CA1109693A - Method and apparatus for mixing in laboratories - Google Patents
Method and apparatus for mixing in laboratoriesInfo
- Publication number
- CA1109693A CA1109693A CA288,522A CA288522A CA1109693A CA 1109693 A CA1109693 A CA 1109693A CA 288522 A CA288522 A CA 288522A CA 1109693 A CA1109693 A CA 1109693A
- Authority
- CA
- Canada
- Prior art keywords
- syringe
- mixing
- dilution
- piston
- apertures
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
- C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
- C12M33/00—Means for introduction, transport, positioning, extraction, harvesting, peeling or sampling of biological material in or from the apparatus
- C12M33/04—Means for introduction, transport, positioning, extraction, harvesting, peeling or sampling of biological material in or from the apparatus by injection or suction, e.g. using pipettes, syringes, needles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F33/00—Other mixers; Mixing plants; Combinations of mixers
- B01F33/50—Movable or transportable mixing devices or plants
Abstract
ABSTRACT OF THE DISCLOSURE
An apparatus and its use in laboratory mixing and testing procedures is disclosed, which apparatus contains a test chamber in the form of a syringe but provided with two separate openings both ending directly in the syringe interior. Less contamination risks and simplified handling are obtained with the two openings, especially in serial dilution of test samples if one opening is connected to the dilution media and intended only for this liquid while the other opening is intended for ejection of mixture. With nonreturn valves on the openings, adapted for flow in different directions, only reciprocating movements with the piston are necessary to obtain serial dilution. The syringe body is preferably flat in order to improve mixing and examination of the con-tent. The apparatus is chiefly intended for microbiological test procedures in which application the cultivation and the examination of colonies can be conducted directly in the syringe.
An apparatus and its use in laboratory mixing and testing procedures is disclosed, which apparatus contains a test chamber in the form of a syringe but provided with two separate openings both ending directly in the syringe interior. Less contamination risks and simplified handling are obtained with the two openings, especially in serial dilution of test samples if one opening is connected to the dilution media and intended only for this liquid while the other opening is intended for ejection of mixture. With nonreturn valves on the openings, adapted for flow in different directions, only reciprocating movements with the piston are necessary to obtain serial dilution. The syringe body is preferably flat in order to improve mixing and examination of the con-tent. The apparatus is chiefly intended for microbiological test procedures in which application the cultivation and the examination of colonies can be conducted directly in the syringe.
Description
`` ll~S6~3 This invention relates to a method and an apparatus for mixing of liquids, especially in laboratories for serial dilutions of microbiological sam~les.
Mixing and dilution of liquids belong to the routine work in most chemical and microbiological laboratories. A large number of such working moments are especially carried out in test laboratories and often in a similar and standardized way. For example, a microbiological sample is often analysed in respect of several different microorganisms, several nutrients, and aerobically as well as anaerobically. It is also typical of microbiologi-cal analyses that test cultivation is carried out at a number of different dilution degrees of the sample to obtain at some dilution of the unknown sample a suitable concentration for quantitative determination of the number of cultures arisen or to establish the presence or absence of growth. In these cases the sample is repeatedly subjected to serial dilution with a nutrient or another diluent for a series of samples with decreasing concen-tration, e.g. with tenfold dilution between each test.
The more the extent of routine testing of this kind increases, the greater the need of mixing, dilution and analysis methods will be that are rationalJ require not much equipment and can be carried out by relatively untrained personnel with little risk arising due to uncontrolled contact with dangerous chemicals or organisms and without increasing risks of erroneous analysis results.
A usual procedure of carrying out a microbiological analysis has previously been to add to a test dish a measured amount of samples by means of a pipette, to add to the dish a measured amount of culture medium, manually stirring the mixture and then to incubate the sample and to examine it in respect of growth.
This procedure involves several disadvantages. The method is time-consuming due to the great number of steps involved relatively numerous pieces of equipment are required for preparation of each sample, which is ., - 1-11~96~3 expensive both in view of procuring and cleaning, involves a need of training and a risk of confusion. The whole procedure takes place quite openly, which means risks of exposure to the personnel and risks of contamination of the samples. In anaerobic cultivation additional moments are added to prevent air admission. The handling steps take place independently of each otherJ
which results in that some steps, even the important mixing, can be forgotten or be carried out insufficiently at a high working pace.
