In the course of working with geothermal-geopressured brines we have developed a slight modification to the general procedure for the use of gas sensing ion selective electrodes which reduces the time between successive samples to about 10 minutes, as well as improving the precision and in the case of the ammonia electrode an improvement in the lower detection limit (to 0.1 ppm) was obtained. We have found that the modified procedure works equally well for both the Orion ammonia (Model 95–10) and the Orion carbon dioxide (Model 95–02) electrodes.