Abstract:
The present invention relates to a sampling system for fluid samples having sample receiving vessel for receiving the sample, which is sealed by a septum and holder for the sample receiving vessel for receiving and holding the sample receiving vessel and also a sample probe for dipping into a fluid volume and for taking a fluid sample from the fluid volume, the sample probe being configured as a hollow volume which, at one end, has a first opening for introducing the holder and the sample receiving vessel and, at another end, is sealed by a first valve which is provided with a hollow needle which projects into the interior of the sample probe said valve being able to be opened by contact with the holder and/or with the sample receiving vessel and then connecting the exterior of the sample probe to the inner volume of the hollow needle.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to a sampling system for fluid samples. Sampling systems of this type are required in particular if a sample is intended to be taken from a liquid or a gas volume. Sampling systems of this type are required in particular in order to monitor the process in bioreactors, i.e. in particular in the field of biotechnology, but also in the chemical industry, pharmaceutical industry, foodstuffs industry and also in the field of environmental technology and for official bodies, for example environmental protection agencies or analysis laboratories. 
         [0002]    In the case of laboratory bioreactors made of stainless steel, normally cocks and valves in the base of the laboratory bioreactor are used for manual sampling. In the case of glass reactors which are used frequently on a laboratory scale and are accessible only from the top, manual sampling is normally implemented with the help of a so-called dip pipe. The sample is hereby conveyed out of the bioreactor via a tube with a syringe and using a pump. This mode of operation has the result that the sample is normally drawn out of the reactor from the top via a dip pipe. If the sample is drawn merely from the surface of the reactor volume, then inaccurate samples can be produced. However, if the dip pipe extends very far into the volume, then a relative large dead volume is produced, which can likewise effect inaccuracy of the sample or entails a large sample loss since the dead volume usually must then be discarded. 
         [0003]    It is therefore the object of the present invention to make available a reliable sampling system which enables manual sampling with a low dead volume. 
         [0004]    This object is achieved by the sampling system as disclosed hereinafter. Advantageous developments of the sampling system according to the invention are also revealed. 
       SUMMARY 
       [0005]    According to the invention, the sampling system which can use all samples, in particular for gases and liquids, has three individual elements which are however coordinated to each other. As the first element, a sample probe is inserted into the bioreactor which can be configured as a hollow volume, in particular as a hollow tube. This sample probe is open at one end thereof and sealed at the other end thereof, which protrudes into the reactor, via a valve. The valve has a hollow needle, via which the outer side of the valve is connected to the inner side of the valve when the valve is open. 
         [0006]    Furthermore, a sample receiving vessel is provided which serves to receive the withdrawn sample. This is sealed with a septum and dimensioned such that it can be introduced into the sample probe. If it is introduced sufficiently far into the sample probe, then the septum which is situated at one end thereof is pierced by the hollow needle. Upon further introduction into the sample probe, the sample receiving vessel presses against the valve and thus opens the valve mechanically. The precise mechanism for opening the valve is described later. In this way, an opening between the outer side of the sample probe and the inner volume of the sample receiving vessel is exposed. If the sample receiving vessel is at least partially evacuated, the sample is now suctioned out of the fluid volume to be sampled via the valve and the hollow needle into the inner volume of the sample receiving vessel. 
         [0007]    As third element, a holder is provided for the sample receiving vessel, into which holder the sample receiving vessel can be introduced. By means of this holder, a defined introduction of the sample receiving vessel into the sample probe is possible. 
         [0008]    The sampling system according to the invention makes it possible to take samples from a fluid volume reproducibly and reliably. It can be used safely and by trained personnel in a simple manner. 
         [0009]    Since conventional standardised sample receiving vessels, for example so-called vacutainers of the company BD GmbH, can be used as sample receiving vessel, the current costs for the sampling system according to the invention can be kept low. In particular the costs for the used articles, such as sample receiving vessels, can be kept reasonable due to the use of standard commercial products. 