In the Swedish patent specification 377,811 it is suggested that mixing is to be carried out in a syringe in such a way that liquid containing a sample and a diluent or nutrient respectively are sucked each by themselves into the syringe and mixed there with each other. This is a considerable simplification of previous technique, especially as cultivation and examina-tion can also be made in the syringe. As the diluent is normally the major liquid amount it is most advantageous, from a mixing point of view first to suck in the sample and then the dilution liquid. When doing this the tip of the syringe must be moved from the vessel containing the sample to a vessel or a hose containing the dilution liquid, and then it cannot be avoided that the kit containing the diluent is contaminated with sample, analysis errors being risked in a subsequent test where the same diluent is utili~ed. Of course the problems can be avoided if the tip is cleaned between the different stages or special intermediate pieces are used between syringe tip and the liquids, which are disposed of after use. However, these procedures compli-cate the mixing process to a large extent, as they must be performed after each moment. Another disadvantage is that the normally placed spout sometimes does not meet the highest demands on mixing effect as minor ranges of rather stationary liquid can form during the suction moments, which results in dilution errors. In serial dilution this method also provides an unnecessary number of handling steps.
It has been suggested that in mixing by means of a syringe the tip thereof is provided with a three-way valve, to which a hose with dilution
Mixing and dilution of liquids belong to the routine work in most chemical and microbiological laboratories. A large number of such working moments are especially carried out in test laboratories and often in a similar and standardized way. For example, a microbiological sample is often analysed in respect of several different microorganisms, several nutrients, and aerobically as well as anaerobically. It is also typical of microbiologi-cal analyses that test cultivation is carried out at a number of different dilution degrees of the sample to obtain at some dilution of the unknown sample a suitable concentration for quantitative determination of the number of cultures arisen or to establish the presence or absence of growth. In these cases the sample is repeatedly subjected to serial dilution with a nutrient or another diluent for a series of samples with decreasing concen-tration, e.g. with tenfold dilution between each test.
The more the extent of routine testing of this kind increases, the greater the need of mixing, dilution and analysis methods will be that are rationalJ require not much equipment and can be carried out by relatively untrained personnel with little risk arising due to uncontrolled contact with dangerous chemicals or organisms and without increasing risks of erroneous analysis results.
A usual procedure of carrying out a microbiological analysis has previously been to add to a test dish a measured amount of samples by means of a pipette, to add to the dish a measured amount of culture medium, manually stirring the mixture and then to incubate the sample and to examine it in respect of growth.
This procedure involves several disadvantages. The method is time-consuming due to the great number of steps involved relatively numerous pieces of equipment are required for preparation of each sample, which is ., - 1-11~96~3 expensive both in view of procuring and cleaning, involves a need of training and a risk of confusion. The whole procedure takes place quite openly, which means risks of exposure to the personnel and risks of contamination of the samples. In anaerobic cultivation additional moments are added to prevent air admission. The handling steps take place independently of each otherJ
which results in that some steps, even the important mixing, can be forgotten or be carried out insufficiently at a high working pace.
In the Swedish patent specification 377,811 it is suggested that mixing is to be carried out in a syringe in such a way that liquid containing a sample and a diluent or nutrient respectively are sucked each by themselves into the syringe and mixed there with each other. This is a considerable simplification of previous technique, especially as cultivation and examina-tion can also be made in the syringe. As the diluent is normally the major liquid amount it is most advantageous, from a mixing point of view first to suck in the sample and then the dilution liquid. When doing this the tip of the syringe must be moved from the vessel containing the sample to a vessel or a hose containing the dilution liquid, and then it cannot be avoided that the kit containing the diluent is contaminated with sample, analysis errors being risked in a subsequent test where the same diluent is utili~ed. Of course the problems can be avoided if the tip is cleaned between the different stages or special intermediate pieces are used between syringe tip and the liquids, which are disposed of after use. However, these procedures compli-cate the mixing process to a large extent, as they must be performed after each moment. Another disadvantage is that the normally placed spout sometimes does not meet the highest demands on mixing effect as minor ranges of rather stationary liquid can form during the suction moments, which results in dilution errors. In serial dilution this method also provides an unnecessary number of handling steps.
