GB2576058A - Reaction station for magnetic stirring and methods and devices relating to magnetic stirring - Google Patents

Abstract

A device for use with a laboratory magnetic stirrer 130, 102 which agitates the contents of a reaction vessel 108 that contains a magnetic stir bar 114, the device comprising a reaction vessel receiver 106 for holding the vessel in a position whereby the vessel is located for stirring with respect to a magnetic field produced by the laboratory magnetic stirrer, and a ferromagnetic locator 118 configured to, in use, to magnetically locate the magnetic stir bar within the vessel held by the receiver wherein the ferromagnetic locator 118 is in a predetermined position relative to the reaction vessel receiver. The locator attracts the magnetic stir bar so that the bar is held in a more definite or predetermined position so that jumping, stuttering or de-coupling from the magnetic field of laboratory magnetic stirrer is avoided. The locator may be a steel disc or split ring which is embedded in the reaction vessel receiver, and is positioned corresponding to the desired position of the magnetic stir bar. The reaction vessel receiver may comprise a body with multiple vessel receivers wherein each vessel receiver has its own ferromagnetic locator. An apparatus comprising a laboratory magnetic stirrer and device is disclosed.

Description

REACTION STATION FOR MAGNETIC STIRRING AND METHODS AND DEVICES RELATING TO MAGNETIC STIRRING

The present invention relates to a device for improving magnetic stirring of the contents of a reaction vessel, specifically but not necessarily exclusively for use in a laboratory environment. The present invention also relates to a reaction station comprising such a device, a process for creating a chemical product using such a device, a method of manufacturing the device, and a method of reducing erratic movement of a magnetic stir bar.

In the field of organic chemistry, it is desirable to perform reliable and repeatable chemical reactions. In order to do so, it is common to use a magnetic stirrer, which produces a rotating magnetic field that interacts with a magnetic stir bar within a reaction vessel such as a test tube or flask. The magnetic stirrer creates a changing magnetic field, which causes the stir bar to rotate and stir the contents of the reaction vessel. Such magnetic stirrers can be used on their own or in conjunction with heating or cooling apparatus in order to further control the reaction conditions.

A problem with magnetic stirrers and stir bars is that the stir bar can disconnect, or become ‘decoupled’, from the magnetic field of the magnetic stirrer, which results in the stir bar bouncing, jumping, spinning erratically, or ceasing to spin at all. This can cause a number of negative consequences, such as the cessation of the regulated mixing of the fluid and/or suspended solids within the reaction vessel, a belowoptimum mixing of the fluid, or, in extreme circumstances, the movement of the stir bar can result in damage or breakage of the reaction vessel. At the least, decoupling of the stir bar can lead to wasted experiments and lost time for the user.

This decoupling of the stir bar from the changing magnetic field happens at relatively high stirring rates and is believed to be because the inertial mass of the stir bar is too high and the stir bar does not have time to move or rotate properly in synchronisation with the changing magnetic field. The stir bar can then be caused to stutter or quiver as the changing magnetic field changes too quickly for it to follow. A similar result can be caused by the changing resistance of the liquid within which the stir bar is located, for example caused by a change in viscosity or the formation of a precipitate.

When parallel reactions are being performed, the decoupling of one or more magnetic stirrers out of the plurality provided means that supposedly identical stirring regimes for parallel reactions are in fact markedly different regimes, which can result in a loss of quality control and variations in the final product.

Decoupling of the stir bar can be initiated or encouraged by a number of factors, including, but not limited to, a high speed of rotation of the magnetic field and thus the stir bar, the viscosity of the liquid within the reaction vessel, or the formation of precipitates within the reaction vessel.

In some cases, a high spin speed of the stir bar can lead to the formation of a vortex within the liquid. Whilst the vortex can enhance mixing, it can also lead to increased instability of the stir bar and its synchronised coupling to the moving magnetic field. The vortex can produce pressure fluctuations that encourage the stir bar to move about in the vessel to positions it does not normally occupy and may therefore assist in decoupling and increasing instability of the stir bar.

As discussed, in some cases, it is further desirable to perform a variety of related chemical reactions simultaneously under similar reaction conditions. The technique for performing such reactions simultaneously is known as parallel synthesis.

One of the problems associated with carrying out parallel syntheses in the laboratory is that many existing laboratory magnetic stirrers are only designed to accommodate and efficiently stir the contents of one reaction vessel at any one time.

In response to this problem, systems are known - in particular the Carousel 6 Plus, Carousel 12 Plus, Mya4, Starfish, and Heat-On reaction stations developed by the applicant - which position multiple reaction vessels in set positions in a ring about a single, central, magnetic stirrer, the specific positioning of the reaction vessels enabling effective stirring of all reaction vessels. It has been noted by the applicant that where multiple reaction vessels are located radially-disposed about or around a single magnetic stirrer, the magnetic stir bar can be drawn by the rotating magnetic field of the magnetic stirrer into a non-central position within each reaction vessel. Whilst this is not an issue under many circumstances, the non-central positioning and/or the formation of a vortex in a non-vertical position can further encourage decoupling of the stir bar.