         [0010]    The sampling system according to the invention has the advantage in addition that the dead volume, namely the through-volume of the valve and of the hollow needle, is small. However, removal from a reactor, in particular even from a glass reactor, is possible via the sample probe. 
         [0011]    The system can therefore be used with any type of bioreactors, in particular even with small or medium-sized glass laboratory reactors. As a result of the constantly ensured seal of the sample to be withdrawn and of the-fluid to be sampled from the exterior, sampling of toxic or health-endangering materials is also possible without further protective precautions or with low protective precautions. 
         [0012]    The sample receiving vessel can be filled in addition with reagents in order to prevent for example undesired reactions in the sample after the sampling. 
         [0013]    It is possible in addition to fill a sample receiving vessel with a sterilising solution and to introduce this sample receiving vessel into the sample probe, after or before a sample is taken. As a result, it is possible to keep the hollow needle sterile immediately after the sampling, before sampling or during the entire time between two samplings. 
         [0014]    The sample probe is advantageously a stainless steel tube which is open at the top and is sealed at the lower end thereof with the valve. Its external diameter should be chosen such that it can be introduced into the standard connection piece of a laboratory reactor. The sample probe can in addition have a spring which is compressed when introducing the sample receiving vessel by the latter so that a force is exerted on the sample receiving vessel which pushes the latter out of the sample probe again after completion of the sampling. As a result, the removal of the sample receiving vessel from the sample probe is assisted in addition. 
         [0015]    The holder for the sample receiving vessel can be configured as a hollow tube, the internal diameter of which is the same or slightly larger than the external diameter of the sample receiving vessel. This must apply at least for a part of the sample receiving vessel since it is merely required to introduce the sample receiving vessel partially into the holder. The holder can have in addition advantageously a gripping element in order to enable simple operation. This can abut in the longitudinal direction against the hollow tube, the diameter of the gripping element being able also to be larger or smaller than the external diameter of the hollow tube. In the latter case, a conical transition between the hollow tube and the gripping element is then advantageous. 
         [0016]    The holder can in addition have spring elements which fix the sample receiving vessel in the holder. This can be effected for example via leaf springs which are disposed on the outer side of the hollow tube and, with their free end or with a free region, press on an introduced sample receiving vessel through an opening in the hollow tube. In this case, the leaf springs are further compressed and the sample receiving vessel is held even more firmly when the holder is introduced into the sample probe. Between the regions of the leaf springs, which press on the sample receiving vessel, and the sample receiving vessel itself, an O-ring can be situated, which is situated on the inner side of the hollow tube of the holder or is inserted in a circumferential groove in the wall of the hollow tube of the holder. In addition, this improves the retaining force and reduces the risk of damage to the sample receiving vessel by the resilient elements. 
         [0017]    In a further advantageous embodiment, the holder has a bolt or a pin which protrudes outwards. A corresponding groove is inserted in the sample probe for this pin so that the holder with the pin can be introduced into the sample probe in such a manner that the pin slides in the groove. The groove can have a first step similar to a bayonet closure in which further introduction of the holder into the sample probe is possible only after rotation of the holder. In addition, it can have an end stop which fixes the position of the holder in the sample probe, in which the holder is introduced to the maximum into the sample probe. 
         [0018]    The first step of the groove can be designed now such that the holder with the pin is introduced only so far into the sample probe that the septum which seals the sample receiving vessel is pierced just by the needle of the valve but the valve is still closed. This position is suitable in particular for sterilising the hollow needle with a sample receiving vessel which contains a sterilising agent or for keeping it sterile in this position. 
         [0019]    After rotating the holder and further introduction of the holder into the sample probe, the holder or the sample receiving vessel then exerts a force on the valve so that the valve is opened and now a sample is drawn into the sample receiving vessel via the valve and the hollow needle. This is the position of the holder in which sampling is effected. 
         [0020]    According to the invention, it is of course also possible to dispose the corresponding groove on the outer side of the holder and to provide the sample probe with an inwardly protruding pin. The same effect is therefore achieved as by a pin on the holder and a stepped groove on the sample probe. 
