Patent Application
20070086924
The invention relates to a pipette having an apparatus that indicates whether the user has admitted an amount of liquid greater than the capacity of the pipette, thereby causing liquid to enter and to contaminate the nosepiece of the pipette dispenser to which the pipette is connected.
It is known in the prior art to provide a white cotton insert in the upper end of a laboratory pipette. The original function of the insert is unknown. In fact, the cotton insert has more functional disadvantages than advantages. Nevertheless, manufacturers continue to make pipettes with said cotton insert.
During pipetting, an operator may unknowingly admit an amount of liquid greater than the capacity of the pipette, thereby causing liquid to enter and to contaminate the nosepiece of the pipette dispenser to which the pipette is connected. The aforementioned traditional cotton insert provides little or no resistance to liquid flow into the nosepiece of the pipette dispenser. Often, and more importantly, the operator may not realize that he has overfilled the pipette and contaminated the pipette dispenser, since the white cotton insert may have no noticeable change in appearance if contacted by a liquid. Therefore, it would be desirable to provide a pipette that indicates whether the pipette has been overfilled, thereby giving an indication that the nosepiece of the pipette dispenser may have been contaminated.
It is known in the prior art to provide a filter in the internal channel of a pipette dispenser. For example, Torti, U.S. Pat. No. 6,123,905, teaches a pipetter having a filter plug located within an interior channel. The filter plug may be treated with a chemical to affect a color change upon contact with liquid. However, because the filter is located internally within the pipetter, it is not visible to the operator without disassembling the pipetter. Therefore, it would be desirable to provide a pipette that includes a contamination indicator that is visible to the operator without disassembling the pipetter.
The invention provides a disposable pipette having an indicator that visually identifies whether the user has admitted an amount of liquid greater than the capacity of the pipette, thereby causing liquid to enter and to contaminate the nosepiece of the pipette dispenser. The disposable pipette has a main body portion with a volume V and a diameter D, an open-ended upper connection portion, and an open-ended lower tip portion. An indicator in the connection portion provides an observable indication that an amount of liquid greater than V has been admitted to the pipette and that liquid may have flown out the open upper end into the nosepiece of the pipette dispenser. Preferably, liquid can not flow out the open end of the connection portion without contacting the indicator. Preferably, the observable indication is irreversible.
In a preferred embodiment, the indicator comprises an insert of porous material that changes color after contacting the liquid. For example, the insert may comprise a cotton swab that has been chemically treated with cobalt chloride, which initially turns the cotton swab blue prior to contact with liquid. After the cotton swab contacts an aqueous solution, the cotton swab turns red, thereby indicating to the operator that he has overfilled the pipette and may have contaminated the nosepiece of the pipette dispenser.
In another embodiment, the indicator reacts with a predetermined agent within the base liquid. The indicator provides an observable indication that the predetermined agent within the liquid has entered the connection portion. The reaction between the indicator and the agent may provide a much more noticeable indication than the reaction between the indicator and the base liquid.
If the indicator is designed to react with any aqueous solution, the pipette may include means for preventing the indicator from absorbing ambient moisture. In a preferred embodiment, the preventing means comprises a deliquescing agent that prevents the insert from absorbing moisture unless the humidity level is greater than about 95%.
In another embodiment, the indicator comprises a coating on the inner surface of the upper connection portion that changes its appearance after contacting liquid. The coating may comprise cobalt chloride.
In a further embodiment, the pipette includes means for preventing liquid from flowing out the open end of the connection portion. Preferably, the preventing means comprises a material that is initially porous to air but becomes impervious to air and liquid upon contact with liquid. For example, the porous material may comprise sintered polyethylene treated with a hydrophilic material such as, for example, starch.
In yet another embodiment, the disposable contamination-indicating pipette includes an indicator in the connection portion that provides an observable indication that a predetermined amount of a particular aerosol created by said liquid has entered the connection portion. The indicator is designed to change color after a predetermined duration of exposure to an aerosol generated from the liquid in the pipette.
In accordance with the method of another embodiment of the invention, a plurality of disposable, contamination-indicating pipettes for metering liquids containing a specified agent are provided. A first pipette is connected to a pipette dispenser, which is used to meter liquid. Each time liquid is admitted to the pipette, the indicator is observed by the operator. The pipette is replaced if an observable characteristic of the indicator changes.
In accordance with the method of a further embodiment of the invention, the pipettes are used to meter liquid and record the contamination history of the dispenser. Initially, a plurality of disposable, contamination-indicating pipettes are provided. A first pipette is connected to the pipette dispenser. Each pipette is used to meter a predetermined quantity of liquid with the pipette and then is replaced. The used pipettes are stored in an ordered series to provide a contamination history of the dispenser.
For the purpose of illustration, there is shown in the accompanying drawings several embodiments of the invention. However, it should be understood by those of ordinary skill in the art that the apparatus and method are not limited to the precise arrangements and instrumentalities shown therein and described below.
