Chemistry: molecular biology and microbiology – Measuring or testing process involving enzymes or...
Reexamination Certificate
1994-02-14
2001-08-14
Gitomer, Ralph (Department: 1623)
Chemistry: molecular biology and microbiology
Measuring or testing process involving enzymes or...
C215S227000
Reexamination Certificate
active
06274304
ABSTRACT:
The invention concerns a system for the preparation of liquids from at least one solid and at least one liquid phase, the system consisting of a storage vessel with the solid and a drying chamber with a desiccant. In addition the invention concerns a process for the production of a solution, suspension or emulsion using the system according to the invention. The process comprises the steps of storing a solid in the system, adding a liquid phase to the solid and mixing in order to produce a solution, suspension or emulsion. In a preferred application the system serves to produce reagent solutions.
A problem which frequently occurs in laboratories is that of preparing solutions from liquids and moisture-sensitive solids. The stability of many solids is limited in the presence of water vapour since they decompose. The occurrence of such problems ranges from everyday examples such as e.g. the preparation of foods from dry powder, over the preparation of solutions in the chemical laboratory, to clinical analytical solutions. Especially in the latter case it is necessary to prepare a solution from a solid and a liquid component shortly before use if the final analytical solution has only a limited stability.
The prevailing problem is often solved by either pre-drying the moisture-sensitive solid and packaging it in a water-vapour-tight package or it is packaged together with hygroscopic substances in order to dry it and maintain dryness. In order to prepare the solution, a certain amount of the substance is weighed and dissolved in a measured amount of liquid. The process is imperfect, in particular for analytical solutions, since the quantitative transfer of the solid into a vessel, the addition of an exactly defined amount of solvent and a complete dissolution is difficult. The said process not only requires trained personnel but also elaborate laboratory equipment.
In the case of so-called test kits the user undertakes the preparation of the liquid by preparing the analytical solution from the portioned, i.e. already weighed solids by addition of liquid according to the instructions of the manufacturer of the kit. Stirrers or mixers can relieve the user of the task of dissolving the solids. However, in these cases it is nevertheless necessary to transfer a solid into a vessel for dissolution. Consequently a defined amount of solid in the form of tablets, powders or granulates has to be introduced into a vessel in order to prepare a solution of a defined concentration. In a known reagent stocking system (DE-40 39 580) the reagent is transferred from a special container into a mixing vessel by the opening of a chamber in which the reagent is located when it is screwed onto the vessel. In order to prepare a solution of an exactly defined concentration it is necessary to rinse the chamber. This necessitates laboratory personnel or an elaborate rinsing device.
The object of the invention is to simplify the preparation of liquids from moisture-sensitive solids and liquids by providing a vessel suitable for drying and maintaining dryness. In particular it is intended to facilitate the preparation of an analytical solution by untrained personnel even under conditions of poor infrastructure.
The object is achieved with the system for the preparation of a liquid from at least one solid and at least one liquid phase by the combination
of a vessel which contains the at least one solid and has a volume which is sufficient to receive the at least one solid and the at least one liquid phase,
a desiccant chamber which contains a desiccant (D)
and a separating element which closes the desiccant chamber in such a way that
the desiccant can exchange water vapour at any time with the contents of the vessel but direct contact of liquid or solid contents of the vessel with the desiccant is essentially impossible.
Accordingly the object is achieved by the combination of the following elements:
A vessel in which at first the solid is situated and in which the dissolution of the solid takes place.
A drying chamber connected to the vessel in which a desiccant is located.
The solid of the solution to be prepared can be present in various forms. These include powder, tablets, granulates, pellets or lyophilisates manufactured by freeze-drying.
A solution of several substances can be prepared by using a solid consisting of several components. If the components are mutually incompatible in solution or in the presence of humidity i.e. they then react with each other in an undesired manner, it is, however, in many cases possible to store the substances together in a dry state without their reacting with each other. The storage stability of the solid is increased by a drying chamber which maintains the humidity in the interior of the vessel at a low level. The presence of a desiccant in a chamber which can exchange water vapour with the vessel interior leads to a decrease in the partial water vapour pressure in the vessel interior. In the case of solids which have a residual moisture content due to the manufacturing process it is additionally possible to store them in the system according to the invention in order to dry them or to remove the residual moisture.
The liquid phase can represent a liquid composed of a pure substance (e.g. distilled water) or a mixture of several liquids. The liquid phase can also for example contain buffers, stabilisers or further dissolved substances so that the stability of the prepared liquid is increased and its function is ensured.
In order to prepare the liquid, the liquid phase is added to the solid in the vessel. This can either be carried out manually or automatically by a device. In cases in which the prepared liquid does not have to have an exact concentration since a wide range of reagent concentrations lead to the same analytical results, the measuring of the liquid phase can for example be achieved by marks on the vessel wall. For example enzymes may completely convert an analyte so that the result of the determination is independent of the enzyme concentration in the reagent over wide ranges. In contrast for the preparation of a suitable standard solution for titration analyses, the addition of a defined amount of liquid phase, characterized by its volume or its weight, to a defined amount of solid is necessary. The preparation of the solution is achieved by manual or mechanical mixing of the solid and the liquid phase. It is possible to standardize the preparation of numerous analytical solutions. In these embodiments the liquid phase already contains further components, e.g. buffer and auxiliary substances, so that always one and the same liquid phase can be used for many different analytical solutions.
The liquids produced from the solid and liquid phase in the system according to the invention can be solutions, suspensions or emulsions. For example an emulsion for the detection of the enzyme lipase can be prepared by addition of water to a solid which comprises the following substances: Tris(hydroxymethyl)aminomethane (Tris), sodium deoxycholate, CaCl
2
, triolein, colipase, NaN
3
.
According to the invention the system contains a vessel and a drying chamber which are separated by a separating layer which prevents entry of liquid into the desiccant. Thus the separating layer fulfils two contradictory requirements. On the one hand it is permeable to water vapour and thus enables transfer of water from the vessel interior into the drying chamber via the gas phase, on the other hand it has a barrier effect for water in a condensed phase. For the preparation process this results in the simplification that the preparation of the solution can take place in the same vessel in which the moisture-sensitive solid has previously been stored. In a preferred embodiment, the solid is already dispensed into the vessel during the manufacture of the system. In this case it is not necessary for the user to transfer the solid into the vessel. This additionally eliminates the problem of the user having to weigh out and transfer substances which may be sensitive to moisture or even hy
Buschek Herbert
Cully Maria
Erler Klaus
Ihrig Roland
Kuehnl Michael
Arent Fox Kintner & Plotkin & Kahn, PLLC
Gitomer Ralph
Roche Diagnostics GmbH
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