USE OF ION SELECTIVE ELECTRODES IN ENZYMIC ANALYSIS - CATION ELECTRODES FOR DEAMINASE ENZYME SYSTEMS

The response, selectivity, and use of the 39047 and 39137 Beckman cationic electrodes for the determination of NH4+ activity are reported. Both electrodes were found to respond to NH4+ in the concentration range 10-1 to 10-5M with a deviation of ± 0.5 mV in the 10-1 23to 10-4 5678M region and ± 20 mV at 10-4 to 10-5 region. The response characteristics of the micro 39047 electrode were found to be Ag+ > H+ > K+ > NH4+ > Na+ > Li+ ≫ Mg2+, Ca2+. Those of the 39137 electrode were Ag+ > K+ > H+ > NH4+ > Na+ > Li+ > Mg2+, Ca2+. At a pH of 7 the only serious interferences in the assay of [NH4+] are Ag+ and K+. Both electrodes were used for the assay of deaminase enzyme systems: urea-urease, glutamine-glutaminase, asparagineasparaginase, D- and L-amino acids-amino acid oxidases. All substrates and enzymes could be assayed with a precision and accuracy of about 2.5%. © 1969, American Chemical Society. All rights reserved.