Abstract: This invention relates to a process for stabilizing the enzyme urate oxidase (commonly known as uricase) in liquid form, and to the relative compositions which can then be obtained, with particular reference to compositions containing a Trinder reagent. According to the process of the invention, uricase can be stabilized in liquid form by adding to the composition containing the enzyme a substituted or unsubstituted dicarboxylic acid containing from 2 to 5 carbon atoms, and preferably 4 or 5. Aspartic acid has shown to be particularly effective in providing said stabilizing activity in liquid uricase compositions containing a Trinder reagent.

Abstract: In a blood gas analyzer, a measurement liquid, advantageously high-purity water, is fed from a suitable vessel to a diffusion cell in which the measurement liquid is brought into contact via a diffusion membrane with the blood sample to be tested. When the gases dissolved in the sample have diffused through the membrane, the measurement liquid which has remained static in the diffusion cell is propelled into a measuring cell in which the value of an electrical quantity related to the pCO.sub.2 is determined. The measurement liquid is then fed to discharge. In a preferred embodiment, the measurement liquid is discharged into the vessel from which it has been initially withdrawn via passage through means for retaining ionic impurities.

Abstract: In a blood gas analyzer, a substantially oxygen-free measurement solution is fed through a measuring cell as far as a diffusion cell in which the measurement solution is brought into contact with a blood sample to be tested. The gases dissolved in the blood sample diffuse through a membrane in the diffusion cell into the solution. The measurement solution is then propelled in the reverse direction to feed into the measuring cell. In the measuring cell, the measurement solution is electrochemically measured to determine a value which is related to the partial pressure of oxygen (pO.sub.2) in the sample.

Abstract: To determine the biological activity of protein S in a sample of human plasma, the suitably diluted sample is added to a substrate formed from plasma deficient in protein S, in which protein C is activated. The functionality of protein is evaluated by a coagulometric test using bovine thromboplastin with added calcium as the phospholipid source. Also disclosed is a kit for determining the activity of Protein S in a human plasma sample. The kit includes a first reagent which is human plasma deficient in protein S, a second reagent which contains an activator for protein C, and a third reagent which contains bovine thromboplastin.