Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
1999-08-11
2001-08-28
Font, Frank G. (Department: 2877)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C250S576000, C356S436000, C356S246000
Reexamination Certificate
active
06281517
ABSTRACT:
FIELD OF THE INVENTION
The present invention refers to an apparatus for monitoring pipetting operations, and in particular the ejection of a first liquid from a pipetting needle having a tip immersed in a second liquid. The apparatus comprises a light source that irradiates the second liquid with a light beam, and a light receiver which receives the light beam emerging from the second liquid and delivers an output signal which corresponds to the received light intensity.
BACKGROUND OF THE INVENTION
Light barriers comprising a light source and a light receiver, e.g. for the detection of passing objects, are generally known. Further, it is known that gas bubbles contained in a liquid column are detectable since their optical density is different from that of the liquid column. Therefore, gas bubbles in a liquid column can be detected by means of a suitable light barrier. An apparatus for this purpose is described by WO-A-97/33154.
With respect to automatic analyzers for the analysis of liquids, it is known that these liquids are handled in small quantities, e.g. in portions of minimally 1 to 2 microliters, by aspiration into and ejection out of pipetting needles. In the analysis process, the appearance of bubbles in the needles constitutes an important source of errors since such bubbles can strongly influence the quantities of the ejected liquids.
SUMMARY OF THE INVENTION
The main aim of the invention is therefore to provide an apparatus which allows for the monitoring of the aspiration and ejection of a liquid into and out of a pipetting needle with high accuracy in order to prevent analysis errors. A further aim of the invention is that this monitoring is obtained by an optical arrangement.
According to the invention, these aims are attained by an apparatus comprising:
a light source having a light beam to irradiate the second liquid;
a light receiver for receiving the light beam emerging from the second liquid wherein said light receiver is adapted for continuously delivering intensity signals;
an output signal emitted by the light receiver corresponding to the received light intensity,
first storage means for storing previously determined threshold values;
second storage means for storing the intensity signals delivered by the light receiver and evaluation parameters derived therefrom; and
at least one logic circuit for comparing said evaluation parameters with said threshold values and for delivering a resulting output signal.
The present invention allows measurements in automatic analyzers which are substantially more reliable, thereby considerably improving the information content and usefulness of such measurements.
REFERENCES:
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patent: 5005434 (1991-04-01), Watanabe et al.
patent: 5125748 (1992-06-01), Bjornson et al.
patent: 5559339 (1996-09-01), Domanik
patent: 42 11 003 (1982-10-01), None
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patent: WO 97/33154 (1997-09-01), None
Patent Abstract of Japan- Publication No. 05223830 A, Date of Publication Mar. 09, 1993; Method and Device for Detecting Dispensated Quantity.
Derwent Abstract of EP 819943 A, Optical system evaluating quality of fluid distribution onto test piece, e.g. medical test strip— compares results of successive illuminations of test zone to establish adequate, even spreading for correct delivery to reactive test zone, e.g. in making blood glucose measurements.
Burkhardt Claudius
Godl Fritz
Seeholzer Reto
Font Frank G.
Gibbons Del Deo Dolan Griffinger & Vecchione
Punnoose Roy M.
Roche Diagnostics Corporation
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