It has been suggested that in mixing by means of a syringe the tip thereof is provided with a three-way valve, to which a hose with dilution
- 2 -" 11()~6~!~
liquid can also be connected while the third aperture is intended as outlet of the finished mixture. A device for a very simple serial dilution of samples is obtained because the three-way valve is provided with suitable non-return valves in such a way that diluent flows into the syringe at suction with the syringe while the outlet aperture is closed whereas the outlet to-wards the diluent supply is closed at ejection of the finished mixture while the outlet is opened. A serial dilution of the concentration ratio of 1:10 and the sample amount 9 ml can e.g. be made so that 1 ml of sample is intro-duced into the syringe, after which the three-way valve is applied. By with-drawing the piston 9 ml of diluent will flow into the syringe, a dilution of 1:10 of the sample being obtained. By an inward movement of the piston 9 ml of this mixture can be sprayed out through the valve and be supplied to a test dish or another vessel. In the syringe l ml of the diluted sample will then remain, to which at a repeated extraction of the piston 9 ml diluent are supplied until a mixture of the concentration 1:100 is obtained, of which 9 ml can be sprayed into a test dish by means of an inward movement of the piston in the same wa~ as before. An arbitrary number of dilutions can be obtained with a concentration decreasing with the factor 1:10 only by means of recip-rocating movements of the piston. However, this method does not solve the problem with contamination of the dilution means unless the three-way valve is replaced when continuing with the next sample. Nor is the mixing effect in the syringe improved but the dilution errors have rather a tendency to increase because ranges with stationary liquid will also arise in the three-way valve. The 10w space in the three-way valve restricted by the main volume of the syringe and the non-return valves on the three-way valve is moreover not subjected to the mixing in the syringe, which adds another dilution error to this procedure. That is to say the space in the three-way valve closest to the syringe forms a channel common for both the liquids to be sucked into the syringe, and hence this space will be filled with a volume of the liquid last sucked into the syringe, which volume will add to the ~l~S6~3 mixture when this is ejected. After ejection of the mixture, the same volume of the three-way valve will be filled with the mixture, which will add to the liquid next sucked into the syringe. Both additions cause measuring faults.
According to the invention there is provided an apparatus for laboratory mixing of two liquids comprising a mixing chamber designed as a syringe, with a syringe body, a front wall, a rear opening, a piston extending through the rear opening and on the front wall two apertures, separated from each other and each connecting the interior of the chamber with the exterior of the chamber, characterized in that the mixing chamber is flat with two substantially parallel walls.
Preferably at least one aperture may be provided with a station-ary or detachable non-return valve and conveniently both aper-tures may be provided with non-return valves, which non-return valves may be arranged for flow in opposite directions.
According to a feature of the invention the syringe body may be provided with means for limiting the movement of the piston between predetermined volume values.
By the arrangement of a separate aperture for one liquid the connection means thereof can be kept practically com-pletely free from contamination with the other liquid or the mixture. This means that the connection means of the mentioned one liquid can be detached from the syringe and attached to another syringe to which the same mentioned one liquid is to be added without any cleaning operation or another measure being necessary to secure the purity of the liquid and to avoid analy-sis errors due to this. This is of course a great advantage e.g. when the same liquid is used as diluent Eor a great number of samples or for many different types of analysis, such as dis-tilled water at chemical analysis, or culture medium at microb-.,~ ~ , . , ;
6~3 iological analysis.
As is preferred, arranging two apertures separated from each other on the syringe at least one aperture will always be displaced from the middle of the syringe front towards the edge of the syringe envelope. This will cause a circulation flow in the main volume of the syringe at suction as well as ejection, which considerably improves mixing in the syringe and reduces the risks of stationary liquid volumes in the same.
Both apertures ~10~6~3 are pxeferably placed eccentrically relatiYe to the centre of the syringe front and as close to the edge and as far from each other as possible. This improved mixing is an advantage as no additional mixing in this way is requlred. It will also be impossible in this manner to forget the mixing as it is carried out as a direct consequence of the necessary suction and ejection operations.
By arranging separate apertures no ranges in the syringe tip with countercurrent flow will arise, where the mixing effects cannot be anticipated and are subjected to random variations.
Nor to any great volumes, which are not subjected to the mixing in the main volume of the syringe and where ranges of stationary liquid may result, arise as at three-way valves. The improvements in these respects contribute to reduced dilution and mixing errors.
The arrangement of two separate apertures for different purposes provides the possibility of designing these in a different way without respect tocompromisesin order that they should fulfil their different functions better. To minimize the risks of contamination the suction nozzle may e.g. be designed with such a length or cross-section that the mixing in the main body of the syringe does not involve the liquid contents in the outer portion of the aperture, to which the supply means for the dilution liquid is connected. In contrast to this the outlet aperture can be formed so that as great a portion as possible of its volume is comprised by the mixing in the main volume of the dilution chamber. This possibility of selective design of the apertures is not available in syringes with only one aperture that has to serve several purposes.
Even if these advantages are obtained in mixing on a ll~g6~3 laboratory scale ~t Is prefexred that the invention is utilized for analyses includin~ m~crobiolo~lcal culti~ation stages. At such analyses organisms dan~erous to the health are often handled, and the closed mixing procedure in a mixing vessel formed as a syringe as well as the slight risk of contamination will here bring special advantages of security. It is a specific problem when analysing living organisms that their number is increased under suitable conditions, and therefore the risk of a non-desired contamination may increase by time and a contamination unimportant per se of e.g. a nutrient solution over a night or a week-end may turn into a serious contamination. The reduced contamination risks of the invention will thus provide special advantages here.
