Chemical apparatus and process disinfecting – deodorizing – preser – Control element responsive to a sensed operating condition
Patent
1997-03-24
1999-03-16
Warden, Robert
Chemical apparatus and process disinfecting, deodorizing, preser
Control element responsive to a sensed operating condition
422 8201, 422 99, 422 81, 436179, B01L 300, B01L 1100
Patent
active
058825991
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a fluid diluter. The invention is particularly, though not exclusively, applicable to a fluid diluter for particle analysis applications.
The person skilled in the art of particle analysis will be aware of the Impedance or Coulter Aperture method of particle counting and sizing. In relation to the analysis of blood cells this method is described in U.S. Pat. No. 2,656,508. For use with powders the method is defined in British Standard BS 3406 pt5.
In the field of haematology the method involves diluting a sample of whole blood in an electrically conductive solution and passing the dilution through a very small hole that has an electric current passing across it. The individual blood cells obscure the hole as they pass and change the current. This current change is a very accurate measure of cell volume and is used to analyse the number and size distribution of red, white and platelet cells in the original sample.
The conventional instrument used in this method has to perform precision dilution of the sample. For example, after a chemical agent has been used to destroy the red cells in a sample of blood, the resulting dilution (typically 250:1) is sent to a white cell counting chamber where the white cells are counted. As there are considerably more red cells than white, the red cell dilution is usually more than 6000:1. This dilution is typically reached by two successive dilutions to preserve accuracy. The dilution of the red cells is sent to a second chamber for counting of the red cells and platelets. After this, all of the chambers and tubes are flushed with clean diluent for minimum contamination of one sample by a previous one. Contamination in this way is commonly known as `carryover`.
The dilution ratios are necessary as the cells must be far enough apart to be counted individually as they pass through the aperture. If particles are too close together in the diluent, an effect termed `coincidence` may occur when two or more cells together are sensed in a distorted reading of the current across the aperture.
One of the problems associated with this technique is the difficulty in making accurate dilutions. Such large dilution ratios allow a very small margin for error and are difficult to maintain. Various methods of dilution have been used. A typical example employs precision pipettes. However, they are bulky, as they require a mechanism to move the pipette nozzle from the sample container to a bath where the pipette's exterior can be washed and a precision volume discharged from its interior. Furthermore, this washing must be done in an open bath which, though shrouded, still presents a risk of infection from, for example, hepatitis and HIV from any blood aerosol release into the atmosphere. Many other types of dilution means are used, such as ceramic plate valves with loops, precision flow measurement means, bellows systems, bubble manometers and precision pressure systems. All tend to be expensive and bulky. Several do not take account of the viscosity of the liquids changing when the temperature changes. Those skilled in the art will be familiar with these various dilution methods and their limitations.
The standard method of counting particles involves sucking them through an aperture in a random fashion from a dilution. Electrical current distribution in the aperture is not uniform across its diameter. When cells pass close to the walls of the aperture they are sensed as being larger than those particles that pass straight through the middle of the aperture. There has been a considerable amount of work done to reduce these errors electronically. This is usually termed editing.
It would be desirable to be able to make every particle follow the same path through the aperture. This is known as hydrodynamic focusing which involves directing the diluted sample such that it flows through the centre of the aperture and does not travel close to the walls. A sheath of particle-free diluent is arranged to flow coaxially round the tip or mouth of a tube or orifice--termed a dire
REFERENCES:
patent: 2656508 (1953-10-01), Coulter
patent: 2712624 (1955-07-01), Beattie
patent: 2977199 (1961-03-01), Quittner
patent: 3186800 (1965-06-01), Strickler
patent: 3192017 (1965-06-01), Kruger
patent: 3301189 (1967-01-01), Kling
patent: 3398689 (1968-08-01), Allington
patent: 3523546 (1970-08-01), Berg
patent: 3525592 (1970-08-01), Buckley
patent: 3661460 (1972-05-01), Elking et al.
patent: 3740143 (1973-06-01), Groner et al.
patent: 3743424 (1973-07-01), Coulter
patent: 3746976 (1973-07-01), Hogg
patent: 3793587 (1974-02-01), Thom et al.
patent: 3810010 (1974-05-01), Thom
patent: 3831618 (1974-08-01), Liston
patent: 3838601 (1974-10-01), Dorman
patent: 3848470 (1974-11-01), Hargash et al.
patent: 3871770 (1975-03-01), Von Behrens et al.
patent: 3900290 (1975-08-01), Hornstra
patent: 3925018 (1975-12-01), Saunders
patent: 3989381 (1976-11-01), Fulwyler
patent: 4001678 (1977-01-01), Berg
patent: 4014611 (1977-03-01), Simpston et al.
patent: 4015628 (1977-04-01), Randolph
patent: 4019134 (1977-04-01), Hogg
patent: 4050904 (1977-09-01), Cramer
patent: 4070617 (1978-01-01), Kachel et al.
patent: 4087209 (1978-05-01), Mahig et al.
patent: 4120202 (1978-10-01), Range et al.
patent: 4120657 (1978-10-01), Nagy et al.
patent: 4135825 (1979-01-01), Kertscher
patent: 4165484 (1979-08-01), Haynes
patent: 4198160 (1980-04-01), Kachel et al.
patent: 4253058 (1981-02-01), Kachel et al.
patent: 4274453 (1981-06-01), Lee
patent: 4315754 (1982-02-01), Ruzicka et al.
patent: 4394372 (1983-07-01), Taylor
patent: 4428669 (1984-01-01), Bessis
patent: 4607526 (1986-08-01), Bachenheimer et al.
patent: 4695431 (1987-09-01), Farrell
patent: 4972137 (1990-11-01), Dunstan et al.
Counting Technology Limited
Moazzam Fariborz
Warden Robert
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