     
    
     
       BRIEF DESCRIPTIONS OF THE DRAWINGS 
         [0021]    Examples of sampling systems according to the invention are now given in the following. There are shown 
           [0022]      FIG. 1  a sampling system in a bioreactor; 
           [0023]      FIG. 2  a sampling probe in section ( FIG. 2A ) and in front view ( FIG. 2B ),  FIG. 2A  representing a section along the line A-A in  FIG. 2B ; 
           [0024]      FIG. 3  an enlarged view of the end of the sampling probe of  FIG. 2 , closed with a valve; 
           [0025]      FIG. 4  a sample receiving vessel; 
           [0026]      FIG. 5  a sample receiving vessel in various positions within a sample probe; 
           [0027]      FIG. 6  three different views or positions of a holder; 
           [0028]      FIG. 7  a further example of a sampling system according to the invention. 
           [0029]      FIG. 8  shows a sampling system according to the invention in which the sample vessel is retained in a retaining clip. 
           [0030]      FIG. 9  shows a sampling vessel. 
           [0031]      FIG. 10  shows the section through a retaining clip according to the invention. 
           [0032]      FIG. 11  shows a valve according to the invention with a canula. 
           [0033]      FIG. 12  shows the section through a valve according to the invention with a needle tip accommodated in a septum. 
           [0034]      FIG. 13  shows a valve corresponding to  FIG. 12  which is accommodated in a sampling probe. 
           [0035]      FIG. 14  shows a valve corresponding to  FIG. 12  which is accommodated in a sampling probe and situated in the open state. 
           [0036]      FIG. 15  shows a sealing screw connection of the sampling probe according to the invention. 
       
    
    
     DETAILED DESCRIPTION  
       [0037]      FIG. 1  shows the construction and mode of operation of a sampling system according to the invention in the example of a laboratory bioreactor  4 . In the laboratory bioreactor  4 , which is closed by a cover  5 , there is situated a cell suspension  7  which is kept in suspension by an agitator  6 . A sampling system which comprises in total three elements is now dipped into this cell suspension  7 . These are, on the one hand, a sample probe  1  which is inserted into the reactor closure or cover  5 . It is dimensioned such that it can be introduced into a standard connection piece  8  of the reactor  4 . 
         [0038]    The sample probe itself is a stainless steel tube which is open at the top and at the lower end of which a sampling valve is situated. 
         [0039]    The sample probe is now dipped into the cell suspension  7  and thus makes possible, at the lower end thereof, a sampling position which is extensively in the interior of the reactor  4 . As a result, the sample is removed, on the one hand, directly in the interior of the cell suspension  7  and, on the other hand, transport of the sample from the cell suspension  7  into a sample receiving vessel  2  is minimised. As a result, it can be ensured that, on the one hand, the dwell time during the sampling until reaching the sample receiving vessel  2  is kept short and, on the other hand, the dead volumes of this path are only small. 
         [0040]    The agitator  6  is actuated by a motor  9  and keeps the cell suspension moving. 
         [0041]    Within the sample probe  1 , there is situated the sample receiving vessel  2  and also a holder  3  for the sample receiving vessel  2 . 
         [0042]      FIG. 2  now shows a sample probe  1  according to the invention with a stainless steel tube  10 .  FIG. 2B  shows a plan view on the arrangement of the sample probe  1  in the reactor closure  5  whilst  FIG. 2A  represents a section through this arrangement along the line A-A in  FIG. 2B . Here as in the following, the same or similar elements are provided with the same or similar reference numbers. The stainless steel tube  10  of the sample probe  1  is recessed in the standard connection piece in the reactor cover  5  and secured with a union nut  11 . The stainless steel tube  10  has in addition a flange  5  which is in engagement with a flange  14  in the reactor closure  5 . The immersion depth of the stainless steel tube  10  is fixed by these two flanges  14  and  15 . In addition, in an externally situated circumferential groove in the stainless steel tube at the height of the reactor closure  5 , an O-ring  19  which forms a seal between the closure  9  and the stainless steel tube  10  is disposed. 
