Abstract: An ultrathin selectively permeable membrane made by glow discharge plasma polymerization of a single siloxane monomer with the deposition of the polymer as a single layer upon a nonporous support material. The resulting membrane has an oxygen content between about 10% and 60% and is highly permselective. The support material can be an electrode, thereby forming an electrode that is resistant to fouling or contamination but readily accessible to oxygen.

Abstract: A method for detecting .beta.-lactamases which may be present in a sample by using a disclosed chromogenic precipitating substrate. A sample is exposed to a disclosed .beta.-lactamase substrate and a colored precipitate forms in the presence of an active .beta.-lactamase.

Abstract: A device and method for permitting the separation of plasma or serum from whole blood. The device comprises a matrix of hydrophilic sintered porous material to which at least one red blood cell agglutinating agent has been applied. According to a first method of using the device, a sample of whole blood is applied to a first end of the matrix and the red blood cells within the sample come in contact with the agglutinating agents present in the matrix. The blood cells agglutinate, and are entrapped in the interstices of the matrix, while substantially blood-cell-free serum or plasma accumulates near the outlet of the device. A filter means in liquid receiving relationship with the matrix functions to wick the serum or plasma from the matrix.According to an alternative aspect of the invention, a filter means in liquid receiving relationship with the outlet of the matrix functions to retain any blood cells which pass through the matrix is the filter means wicks the plasma or serum from the matrix.