GB1535361A - Electrochemical cell - Google Patents

Abstract

1535361 Glass electrode; ammonia solution determination OWENS ILLINOIS Inc 17 March 1976 10614/76 Heading G1N A glass electrode component comprises a chemically resistant glass tube 2 of diameter 0À2-0À5 inch with a pH sensitive glass tip 3 having a convex surface of arc height 0À005-0À015inch. Preferred tube diameter is 1/3 inch and arc height 0À005- 0-01 inch. The glass electrode 11 is used in an ammonia sensor 10 which comprises an electrolyte chamber 13 into which the glass electrode (containing an Ag/AgCl reference electrode in HCl) and a reference electrode 12 are positioned. Thin, flexible, semi-permeable, micro-porous plastics membrane 14 which is selective to ammonia closes the electrolyte chamber 13 and defines an electrolyte film of substantially uniform thickness between membrane 14 and the glass electrode tip. The solution under test flows via passage 17 into test area 23, passage 17 being narrow enough to cause turbulent flow. The reference electrode 12 may be Ag/AgCl on platinum. The membrane 14 is preferably hydrophobic with a thickness of 0À0001-0À01 inch, a porosity of 10-85% and a pore diameter of 0À05- Smicrons. The membrane may comprise an acrylonitrile-vinyl chloride copolymer on nylon support, hydrophobic cellulose acetate, P.T.F.E., polypropylene or polyvinylidene fluoride. The sensor 10 may be used for urea determination. A urea specimen is injected into a flowing stream of buffered diluent (pH 5-9) and passed through a bed of immobilized urease. The hydrolysis product formed contains ammonium ions which are converted to ammonia solution by reaction with a base (Group I or Group II hydroxide) to adjust the solution pH to a least 11. This solution is then flowed through sensor 11 where the ammonia is determined.