At low speeds, such as lower than 100 revolutions per minute (rpm), there are hardly any stir bar decoupling problems. Depending upon the reagents and the set-up of the reaction station, there can be a speed of revolution of the stir bar where it stops following the changing magnetic field (e.g. rotating magnetic field). This might be at 700 rpm, or 500 rpm, or 800 rpm, or 900 rpm, or 1000 rpm. The specific speed at which decoupling occurs will be dependent upon the reagents, set-up of the machine, and size of the reaction vessels, for example.

As the viscosity of the reaction mixture changes as the chemical reaction in the reaction vessel progresses, the critical speed at which the stir bar stops working properly can be influenced by fluidic properties of the reactants, with variance in viscosity limiting the speed of the stir bar. This means that a stir bar might work well at the start of a reaction but later on in the reaction, for example after one or two hours, the stir bar might stop rotating and stirring effectively. It is impractical for a lab technician to sit and watch the reaction for hours in order to await a situation in which they might be required to intervene.

According to a first aspect, there is provided a device for improving magnetic stirring of the contents of a reaction vessel, the device comprising:

a reaction vessel receiver for holding a reaction vessel in a position whereby the reaction vessel is effectively located for stirring with respect to a magnetic field produced by a laboratory magnetic stirrer; and a ferromagnetic locator configured to, in use, magnetically locate a magnetic stir bar within the reaction vessel held by the reaction vessel receiver, the ferromagnetic locator being in a predetermined position relative to the reaction vessel receiver.

The provision of a ferromagnetic locator enables the position of a magnetic stir bar to be altered compared to where it would otherwise naturally position itself within the magnetic field of the magnetic stirrer, in use. Due to the ferromagnetism of the ferromagnetic locator, the magnetic stir bar will be drawn towards the ferromagnetic locator as well as being caused to spin by the changing or rotating magnetic field of the magnetic stirrer. The magnetic field generated by the magnetic stirrer, in use, will also be perturbed and modified by the presence of the ferromagnetic locator, and may be made stronger near the reaction vessel receiver, for example by channelling or focussing the magnetic field.

The magnetic stir bar being attracted to the ferromagnetic locator and the magnetic field of the magnetic stirrer being made stronger in the vicinity of the stir bar by the ferromagnetic locator will both help to locate and hold the stir bar in a more definite or predetermined position, assisting in the effectiveness of the stirrer.

Magnetic stir bars comprise a permanent magnet, for example a rare earth magnet typically formed from rare earth elements or their alloys, such as, but not limited to, neodymium or samarium-cobalt, and may be coated in a chemicallyresistant/chemically-inert material to avoid influencing the reaction. The shape of a magnetic stir bar may be designed to provide effective and predictable stirring, for example by providing a stir bar that is elongate and symmetrical about a central axis. A ridge or other feature may be provided to assist with the spinning of the stir bar by, for example, creating a pivot point.

The ferromagnetic locator may be disposed adjacent to the reaction vessel receiver. For example, the ferromagnetic locator may be positioned below the reaction vessel receiver. Positioning the ferromagnetic locator adjacent to the reaction vessel receiver will, in use, provide a stronger attraction of the magnetic stir bar to the ferromagnetic locator. By providing the ferromagnetic locator below the reaction vessel receiver, the stir bar may be drawn down towards the lowest part of the reaction vessel within which it is housed, in use.

The ferromagnetic locator may be configured to, in use, magnetically locate the magnetic stir bar by virtue of magnetic forces between the stir bar and the ferromagnetic locator.

The device may further comprise a body that defines the reaction vessel receiver, the body being non-ferromagnetic or substantially non-ferromagnetic, for example an aluminium body.

The body may comprise a plurality of reaction vessel receivers and a plurality of ferromagnetic locators, each ferromagnetic locator being associated with a respective reaction vessel receiver. The plurality of ferromagnetic locators may be formed as a single unit, or they may be separate units, or there may be a plurality of ferromagnetic locators forming a single unit, the body having multiple units.

The body may be circular or substantially circular. The plurality of reaction vessel receivers may be evenly spaced about the body, for example at an even distance from the centre and/or with an even angular spacing between reaction vessel receivers.

The plurality of reaction vessel receivers may be unitarily-formed. For example, the reaction vessel receivers may be manufactured as a single block. Alternatively, the reaction vessel receivers may be formed of multiple pieces that are joined together to form a single block.

The ferromagnetic locator may be embedded within the reaction vessel receiver. The ferromagnetic locator may therefore be securely retained in position within the reaction vessel receiver and may be protected from damage, for example, physical damage or chemical damage.

The ferromagnetic locator may be located in a recess in the reaction vessel receiver.

By positioning the ferromagnetic locator in a recess in the reaction vessel receiver, manufacture of the device may be made simpler. The recess may be formed by, for example, machining or drilling away part of the reaction vessel receiver or by forming the recess during moulding or casting of the reaction vessel receiver. The ferromagnetic locator may be embedded within the recess by providing a cover over the ferromagnetic locator, or may be left uncovered.

The device may comprise a reactor block and the reaction vessel receivers may be provided in the reactor block or as a part of the reactor block. The reactor block may be adapted to be a good conductor of heat in order to allow sufficient heating and/or cooling to be delivered to the reaction vessels, in use. The reactor block may therefore be formed of a material that includes these properties or include a material that enables these properties. A suitable material is aluminium.