It is also preferred that the invention be utilized in serial dilutions. As two apertures are present each with their function, no shifting or transfer of various vessels will be required between each dilution moment, which b~ings especially great advantages at a great number of dilutions with the same starting liquids.
As has been indicated, it is further preferred that the device be given a non-circular cross-section with two substant- ~ ~-ially parallel walls. With a syringe of a flat design the apertures can be arranged further away from each other and from the centre of the syringe front than what is possible at a circular syringe with a corresponding volume, which improves the circulating mixture described above in the syringe. Mixing will also be improved because the syringe form in this case is better adapted to the form of the circulation flow arisen, whereas in a syringe of a circular cross-section zones of relatively stationary liquid may arise more easily in the spaces existing " 11~9~3 here above and below the level of the ci~culation flow. The flat syringe wtll also make it easier to o~serve the contents of the syringe without the distortions of the picture arising when looking through heavily curved surfaces. The flat syringe form with two apertures is especially preferred for micro-biological analyses due to the possibility of a direct examin-ation of a cultivation result in the syringe. Moreover, its good mixing effect in this connection is especially important as the only mixing obtained in such a syringe culturing is at the suction of the dilution liquid, whereas in other mixing situations ejection and possible collection of the mixture in a vessel also contribute to the mixing effect.
Again, another preferred embodiment of the device is characterized in that at least one aperture is provided with a stationary or detachable non-return valve. Both apertures are preferably provided with non-return valves, which are then mounted for flow in different directions through the two apertures. This design will simplify the mixing procedure in about the same way as the use of the three-way valve described above, however without the same disadvantages. Thanks to the non-return valves the liquids will always flow in a correct direction without any closing measure or the like being necessary after the initial changing of the syringe. Therefore the embodiment is especially suitable at serial dilution, as only reciprocating movements of the piston are required for the number of times corresponding to the desired t ~` - 7a -,~ .
6~3 number of dilutions of the sample. If only one of the apertures is equipped with a non-return valve, the simplification is only gained at this aperture whereas the other aperture must be closed when no flow is desired through it.
Closing can be carried out for example by flattening a supply or spray hose, by a special stop valve or by application of a plug over the aperture.
The following is a description by way of example of an embodiment of the present invention with reference to the drawings which show a syringe with a flattened cross-section, as seen from above, in figure 1 and in a front view in figure 2.
The dilution chamber designed as a syringe consists of a syringe body 1 of a substantially rectangular cross-section, the biggest walls of which are parallel to each other. 2 is a piston with sealing against the inside of the syringe body 1 and a handle in conventional manner, however with its forms adapted to the rectangular cross-section of the syringe body 1.
The front wall of the chamber is provided with two apertures 3 in the form of spouts, which are placed close to the sides of the syringe body 1 located ,- -~urthest away from each other. According to the above one or two non-return valves can be mounted on the spouts 3 of the apertures in a detachable manner, and at two non-return valves so that they permit a flow in different direction through the two apertures 3. In order to simplify the determination of the sucked and ejected amounts at serial dilutions the syringe can be provided with means limiting the motion of the piston 2. In the figure such a form of limiting means is shown consisting of a clamp shown above the syringe in .
figure 1 that can be attached over the syringe body 1 and is provided with a stop means in the form of a pin intended to be inserted into a hole through the syringe body 1 so that it penetrates the cross-section of the syringe body a little and ends between two ribs located on the piston, which ribs are arranged in right angle to the movement direction of the piston~ In this way the movements of the piston are limited so that the syringe can only contain a volume in a preselected range, e~g. 1 - 10 ml. ~hus reading of the volume `-` 11096~3 need not be carried out at serial dilution, but the piston is alternatingly brought to the one or the other of the two end positions.
As mentioned above a flattened-out cross-section form of the syringe body is preferred to facilitate the examin-ation of the contents of the chamber, preferably with two sub-stantially parallel sides. If the chamber is to be used for cultivation and examination, the height of the cross-section should not exceed 20 mm and should preferably be 5 - 12 mm.
The greatest length of the section can vary within a wide range.
Usually it is within the range 20 - 70 mm, preferably 25 - 50 mm. Preferably the greatest length is more than twice the length of the shortest dimension. If examination is not impor-tant the measures can of course be selected in another way. The syringe body is preferably made from a transparent material, such as glass or a transparent plastic, e.g. polystyrene plastic, and can in that case be prepared by means of injection moulding.
