Measuring and testing – Gas content of a liquid or a solid – By pressure of the gas
Patent
1994-10-17
1996-02-06
Raevis, R.
Measuring and testing
Gas content of a liquid or a solid
By pressure of the gas
G01N 700
Patent
active
054888549
DESCRIPTION:
BRIEF SUMMARY
REFERENCE TO RELATED APPLICATIONS
This application is the U.S. national phase of patent application Ser. No. PCT/JP92/01681 filed on Dec. 22, 1992 and is the U.S. equivalent of Japanese patent application No. 45171/92 filed on Mar. 3, 1992 and still pending.
DETAILED DESCRIPTION OF THE INVENTION
1. Field of Industrial Utilization
The present invention relates to a pipetting apparatus, and more particularly relates to a pipetting apparatus having the ability to determine if the volume of a sample dispensed is insufficient, during the dispensing of samples into containers with the use of a nozzle, by detecting the presence of air bubbles inside the nozzle, for instance.
2. Description of the Prior Art
There are known pipetting apparatuses for pipetting samples, which are used, for example, as distribution apparatuses that distribute blood extracted from human bodies and the like into a plurality of containers.
In such apparatuses, aspiration of the sample is performed through a disposable nozzle. In this case, in order to make certain that a prescribed volume of sample is pipetted, it is required to make sure that an appropriate volume of sample is aspirated into the inside of the nozzle at the aspirating operation. However, when such aspiration is taken place without considering presence of bubbles, the accuracy of the volume of sample aspirated will not be precise if bubbles get aspirated together with the sample. Consequently, the volume of such sample pipetted will have a lower degree of accuracy.
In this connection, the applicant of this application previously proposed in Japanese Laid-Open Publication No. 2-196963, a pipetting apparatus, in which the pressure within an air tube connected to the nozzle is detected by a pressure sensor when aspirating sample, whereby an insufficient aspiration of the sample is determined when an integrated value of the detected pressure is lower than a predetermined reference value.
However, if the volume of sample being dispensed is not precise at the time when the sample is dispensed, it is not possible to improve the pipetting accuracy. Namely, when tiny bubbles like foams seen in beer are generated due to vibrations and the like caused when the nozzle is being moved, and then thus generated tiny bubbles float up to collect near the top part of the sample contained in the nozzle, there is a case that these bubbles remain in the inside of the tip of the nozzle even after the sample has been dispensed, resulting in an inaccurate volume of sample being dispensed. Moreover, after a sample has been dispensed, there is a case that a small amount of the sample remains in the form of a balloon-shaped bubble that is formed around the tip of the nozzle and dangles down therefrom, and this also results in an inaccurate volume of sample being dispensed. Of course, in the conventional apparatus, factors such as the adhesion of the sample on the inside walls of the nozzle have been taken into account when determining the volume of sample to be aspirated. However, the above-mentioned unexpected cases have not been taken into their accounts.
Moreover, in the apparatus disclosed in Japanese Laid-Open Publication No. 2-196963, since the method for detecting an insufficient volume of sample is carried out only at the time of aspirating the sample, it is not possible for the apparatus to detect an insufficient volume of sample dispensed as a result of some volume of the sample remaining behind at the time of dispensing. Furthermore, as bubbles may momentarily go undetected during the aspiration of a sample, this further emphasizes the need for a way of detecting the presence of bubbles at the time of dispensing of a sample in order to improve the accuracy of the volume of sample pipetted.
The present Invention has been made in view of the above-mentioned problems. Therefore, it is an object of the present invention to provide a pipetting apparatus which can detect presence of bubbles inside the nozzle or in the vicinity of the tip thereof just before the dispensing of the sample is c
REFERENCES:
patent: 4117727 (1978-10-01), Friswell et al.
patent: 5054650 (1991-10-01), Price
patent: 5059171 (1991-10-01), Bridge et al.
patent: 5182938 (1993-02-01), Merkel
Katagi Hitomi
Kato Yuko
Kawanabe Junichi
Pelletier Brent A.
Takeda Masaaki
Abbott Laboratories
Bach Mark C.
Raevis R.
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