The ferromagnetic locator may be located on or adjacent to a surface of the reaction vessel receiver.

The reaction vessel receiver may be formed as a hole in the body. The body may define a surface that defines the reaction vessel receiver. The surface may be concave and may conform or substantially conform to a reaction vessel it is designed to receive. The reaction vessel receiver may include a base, for example the base of the hole, and the ferromagnetic locator may be located within the base.

The hole may be cylindrical or substantially cylindrical and include a flat or curved base. For example, the base may be part-spherical, i.e. may conform to a sphere with an equal radius of curvature.

The ferromagnetic locator may be located centrally relative to the hole or surface, for example radially centrally to a circular hole or circular surface. The ferromagnetic locator may be located within 2 mm of the surface, or within 5 mm of the surface, or within 10 mm of the surface, for example.

The ferromagnetic locator may be bonded to the surface of the reaction vessel receiver, such as by chemical bonding. Additionally or alternatively, the ferromagnetic locator may be affixed to the reaction vessel receiver, such as by a mechanical fastener. The mechanical fastener may, for example, be a screw, clip, or other fixing means.

The ferromagnetic locator may be manufactured from a ferromagnetic material, common materials being, but not limited to, iron, cobalt, nickel, gadolinium, or alloys or compounds containing one or more of these elements.

The ferromagnetic locator may comprise a plug, screw, or washer.

The ferromagnetic locator may include an area having less or no ferromagnetic material. This area may help to more precisely position the stir bar, in use.

The area may be formed as a recess, area of reduced thickness, or aperture, in the ferromagnetic locator, for example. The area may be central or substantially central to the ferromagnetic locator.

The ferromagnetic locator may be annular, substantially annular, toroidal, substantially toroidal, ring-shaped, substantially ring-shaped, or another shape with an aperture, or may be substantially toroidal or ring-shaped with an area of reduced thickness in place of the aperture.

The provision of an area having less or no ferromagnetic material may help to position the stir bar relative to the aperture. This can occur by providing a pull on the stir bar laterally from the other parts of the ferromagnetic locator, whilst less or no pull is provided by the area have less or no ferromagnetic material - i.e. the outer parts of the ferromagnetic locator have a greater influence on the position of the stir bar than the inner parts or aperture. The ferromagnetic locator may be adapted to provide an even magnetic pull on the stir bar in all lateral directions, causing the stir bar to sit centrally relative to this even magnetic pull.

The ferromagnetic locator may be a temporary magnet, i.e. the ferromagnetic locator may only exhibit magnetic properties in the presence of another magnetic device, such as a magnetic stir bar or a magnetic stirrer; the ferromagnetic locator may be formed from a magnetically ‘soft’ material. By providing the ferromagnetic locator as a temporary magnet, magnetic clamping due to having magnetic attraction between the ferromagnetic locator and the stir bar at a too high a level can be limited or prevented.

The term magnetic clamping is used to mean an inability of the stir bar to rotate within the reaction vessel, in use. This can be caused by poles of the stir bar being aligned with those of the ferromagnetic locator, in use, keeping the stir bar in a single position and preventing its rotation by the magnetic stirrer. By using a temporary magnet, the attraction between the ferromagnetic locator and the stir bar can be avoided from being so great that it causes this magnetic clamping.

The body of the device may incorporate a guide for ensuring that the device is effectively positioned with respect to the magnetic field generated by the laboratory magnetic stirrer, in use.

The guide may be configured to receive a part of a laboratory magnetic stirrer. For example, the guide may be configured to receive a plate of a laboratory magnetic stirrer. Where the laboratory magnetic stirrer includes a temperature-controlled plate, such as a hotplate, the guide may be configured to receive said hotplate.

The plate may project or protrude from the laboratory magnetic stirrer. The guide may comprise a guide recess adapted to receive the plate. The guide recess may be provided in a lower face of the device, for example in the body. The guide recess may be provided centrally or substantially centrally within the device or body.

The reaction vessel receiver may comprise a socket configured to securely accommodate a reaction vessel. The socket may be configured to securely accommodate a particular reaction vessel such as a test tube, boiling tube, beaker, flask, or jar, for example.

The reaction vessel receiver may be made of heat-conducting material. This material may therefore assist with the spread of heat throughout the device, for example when the device is used in conjunction with a magnetic stirrer with a hotplate. The heatconducting material may be aluminium or an aluminium-based alloy.

The reaction vessel receiver may be made of a chemically-resistant material or may have a chemically-resistant coating. The chemically-resistant material or chemicallyresistant coating may be formed from a material such as HDPE or PTFE.

According to a second aspect, there is provided a reaction station, comprising:

a magnetic stirrer; and a device according to the first aspect.

The magnetic stirrer may be a temperature-controlled magnetic stirrer. Such magnetic stirrers can not only stir but also act as a heat-source, a cold-source, or a heat- and/or cold-source for a reaction vessel, in use.

The reaction station may include a magnetic stir bar and/or a reaction vessel, the stir bar being receivable within the reaction vessel, in use, and the reaction vessel, in use, being received by the reaction vessel receiver.