The design of the piston 2 is not critical. However, its front portion must seal against the inside of the syringe body 1 and be made from a material capable of withstanding the treated liquids. The form is preferably adapted to the front wall of the syringe and can be provided with protrusions dimen-sioned and shaped to completely enter and fill the spouts 3 of the apertures when the piston is completely pushed in. It can also be provided with recesses to form an air-cushion for aero-bic cultivation tests or be designed for modification of the flow -;
in the chamber in order to obtain the best mixing effect. That is to say the front of the piston can be provided with a groove or notch, so that with the piston fully advanced and before suction of liquid into the syringe, this contains air suitable for aerobic cultivation. Alternatively, the front of the piston e~ 9 11()~6~!3 can be provided with tracks or guiding means for causing tur-bulence or additional circulation movements to the liquid stream coming into the syringe during suction.
The apertures 3 are preferably placed as far from ~ :
each other as is - 9a :, ll~S6~3 practically possible, but other positions are also possible which need not be symmetrical. According to the invention two apertures must be present, but of course more apertures for special purposes are not excluded, e.g. when mixing more liquids than two. As indicated above the design of the apertures can vary and they can possibly be different. They are conveniently made so that hoses, nozzles or the like can be easily attached to the aperture, e.g.
as spouts integral with the syringe body 1.
The non-return valves can be formed as a part of the syringe or be detachably fastened to the apertures as a special unit or as a part of an inlet or outlet hose.
A method of using the device according to the figure will be described. 1 ml of a sample containing microorganisms is sucked into the device through one aperture. This aperture is then provided with a non-return valve only permitting outflow. The other aperture is provided with a non-return valve only permitting inflow and with a supply hose for culture medium.
The piston is moved back so far that 9 ml culture medium enter and are mixed with the sample. The piston is thereafter moved forwards so that 9 ml mixture flow out through the outlet aperture and are supplied to a collecting vessel, while 1 ml of the mixture remains in the syringe. The piston is now moved back again and forwards once more, whereby two dilution degrees, 1/10 and 1/100, have been obtained. The procedure is repeated until a desired number of dilutions has been obtained, the last dilution, however, not being ejected but left in the device and subjected to incubation and examination of the cultivation result. The other dilution degrees of the sample can be incubated in their collecting vessels or rather be supplied to a syringe according to the invention or a syringe according ~o the Swedish patent specification 377,811 with only one spout and there be subjectcd to cultivation and examina-tion. ~hen ejecting the mixtures according to the above they can be directly supplied to such another syringe via a connection without first being sup-plied to a collecting vessel.
- 10 `
``" 11096~3 Of course the invention is not limited to the embodiments shown above but can be varied in several manners within the scope of the following claims.
~ 11 ,~
liquid can also be connected while the third aperture is intended as outlet of the finished mixture. A device for a very simple serial dilution of samples is obtained because the three-way valve is provided with suitable non-return valves in such a way that diluent flows into the syringe at suction with the syringe while the outlet aperture is closed whereas the outlet to-wards the diluent supply is closed at ejection of the finished mixture while the outlet is opened. A serial dilution of the concentration ratio of 1:10 and the sample amount 9 ml can e.g. be made so that 1 ml of sample is intro-duced into the syringe, after which the three-way valve is applied. By with-drawing the piston 9 ml of diluent will flow into the syringe, a dilution of 1:10 of the sample being obtained. By an inward movement of the piston 9 ml of this mixture can be sprayed out through the valve and be supplied to a test dish or another vessel. In the syringe l ml of the diluted sample will then remain, to which at a repeated extraction of the piston 9 ml diluent are supplied until a mixture of the concentration 1:100 is obtained, of which 9 ml can be sprayed into a test dish by means of an inward movement of the piston in the same wa~ as before. An arbitrary number of dilutions can be obtained with a concentration decreasing with the factor 1:10 only by means of recip-rocating movements of the piston. However, this method does not solve the problem with contamination of the dilution means unless the three-way valve is replaced when continuing with the next sample. Nor is the mixing effect in the syringe improved but the dilution errors have rather a tendency to increase because ranges with stationary liquid will also arise in the three-way valve. The 10w space in the three-way valve restricted by the main volume of the syringe and the non-return valves on the three-way valve is moreover not subjected to the mixing in the syringe, which adds another dilution error to this procedure. That is to say the space in the three-way valve closest to the syringe forms a channel common for both the liquids to be sucked into the syringe, and hence this space will be filled with a volume of the liquid last sucked into the syringe, which volume will add to the ~l~S6~3 mixture when this is ejected. After ejection of the mixture, the same volume of the three-way valve will be filled with the mixture, which will add to the liquid next sucked into the syringe. Both additions cause measuring faults.
