Comparison of two pH meters used for skin surface pH measurement: the pH meter 'pH900' from Courage & Khazaka versus the pH meter '1140' from MettlerToledo

Background/aims: Measurement of skin surface pH is used in clinical researc h to evaluate hazardous shifts in pH following external exposures and to ev aluate the state of diseased skin with acute or chronic changes. It is ther efore important to measure skin surface pH as precisely as possible. The ai m of this study was to compare two commercially available pH meters used fo r skin surface pH measurement, to reveal differences between them in measur ed skin pH on the forearm. Methods: The first pH meter (pH900) had a pointed electrode and a stabilisa tion period of 3 s. The second pH meter (pH meter 1140) had a circular elec trode and no fixed stabilisation period. Twelve healthy subjects (6 male an d 6 female Caucasians) entered the study. The pH measurements were performe d once an hour from 8 a.m. to 3 p.m. on both forearms in five areas from th e elbow to the "wristwatch" zone. In each area. three measurements were per formed next to each other with both pH meters (15 measurements per arm per hour per pH meter). Results: The pH900 has a higher measuring level and a higher variation than the pH meter 1140. Conclusion: A skin surface pH meter with a circular electrode and with no f ixed stabilisation period is preferable. It is recommended that the pH mete r be allowed to stabilise for at least 7 s before the result is read.