According to a third aspect, there is provided a process for creating a chemical product, the processing comprising the steps of:

providing reagents within a reaction vessel;

providing a magnetic stirrer provided with a device in accordance with the first aspect; and stirring the reagents using the magnetic stirrer and reacting the reagents to form a chemical product.

The term “reagents” is considered to encompass any reactant, reagent, starting material, or other precursor to a chemical reaction.

According to a fourth aspect, there is provided a chemical product formed by the process of the third aspect.

According to a fifth aspect, there is provided a method of manufacturing a device for improving magnetic stirring of the contents of a reaction vessel, the method comprising the steps of:

affixing a ferromagnetic locator in a predetermined position relative to a reaction vessel receiver, the ferromagnetic locator being configured to locate, in use, a magnetic stir bar relative to a reaction vessel received by the reaction vessel receiver.

A recess may be created in a predetermined position with the reaction vessel receiver, into which the ferromagnetic locator may be inserted. The recess may be drilled.

The method may comprise capping or closing the recess, for example by use of a cap, plug, screw, or filler. The ferromagnetic locator may be held in place by the cap, plug, screw, or filler, or the cap, plug, screw, or filler may be introduced into the recess behind the ferromagnetic locator. The cap, plug, screw, or filler may hold the ferromagnetic locator in place. A fillet - or sliver of material - may additionally or alternatively be provided, the fillet covering over the recess without necessarily filling the recess. The fillet may also hold the ferromagnetic locator in place within the recess.

The recess may be provided in an upper surface or a lower surface of a body defining the reaction vessel receiver. The ferromagnetic locator may be positioned at or adjacent to an end of the recess that is itself at or adjacent to the upper surface of the body.

The ferromagnetic locator may be affixed by gluing, adhering, or chemically-fixing the ferromagnetic locator to the reaction vessel receiver.

According to a sixth aspect, there is provided a method of reducing erratic movement of a magnetic stir bar in a reaction vessel associated with a magnetic stirrer, the method comprising:

using a ferromagnetic locator disposed adjacent the reaction vessel to influence magnetic forces on the stir bar to hold the stir bar in a more controlled position than it would otherwise be held in the absence of the ferromagnetic locator.

Non-limiting embodiments of the present invention will now be described with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of a first embodiment of a device according to the first aspect, positioned on a magnetic stirrer;

Figure 2 is a cross-sectional view of a prior art device showing a stir bar that has generated a non-vertical vortex;

Figure 3 is a cross-sectional view of the device of Figure 1 showing the effect of a ferromagnetic locator within the device;

Figures 4a and 4b show a second embodiment of a device according to the first aspect, including a ferromagnetic locator in the form of an annulus;

Figures 5a and 5b show a third embodiment of a device according to the first aspect, including a ferromagnetic locator in the form of a screw;

Figures 6a and 6b show a fourth embodiment of a device according to the first aspect, including a ferromagnetic locator in the form of a large annulus;

Figure 7 shows a fifth embodiment of a device according to the first aspect, including a socket and ferromagnetic locator that are positioned centrally in relation to the magnetic stirrer, in use;

Figure 8 shows a sixth embodiment of a device according to the first aspect, including a socket and ferromagnetic locator positioned around the periphery of the magnetic stirrer, in use;

Figure 9 shows a seventh embodiment of a device according to the first aspect, including a socket and ferromagnetic locator positioned within the periphery of the magnetic stirrer, in use;

Figure 10 shows an eighth embodiment of a device according to the first aspect, including a ferromagnetic locator in the form of a screw inserted from the bottom surface of the body;

Figures Ila and 11b show two arrangements of ferromagnetic locator using a screw;

Figure 12 shows a ninth embodiment of a device according to the first aspect, the ferromagnetic locator being located within an annular recess in the upper surface of the body;

Figures 13a and 13b show a tenth embodiment of a device according to the first aspect, the ferromagnetic locator being provided as a plurality of screws;

Figure 14 shows an eleventh embodiment of a device according to the first aspect, the ferromagnetic locator being provided as a split ring within a notch in the upper surface of the body; and

Figures 15 to 17 depict methods according to the third, fifth, and sixth aspects of the invention.

Referring firstly to Figures 1 and 3, there is shown a reaction station 100 including a magnetic stirrer 102 and a body 104 forming six reaction vessel receivers in the form of sockets 106 in the body 104. The body 104 containing sockets 106 is seated on the magnetic stirrer 102 and is configured to receive six reaction vessels 108 within the sockets 106 forming the reaction vessel receivers. The reaction vessels 108 in this embodiment are round-bottom flasks. The magnetic stirrer 102 provides a changing magnetic field which in this embodiment is a rotating magnetic field for inducing spinning of magnetic stir bars positioned within the reaction vessels 108. The body 104 is an aluminium block which allows good heat transfer from the magnetic stirrer 102 to the reaction vessels 108 held by the sockets 106. A bumper 128 surrounds the periphery of the body in order to provide protection from thermal contact with the user. The bumper 128 may be formed of a thermally- and chemically-resilient material. For example, this material could be a mechanically-stable fluoropolymer.

