Chemistry: analytical and immunological testing – Including sample preparation – Volumetric liquid transfer
Patent
1996-04-10
1998-05-19
Pyon, Harold Y.
Chemistry: analytical and immunological testing
Including sample preparation
Volumetric liquid transfer
422 99, 422100, 422103, 422104, 436174, 436179, 7386411, 7386412, 7386424, G01N 110
Patent
active
057535140
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/SE94/00940 which filed in Oct. 7, 1994.
FIELD OF THE INVENTION
The present invention relates to a method of collecting and handling small liquid quantities, i.e. liquid quantities which are so small that the surface tension brings about certain difficulties. The invention also relates to a particular design of a sample container and also to a connecting device therefor.
BACKGROUND OF THE INVENTION
The handling of small quantities of liquid samples becomes particularly difficult as soon as one works with volumes at which a droplet (in the case of water, it can be expected that a droplet which falls freely from a narrow tube will be about 15 .mu.l) is not a negligible volume. The handling of such minute volumes presumes that one and the same volume is maintained and that the delivery and withdrawal of such volumes is effected with the aid of hollow tubes (cannula) in contact with the liquid surface. Examples of such handling procedures are described in EP-B-0,223,758, JP-A-55-39029 and JP-A-60-21455. A common factor of this technique is that the samples are collected on and taken from the bottoms of small sample containers with the aid of cannula which is inserted through an opening located opposite the container bottom. The opening is fitted with an elastomeric stopper through which the cannula is inserted and which reseals the hole made by the cannula as the cannula is withdrawn from the stopper.
A primary object of the invention is to provide for improved handling of small or minute sample quantities, primarily liquid samples, both when taking a sample and when later taking quantities of sample for analysis.
SUMMARY OF THE INVENTION
The invention is based on the realization that it is not necessary to work with conventional liquid vessels, i.e. with the liquid on a bottom, when dealing with such minute volumes. The main aim is to be able to work with maintained volumes that can be repeatedly delivered to and withdrawn from a known position. The surface tension is one of the factors that contributes thereto, as with the known technique. However, according to the starting point of the present invention, the liquid shall be contained in a tubular part of a sample container, this tubular part having a small diameter and being located close to a cannula inlet, preferably in the upper part of the container. The sample container can be handled in any desired position in relation to the vertical, and can even be handled with the container standing upright with the liquid in the upper part of the container. However, in view of the fact that the effect of gravity on such small droplets will be small in relation to the capillary force, the sample container may be positioned in any direction whatsoever in relation to vertical.
To enable slightly larger quantities to be handled, the sample container can be widened in the extension of a narrow, substantially cylindrical part at the mouth or orifice of the container, for instance widened conically. In this case, much larger quantities of liquid can be retained in a unified state in the widened part of the container, through the medium of its cylindrical part. The elongated part of the container at the orifice-end thereof will preferably have a diameter which is not greater than about 3 mm, although the diameter may be smaller as required and as is possible.
One particular advantage gained by allowing the small quantity of liquid to be held in a capillary which lies close to the inlet opening that is closed by an elastomeric stopper is that the liquid will present significant stability against impact forces from a purely mechanical aspect, and it is often possible to avoid the liquid being spread into the sample container and therewith difficult to recollect should the tube be dropped.
It is suitable to provide a small leakage facility, especially at the opposite end of the sample container, with the intention of achieving pressure equalization. According to one preferred embodiment of the invention, this is achieved by fitting i
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patent: 5270219 (1993-12-01), DeCastro et al.
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Karlsson Hans
Ungerstedt Urban
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