EP0642829A1 - Plastic pipette - Google Patents

Abstract

The present invention relates to a pipette having a pipette body and a pipette piston, this pipette being usable as a liquid detector, either the pipette body or the pipette piston being electrically conductive. The pipette body and the pipette piston are separated by an easily sliding water-insoluble layer which is not attached, or is attached only insignificantly, by detergent-containing solutions.

Description

The present invention relates to a pipette with a pipette body and a pipette piston, this pipette being usable as a liquid detector, with either the pipette body or the pipette piston being electrically conductive.

Such a pipette is e.g. B. described in EP-A-0 226 867. The execution of such a plastic syringe usually consists of two different materials such. B. polypropylene (PP) and polyethylene (PE). A lubricant in the form of e.g. B. oleic acid amide added so that good sliding between the pipette piston and body is achieved. In order to achieve precise volume absorption and delivery, the body is preferably made from the mechanically more stable material (PP). Since the conductivity z. B. is achieved by embedding graphite in the plastic, it is obvious to make the pipette piston from the conductive material, so that the possibility of optical control of the liquid sucked into the pipette is not affected by the coloring of the pipette body.

By design, such pipettes have at least one sealing lip that comes into contact with the media to be pipetted.

If you place such a pipette in automatic analyzers such as z. B. used in medical diagnostics, these pipettes mainly come into contact with solutions that contain detergents. These detergents quickly wash off the sliding layer, which has the consequence that the sliding properties between the pipette piston and the pipette body are severely disrupted. The sudden increase in static or sliding friction leads to uncontrolled, jerky outflow velocities when dispensing liquids from the syringe. As a result, parts of the liquids to be transferred can spray around in an uncontrolled manner, which leads to incorrect dosing.

Detergents for use in such solutions and the detergent concentrations used are known to the person skilled in the art.

The object underlying the present invention was therefore to find a pipette which does not have the above disadvantages.

This object was achieved in that pipette bodies and pipette pistons are separated by a well lubricious water-insoluble layer which is not or only insignificantly, preferably not, attacked by detergent-containing solutions, the conductivity of the pipette piston being retained.

Such a separation can be achieved by various measures.

The pipette according to the invention thus preferably has an electrically conductive pipette plunger, which is essentially made of plastic, and an essentially transparent pipette body, the pipette plunger and pipette body being separated, at least in the areas in which they are in contact, by a layer of a sufficiently lubricious material are.

According to the invention there is also a pipette in which the pipette body is conductive - but it is fundamentally of no importance for the invention which part of the pipette is conductive.

For the production of pipette bodies, for. B. PPX 655 natural (HOECHST AG, Frankfurt, Germany), polypropylene VC 10 64K (NESTE Chemicals) or Daplen KS 131 S (PCD) can be used. For the production of pipette pistons z. B. Polycam PP 2261 EC (HOECHST AG, Frankfurt, Germany) or Lupolen® V3510 K 80% with Lupolen® 6031 M 20% (BASF, Ludwigshafen, Germany) can be used.

In a preferred embodiment, the pipette is a so-called "positive displacement pipette" (dead volume-free pipette), the separation between the pipette body and pipette piston preferably being coated by coating the pipette body and / or the pipette piston with silicone oil at temperatures above 50, very preferably at temperatures of about 70 ° C. Suitable silicone oils are known per se to the person skilled in the art, e.g. B. Baysilone® oil MPH 1000 or paste (Bayer, Leverkusen, Germany) and oil AK 12500 (WACKER).

In a further preferred embodiment, this sliding layer is coated with materials known to the person skilled in the art, such as, for. B. a liquid PTFE product, e.g. B. VYDAX®500 or OSIXO TS (Costenoble) or a chemically related product.

In a further preferred embodiment, this sliding layer is generated in that a seal between the piston and body z. B. an O-ring is inserted so that the piston and body no longer touch directly. Suitable materials are known per se to the person skilled in the art. The ring is preferably made of silicone rubber, rubber or another plastic which has low friction.

In a further preferred embodiment, a, preferably mechanically self-supporting insert made of a particularly slidable plastic, e.g. B. PTFE inserted.

• Figur 1: teilweise aufgebrochen dargestellte Ansicht eines Ausführungsbeispiels einer erfindungsgemäßen Pipette;
• Figur 2: Ausführungsbeispiel mit Dichtlippe aus dem Kolbenmaterial;
• Figur 3: bevorzugte Ausführungsform mit O-Ring aus gleitfähigem Material;
• Figur 4: bevorzugte Ausführungsform mit aufgesetzter, gleitfähigen Dichtlippe;
• Figur 5: bevorzugte Ausführungsform mit einer selbsttragenden Innenbeschichtung aus gleitfähigem Material.

The invention is explained in more detail below with reference to the accompanying drawings. Show it:

• Figure 1: partially broken away view of an embodiment of a pipette according to the invention;
• Figure 2: embodiment with a sealing lip made of the piston material;
• Figure 3: preferred embodiment with O-ring made of slidable material;
• Figure 4: preferred embodiment with attached, slidable sealing lip;
• Figure 5: preferred embodiment with a self-supporting inner coating made of lubricious material.

The pipette according to FIG. 1 consists of a pipette body (3) with the inside (4) and a pipette piston (2), the pipette piston (2) consisting of plastic made electrically conductive and the piston (2) provided with a sealing lip (7) is. The pipette piston (2) has an end section (1) consisting essentially of two disks, on which the pipette piston (2) can be manipulated in an automatic analyzer with the aid of a receiving device. The pipette body (3) has a predominantly disc-shaped end section (8) which is used for manipulation in the automatic analyzer.

Claims (7)

A pipette in which the piston (2) and / or body (3) are electrically conductive is characterized in that between the piston (2) and body (3), at least at the location of the sealing lip (7), there is a water-insoluble sliding layer, which contains detergent-containing solutions is not attacked or is attacked only insignificantly. The pipette according to claim 1, characterized in that it is a pipette free of dead volume. The pipette according to claim 2, characterized in that the pipette piston (2) is electrically conductive. The pipette according to claim 3, characterized in that the sliding layer consists of silicone oil, which is preferably applied at about 50 to 150 ° C, particularly preferably at about 70 ° C. The pipette according to claim 3, characterized in that the sliding layer is an O-ring (5a) made of a lubricious material. The pipette according to claim 3, characterized in that the sliding layer is a sealing lip which consists entirely or at least in its outer periphery of a lubricious material. The pipette according to claim 3, characterized in that the sliding layer consists of an insert (6) made of a lubricious material.

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