         [0043]    In the stainless steel tube  10 , a valve  12  with a valve body  120  is disposed to form a seal at the lower end of said tube. The valve body  120  has a through hole  17  in the longitudinal direction of the sample probe  1 . As can be detected in  FIG. 3 , in an enlarged representation, a valve cylinder  18  is introduced into this boring  17 , said valve cylinder abutting for its part against the walls of the boring  17  to form a seal. This seal is improved in addition by an O-ring  123 . 
         [0044]    The valve cylinder  18  is mounted resiliently via the spring  124  in the valve body  120  and can be displaced from the position shown in  FIG. 3  downwards in opposition to the force of the spring  124  in the longitudinal direction of the sample probe  1 . 
         [0045]    The valve body  120  has a recess  130  at the end of the sample probe  1 , at which recess the valve cylinder  18  protrudes. The valve cylinder  18  is provided there with a circumferential rubber ring seal  122  which seals the gap between the valve cylinder  18  and the valve body  120  when the valve cylinder  18  is displaced by the spring  124  to the maximum into the interior of the sample probe  1 . 
         [0046]    The valve cylinder  18  has for its part in addition an internal hole  128 . Starting from this internal hole  128  there are located in the side walls of the valve cylinder  18  through-openings  127  which connect the outer side of the wall of the valve cylinder  18  to the boring  128 . 
         [0047]    If the valve cylinder  18  is now pressed downwards in opposition to the spring force of the spring  124 , then the borings  127  are exposed and a fluid can flow into the boring  127  and the boring  128  from outwith the sample probe  1 . 
         [0048]    As can be detected in  FIGS. 2 and 3 , a hollow needle  13  is disposed in addition in the valve cylinder  18  and communicates with the boring  128  and hence with the inner volume of the valve cylinder  18 . This hollow needle  13  is orientated in the longitudinal direction of the sample probe  1  and protrudes by its end orientated away from the valve cylinder  18  beyond the valve cylinder  18 . 
         [0049]      FIG. 4  shows a sample receiving vessel  2  according to the invention. This essentially comprises a test tube  20  made of glass or plastic material, which is closed with a septum  21 . Above the septum  21 , in the present example made of silicone, a protective cap  22  is disposed in addition which however has an opening  23  in the central axis of the test tube  20 . Through this opening  23 , the hollow needle  13  can pierce the septum  21  in the application case. 
         [0050]    There are suitable in particular as sample receiving vessels  2  conventional so-called “vacutainers” which are already commercially available and are obtainable both empty and filled with different buffers and reagents. They are normally used in the medical field for preparing blood samples. The content of this vessel is therefore also normally already characterised unequivocally by the colour of the protective cap  22  and of the septum  21  and each vessel  2  is already provided with an inscription area. 
         [0051]    Vacutainers of this type are obtainable in different volumes and very cheaply. These standardised sample receiving vessels enable use of the present invention in the case of routine checks of processes and plants, for example also by shift personnel or also by official bodies. The analysis which often requires costly and qualified personnel can be affected subsequently in correspondingly qualified and certified laboratories. 
         [0052]    The closed construction of the sample receiving vessel  2  is of particular advantage since tampering during sampling and subsequent transport for analysis can be precluded by simple means. Because of the closed construction, also health-endangering or toxic samples can be taken from apparatus, plants or channels without endangering the personnel. 
         [0053]    In the non-certified laboratory field, it is also possible to fill with suitable reagents the present sample receiving vessels  2  which are already commercially available, with the help of a syringe, e.g. the vessels  2  can be filled with cold methanol in order immediately to stop biological reactions taking place in the sample during sampling. 