Although described as sockets 106, each reaction vessel receiver may comprise any arrangement of features that are configured to hold a reaction vessel 108 in a set position relative to the magnetic stirrer 102. The reaction vessel receiver may therefore be a socket, preferably having a surface that is contiguous with that of the reaction vessel it is designed to hold, a stand, a shaped protrusion or plurality of protrusions, or any other feature or combination of features. Each reaction vessel receiver may be identical to the others of the device, or any one may be different to any other, for example where differently-shaped reaction vessels are required to be used with one device.

A condenser and gas distribution manifold 111 is supported by the body 104 and attaches to the top of the reaction vessels 108. The condenser and gas distribution manifold 111 assists in condensing any vapours produced within the vessels 108 and may also be configured to introduce or remove gas or air to or from the vessels 108.

The magnetic stirrer 102 includes a temperature-controlled plate 130 for providing heating and/or cooling to the body 104 and hence to the reaction vessels 108. The temperature of the temperature-controlled plate 130 can be adjusted by use of a temperature controller 132 and associated electronics (not shown). In addition, the speed of rotation of the rotating magnetic field can be adjusted by use of the speed controller 134 and associated electronics (not shown). The display 135 shows the speed and/or temperature being provided by the magnetic stirrer.

The magnetic stirrer 102, body 104, and condenser and gas distribution manifold 111, are all separate components and may be used in combination or separately. For example, the body 104 may be dismounted from the magnetic stirrer 102 simply by lifting it off the top of the temperature-controlled plate 130. Thus, a number of different embodiments or designs of body 104 and socket 106 can be mounted and used with a single magnetic stirrer 102. For example, bodies suitable for use with different numbers or shapes of reaction vessels can be mounted and dismounted as desired. Alternatively, the magnetic stirrer 102, body 104, and/or condenser and gas distribution manifold 111 may be provided as a single unit.

The speed controller 134 allows the rotating magnetic field to be controlled between zero and around 1500 rpm. By doing so, the speed of rotation of stir bars being used in the apparatus can be controlled accordingly. In a tested prior art system, decoupling of the stir bar from the rotating magnetic field occurred at speeds of around 700 rpm, but this decoupling speed can be raised higher or removed entirely by the present invention, in order to allow use of the full speed range of the magnetic stirrer. The use of other magnetic stirrer systems, along with other variables including the stir bar used and the reaction being processed, will result in the decoupling speed differing between set-ups. However, despite these variables, there will come a point when any system is subject to decoupling of the stir bar.

Figure 2 shows a cross-sectional view through a prior art device similar to those shown in Figure 1, including a body 4 and socket 6. The magnetic stirrer 2, received within a guide 12 in the body 4, is offset relative to the stir bar 14, which means that whilst the magnetic stir bar 14 is still induced to spin in accordance with the rotation of the magnetic field generated by the magnetic stirrer 2, the stir bar 14 is also pulled towards the magnetic stirrer 2 due to the magnetic attraction. As such, when the stir bar 14 is rotated at sufficiently high speeds, the stir bar 14 can be caused to jump around the reaction vessel 8 and to generate a vortex 16. In the manner described in the above parts of the application, sub-standard stirring and decoupling of the stir bar 14 from the magnetic stirrer 2 can therefore be caused.

For example, at low speeds, such as lower than 100 rpm, there may be hardly any stir bar decoupling problems. Depending upon the reagents and the set-up of the reaction station, there can be a speed of revolution of the stir bar where it stops following the rotating magnetic field and is considered decoupled. This is commonly at about 700 rpm using many reagents, but can vary depending on the set-up to be 500 rpm, or 800 rpm, or 900 rpm, or 1000 rpm. The specific speed at which decoupling occurs will be dependent upon the reagents, set-up of the machine, and size of the reaction vessels, for example.

As the viscosity of the reagents changes or on the formation of solid materials as the chemical reaction in the reaction vessel progresses, the critical speed at which the stir bar stops working properly can change, with variance in viscosity limiting the speed of the stir bar. This means that a stir bar might work well at the start of a reaction but later on in the reaction, for example after one or two hours, the stir bar might become decoupled and stop rotating and stirring effectively.

Decoupling of a stir bar can occur with or without the generation of a vortex, but it has been shown that a vortex, commonly induced at higher spin speeds, can have a detrimental effect on the coupling of stir bars, due to the pressure changes induced within the vortex.

The body 104 of Figure 1 is shown in cross-section in Figure 3. Embedded within the body 104 is a ferromagnetic locator 118, which is in the form of a steel disc. The ferromagnetic locator 118 is positioned centrally relative to the socket 106 that receives the reaction vessel 108. The position of the ferromagnetic locator 118 corresponds to the desired position of the stir bar 114 when in use within the reaction vessel 108. The ferromagnetic locator 118 acts to draw the stir bar 114 towards the centre of the socket 106, as shown in Figure 3, preventing or limiting unwanted movement of the stir bar 114 and straightening the vortex 116 caused at high spin speeds. This can help to prevent or limit decoupling of the stir bar 114 from the magnetic stirrer 102.

