PH is dissolved in water, the pH will be greater than 7. A solution of a strong acid, such as hydrochloric acid, at concentration 1 mol dm has a pH of 0. A solution of a strong alkali, such as sodium hydroxide, at concentration 1 mol dm, has a pH of 14. Thus, measured pH values will lie mostly in the range 0 to 14, though negative pH values and values above 14 are entirely possible. Since pH is a logarithmic scale, a difference of one pH unit is equivalent to a tenfold difference in hydrogen ion concentration. <br> The pH
Impedance–pH monitoring Impedance–pH monitoring Impedance–pH monitoring is a technique used in the diagnosis of gastroesophageal reflux disease (GERD), by monitoring both impedance and pH. Patients with ongoing symptoms while on proton-pump inhibitor (PPI) therapy are commonly diagnosed with impedance–pH monitoring while continuing their medications. The impedance–pH monitoring diagnostic test determines the frequency of reflux episodes and the time relationship of reflux episodes and symptoms. The impedance–pH monitoring test determines if the patient's symptoms are related to acid reflux, related to nonacid reflux, or not related to reflux of any type. A positive GERD diagnosis is made if acid or nonacid reflux precedes