Chemistry: analytical and immunological testing – Automated chemical analysis – With aspirator of claimed structure
Patent
1999-03-17
2000-05-16
Le, Long V.
Chemistry: analytical and immunological testing
Automated chemical analysis
With aspirator of claimed structure
436 49, 436 50, 436179, 436180, 422 67, 422100, G01N 3510
Patent
active
060636351
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a dispensing method for automatic sample analysis systems, particularly a method for removing bubbles generated when a sample is diluted in automatic sample analysis systems, fully automatic analysis systems or the like performing multiple random determinations.
PRIOR ART
In order to improve performance of random-access multiple sample analysis systems automatically operating from the sample dispensing step to the determination step, there has recently been an increasing need for random access to even test items that should be determined after the sample or reagent has been diluted.
The sample or reagent is diluted typically by discharging a diluent from a nozzle into a dilution vessel at a suitable speed to omit stirring action and shorten the time for discharging by simultaneous mixing and discharging, with the result that many small bubbles may be generated in upper layers of the diluted sample.
In systems for sequentially and automatically determining a single item on a plurality of samples, the plurality of samples are sequentially diluted and then successively mixed with a reagent for determination so that many bubbles generated during dilution decrease or disappear after the lapse of a given period. Residual bubbles are impelled toward the wall of the vessel by inertia force or centrifugal force without causing significant problems during dispensing, because the samples are typically moved on a carousel.
However, bubbles generated in automatic sample analysis systems for randomly performing various types of multiple determinations tend to remain because samples are not moved during a short interval from dilution to determination for the reason that it is more efficient to mix a sample with a reagent for determination immediately after the sample is diluted without moving the vessel.
In addition, automatic sample analysis systems for performing multiple random determinations are less likely to form a bubble-free liquid surface at the center of the dilution vessel, because each vessel is designed to be small for the purpose of diminishing the overall system size and mixing requires some discharge speed.
Bubbles generated during dilution enter the pipette to impair dispensing precision when the diluted fluid is dispensed, which results in deterioration of the precision and reproducibility of test results.
Various apparatus for forcedly removing bubbles from the channel have been proposed, e.g. an apparatus having an upper bubble reservoir, an apparatus for pumping away bubbles detected by a sensor provided in the channel, an apparatus having a dispensing nozzle with one of the branched ends connected to a discharge channel an apparatus having an upper constricted zone to remove bubbles under reduced pressure, etc.
Such apparatus for removing bubbles from the channel add a sensor or pipeline to automatic sample analysis systems already having a complex structure with many movable parts, which further complicates the structure of the entire system to hinder handling and prolong the cycle time for determination.
Other apparatus than those for forcedly removing bubbles have also been proposed, e.g. an apparatus for dispensing samples after detecting bubble sites in the channel to confirm the absence of bubbles, an apparatus for retrying suction once bubbles have entered during suction, an apparatus for acting to expel the air at the end of the dispensing tube before dispensing, an apparatus for correctly detecting the liquid level during suction even when bubbles exist.
However, automatic sample analysis systems with these apparatus also require a special sensor or operation to hinder handling and prolong the cycle time.
In order to overcome the above problems, an object of the present invention is to provide a dispensing method for automatic sample analysis systems, which can dispense samples from which have been removed bubbles generated during dilution without adding any special structure or time-consuming operation.
SUMMARY OF THE INVENTION
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Ishii Yuko
Morikawa Tetsuya
Ohta Yumi
Saito Mitsuhiro
Shiga Tetsuya
Abbott Laboratories
Bach Mark C.
Le Long V.
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