         [0054]      FIG. 5  now shows a sample receiving vessel  2  in two different arrangements relative to the valve  12  of a sample probe  1 . In  FIG. 5A , a position is thereby represented in which the sample receiving vessel does not yet compress the return spring  125  which surrounds the valve cylinder  18 . Since the hollow needle  13  protrudes however sufficiently far out of the valve cylinder  18 , it already pierces the septum  21  through the opening  23 . In this way, contact between the interior of the hollow needle  13  and the interior of the sample receiving vessel  2  is hence already produced. If the sample receiving vessel  2  is charged with a sterilising solution, then the needle  13  can be sterilised or kept permanently sterile. 
         [0055]    The needle  13  for its part can have a cover (not shown here) which normally covers it and which is pressed back when the sample receiving vessel  2  is pressed thereon and hence releases the tip of the hollow needle  13 . 
         [0056]      FIG. 5B  shows a further position in which the protective cap  22  of the sample receiving vessel  2  presses on the valve cylinder  18  and, in this way, presses the foremost part  121  of the valve cylinder  18  out of the recess  130 . As a result, the rubber ring  122  is pressed out of its seat and the openings  127  come into contact with the exterior of the sample probe  1 . The arrows  129  now show a possible flow path for the fluid to be sampled through the opening  127 , the inner volume  128  of the valve cylinder  18  and also the inner volume of the hollow needle  13  into the interior of the sample receiving vessel  2 . The spring  125  thereby exerts a restoring force on the sample receiving vessel  2  which however is overcome by the operator during sampling. 
         [0057]    Also the spring  124  is compressed by the valve cylinder  18  and thus exerts a restoring force on the valve cylinder  18 . With decreasing pressure of the sample receiving vessel  2  on the valve cylinder  18 , firstly the valve pin  121  is thus again pushed back into its sealing seat and only thereafter is the sample receiving vessel  2  withdrawn from the hollow needle  13 . 
         [0058]      FIG. 6  shows a holder of a sampling system according to the invention. This holder  3  is represented in  FIG. 6B  in plan view and in  FIG. 6A  in a sectional view along the section A-A in  FIG. 6B . The holder  3  has a gripping element  30  which narrows over a conical region and merges into a hollow cylinder  32 . This hollow cylinder  32  is chosen such that the sample receiving vessel  2  can be inserted into it. On the outer side of the hollow cylinder  32 , leaf springs  33  are disposed which extend in the axial direction of the hollow tube  32 . These leaf springs engage through the hollow tube  32  at recesses (grooves)  35  and, with the free end here, press on a rubber O-ring  34  which is disposed within the wall of the hollow tube  32 . 
         [0059]    If a sample receiving vessel  2  is introduced into the hollow cylinder  32  ( FIG. 6C ), then the leaf springs  33  press via the O-ring  34  on the sample receiving vessel  2  and hold it securely in its position. Hence the sample receiving vessel  2  is fixed in the holder  3 . 
         [0060]    If a sample is intended to be removed from the bioreactor  4 , then the sample receiving vessel  2  is firstly inserted into the holder  3 . The holder  3  is then introduced into the sample probe  1 , the leaf springs  33  situated on the holder  3  being squeezed. They consequently exert an even greater pressure on the sample receiving vessel  2  in the sample probe  1 . Upon further introduction of the holder  3  into the sample probe  1 , the valve-side hollow needle  13  pierces the septum  21 . By means of farther pressure on the holder  3  and hence on the sample receiving vessel  2 , the spring  125  is compressed and the valve cylinder  18  is moved downwards. Hence the sealing ring  122  is then removed from its sealed seat and the openings  127  in the valve cylinder  18  are exposed. Hence the valve in the sample probe  1  is opened and the sample is conveyed by the pressure difference between the sample receiving vessel  2  and the interior of the reactor  4  into the sample receiving vessel  2  until there is pressure equalisation. 
         [0061]    If the sample receiving vessel  2  is removed again from the sample probe  1  by pulling on the gripping element  30  of the holder  3 , then the valve in the sample probe  1  is closed firstly by the spring force of the spring  124  and subsequently the sample receiving vessel  2  is pushed out of the sample probe  1  with assistance from the spring  125 , the connection between the hollow needle  13  and the septum  21  being separated. The septum  21  then closes again. 
