Chemistry: analytical and immunological testing – Including sample preparation – Dilution
Patent
1996-07-10
1998-03-24
Le, Long V.
Chemistry: analytical and immunological testing
Including sample preparation
Dilution
436 52, 436174, 436180, 422 681, 422 81, G01N 138
Patent
active
057312117
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a method for analysing a liquid sample, preferably in different dilutions, in which a sample contained in a sample receptacle is diluted to a predetermined concentration.
When testing blood in respect of different characteristic parameters or properties it is common practice to prepare from a sample of whole blood two or more subsamples which are diluted to different predetermined dilutions or concentrations. A test which requires dilution to at least two widely differing concentrations may be directed, for example, to determinations of parameters of red blood cells and blood platelets carried out on a subsample diluted to a first, low dilution (high concentration) and to determinations of parameters of white blood cells and haemoglobin carried out on a subsample diluted to a second, substantially higher dilution (lower concentration).
Generally, the subsamples are prepared by first diluting the sample of whole blood, or a portion thereof, to the low dilution in a first vessel for forming a first subsample. A portion of the first subsample is transferred to a second vessel together with a predetermined volume, e.g. 200 times the volume of the transferred subsample portion, of a diluent for forming a second subsample. An example of such serial dilution and apparatus for performing it is disclosed in U.S. Pat. No. 4,746,491.
An object of the invention is to provide a method of the nature indicated above which can be performed rapidly and by simple apparatus in an automated analyser.
To this end, there is provided according to the invention a method and apparatus having the characterising features set forth in the independent claims. The dependent claims define preferred embodiments of the method and apparatus.
BRIEF DESCRIPTION OF THE DRAWING
The invention will be described in greater detail below with reference to the accompanying diagrammatic drawing which illustrates an example of an apparatus for carrying out an embodiment of the method according to the invention.
The analyser illustrated diagrammatically in the drawing is adapted for serial examination of blood samples, namely for analysing each blood sample in respect of the number of red blood cells, the number of white blood cells and the number of platelets per unit volume to the sample and also the haemoglobin content and additional characteristic parameters or properties.
The analyser comprises a dual piston pump, generally designated by 11, which comprises a drive mechanism 12 driving a pair of piston pumps 13 and 14 serving as volume metering devices, and a valve mechanism 15. Piston pump 13 comprises a common inlet and outlet passage 13A and has a stroke volume which is substantially greater, 200 times greater, than the stroke volume of piston pump 14, which likewise comprises a common inlet and outlet passage 14A.
By way of a common conduit 16 the inlet-outlet passages 13A and 14A of both pumps 13, 14 are connected with one end of a pipette tube 17. A supply conduit 18, which can be blocked by means of a valve 15A of valve device 15, extends from a supply container 19 for isotonic diluent to the inlet-outlet passage 13A of pump 13. A section of the common conduit 16 extends between inlet-outlet passage 13A and inlet-outlet passage 14A and can be blocked by means of a valve 15B of valve device 15.
Pipette tube 17 is mounted on the body or housing (not shown) of the analyser such that it can take either of two predetermined positions, namely a position for aspirating a sample from a sample receptacle and a position for dispensing the aspirated sample to a receiving vessel together with a liquid diluent as will be described below. In the drawing, the pipette tube 17 is shown in full lines in the dispensing position at A, while it is shown in phantom lines in the aspirating position at B. A beaker-type sample receptacle P, into which the free end of the pipette tube 17 extends, is also indicated in phantom lines at the aspirating position. Shifting of the pipette tube 17 between positions A and B takes place by pivotal
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Le Long V.
Swelab Instrument AB
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