The presence of the ferromagnetic locator 118 perturbs the magnetic field produced by the magnetic stirrer 102 to cause the magnetic field to be focussed towards the ferromagnetic locator 118. The presence of the ferromagnetic locator 118 also causes the stir bar 114 to be attracted towards the position of the ferromagnetic locator 118. Hence, the stir bar is attracted to be central within the vessel. The magnetic interaction that holds the stir bar centrally in place in the vessel makes it far less likely that decoupling from the magnetic field of the magnetic stirrer 102 will occur, in use, compared to apparatus not including a ferromagnetic locator 118. Moreover, the operational speed range of the stir bar can be increased due to the more preferable position of the magnetic stirrer - central in the vessel - being maintained, unlike in the prior art devices.

Figures 4a and 4b show a second embodiment of a body 204 forming a socket 206, which is identical to the first embodiment apart from the following differences. The ferromagnetic locator 218 of the second embodiment is annular and includes an aperture 220 in its centre, which can be seen in the plan view of the ferromagnetic locator 218 in Figure 4a. The ferromagnetic locator 218 is, similarly to the first embodiment, embedded below the socket 206, and the aperture 220 of the ferromagnetic locator 218 is aligned with the centre of the socket 206.

By providing an aperture 220, the magnetic field in the vicinity of the ferromagnetic locater 218 is perturbed by the ferromagnetic locator 218 to provide a further advantageous shape that encourages the stir bar to remain central to the ferromagnetic locator 218, in use.

A third embodiment of a body 304 forming a socket 306 is shown in Figures 5a and 5b. In the third embodiment, a recess 322 has been provided in the body 304 defining the socket 306. The recess 322 has been created within the socket 306, for example by drilling or otherwise forming during the manufacturing process and the ferromagnetic locator 318 takes the form of a screw that is inserted into the recess 322. This method of production may be quicker and more cost-effective than the previous embodiments. It may also be beneficial that the ferromagnetic locator 318 of the third embodiment is thus positioned closer to a reaction vessel, in use. Figure 5a shows the screw in plan view, with the screw head 324 visible. The screw head may be covered over with a cap, for example an inert polymer coating or film, or a plate or plug above it, such that the surface on which the reaction vessel rests may still be inert and/or smooth. This material may be the same material as that forming the body, for example aluminium. This may have advantages for the heat transfer characteristics of the device.

In Figures 6a and 6b, a fourth embodiment of a body 404 forming a socket 406 is provided. This embodiment differs from the preceding embodiments in that the ferromagnetic locator 418 is formed as a ring and positioned within a recess in the surface of the socket 406. The ring can be seen in plan view in Figure 6a, including an aperture 420. The ring is affixed within the socket 406 by the use of an adhesive, although other bonding or mechanical fixation may be used in its place. The ferromagnetic locator 418 in the form of a ring is part of a part-spherical surface that is complimentary to the part-spherical surface of the base surface of the socket 406.

In both the second and fourth embodiments, the lack of ferromagnetic material, formed by the apertures 220, 420 in the centre of the ferromagnetic locators 218, 418 may help, in use, to centre the stir bar within the socket 206, 406, due to the shape of the magnetic field caused by the shape of the annular-shaped ferromagnetic locator in each case. This is discussed in more detail in relation to Figure 4.

A fifth embodiment of a body 504 forming a socket 506 is shown in Figure 7 and differs from the previous embodiments in that the socket 506 is located centrally with respect to the guide 512, which receives the magnetic stirrer, in use. The ferromagnetic locator 518 itself is the same as that provided in the first embodiment, and is provided in the same position relative to the socket 506. Whilst, in use, a stir bar used with this embodiment would therefore not be subjected to the same lateral magnetic force as the other embodiments, the ferromagnetic locator 518 still acts to locate the stir bar (not shown), for example preventing excess motion within the reaction vessel that may be caused by other factors. As can be seen, a single reaction vessel 508 is held within the socket 506, this reaction vessel 508 being held centrally relative to the body 504 and therefore also relative to a magnetic stirrer receivable within the guide 512, in use.

Also in Figure 7, it can be seen that the body 504 has been manufactured in two parts 504a, 504b. These parts 504a, 504b enable the ferromagnetic locator to be sandwiched between the parts 504a, 504b during the manufacturing process, the parts then being glued, adhered, welded, or otherwise fixed together. Manufacturing may therefore be simpler. The parts 504a, 504b may also be mechanically-fixed, such as by screwing, pinning, bolting, clipping, or any other means of mechanical fixation. Manufacturing the body in two parts in this way may also be applied to all other embodiments described, to effectively sandwich the ferromagnetic locator.

Figure 8 shows a sixth embodiment of a body 604 forming a socket 606. The socket 606 is shaped for the receipt of a reaction vessel 608 in the form of a test tube, which is shown in situ within the socket 606. A support 626 is also provided to provide additional stability to the test tube. The side walls of the socket 606 will also help to support the test tube laterally, in use. The test tube is located such that the bottom of the test tube will, in use, be positioned within the plane of a rotating magnetic field generated by the magnetic stirrer. Such positioning has been shown to maximise the effectiveness of the rotating magnetic field on a stir bar placed within the reaction vessel 608. The ferromagnetic locator 618 is positioned to assist with the location of the stir bar, and adapts the magnetic field in a way to ensure that the stir bar can spin at higher speeds without magnetically decoupling from the rotating magnetic field.

