The ion sensitive field effect transistor (ISFET) pH electrode: a new sensor for long term ambulatory pH monitoring.

Dynamic Characteristics of Gastro-oesophageal Reflux in Ambulatory Patients with Gastro-oesophageal Reflux Disease and Normal Control Subjects

“…In in vitro and in vivo studies ISFET pH sensors have been shown to be at least as good as glass electrodes, currently considered to be the best in 24-h pH monitoring (2,3). ISFET pH sensors are small and respond fast to pH changes (3,6), making them more suitable for studies on spatiotemporal characteristics of gastro-oesophageal reflux.…”

“…We recently reported on the use of a catheter containing five ISFET pH sensors in a study of the dynamic characteristics of physiologic reflux in healthy volunteers (4). In in vitro and in vivo studies ISFET pH sensors have been shown to be at least as good as glass electrodes, currently considered to be the best in 24-h pH monitoring (2,3). ISFET pH sensors are small and respond fast to pH changes (3,6), making them more suitable for studies on spatiotemporal characteristics of gastro-oesophageal reflux.…”

“…Earlier studies have shown that ISFET pH sensors are reliable, with a drift comparable to that of combined glass electrodes (2,3). Response times of ISFET sensors are much lower than those of glass electrodes (intrinsic response times of ISFET sensors are probably less than 2msec per pH step) (3,6). The pH sensors were mounted at 3-cm intervals, the most distal sensor being located at 1.5 cm from the tip of the catheter.…”

“…Before the measurement the catheter was immersed in a neutral buffer solution for at least 5 h, to overcome the time of initial non-linear drift (3). Directly before the test all sensors were calibrated at 37°C in pH7 and 4 buffered solutions, using a calomel reference electrode.…”

“…Recently, ion-sensitive field effect transistor (ISFET) pH electrodes have been developed, providing small, linear, reliable pH sensors with fast response rates (1)(2)(3). This has made it possible to measure intraluminal pH at multiple sites, using one small-caliber catheter.…”