 seconds. The minimum number n_vb of prewetting steps was counted in order to calculate an algorithmic function that predicts how many steps are required for the pipetting of a certain volume and a certain liquid. Also, gravimetric tests were performed as a check.

[0137] Based on the determined data, linear functions could be assembled for all tested pipettes (filling level 10%-50% and 50%-100%), which describe the relation between the filling level FV_nom of the pipette tip and the number of prewetting steps n_vb. The resulting liquid classes can be used to pipette any kind of liquid with a vapor pressure higher than water and in particular a vapor pressure lower than 250 hPa using at least one prewetting step.

[0138] For the organic solvents ethanol, methanol and acetone, it was possible to determine the minimum number of prewetting steps n_vb for the tested variants of pipettes. Based on these data, the relation between the filling level of the pipette and the number of prewetting steps can be calculated. Three liquid in their pure form were chosen for the study:

TABLE-US-00001 vapor pressure [hPa] ethanol 58 methanol 129 acetone 246

[0139] These liquids were tested at 100%, 50% and 10% of the nominal volume with each volume variant of the pipette “Xplorer Plus”. In order to be able to pipette these liquids, a certain number of prewetting steps has to be executed, so that the liquid does not drip from the pipette tip for at least 30 seconds (Δt).

[0140] This minimum number of prewetting steps was counted in order to calculate a function n_vb(V) that predicts how many step are required for pipetting a certain volume V and a certain liquid.

[0141] The smaller the volume to be pipetted V resp. FV_nom is selected, the more prewetting steps have to be executed. Correspondingly, also the duration of the prewetting phase is extended.

[0142] For all pipettes with a nominal volume bigger than 100 μl, the dripping of the liquids could not be prevented for more than 30 seconds even after 99 prewetting step at a setting of 10% of the nominal volume.

[0143] Between the considered prewetting steps from 100% to 50% and from 50% to 10%, linear functions can be formed that determine the sufficient prewetting steps in these ranges in a reasonable approximation. From the following evaluation, the axis intercept and the slope of the functions can be referred for all volume variants. With these functions, the desired liquid classes can then be formed.

[0144] There does not appear to be a difference between single channel pipettes and the corresponding multi channel pipettes. For future test for the determination of the prewetting steps, presumably not all variants of a pipette need to be tested individually. Of different variants with the same air cushion, only one has to be tested.

[0145] The higher the speed setting is selected, the shorter is the prewetting time. For this reason, for all prewetting steps speed setting 8 is selected.

[0146] The experiments were executed with the Xplorer Plus ® and with the volume variants mentioned in the evaluation. If more than one prewetting step was used, the mode “pipetting followed by mixing (P/Mix)” was employed. By this, the user-related time between the uptake and the release can be reduced. For fewer prewetting steps, the mode “pipetting” was employed.

[0147] In the tests, the time was measured until the first drop was released from the pipette tip. If this time was under Δt=30 seconds, the number of prewetting steps was increased until this value was reached (up to a maximum of 99 steps). All results of the series of tests are reported in the evaluation.

[0148] Procedure of the Execution

[0149] If several liquids were tested, the one with the lowest vapor pressure was tested first. By this, the testers could orientate themselves on the previous sample, regarding the prewetting steps. The results were entered in a table of the following type:

TABLE-US-00002 Pipette Volume fraction Required prewetting-steps (steps) Liquid/vapor 100%  pressure 50% 10%

[0150] Structure of the experimental procedure: A charger stand was placed in an elevated position, so that the pipette including the pipette tip could be hung over a beaker filled with the liquid. Furthermore, a stop watch was made available. The entire test was executed with the speed setting “8” executed. In the first run, liquid was taken up to the 100% of the nominal volume and it was checked without a prewetting step whether the pipette started to drip after 30 seconds. If that was not the case, the value “0” was entered. Otherwise, the prewetting steps were increased step by step until the of of 30 seconds was observed or until the maximum value of 99 prewetting steps was reached. The values were entered correspondingly. This approach was also applied correspondingly with 50% and subsequently with 10% of the nominal volume. At each first run, one could start with the number of prewetting steps of the previous volume fraction. After the prewetting, the pipette was placed on an elevated charger stand and the stop watch was started.

[0151] The linear functions can be determined as demonstrated in the following example of the 100 μl-pipette: Calculation of the axis intercept 100% to 50%; and 50% to 10%: prewetting steps calculated: =slope (a)*desired volume V)+axis intercept (b)

TABLE-US-00003 Required Axis Selected 100 μl Volume Prewetting intercept volume Steps pipette fraction steps b Slope a V calculated Ethanol 100%  1 3 −0.02 100 1 58 hPa 50% 2 10% 4 4.5 −0.05 10 4

[0152] The second linear function was determined correspondingly with the value of 50% to 10%. The calculated prewetting steps are reported as a check. Axis intercept and slope are the required values.

[0153] Results of the series of tests for the 10 μl pipette and the 100 μl Pipette of a pipette set in for of a data assignment table of the function n_vb(x):

TABLE-US-00004 Pipette Volume Speed Fraction Required Time % Steps Time Speed at 100% Multiplier 10 μl Ethanol 100 0 0 8 1.8 1 58 hPa 50 0 0 8 1.8 0.5 10 0 0 8 1.8 0.1 Aceton 100 0 0 8 1.8 1 246 hPa 50 0 0 8 1.8 0.5 10 0 0 8 1.8 0.1 Methanol 100 0 0 8 1.8 1 129 hPa 50 0 0 8 1.8 0.5 10 0 0 8 1.8 0.1 100 μl Ethanol 100 1 1.8 8 1.8 1 58 hPa 50 2 1.8 8 1.8 0.5 10 4 0.72 8 1.8 0.1 Aceton 100 2 3.6 8 1.8 1 246 hPa 50 14 12.6 8 1.8 0.5 10 20 3.6 8 1.8 0.1 Methanol 100 2 3.6 8 1.8 1 129 hPa 50 9 8.1 8 1.8 0.5 10 70 12.6 8 1.8 0.1

TABLE-US-00005 Axis intercept + slope * desired volume = calculated steps Axis Desired Steps Volume Intercept Slope Volume Calculated Fraction Time 0 0 100 0 1 0.0 0 0 10 0 0.1 0 0 0 100 0 1 0.0 0 0 10 0 0.1 0 0 0 100 0 1 0.0 0 0 10 0 0.1 0 3 −0.02 100 1 1 1.8 4.5 −0.05 10 4 0.1 0.72 26 −0.24 100 2 1 3.6 21.5 −0.15 10 20 0.1 3.6 16 −0.14 100 2 1 3.6 85.25 −1.525 10 70 0.1 12.6