According to the invention there is provided an apparatus for laboratory mixing of two liquids comprising a mixing chamber designed as a syringe, with a syringe body, a front wall, a rear opening, a piston extending through the rear opening and on the front wall two apertures, separated from each other and each connecting the interior of the chamber with the exterior of the chamber, characterized in that the mixing chamber is flat with two substantially parallel walls.
Preferably at least one aperture may be provided with a station-ary or detachable non-return valve and conveniently both aper-tures may be provided with non-return valves, which non-return valves may be arranged for flow in opposite directions.
According to a feature of the invention the syringe body may be provided with means for limiting the movement of the piston between predetermined volume values.
By the arrangement of a separate aperture for one liquid the connection means thereof can be kept practically com-pletely free from contamination with the other liquid or the mixture. This means that the connection means of the mentioned one liquid can be detached from the syringe and attached to another syringe to which the same mentioned one liquid is to be added without any cleaning operation or another measure being necessary to secure the purity of the liquid and to avoid analy-sis errors due to this. This is of course a great advantage e.g. when the same liquid is used as diluent Eor a great number of samples or for many different types of analysis, such as dis-tilled water at chemical analysis, or culture medium at microb-.,~ ~ , . , ;
6~3 iological analysis.
As is preferred, arranging two apertures separated from each other on the syringe at least one aperture will always be displaced from the middle of the syringe front towards the edge of the syringe envelope. This will cause a circulation flow in the main volume of the syringe at suction as well as ejection, which considerably improves mixing in the syringe and reduces the risks of stationary liquid volumes in the same.
Both apertures ~10~6~3 are pxeferably placed eccentrically relatiYe to the centre of the syringe front and as close to the edge and as far from each other as possible. This improved mixing is an advantage as no additional mixing in this way is requlred. It will also be impossible in this manner to forget the mixing as it is carried out as a direct consequence of the necessary suction and ejection operations.
By arranging separate apertures no ranges in the syringe tip with countercurrent flow will arise, where the mixing effects cannot be anticipated and are subjected to random variations.
Nor to any great volumes, which are not subjected to the mixing in the main volume of the syringe and where ranges of stationary liquid may result, arise as at three-way valves. The improvements in these respects contribute to reduced dilution and mixing errors.
The arrangement of two separate apertures for different purposes provides the possibility of designing these in a different way without respect tocompromisesin order that they should fulfil their different functions better. To minimize the risks of contamination the suction nozzle may e.g. be designed with such a length or cross-section that the mixing in the main body of the syringe does not involve the liquid contents in the outer portion of the aperture, to which the supply means for the dilution liquid is connected. In contrast to this the outlet aperture can be formed so that as great a portion as possible of its volume is comprised by the mixing in the main volume of the dilution chamber. This possibility of selective design of the apertures is not available in syringes with only one aperture that has to serve several purposes.
Even if these advantages are obtained in mixing on a ll~g6~3 laboratory scale ~t Is prefexred that the invention is utilized for analyses includin~ m~crobiolo~lcal culti~ation stages. At such analyses organisms dan~erous to the health are often handled, and the closed mixing procedure in a mixing vessel formed as a syringe as well as the slight risk of contamination will here bring special advantages of security. It is a specific problem when analysing living organisms that their number is increased under suitable conditions, and therefore the risk of a non-desired contamination may increase by time and a contamination unimportant per se of e.g. a nutrient solution over a night or a week-end may turn into a serious contamination. The reduced contamination risks of the invention will thus provide special advantages here.
It is also preferred that the invention be utilized in serial dilutions. As two apertures are present each with their function, no shifting or transfer of various vessels will be required between each dilution moment, which b~ings especially great advantages at a great number of dilutions with the same starting liquids.
As has been indicated, it is further preferred that the device be given a non-circular cross-section with two substant- ~ ~-ially parallel walls. With a syringe of a flat design the apertures can be arranged further away from each other and from the centre of the syringe front than what is possible at a circular syringe with a corresponding volume, which improves the circulating mixture described above in the syringe. Mixing will also be improved because the syringe form in this case is better adapted to the form of the circulation flow arisen, whereas in a syringe of a circular cross-section zones of relatively stationary liquid may arise more easily in the spaces existing " 11~9~3 here above and below the level of the ci~culation flow. The flat syringe wtll also make it easier to o~serve the contents of the syringe without the distortions of the picture arising when looking through heavily curved surfaces. The flat syringe form with two apertures is especially preferred for micro-biological analyses due to the possibility of a direct examin-ation of a cultivation result in the syringe. Moreover, its good mixing effect in this connection is especially important as the only mixing obtained in such a syringe culturing is at the suction of the dilution liquid, whereas in other mixing situations ejection and possible collection of the mixture in a vessel also contribute to the mixing effect.
