pH-Fix 3.1-8.3 indicator strips with chemically bound indicators are the bench mark for pH testing with test strips. The fixation prevents bleeding and therefore contamination of the sample. measuring range: pH 3.1-3.5-3.9-4.3-4.7- 5.1-5.5-5.9-6.3-6.7-7.1-7.5-7.9-8.3