Chemical apparatus and process disinfecting – deodorizing – preser – Control element responsive to a sensed operating condition
Patent
1988-06-01
1991-01-29
Warden, Robert J.
Chemical apparatus and process disinfecting, deodorizing, preser
Control element responsive to a sensed operating condition
422 63, 422104, G01N 3500, B01L 302
Patent
active
049884824
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method and apparatus for chemical analysis and a method and apparatus for dispensing liquid chemical reagents during chemical analysis.
BACKGROUND OF THE INVENTION
Chemical analysis using liquid reagents is widely practiced in many fields, and most especially in medical diagnosis. The term "liquid reagents" encompasses reagents which in their pure or normal state might not be liquid but which have been rendered liquid in some manner such as by dissolving the reagent in a suitable carrier.
Typically, in chemical analysis a sample of the substance to be analysed is placed, sometimes following dilution, in a receptacle commonly known as a cuvette. Measured quantities of one or more liquid reagents are added to the sample in the cuvette and the resulting mixture is then monitored for a change in some selected property. In theory, almost any property could be monitored, but for reasons of practical convenience the property monitored is almost always an optical property. Commonly the mixture will be monitored for a change in colour (i.e. a change in the degree to which one or more specific wavelengths of light are absorbed or transmitted). Other optical properties which may be monitored are turbidity and fluorescence. Non-optical properties which may be monitored are electrical conductivity and pH. In all cases, the chemical reagent or reagents chosen and the property monitored are selected so that the presence or absence of a chemical or type of chemical in the sample can be detected by the presence or absence or the nature of a change in the monitored property of the mixture.
Presently available analytical equipment normally uses peristaltic or piston pumps to deliver the reagents to the cuvette containing the sample. However, these pumps are unreliable and may suffer from leaking seals and split pump tubes. Additionally, the analysers suffer from poor reproducibility of analytical results because the pumps cannot be highly accurate in the quantities of reagents delivered.
A further requirement for accurate analysis is that the liquid reagent should be of good quality and uncontaminated. It is increasingly common for liquid reagents to be pre-packed in bottles which allow improved quality control and security and minimises contamination during storage. When needed, a bottle of a particular reagent is opened and provided as a reservoir for a pump in the analyser apparatus. However, once opened the bottles are subject to contamination if the entire contents of the bottle is not used immediately.
The pumps increase the weight and bulk of the apparatus, and normally need to be driven by motors powered by main electricity. This limits the degree to which such apparatus is portable. Additionally, the pump motors are a source of heat whereas many chemical reagents are heat sensitive. Accordingly, if heat from the pump motors is not to cause deterioration of the reagents the apparatus must be designed to hold the reagent reservoirs or bottles spaced from the pump motors, which tends to increase the size of the instruments and also increases the length of pump tubing which must be employed.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention there is provided a method of dispensing liquid reagents in chemical analysis in which a known volume of reagent is released by the actuation of a 1-shot metering dispenser.
A 1-shot metering dispenser is one in which movement of an actuator from an initial position through an actuating stoke, delivers a single precise volume of liquid and in which no further liquid can be released until the actuating member is allowed to return to its initial position.
Since the dispenser can contain a considerable volume of a reagent it combines the functions of both reservoir and pump, thereby avoiding the need for motor-operated pumps and the like.
Additionally, it is a feature of such dispensers that provided the actuating member travels over the full actuating stroke the quantity of liquid dispensed is
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patent: 4361253 (1982-11-01), Flynn et al.
patent: 4675163 (1987-06-01), Mybeck
patent: 4798705 (1989-01-01), Jakubowicz
patent: 4818493 (1989-04-01), Coville et al.
patent: 4844868 (1989-07-01), Rokugawa
Griffith Jr. D. John
Microvol Limited
Warden Robert J.
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