         [0062]    Outwith the sample probe  1 , the leaf springs  33  of the holder  3  still exert only a slight pressure on the sample receiving vessel  2  so that the now filled sample receiving vessel  2  can be removed easily from the holder  3 . 
         [0063]    The sample can then be used for further processing, in particular it can be centrifuged off directly in the sample receiving vessel  2  when using a suitable centrifuge insert. 
         [0064]      FIG. 7  shows a particular embodiment of the holder  3  and of the sample probe  1  with which contamination of the bioreactor can be reliably precluded in a simple manner. The sample probe  1  is hereby provided with a groove  16 . This groove is introduced into the inner wall of the sample probe  1  as a stepped groove  16 . It has a first step  19   a  and also an end stop  19   b . A pin  37  which is disposed on the holder  3  can be introduced into this groove  16 , If the pin  37  is now introduced into the groove  16 , then firstly a guided axial movement of the holder  3  is effected. Upon reaching the step  19   a , the holder  3  must then be rotated in order to guide the pin subsequently further along the groove in order then to implement again an axial movement of the holder  3  up to the stop  19   b  at the end of the groove  16 . 
         [0065]    If the sampling system is now to be kept sterile between the samplings, then the holder  3  is fitted with a sample receiving vessel  2  which is filled with disinfectant. The holder  3  is thereby introduced only so far into the sample probe  1  that the pin  37  is situated in the step  19   a  of the groove  16 . In this position, the needle  13  already penetrates through the septum  21  so that the needle is already disinfected or sterilised by the disinfectant contained in the sample receiving vessel  2 . The valve of the sample probe  1  in this state is however closed, as is represented for example in  FIG. 5A . 
         [0066]    In the case where a sample is intended to be taken, the disinfectant vessel is removed and the holder is fitted with a suitable sample receiving vessel  2 . Said holder is then introduced again into the sample probe  1 , an axial movement of the pin in the groove  16  being implemented first and subsequently a lateral movement of the pin  37  in the groove  16  along the shoulder  19   a  and subsequently again an axial movement of the pin  37  in the groove  16  up to the stop  19   b . In the latter position, the needle  13  pierces the septum  21  of the sample receiving vessel  2  and the valve cylinder  18  is displaced, as represented in  FIG. 5B , in order to open the valve  12 . 
         [0067]    Hence the sample can flow into the sample receiving vessel  2 . 
         [0068]    As a result of the bayonet-type closure of the holder  3  in the sample probe  1 , it is ensured that the different positions of the sample receiving vessels  2  can be adjusted safely and reliably for the different functions even by only slightly trained personnel. 
         [0069]      FIG. 8  shows a sampling system according to the invention in which the sample receiving vessel  2  is retained on the holder  3  by means of a retaining clip  41 . The right partial image shows the holder  3  with the retaining clip  41  outwith the sample probe  1  and the left partial image shows the same system introduced into the sample probe  1 . The retaining clip  41  has a cylindrical basic body  42  with slot-like milled parts  43  in the sides of the receiving hole  44  for the sample vessel  2 . 
         [0070]      FIG. 10  shows, enlarged, the section through such a retaining clip  41 . The boring  44  is provided with a corresponding undercut  45  for receiving the cap  22  of the sample vessel  2 . A corresponding sample vessel  2  is shown in  FIG. 9 . For easier introduction of the sample vessel  2  into the receiving hole  44 , chamfers  46  are provided at the receiving opening. The mounting of the retaining clip  41  on the holder  3  can be effected via a threaded hole  47 . If now a sample is intended to be taken from a bioreactor, then a sample vessel  2  with the spherical end  48  is inserted in advance in the retaining clip  41 . The two halves  49  of the retaining clip  41  are thereby pushed apart until the cap  22  of the sample vessel  2  locks in the undercut. In this state, the two halves  49  of the clip  41  are pressed outwards slightly conically, only by introduction into the probe  1  is the cap  22  of the vessel  2  compressed again and does the clip  41  assume a cylindrical shape. Since the clip halves  42  in the probe  1  cannot yield in the radial direction, the vessel is retained securely in the clip  41  and sliding out is prevented. For removing the sample vessel  2 , the two clip halves  49  must be bent up slightly manually, as a result of which the sample vessel  2  can be removed easily. 