Whilst all embodiments shown thus far are shown with a socket 106, 206, 306, 406, 506, 606 as a reaction vessel receiver to locate a reaction vessel, other features to help align a reaction vessel in the device may be used in addition to or in place of a socket. These may include a frame, mounts, or physical support, or, for example, written or engraved indicia that indicate the correct positioning of a reaction vessel. Each of these, including a socket, may be considered to be a reaction vessel receiver.

Figure 9 shows a seventh embodiment of a body 704 forming a socket 706. The seventh embodiment is similar to the sixth embodiment except that the socket 706 and ferromagnetic locator 718 are located above and out of the plane of the magnetic stirrer and inside the periphery of the magnetic stirrer, in use, the magnetic stirrer being located within the guide 712. The reaction vessel is omitted from this view. By locating the socket 706 and ferromagnetic locator 718 out of plane, above the magnetic stirrer, the seventh embodiment allows multiple reaction vessels to be used with one magnetic stirrer, whilst the overall lateral extent of the body 704 can be limited, saving laboratory worktop space. For comparative purposes, a socket 706’ and a ferromagnetic locator 718’ that are outside the periphery of the magnetic stirrer are shown in dotted lines, highlighting the different offset provided by the seventh embodiment relative to the magnetic stirrer, in use.

The eighth embodiment of a body 804 defining a socket 806 shown in Figure 10 highlights another method of positioning a ferromagnetic locator 818 in the body 804. As shown, the ferromagnetic locator 818 is embedded in a recess 822 formed in a bottom surface 836 of the body 804. Hence, the upper surface 838 of the socket 806 remains untouched and therefore may be prevented from any damage during manufacture that could be detrimental to the receipt of reaction vessels.

As well as being provided as a ferromagnetic screw, it is possible to provide the ferromagnetic locator within a recess in other forms. Two such forms are shown in Figures Ila and 11b. In Figure Ila, a ferromagnetic locator 918 is provided as a ferromagnetic plug 940 which can be placed within a recess and capped by the screw 942, which may or may not be ferromagnetic itself. The plug 940 may be formed as part of the screw 942 or separately from the screw 942. In Figure 1 lb, a ferromagnetic plug 1040 is provided on the end of a screw 1042, the plug 1040 being seated around a boss 1044 on the end of the screw 1042. Hence, the screw 1042 and plug 1040 can be provided as a one-part ferromagnetic locator 1018, easing the assembly process. Of course, various other solutions to the provision of the ferromagnetic locator may be provided or will be obvious to the skilled person when taking into account the teaching of the present application. Although it is shown capped, it is also possible to provide the recess without being capped, leaving a small imperfection in the surface of the socket. Depending on the design of the recess, this may have limited or no effect on the use of the device.

Figure 12 shows another variation of the manufacturing process, whereby the ferromagnetic locator 1118, which in the depicted embodiment is provided as a ring, is positioned within an annular recess 1122 provided in the upper surface 1138 of the socket. The recess 1122 may then be filled with a filler 1146, for example a polymer filler, in order to provide a contiguous surface of the socket 1106. Of course, although the depicted embodiment shows the ring being provided in a recess 1122 in the upper surface 1138, the recess may instead be provided in another surface of the body 1104. Although described as a ring or annulus, a ferromagnetic locator described as such could also be provided in the form of a coiled wire or other substantially ring-shaped or annular body.

Figure 13b shows a variation of the device shown in Figure 10. In Figure 13, the body 1204 includes a plurality of ferromagnetic screws 1242, in this case eight screws 1242, forming, cumulatively, the ferromagnetic locator 1218. Thus, a substantially annular ferromagnetic locator 1218 is formed from simple components. Each screw 1242 forming the ferromagnetic locator 1218 is inserted from the bottom surface 1236 of the body 1204, leaving the socket 1206 unaltered. Figure 13a shows the layout of the ferromagnetic locator 1218 in plan view.

Figure 14 shows a variation of the device shown in Figure 12. Rather than providing an annular recess, a notch 1348 is provided in the upper surface 1338 of the socket 1306 in the body 1304. A ferromagnetic locator 1318 can then be inserted into the notch 1348. In order to do so, the ferromagnetic locator 1318 is formed as a split ring in the present embodiment. Hence, the split ring can be compressed for insertion into the notch 1348 at which point it expands to fit within the notch 1348. As will be obvious to the skilled person, this will leave a small gap in the ferromagnetic locator 1318 where the split ring is split, but this will have a minimal effect on the operation of the device.

Figures 15 to 17 are flow charts of the various methods that are described above. A summary can therefore be provided and depicted by the flow charts.

Figure 15 depicts a method of manufacturing a device for improving magnetic stirring of the contents of a reaction vessel. A recess is created in a predetermined position within a reaction vessel receiver, such as a socket, in step SI. The recess may be created in an upper surface or a lower surface of the body defining the reaction vessel receiver and the ferromagnetic locator may be positioned at or adjacent to an end of the recess that is itself at or adjacent to the upper surface of the body.

In step S2, a ferromagnetic locator is provided in a predetermined position relative to a reaction vessel receiver, the ferromagnetic locator being configured to locate, in use, a stir bar relative to a reaction vessel receiver. In the depicted method, the ferromagnetic locator may be placed in the recess created in step SI.