Again, another preferred embodiment of the device is characterized in that at least one aperture is provided with a stationary or detachable non-return valve. Both apertures are preferably provided with non-return valves, which are then mounted for flow in different directions through the two apertures. This design will simplify the mixing procedure in about the same way as the use of the three-way valve described above, however without the same disadvantages. Thanks to the non-return valves the liquids will always flow in a correct direction without any closing measure or the like being necessary after the initial changing of the syringe. Therefore the embodiment is especially suitable at serial dilution, as only reciprocating movements of the piston are required for the number of times corresponding to the desired t ~` - 7a -,~ .
6~3 number of dilutions of the sample. If only one of the apertures is equipped with a non-return valve, the simplification is only gained at this aperture whereas the other aperture must be closed when no flow is desired through it.
Closing can be carried out for example by flattening a supply or spray hose, by a special stop valve or by application of a plug over the aperture.
The following is a description by way of example of an embodiment of the present invention with reference to the drawings which show a syringe with a flattened cross-section, as seen from above, in figure 1 and in a front view in figure 2.
The dilution chamber designed as a syringe consists of a syringe body 1 of a substantially rectangular cross-section, the biggest walls of which are parallel to each other. 2 is a piston with sealing against the inside of the syringe body 1 and a handle in conventional manner, however with its forms adapted to the rectangular cross-section of the syringe body 1.
The front wall of the chamber is provided with two apertures 3 in the form of spouts, which are placed close to the sides of the syringe body 1 located ,- -~urthest away from each other. According to the above one or two non-return valves can be mounted on the spouts 3 of the apertures in a detachable manner, and at two non-return valves so that they permit a flow in different direction through the two apertures 3. In order to simplify the determination of the sucked and ejected amounts at serial dilutions the syringe can be provided with means limiting the motion of the piston 2. In the figure such a form of limiting means is shown consisting of a clamp shown above the syringe in .
figure 1 that can be attached over the syringe body 1 and is provided with a stop means in the form of a pin intended to be inserted into a hole through the syringe body 1 so that it penetrates the cross-section of the syringe body a little and ends between two ribs located on the piston, which ribs are arranged in right angle to the movement direction of the piston~ In this way the movements of the piston are limited so that the syringe can only contain a volume in a preselected range, e~g. 1 - 10 ml. ~hus reading of the volume `-` 11096~3 need not be carried out at serial dilution, but the piston is alternatingly brought to the one or the other of the two end positions.
As mentioned above a flattened-out cross-section form of the syringe body is preferred to facilitate the examin-ation of the contents of the chamber, preferably with two sub-stantially parallel sides. If the chamber is to be used for cultivation and examination, the height of the cross-section should not exceed 20 mm and should preferably be 5 - 12 mm.
The greatest length of the section can vary within a wide range.
Usually it is within the range 20 - 70 mm, preferably 25 - 50 mm. Preferably the greatest length is more than twice the length of the shortest dimension. If examination is not impor-tant the measures can of course be selected in another way. The syringe body is preferably made from a transparent material, such as glass or a transparent plastic, e.g. polystyrene plastic, and can in that case be prepared by means of injection moulding.
The design of the piston 2 is not critical. However, its front portion must seal against the inside of the syringe body 1 and be made from a material capable of withstanding the treated liquids. The form is preferably adapted to the front wall of the syringe and can be provided with protrusions dimen-sioned and shaped to completely enter and fill the spouts 3 of the apertures when the piston is completely pushed in. It can also be provided with recesses to form an air-cushion for aero-bic cultivation tests or be designed for modification of the flow -;
in the chamber in order to obtain the best mixing effect. That is to say the front of the piston can be provided with a groove or notch, so that with the piston fully advanced and before suction of liquid into the syringe, this contains air suitable for aerobic cultivation. Alternatively, the front of the piston e~ 9 11()~6~!3 can be provided with tracks or guiding means for causing tur-bulence or additional circulation movements to the liquid stream coming into the syringe during suction.
The apertures 3 are preferably placed as far from ~ :
each other as is - 9a :, ll~S6~3 practically possible, but other positions are also possible which need not be symmetrical. According to the invention two apertures must be present, but of course more apertures for special purposes are not excluded, e.g. when mixing more liquids than two. As indicated above the design of the apertures can vary and they can possibly be different. They are conveniently made so that hoses, nozzles or the like can be easily attached to the aperture, e.g.
as spouts integral with the syringe body 1.