A pipette in accordance with a first embodiment of the present invention is shown in
Referring to
The pipette 10 has a predetermined maximum volume indicated by reference letter “V” on the main body portion. The diameter of the upper connection portion 14 is selected from standard sizes to cooperatively engage common pipette dispensers, such as the gun-type dispenser manufactured by Drummond Scientific Company and sold under the trademark PIPET-AID®. The diameter of the main body portion 12 may be different than the diameter of the connection portion 14, as shown in
In the embodiment shown in
The location of the insert 18 within the connection portion is selected so that the insert 18 is visible by the technician when the pipette is connected to the nosepiece 42 of the pipette dispenser 40. For example, in the embodiment shown in
Preferably, the indicator 18 comprises an insert of material that changes its appearance after contacting liquid. For example, the indicator may change color or shape, or display an alpha or numeric message after contacting liquid. The insert may be a disc, plug, or any irregularly-shaped swab of material that can be easily inserted into the connection portion 14. The insert should be large enough that friction securely holds the insert in the connection portion 14 of the pipette 10. In the preferred embodiment, the observable indication from the indicator is irreversible to ensure that the technician is alerted to the contamination.
During metering, an aerosol may be generated from the liquid within the pipette. Depending on the volatility of the liquid, aerosol may be drawn into the connection end and through the indicator, thereby initiating a gradual change in appearance of the indicator. Further, depending on the chemical makeup of the indicator, ambient moisture may also initiate a change in the appearance of the indicator. Therefore, the indicator should preferably be treated with a deliquescing agent to prevent the indicator from changing color until contacted with liquid.
In the embodiment shown in
Other agents may be used to treat the insert 18 without departing from the scope of the invention. For example, the indicator 18 may comprise a cotton swab that has been treated with a chemical agent that does not initially discolor the cotton swab; however, upon contact with an aqueous or organic solution, the cotton swab becomes colored. Additional formulations using contamination indicators other than cobalt chloride may cause different color changes.
The insert 18 may be fabricated from man-made or organic materials, or a combination thereof. The insert preferably comprises a swab of single fibrous material or combination of fibrous materials that is packed into the pipette. Alternatively, the insert could be preformed into a shape that facilitates easy insertion into the pipette.
In a further embodiment of the invention, the insert may be custom designed to react with a predetermined agent present within the liquid being metered. The insert may be made of a material, infused with a material, or chemically treated with a material that reacts with the predetermined agent, thereby providing an observable indication that the predetermined agent is contained within the liquid. In this embodiment, the insert may provide a much more glaring indication when contacted by a liquid containing the predetermined agent. For example, if the pipette is intended to be used for metering liquids containing blood, the insert may be treated with luminol, which creates a vivid fluorescent reaction upon contact with blood. This embodiment also has particular application when contamination due to the intake of an aerosol is of particular concern since the color change of the insert after repeated exposure to the aerosol will be visible more quickly.
Preferably, the insert is located within the connection portion of the pipette and is only contacted if the pipette is overfilled. However, if it is desired to use the pipette as a disposable test device to detect the presence of the predetermined agent, the insert could be located within the central portion of the pipette so that the insert can be wetted without overfilling the pipette. Once the observable indication of the insert is triggered, the pipette is replaced with another.
In a yet another embodiment of the invention shown in
The pipette 210 further includes a plug 50 intermediate the upper open end 222 and the indicator 218. The plug 50 acts as a barrier to passage of liquid into the nosepiece in the event the pipette 210 is overfilled with liquid. The plug 50 allows air to freely flow therethrough until the plug 50 contacts liquid. Once the plug 50 is wetted, it seals and becomes impervious to liquid or air flow. The plug 50 prevents liquid from entering the nosepiece of the pipette dispenser if the pipette is overfilled.
In the preferred embodiment, the plug 50 is made of a porous, hydrophobic sintered polyethylene material, which has been treated with a hydrophilic chemical. Upon contact with liquid, a reaction with the hydrophilic chemical closes the pores of the plug 50 and prevents further liquid from passing through the plug 50 and into the nosepiece of the pipetter. When the plug 50 seals and becomes impervious to air flow, liquid can no longer be admitted or expelled from the pipette 210, thereby forcing the operator to change pipettes.
Similar to the indicator 10 described above, the plug 50 can be treated with a chemical that reacts with a particular agent within the liquid. Additional plugs may also be added to the combination of the primary and secondary plug to affect a reaction that is indicated by a physical change or other visible or measurable change in properties of the combination of plugs.
In an additional embodiment shown in
A plurality of pipettes 10 can be provided and used to keep a record of the contamination history of the pipette dispenser. The record can be helpful to pinpoint the time or location of contamination if the contamination is not immediately noticed by the operator. For example, a protocol may be established whereby the pipette is changed after metering a predetermined quantity of liquid. After the predetermined quantity is metered, the pipette is replaced. Each used pipette is stored in an ordered series in a rack or other collection bin. The source of belatedly-discovered contamination could be traced back by reviewing the series of used pipettes and calculating the step in which the contamination occurred.
Alternatively, a plurality of pipettes could be used as a record to demonstrate that contamination did not occur if, for example, unexpected results are produced in an experiment. The used pipettes could be reexamined to confirm that none of the indicators had reacted.
While the principles of the invention have been described above in connection with specific embodiments, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of the invention. For example, although the invention has been described and illustrated with respect to a serological pipette connected to a gun-type pipette dispenser, the scope of the invention encompasses other types of pipettes useful with other types of pipette dispensers.