Step S3 included the fixation of the ferromagnetic locator. In the depicted embodiment, the ferromagnetic locator may be affixed using glue or another chemical adherent, or by capping the recess as described in the above embodiments.

Figure 16 shows a method of reducing erratic movement of a magnetic stir bar in a reaction vessel associated with a magnetic stirrer. In step S4, a stir bar is provided in a reaction vessel. In step S5, a ferromagnetic locator is used, disposed adjacent to the reaction vessel, to influence the magnetic forces on the stir bar to hold it in a more controlled position that it would otherwise be held.

In Figure 17, a process for creating a chemical product is shown. In step S6, the reagents for the chemical process are provided in a reaction vessel. A magnetic stirrer is then provided in step S7, which is then used to stir the reagents in step S8. In step S9, the chemical product is formed.

Except where specifically stated or necessarily required, all features described in relation to one embodiment may be provided in conjunction with any other features of another embodiment.

Claims (25)

1. A device for improving magnetic stirring of the contents of a reaction vessel, the device comprising:

a reaction vessel receiver for holding a reaction vessel in a position whereby the reaction vessel is effectively located for stirring with respect to a magnetic field produced by a laboratory magnetic stirrer; and a ferromagnetic locator configured to, in use, magnetically locate a magnetic stir bar within the reaction vessel held by the reaction vessel receiver, the ferromagnetic locator being in a predetermined position relative to the reaction vessel receiver.

2. A device according to claim 1, wherein the ferromagnetic locator is disposed adjacent to the reaction vessel receiver.

3. A device according to claim 1 or claim 2, wherein the ferromagnetic locator is configured to magnetically locate the magnetic stir bar by virtue of magnetic forces between the stir bar and the ferromagnetic locator.

4. A device according to any preceding claim, further comprising a body that defines the reaction vessel receiver, the body being non-ferromagnetic or substantially non-ferromagnetic.

5. A device according to claim 4, wherein the body comprises a plurality of reaction vessel receivers and a plurality of ferromagnetic locators, each ferromagnetic locator being associated with a respective reaction vessel receiver.

6. A device according to claim 4 or claim 5, wherein the body is circular or substantially circular.

7. A device according to any of claims 4 to 6, wherein the plurality of reaction vessel receivers are unitarily-formed, for example as a single block.

8. A device according to any of claims 4 to 7, wherein the body incorporates a guide for ensuring that the device is effectively positioned with respect to the magnetic field generated by the laboratory magnetic stirrer, in use, the guide preferably being configured to receive a part of a laboratory magnetic stirrer.

9. A device according to any preceding claim, wherein the ferromagnetic locator is embedded within the reaction vessel receiver.

10. A device according to any preceding claim, wherein the ferromagnetic locator is located in a recess in the reaction vessel receiver.

11. A device according to any preceding claim, wherein the ferromagnetic locator is located on or adjacent to a surface of the reaction vessel receiver.

12. A device according to claim 11, wherein the ferromagnetic locator is bonded to the surface of the reaction vessel receiver, such as by chemical bonding.

13. A device according to claim 11 or claim 12, wherein the ferromagnetic locator is affixed to the reaction vessel receiver, such as by a mechanical fastener.

14. A device according to any preceding claim, wherein the ferromagnetic locator comprises a plug, screw, or washer.

15. A device according to any preceding claim, wherein the ferromagnetic locator includes an area having less or no ferromagnetic material.

16. A device according to claim 15, wherein the area is formed as a recess, area of reduced thickness, or aperture, in the ferromagnetic locator.

17. A device according to claim 15 or claim 16, wherein the area of reduced magnetism is central or substantially central to the ferromagnetic locator.

18. A device according to any preceding claim, wherein the ferromagnetic locator is a temporary magnet.

19. A device according to any preceding claim, wherein the reaction vessel receiver comprises a socket configured to securely accommodate a reaction vessel.

20. A device according to any preceding claim, wherein the reaction vessel receiver is made of heat-conducting material and/or a chemically-resistant material.

21. A reaction station comprising:

a magnetic stirrer; and a device according to any preceding claim.

22. A process for creating a chemical product, the process comprising the steps of: providing reagents within a reaction vessel;

providing a magnetic stirrer provided with a device in accordance with any of claims 1 to 20; and stirring the reagents using the magnetic stirrer and reacting the reagents to form a chemical product.

23. A method of manufacturing a device for improving magnetic stirring of the contents of a reaction vessel, the method comprising the steps of:

affixing a ferromagnetic locator in a predetermined position relative to a reaction vessel receiver, the ferromagnetic locator being configured to locate, in use, a magnetic stir bar relative to a reaction vessel received by the reaction vessel receiver.

24. A method according to claim 23, wherein a recess is created in a predetermined position within the reaction vessel receiver, for example by being drilled, and the ferromagnetic locator is introduced into the recess, the ferromagnetic locator optionally being provided as a part of, or being held in place with, a screw.

25. A method of reducing erratic movement of a magnetic stir bar in a reaction vessel associated with a magnetic stirrer, the method comprising:

using a ferromagnetic locator disposed adjacent the reaction vessel to influence magnetic forces on the stir bar to hold the stir bar in a more controlled position than it would otherwise be held in the absence of the ferromagnetic locator.