The non-return valves can be formed as a part of the syringe or be detachably fastened to the apertures as a special unit or as a part of an inlet or outlet hose.
A method of using the device according to the figure will be described. 1 ml of a sample containing microorganisms is sucked into the device through one aperture. This aperture is then provided with a non-return valve only permitting outflow. The other aperture is provided with a non-return valve only permitting inflow and with a supply hose for culture medium.
The piston is moved back so far that 9 ml culture medium enter and are mixed with the sample. The piston is thereafter moved forwards so that 9 ml mixture flow out through the outlet aperture and are supplied to a collecting vessel, while 1 ml of the mixture remains in the syringe. The piston is now moved back again and forwards once more, whereby two dilution degrees, 1/10 and 1/100, have been obtained. The procedure is repeated until a desired number of dilutions has been obtained, the last dilution, however, not being ejected but left in the device and subjected to incubation and examination of the cultivation result. The other dilution degrees of the sample can be incubated in their collecting vessels or rather be supplied to a syringe according to the invention or a syringe according ~o the Swedish patent specification 377,811 with only one spout and there be subjectcd to cultivation and examina-tion. ~hen ejecting the mixtures according to the above they can be directly supplied to such another syringe via a connection without first being sup-plied to a collecting vessel.
- 10 `
``" 11096~3 Of course the invention is not limited to the embodiments shown above but can be varied in several manners within the scope of the following claims.
~ 11 ,~
Claims (4)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An apparatus for laboratory mixing of two liquids comprising a mixing chamber designed as a syringe, with a syringe body, a front wall, a rear opening, a piston extending through the rear opening and on the front wall two apertures, separated from each other and each connecting the interior of the chamber with the exterior of the chamber, characterized in that the mixing chamber is flat with two substantially parallel walls.
2. The apparatus of claim 1, characterized in that, at least one aperture is provided with a stationary or detachable non-return valve.
3. The apparatus of claim 2, characterized in that, both apertures are provided with non-return valves and that the non-return valves are arranged for flow in opposite directions.
4. The apparatus of claim 1, characterized in that, the syringe body has means for limiting the movement of the piston between predetermined volume values.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE7611374A SE7611374L (en) | 1976-10-13 | 1976-10-13 | PROCEDURE AND DEVICE FOR LABORATORY MIXING |
| SE7611374-5 | 1976-10-13 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1109693A true CA1109693A (en) | 1981-09-29 |
Family
ID=20329118
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA288,522A Expired CA1109693A (en) | 1976-10-13 | 1977-10-12 | Method and apparatus for mixing in laboratories |
Country Status (10)
| Country | Link |
|---|---|
| AT (1) | AT360494B (en) |
| AU (1) | AU504275B2 (en) |
| BE (1) | BE859687A (en) |
| CA (1) | CA1109693A (en) |
| ES (1) | ES463057A1 (en) |
| GR (1) | GR66163B (en) |
| IE (1) | IE45623B1 (en) |
| IT (1) | IT1090192B (en) |
| PT (1) | PT67099B (en) |
| SE (1) | SE7611374L (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0088971B1 (en) * | 1982-03-13 | 1985-06-19 | Roche Diagnostics GmbH | Device for the detection of bacteria, fungi and viruses in blood |
-
1976
- 1976-10-13 SE SE7611374A patent/SE7611374L/en unknown
-
1977
- 1977-09-30 PT PT67099A patent/PT67099B/en unknown
- 1977-10-04 AU AU29342/77A patent/AU504275B2/en not_active Expired
- 1977-10-08 ES ES463057A patent/ES463057A1/en not_active Expired
- 1977-10-11 GR GR54542A patent/GR66163B/el unknown
- 1977-10-12 IT IT5138877A patent/IT1090192B/en active
- 1977-10-12 IE IE2033/77A patent/IE45623B1/en unknown
- 1977-10-12 CA CA288,522A patent/CA1109693A/en not_active Expired
- 1977-10-13 AT AT730777A patent/AT360494B/en not_active IP Right Cessation
- 1977-10-13 BE BE181709A patent/BE859687A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| IT1090192B (en) | 1985-06-18 |
| GR66163B (en) | 1981-01-20 |
| ATA730777A (en) | 1980-06-15 |
| AU2934277A (en) | 1979-04-12 |
| AT360494B (en) | 1981-01-12 |
| IE45623B1 (en) | 1982-10-06 |
| BE859687A (en) | 1978-04-13 |
| AU504275B2 (en) | 1979-10-11 |
| ES463057A1 (en) | 1978-07-01 |
| SE7611374L (en) | 1978-04-14 |
| PT67099A (en) | 1977-10-01 |
| PT67099B (en) | 1979-02-23 |
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