         [0071]      FIGS. 11 ,  12 ,  13  and  14  show an embodiment of the valve  12  according to the invention. In  FIG. 11 , an outer view of the valve can be seen,  FIG. 12  shows a section through the valve according to the invention and  FIGS. 13 and 14  shows the valve according to the invention when it is incorporated in the sampling probe  1  and connected to a sampling vessel  2 .  FIG. 13  hereby represents the closed state and  FIG. 14  the opened state of the valve. Mounting of this valve is affected in that the canula  13  is arc welded on at one end; subsequently a tip  61  is ground and is provided with a cross-hole  62  just above the tip. The canula  13  is soldered into the needle body  63 . For this purpose, a boring  64  is situated in the needle body  63  for introducing the solder. The catch  65  is screwed into the basic body  120  up to the stop and pretensions the spring  124  towards the pressure plate  66  and the septum  67  via the needle body. Subsequently, the stop  68  can be screwed onto the needle body  63 . The mounted valve  12  is screwed into the tube  1  of the sampling probe from the bottom and sealed with an O-ring  69 . 
         [0072]    As can be detected in  FIG. 13 , the spring  124 , in the closed state, presses the canula  13  via the needle body  63  in the direction of the sample vessel  2  and hence holds the cross-hole  62  in the septum  67 . As a result of the pretension of the septum  67  by the catch  65 , the septum  67  seals the cross-hole  62  of the needle  13  reliably. A sample vessel  2  introduced into the sampling probe  1  can be pressed onto the needle  13  in opposition to a slight resistance until the cap  22  of the vessel  2  is situated on the stop  60 . A clear pressure point can thereby be felt. The pretension of the spring  124  prevents opening of the valve  12 . Sealing of the needle cross-hole  62  by the septum  67  produces the vacuum in the sampling vessel  2 . 
         [0073]    As can be detected in  FIG. 14 , by increasing the pressure in opposition to the pressure spring  124 , the needle tip  61  is pushed out of the septum  67  until reaching a second pressure point, as a result of which it is situated freely in the medium which is to be suctioned in. As a result, a continuous connection between the reactor interior and the sample vessel interior  2  is created and a sample can be suctioned into the sampling vessel  2  by means of the vacuum. By reducing the pressure on the valve  12 , the spring  124  draws the canula  13  back into the septum  67  and hence closes the valve  12 . The sampling vessel  2  can subsequently be withdrawn from the needle  13  in opposition to a slight resistance. 
         [0074]      FIG. 15  shows the possibility of a sealing cover screw connection. A ring  51  is hereby shrunk onto the tube  32  of the sampling probe  1 . Said ring has an internally situated chamfer  52 . An O-ring  53  is placed in the latter. With the help of the union nut  11 , the O-ring  53  is pressed against the screw-in cup  54  and consequently forms a seal against the tube  32  and the cover  5 . By using a shrunk-on ring  51 , sampling probes  1  of different lengths can be manufactured very easily in production. 
         [0075]    In summary, it can be established that, in contrast to previously implemented manual sampling with a dip pipe, in the case of the present invention, the dead volume can be reduced to a few μl directly in the reactor due to the sampling position. This is relevant in particular for laboratory reactors made of glass which are only accessible from the top. In addition, the practical implementation of a sampling operation is simplified greatly with the system according to the invention. Hence manual errors which occur frequently in the normal sampling operation according to the state of the art are avoided, so that the sampling operation can be implemented more reliably, more reproducibly and more safely.