JPH0535823B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a carbon dioxide measuring electrode for detecting carbon dioxide dissolved in blood fluid.

B. Prior art Analysis of carbon dioxide dissolved in a liquid is performed using a gas permeable membrane A that allows only the gas in the liquid to pass through, as shown in Figure 3, and an internal liquid that reacts with carbon dioxide and changes the hydrogen ion concentration. This is carried out by immersing a measurement electrode consisting of an ion-sensitive electrode C and an ion-sensitive electrode C that detects the hydrogen ion concentration of the internal solution into the channel E of the flow cell D through which the sample flows.

By the way, a film made of fluororesin is usually used for the gas permeable membrane of this measurement electrode, but fluororesin itself has a relatively low permeability to carbon dioxide gas, so it is necessary to make it as thin as possible. However, since it has low elasticity, it is difficult to attach it to the electrode body.

C. Purpose In view of these problems, an object of the present invention is to provide a carbon dioxide measuring electrode whose gas permeable membrane is easy to replace and which has high carbon dioxide detection sensitivity.

D. Structure of the Invention That is, the present invention is characterized in that silicone rubber subjected to hydrophilic treatment is used for the gas permeable membrane.

E. Embodiments Therefore, details of the present invention will be explained below based on illustrated embodiments.

FIG. 1 shows an embodiment of the present invention, in which reference numeral 1 denotes an electrode case that houses an internal liquid 2 and that allows an ion-sensitive electrode 3 with its ion-sensitive membrane to protrude from the case 1. Let and hold.
Reference numeral 4 denotes a gas permeable membrane, which is a feature of the present invention, and is brought into contact with the sensitive membrane of the ion-sensitive electrode 3 via a spacer (not shown), and is fixed to the electrode case 1 by an O-ring 5. This gas-permeable membrane is made of a highly elastic silicone rubber membrane that has a carbon dioxide gas permeability 20 times higher than that of fluororesin and has been processed as described below. In other words, silicone rubber is housed in a vacuum container filled with air, water, or argon gas at 0.01 to 0.1 Torr, and high-frequency output is generated.
Generate plasma at 10 to 200W and leave for 1 to 5 minutes. As a result, hydrophilic groups are generated on the surface of the silicone rubber. After the treatment time has elapsed, the silicone rubber from the vacuum container has extremely improved hydrophilicity without any decrease in carbon dioxide permeability or elasticity, and as shown in Figure 2B, the silicone rubber before treatment (Fig. ) The wetting angle with respect to water has become extremely small.

When the measurement electrode according to this embodiment is immersed in a liquid such as blood, the hydrophilic groups formed on the surface layer of the silicone rubber have an affinity for the liquid, and the entire surface of the gas permeable membrane 4 is wetted.

As a result, carbon dioxide dissolved in the liquid is
Combined with the high carbon dioxide permeability of silicone rubber, the ion concentration of the internal liquid 2 is changed by passing through the gas permeable membrane 4 without forming bubbles on the surface of the gas permeable membrane 4.

On the other hand, even when replacing the gas permeable membrane 4 after long-term use, silicone rubber has high elasticity, so it conforms well to the electrode case 1 and can be stretched very easily.

Additionally, if silicone rubber is left in a dry state after plasma treatment, its wettability will gradually decrease.
This can be prevented by storing it in water.

(Effects) As explained above, according to the present invention, the gas permeable membrane is made by introducing hydrophilic groups into the surface of the film made of silicone rubber by plasma treatment. In addition to its properties, it also has hydrophilic properties, and can effectively capture only the carbon dioxide from the sample without causing bubbles to adhere to the electrode surface. The high elasticity of silicone rubber makes it possible to create a carbon dioxide electrode that not only allows for high sensitivity measurements, but also allows for easy membrane replacement.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of an apparatus showing an embodiment of the present invention, and Fig. 2 A and B are explanatory diagrams showing the degree of hydrophilicity, respectively, where A is before treatment and b is after treatment. and FIG. 3 are cross-sectional views showing an example of a blood carbon dioxide measuring device. 1... Electrode case, 2... Internal liquid, 3... Hydrogen ion sensitive electrode, 4... Silicone rubber.

Claims (1)

[Claims] 1. A carbon dioxide measuring electrode comprising a silicone rubber membrane whose surface has been made hydrophilic by plasma treatment, airtightly provided on the hydrogen ion sensitive side of the electrode case that houses the hydrogen ion sensitive electrode and internal liquid.