Abstract: A first embodiment of a filter includes a circuit board, a metallic tube, and a metallic cap; the tube has an annular groove on outer side of first end, and a leak-stoppage ring fitted onto the groove; the board is held in the tube, and is secured to the tube by solder; the cap is tightly fitted around the first end of the tube such that the board is protected, and the leak-stoppage ring is sandwiched between the cap and the tube; in a second embodiment, annular groove is formed on outer side of a fitting end portion of the cap instead, and leak-stoppage ring is fitted onto the groove; the board is partially held in the cap, and is secured to the cap by solder; the tube is tightly fitted around the cap such that the board is protected, and the ring is sandwiched between the cap and the tube.

Abstract: A method is disclosed for the measurement of acid and alkaline phosphatase activity, whereby an aromatic phosphate ester substrate containing a nitro group is reacted with acid or alkaline phosphatase under appropriate reaction conditions and the hydrolytic process is monitored at electrodes which measure the current produced by the reduction of the nitro groups of the product and/or substrate. Alternatively, an aromatic phosphate ester substrate containing an amino group is reacted with acid or alkaline phosphatase under appropriate reaction conditions with the hydrolytic process being monitored at solid electrodes which measure the current produced by the oxidation of the amino groups of the product and/or substrate.